The undercut and stepped hole is the best way to make the threaded inserts work well by far for epoxy, in my experience. However, with resin prints I would recommend an alternative approach. The heat-set inserts you are using are really designed for melting the surrounding area to get a similar geometry in the bonding area as the undercut and stepped hole. It really isn't ideal at all for thermoset plastics. What I predict would work much better in a thermoset resin part are threaded inserts like those used for metal thread repairs. You can use the strongest method, printed threads, and then add EZ-LOK or EZ-Coil (these are the brand name ones) style inserts. I bet you'd get the best of both worlds -- perhaps even as strong as the PLA, or stronger, up to the limit of the differences in material strength between the plastics. There would also be an additional advantage, that this style of threaded insert would improve the precision of the threads in the end while working even with looser tolerances -- this is what they are designed for in metal applications. The geometry is optimized for more brittle failure modes, rather than extended plastic deformation, and this matches the material's failure mode.
Would love to see a test being done with those type of inserts. Really curious to see their performance. By the sounds of it, I expect it to perform really well.
The coil-type inserts (EZ-Coil, Helicoil, etc.) tend to rely a bit on the tolerances of the threads they are screwed in into so they might need tight control of the printed hole dimensions to work correctly. The insert that have solid wall (like EZ-LOK) would work better. If trying to go this route and have the possibility to manufacture your own inserts, there might even be better thread profiles more suitable for inserting into the plastic than the standard metric / imperial thread profiles.
I recently came across screw in inserts which have a slot in them for using a screwdriver to fit them in the hole, and they are self tapping in a way. I really love their convenience and ease of assembly
@@CNCKitchen You could model the _insert_ threads into the part, dab some CA glue/epoxy onto the insert, screw it into the threaded hole, and have the best of both worlds: the strength of printed threads and the re-usability of an insert.
I've been using brass inserts in my resin prints and found what works for me is really simple. Round hole the same OD as the insert. Before curing, press the insert in the hole The uncured resin is soft enough for the knurling to bite into. Mine don't have a very big step, but you could match the profile if needed. I have not torture tested them, but they work for light duty applications. If someone is actually hanging a 50KG load on an m3 anything, well, just don't. LOL.
I've always wondered why everyone uses them in the front side of the hole instead of the backside of the hole. This would leave intact plastic in front of the insert making it much stronger, I believe. EDIT: I see I'm not the only one that has had this thought. And I see that this thought simply confuses the hell out of some people. Basic physics, an insert will pull out of a hole in plastic easier than it will pull through layers of plastic while pulling out of a hole in the backside of the plastic. Not sure how that's confusing in any way. 🤔
in my experience they melt/goo the displaced material mostly further into the hole. if inserted from the rear (inb4 inappropriate comments) it could/would push the excess in the screw path.
What frollard said is correct, but there's a way around it. I use a slight taper in the holes for the inserts and I often also use a ring cutout at the end of the hole (usually the former is enough). I never have any residue in the screw holes doing this and it is much stronger as you said and also mitigates the risk of ripping out the insert.
I figured it was to present the worst-case data instead of best-case data, but also the hole was modeled cylindrical instead of conical so there might not be that much of a difference.
@@frollard This is true, but I've found it's pretty easy to push that excess out by simply threading the screw in from the back. It takes more time, but is worth it in my opinion.
While pla is common, technical parts are often made of petg or better ASA/ABS. Maybe it would be good in the future to add at least a couple of samples in ABS/ASA as reference.
For resin prints, just print out threads for the inserts used on wood furniture. Coat the insert with superglue, and install it in the print. You’ll love the results!
I know this video is about heat-set inserts specifically, but where I work we often use "keenserts" to add metal threads to plastic parts. You drill & tap (or print as the case may be) a larger threaded hole, the keensert has an external thread to match, and then you thread it in and drive in a couple of locking pins that are included with the insert. Then the insert has an internal thread at the desired size. Our machinist likes them because they don't involve adhesives or heat, you just drill & tap the external thread of the insert. Would be interesting to see how those compare.
If you want higher load you need to use flexible resin. A mix of 95 to 5, which gives you minimal flexibility under load, can hold out more before ripping apart.
One of the proven optimal resins for that would be Siraya Blu (original) for 95% and Siraya Tough for 5%, instead of wasting time and money for some obviously proven inferior crap (in this very video) like that marketing-wanky-named Prusa Anthrashite...
For my functional resin prints I use a mix of 70% Siraya Tech Blu and 30% Tenacious. I'd highly recommend this mix or anywhere from 50%/50% to 90%/10% depending on the part stiffness requirements.
It's definitely worth it, the high strength resins are strong but brittle, adding something flexible like tenacious makes parts that are much more tolerant to impacts and keeps it from shattering making for a much more useful part
If tapped or printed threads have great strength already without bonding (which can be very surface prep dependent), print or tap oversized holes and use steel thread inserts. There are so many options to choose from, are easier to put in than heat setting, and can be just as cheap or maybe slightly more expensive. But they extra cost is worth it IMO for not having to mess with soldering irons or glues.
With the super glued resin inserts you should try over drilling the resin, roughing the inside of the hole, then using baking soda and super glue to glue in the insert without using an accelerator. Alternatively try a two part copper epoxy to fix the insert after roughing out the hole.
@@whatevernamegoeshere3644 superglue and baking soda however do seem to make quite a tough bond. Still it won't do any good if it can't adhere to the surface, so you still need to 'rough up' the edge of the hole. Or just make some kind of rough edges on the resin printed wall surface while printing.
Hi Stefan, thank you very for sharing these experiments. I usually manually thread holes into resin parts with Isopropanol BEFORE post UV curing these parts. It is much stronger than doing it AFTER post UV curing like you did.
I recently tried to add heat inserts into a cast resin version of a 3D printed product I made for a client. I didnt quite expect the powdery results I got, I went to recasting the piece and then drilled and glued the inserts into the design. Thankfully the part did the job it was intended. I do still worry that the mechanical fixing of the resin and insert are not as strong as the insert and the 3D printed parts.
PLEASE READ IT, STEFAN! I may have an explanation for why the resin prints underperformed so much and why they exploded so easily. The devil's in the detail. In the jig to be specific. You use PLA holder with PLA plates. But you also use PLA holder for resin plates. With PLA+PLA combo, you see significant deflection in the holder. It's not critical since the PLA plate also has as much elasticity. For the resin plates, however, because of the holder deflection, most of the force on plates is on the edges, resulting in bending forces rather than thread shearing. For real-life strength approximation, you could be testing plates and holders from the same material (as you mostly print all the mating parts from the same printer), but for more universal results and thread testing strictly, the holder should be from something more rigid (like aluminum - you can cheaply order such a part online). Great insights, as always, Stefan! Your videos are the best out there on 3d printing. One or two of them combined usually have a similar scope of testing to the engineering thesis I review.
What a thoughtful, interesting video, as always. It seems there is some opportunity for someone to make something like an “E-Z Lok” style insert specially tweaked for plastic applications.
Ive been using them in my resin parts. You just use a little resin around the outside of the part and uv and it works great...especially when, like me, you use translucent ABS-like resins for parts. If i design the parts my resin prints have threads, if someone else designed it for these... I use em. Works fine as long as you drill it just barely oversize, then resin, then uv pen or rig your curing light to be on. Honestly if you want a truly "tough" resin, use anycubic abs like plus or abslike v2. Both are good and strong and i used them for my voron parts
Great video. I hope someone is inspired by this and finds the perfect solution for threaded inserts with resin. Loved seeing you dip your toe into resin printing again (I laughed out loud), and always love your unique subscribe segments.
A friend of mine used these in non-3D-Printed plastic parts and he saw some really impressive durability increases, specifically it was for RC Car Wheels and it prevented the screws from coming loose, he saw I think it was 4-5x more usage on those wheels
Using inserts in PLA and HTPLA, especially in fixtures needing frequent cycling of the fasteners. Your videos are a huge help! Your work is inspiring and educational. Thank you for investing so much time capturing details and wonderful editing.
finde die aktuell noch eins der besten lösungen für verbindungen die unter dauerbelastung sind im sinne von rein und raus schrauben. nutze sie für die meisten parts oder auch für cosplay sachen, wo man sachen einfach schnell wechseln soll.
inserts work very well in resin prints in situations where screws have to be screwed in and out many times. The insert is then saved by the thread in the resin or the hole in which the screw is placed. It is best to place the inserts immediately after printing the object, before washing it in alcohol. They may not provide the force of your test, but they will protect the printed hole from the screw that will be screwed in.
I've been using inserts in resin glued with epoxy glue into backwards papered holes so even if the epoxy doesn't bond properly it can't just pull out. Tough my applications aren't high force normally. But they do want to be able to be disassembled and assembled regularly.
I recently made a new carriage for my Ender 3 that is cast from polyurethane resin and has the inserts directly molded in. Making the mold was difficult, but it was fun figuring out the silicone mold design.
This application really depends on the amount of times the part is expected to be accessed and taken apart. Has a hard-core scale RC geek, I will print undersized holes into the part if it is part of something that likely will not be touched again for a long while. But, for things like receiver boxes, where access is likely, a threaded brass insert is perfect.
I use a hex recessed hole for the nut and bolt through load bearing parts, just like standard model parts for 90s helis and model cars. No insert needed and rely on compression strength.
I tried numerous ways with resin, including 2000 degree C heat (not pretty), and in the end I just use epoxy. (Shown in my Universal Atari Keyboard video.)
I use them as a glued in place nut. I make the big hole on the back side of the part and a smaller one on the front, that way when you tighten the screw it pulls the insert into the part, not out of the part.
4:08 thermoset resin doesn’t mean it doesn’t melt enough to apply an insert. That’s precisely how I do it. In paper yes it’s thermoset and on paper no it doesn’t melt depending on your definition but for your use case, “melt” is an inappropriate benchmark. You mean soft enough to insert and allow the resin to harden around it. That you can achieve with heat. What you show at the timestamp also doesn’t satisfy the amount of heat needed given you’ve indirectly heating the resin. The part won’t pass enough heat off to effectively soften the surrounding area. So it’s essentially a false positive based more on confirmation bias. You are applying a lot of heat to one local area . Of course that will crack it. Do you have a heat chamber? I use an old mini fridge I sealed shut and removed the electronics then heat on a spinning tray for 10 minutes with a small heater inside the unit. THEN try the insert way with your soldering iron and adapter. Or Use a heat gun and monitor carefully applying heat to the full surface for a few minutes and then apply the insert adapter and insert
Other resins may be different but that's never been my experience. They're more brittle before curing, you're more likely to shatter everything before you could push something in
Stefan - thank you for this interesting data. However, there’s a flaw in you testing setup in that your jig is not rigid enough… One can see it bend as the force on the insert increases. This would cause bending of your test piece as well, which in case of brittle resin prints explains the catastrophic failures. So the test results are not only influenced by the pullout strength of the inserts, but also on the rigidity and flexibility of the test piece. You could fix that by inserting a thick steel washer (or a few of them) between your test piece and your test jig!
I have used inserts but I added an undercut on the insert and made it alingn with an undercut on the resin printed part and then I put the epoxy on both the hole and undercut and the insert and its undercut... these hold magnificently, they are as strong as the part itself. In reality this should be a kit available for resin prints...
...last week I had a costomer who wanted a SLA Print whith a m5 Tab. To this time I didn't know that heatinserts didnt behave like in FDM print...and now I see this Tutorial...damn
In the setup the resin test plates break at the given pull force, because it is brittle and the holder has not the dimensional/flatness stability in the range of pull forces. That makes it more of a break test than the pull force needed to pull the insert out of the hole. A 5mm thick steel plate with a 10mm hole on top of the test plates in the holder would give more accurate results. Big thumbs up for this laboratory testing effort though, and have a center of discussion. Love it! Thank you.
Very interesting comparison yet I see a major fault in the test methodology: the fixture used to hold the samples is prone to bending leading to stress the the less flexible resin samples until they shatter . The load values seems more related to the destruction of the resin samples than the failure of the screw/insert. I would use a more rigid fixture with a smaller pass-through hole to contain the stresses only on the screw/insert section. Maybe for the next chapter it would be very interesting also to see how the situation changes upon temperature and applicable torque.
5:10 Keep in mind some tests have shown accelerated superglue to not be as strong as without. 10:00 Since the resin has to at least partially absorb the UV for it to be cured, this might be dependent on the shape of the part. E.g.: on a corner, or as part of a wall, parallel to it, it might fare better. And maybe increased curing time.
could you possibly test the differences in performance for standard resin vs water soluble resin? like is there even a good reason to use standard resin when its so much easier and less toxic to use water soluble resins?
I find that water soluble resin doesn't clean up as well and you have basically no options for engineering resins for functional parts. Water soluble resins are also still very toxic. Imo if you get a decent set up for recycling your alcohol there's no reason to use water washable resins
@@lnfotron set it out in the sun in an airtight container, this will cure the resin diluted in the alcohol which then will fall out. After that you can shake it up to break up the particles and run everything through a filter. Also don't let it get too dirty or it will not break up and it'll just kinda turn into a blob
Seems to me that threaded inserts like the ones used for MDF furniture, where the outside is threaded as well, would be the ultimate. Just model the threads and maybe a touch of CA to stop them from coming out. They normally have a recessed allen key head for convenient insertion.
They are still limited by the strength of the resin printed threads. The only thing I can see them or helicoils helping with is how long they last screwing and unscrewing the bolts.
@@conorstewart2214 The threads are bigger than the target bolt and seem to cut deeper into the material, so it could have more strength for the same sized bolt.
I'm not sure about the resin you are printing in, but it seems very brittle. With many years of experience using a Formlabs printer, I can say their fiber reinforced resin (Rigid 10k) holds inserts very well. We would print them with a 0.003" to 0.007" interference fit, with the insert being pressed in from the opposite side from the screw. This would allow for a small lip, or big lip depending on geometry, for the insert to press against. The inserts we used had no taper to them and a very precise flat bottom. We would then put a little CA glue on both the insert and inside the hole and press in insert into place. Never had any pull out, pull through, nor break. Our application was over-molding PCBs with thermally conductive encapsulant for use in tools for oil well drilling.
Hmm... Given the relatively good results from printed helical threads, I bet helicoil-type inserts would work well. Or, for that matter, the inserts intended for wood that have huge aggressive external threads.
I've had good luck using slightly undersized holes with a heated press fit using elegoo water washable resin. It seems to soften when heated, but not melt.
I never used inserts but I have installed/ glue nuts on the backside of the prints. So it’s squeezed the two pieces together. You should try a test to see what it would take to pull a nut thru the resin print in you imbedded it on the backside. Love your RUclips channel.
not really a resin guy. but i do plan on using inserts on some of my PLA projects. not fro strength as much as reliability. thanks Stephan really helpful.
Very interesting. One thing to note, when it comes to small bolts and machine screws people often exceed the rated torque values by as much as 300% because "it just feels right". Which is why they often strip threads in softer materials.
Imho why would anyone expect only 1 small M3 thread into a plastic part to hold over 40kg.....in most of your tests you are at about that weight with brass inserts...plenty strong enough for 99% off applications.
Component parts review request. Thoughts on using 'compression limiters' along with the threaded inserts on plastic parts. This would be to avoid plastic part damage in higher component part stress applications. --- Compression Limiters --- threadless sleeves installed into mating parts where threaded inserts are used for attachments. They stop the mating plastic part from being damaged from excess screw torque/pressures and stop pullout of threaded insert through aggressive assembly torqueing of screws.
When you cure resin, only part that is outside will be cured properly. It is not because of its color but simply because UV doesn't have enough penetration. Even transparent resin is not transparent for UV. The reason you are able to create resin prints is the fact that UV light doesn't penetrate it very deep (not deeper than 0.2-0.5mm), otherwise you'd just cure one single block of material continuing from buildplate to the top of the print if it was the case. Similar with CA activator, you supposed to cover one part with activator and another with glue. Otherwise activator only works for outer layer.
@@rynnjacobs8601 he did what I said he shouldn't have been doing in comment. It is not resin that was inside print, it is resin he put there to mount insert. During printing UV light cures layers thoroughly because layer height is only about 0.05mm which is less than what UV able to penetrate through.
Careful when using the CA kicker so it doesn't skew the results. When kicker is added, the CA bond is brittle compared to normal. If you want to test the bond as strong as possible, use baking soda.
Try eyelet inserts for tear out strength vs normal holes printed in parts. It's an idea I've had and implemented but don't have any data to backup if it's any stronger. The idea is the eyelet fused around the entire hole opposed to having pressure applied to just the weaker points of the holes connection.
Always love your comparisons. Thank you for sharing. I wonder if you were to model the insert more precisely so that it fits the hole like a glove if you'd get even more strength. If it improves strength, you could have 3d models of the inserts you sell differentiating them even further from other sources. A one time investment of modeling time could pay off long term. I know it would affect which inserts I would buy if it came with models that I could use to directly create precise holes.
Really good information, as always. Ever since I saw heatserts used (I think, actually, in one of your or Thomas' videos) I bought a small assortment pack and use them wherever it makes sense. Just a simple little thing that makes such a difference to projects.
So I am relieved, that my method of modeling the threads in cad, is actually the best method for ultimate strength. But I wonder how thread repair kits would perform. U know, those inserts with a m3 internal thread and a m4 or m5 external thread.
i would really go for undercut stepped holes in resin, you can make the "positive" shape of the cavity as a component in your CAD program, and just paste it wherever you need a hole, then a cut-combine / subtract command would give you the perfct holes with undercut features for extra grip!
Since resin tends to shrink when curing placing the inserts before curing might make a okay interference fit. Maybe even put relief slots around the insert location to reduce the force the inserts put on the part as a whole.
Hello, this won't work. The hole gets larger after being cured since the resin shrinks, which lessens the material at the hole, hence decrease in diameter.
I don't think it is ideal to compare a M3-screw to a M3-threaded insert, because for the insert you need a bigger hole and therefore you have a larger surface area. A better comparison would be a M4-Screw vs a M3-Insert resulting in a smaller difference for PLA parts and strong win for directly printed SLA-threads.
With epoxy, having a surface for the epoxy to "grab onto" for both sections being glued is key. Really rough surfaces or hard undercuts is a great thing for strength. I would be using an epoxy more like JB Weld or better yet PC-7 two-part reinforced epoxies, as they have proven themselves to me to be a winner for such type applications as holding dissimilar materials solidly in place with great strength. I do not like the "paste" type versions, but the two-part in different containers. Threaded inserts will always have their place, but a person can never expect the force required to break the insert loose be more than the parent strength of the material they are inset into. The situation is great if you even achieve that level of adhesion. Off topic, I wonder why no-one has designed a new type of FDM printer that uses chemical set two-part epoxy. Some of the thicker consistency epoxies, such as PC-7, should lay down a nice strand through an extrusion process and would make extremely tough plastic parts where layer separation would be a thing of the past. JB weld would probably be too thin, but some of the reinforced epoxies would definitely be thick enough. Instead of using a hot-end, you would use a replaceable mixing tip like used on some epoxy caulking guns. Could be tube fed using the same principle as a caulking gun by hydraulic pressure using a refillable set of tubes, and a "gun" pressed by two stepper motors driving feed screws, one for each tube. A thought I have been kicking around.
Threaded rivet nut inserts are by far and away the better solution, and are way stronger than heat-set inserts even in FDM prints. It's worthwhile designing out blind holes to use them.
I have been using the stock thread minor hole diameters in SolidWorks, starting with the correct tap size drill in a drill chuck without the drill by hand. This normally removes only a bit of material as the holes print just a bit undersize. Then I use the drill chuck holding the correct tap and turn by hand or use my tapping jig tool. DO NOT use a drill motor: it creates too much heat and either melts the plastic or the tap trashes out way too much material. On my Ender 3 V2, I printed a 50mm dia x 40 mm long cylinder with a 5mm wall thickness split in half with a female recess and a flange both with 1/2 wall thickness 2.5 mm tall and thick, in PLA each half printed with the cylinder end down. The dims printed less than 0.5mm with the two halves fitting into each other perfectly with NO allowance made in any way as a test in SolidWorks. FYI. Will be starting to use the brass inserts as you demonstrate; great work on the videos, super informative.
1 Put the inserts upside down so the widest point is at the bottom (this would work for glue and resin) which would make it easier to flow material around the fitting, allow light to transmit deeper around the fitting and when cured would provide a more mechanically retentive layout. 2 Use translucent resin and a stronger UV light source (dental unit would work sweet) 3 Use a duel cure light-cured resin. Common in dental industry
Would it be possible to make a machine that tests thread strength until a certain load, then backs off, and then measures how much "slack" was created? Perhaps only strength isn't enough of a metric for this. Initially I was blown away by the strength rating of the tapped PLA but your explanation makes a lot of sense.
I would have been interested in seeing how they performed glueing them into the screwed in holes with printed threads, combining the 2 best performing methods if you will :-)
I still think that inserting regular nuts or square nuts is the better solution for prints. Especially when dealing with vibration. Over time I've seen any type of insert vibrating out of the parts. But having a clipped in nut with a drop of Loctite on the screw, they hold much better and are stronger as they sandwich both plastic parts between each other. Regards, Etna.
I've used a few different styles of E-Z Press branded press-in threaded inserts. They're specifically manufactured for use in thermoset plastics. They work well enough for my application. I wonder how they would perform in the pull tests. A quick tip though, I used 2 different versions of the E-Z Press inserts. The ones with the slot through the opening where you insert the bolt were too deformed to thread in a bolt easily. The version with the slot on the side of the insert that gets pressed into the material first we're way easier to thread into. That may effect the pull out strength though.
Try to use a mix of sodium bicarbonate with superglue, you gotta move pretty fast or it will cure before you are ready, so go small batches as for one insert only at the time, also make some circular channels around the insert in the resin to create more groves of glue plus bicarbonate to hold into.
Would it be possible to print the negative of a threaded insert and use those in resin instead? The kind designed for wood tend to have wide ‘blades’ that allow them to spread any force on the threads through quite a bit of wood. I’m wondering if printing the negative of that in resin so that you could screw in a wood insert would be much stronger than more typical plastic heat set inserts. I’m also curious if ultrasonic installation of heat set inserts (generally how they’re installed industrially as far as I can tell) would allow the part to be stronger.
I tested printing threaded holes in PLA and PETG. I was surprised to find out my Prusa MK3s was able to print M3 size that still worked well (but was a bit tight). Larger sized like M4 were very smooth. That is something one can try out and see how it workes. Often I need screws just to keep a lid closed or similar situations where printed threads can work just fine. Sure, if it is something you open and close multiple times (like a battery compartment), inserts are better and will not wear like plastic probably will in time. I've got no resin printer and no experience how well printed threads work or not in those type of prints.
what about superglue and baking soda (and other material/powders) for threads?? make a oversize hole, put in bolt, fill with baking soda and superglue. bolt unscrews and viola you have a threaded part. please test this out!!
so depending in the resin the properties change drastically. Not to mention tough means different things for different manufacturers. That being said you can heat set without glue. At least I've managed to do that in the resin i use which is a 25% Sirayatech Blu in clear, 25% tenacious clear yellow and 50% Anycubic Standard+ in clear. But you need to preheat the entire part. Like I put it in an insulated heated chamber for like an hour at around 90C. I haven't tested the strength but since i'm not really creating load bearing parts i'm not worried and it hasn't failed so I'm happy and it works at least for me
What about a vacuum chamber ? Certainly not for all of us, but some like you might try that :) Printing under low atmospheric presure means less air in the gaps in the end, and you could heat it in an oven to help shrink the gaps. Something to try for science, maybe ? :)
I use the UV resin pens with the wee UV light attached to the pen for repairs in resin as it cures really strong in the wash and cure station to the wee uv light on top of the pen! They are a brilliant must have for any 3D printing I say! Give it a try as it actually cures into the teeth amd grooves unlike super glue you need an activator that fast cures it but also turn it brittle
So far I have only worked with FFF, not resin but I would think this method would work similarly. I like to design a hole just wide enough for the bolt to fit easily and run it all the way through the part. Then I put the wider area for the heatset insert on the opposite side of the part from where the bolt is going in. This way any pulling on the bolt has to pull the insert further in and all the way through the part instead of just out the side it was inserted. I'd love to see you run that test! You have to be more careful this way about not filling the hole with molten plastic. Often for that I will actually run an extra-long bolt through the part and screw it part way onto the back of the insert before I set it so that plastic cannot get into the hole. Sometimes a little plastic even squeezes into the gap between the bolt and the hole, forming into threads giving the bolt even more to lock into. I guess with Resin printing it would be glue or resin runnig into the bolt hole, not molten plastic but same situation.
It would be interesting to see how strong a through hole is. Put the bolt through and thread a nut on the back. For the resin prints, maybe it wasn't the joint between the insert and the print failing, but the material itself failing. If you got similar results with just a through hole, you could assume it was the material.
This one was - again - excellent. Thanks for the hint with your shop! I'll buy all my threaded inserts now there. Even if they cost a little more than in china. But they're then more reliable, tested, well made and help you. That's actually very satisfying :-)
I usually use sheet metal or wood screws and they seem to work best and are easy to do you make the holes the same size you would drill into wood or sheet metal (self tapping screws)
Apart of why resin broke completely might be that the mounting jig flexed, while the resin print is rigid, resulting in force redistribution where the jig is applying force on the edges, with the screw in the middle. It becomes a doubly supported beam, not just strength of the insert mount.
What is the likelihood that it isn't the insert, rather, the PLA-holder combined with the brittleness of the SLA/resin part that is the real limiting factor? Look at 7:13 (freeze-frame). The blue PLA part is able to arch when loaded, as it is relatively thin-walled. The "DUT" is then no longer loaded in the middle, rather at the sides. This shall put a bending load on the SLA/resin part, causing it to explosively fracture at the weakest point (around the point where the insert is, well, inserted). In that sense, a steel "blue frame" (or anything else that is orders-of-magnitude stiffer) shall give an apples-to-apples comparison between PLA and SLA/resin, IMO.
thought: what about making the stepped hole so the threaded insert is inserted from the back of the part, and held in place with CA or thickened epoxy (if epoxy than additional ridges to increase bonding area). This way you are pulling on the part not on the bond as your primary source of resistance.
Super glue kicker quickens the bond, but it's weaker than letting it set on its own. I think one of the woodworking channels tested many different glues and that was one of the conclusions. I don't know whether it would change much on such a small contact area.
The undercut and stepped hole is the best way to make the threaded inserts work well by far for epoxy, in my experience. However, with resin prints I would recommend an alternative approach. The heat-set inserts you are using are really designed for melting the surrounding area to get a similar geometry in the bonding area as the undercut and stepped hole. It really isn't ideal at all for thermoset plastics. What I predict would work much better in a thermoset resin part are threaded inserts like those used for metal thread repairs. You can use the strongest method, printed threads, and then add EZ-LOK or EZ-Coil (these are the brand name ones) style inserts. I bet you'd get the best of both worlds -- perhaps even as strong as the PLA, or stronger, up to the limit of the differences in material strength between the plastics. There would also be an additional advantage, that this style of threaded insert would improve the precision of the threads in the end while working even with looser tolerances -- this is what they are designed for in metal applications. The geometry is optimized for more brittle failure modes, rather than extended plastic deformation, and this matches the material's failure mode.
Would love to see a test being done with those type of inserts. Really curious to see their performance. By the sounds of it, I expect it to perform really well.
I was thinking the same thing by the end of the video and would also like to see testing on this method.
The coil-type inserts (EZ-Coil, Helicoil, etc.) tend to rely a bit on the tolerances of the threads they are screwed in into so they might need tight control of the printed hole dimensions to work correctly. The insert that have solid wall (like EZ-LOK) would work better.
If trying to go this route and have the possibility to manufacture your own inserts, there might even be better thread profiles more suitable for inserting into the plastic than the standard metric / imperial thread profiles.
Daniel, great comment.
not realy, the resin part wil give in, exploding, long before the insert wil give in, so the weak link in the chian remains the resin print itself
I recently came across screw in inserts which have a slot in them for using a screwdriver to fit them in the hole, and they are self tapping in a way. I really love their convenience and ease of assembly
These are mainly used for wood and if you are careful can also be used in 3D prints and are usually available in hardware stores.
@@CNCKitchen You could model the _insert_ threads into the part, dab some CA glue/epoxy onto the insert, screw it into the threaded hole, and have the best of both worlds: the strength of printed threads and the re-usability of an insert.
I've been using brass inserts in my resin prints and found what works for me is really simple. Round hole the same OD as the insert. Before curing, press the insert in the hole The uncured resin is soft enough for the knurling to bite into. Mine don't have a very big step, but you could match the profile if needed.
I have not torture tested them, but they work for light duty applications. If someone is actually hanging a 50KG load on an m3 anything, well, just don't. LOL.
I've always wondered why everyone uses them in the front side of the hole instead of the backside of the hole. This would leave intact plastic in front of the insert making it much stronger, I believe.
EDIT: I see I'm not the only one that has had this thought. And I see that this thought simply confuses the hell out of some people. Basic physics, an insert will pull out of a hole in plastic easier than it will pull through layers of plastic while pulling out of a hole in the backside of the plastic. Not sure how that's confusing in any way. 🤔
in my experience they melt/goo the displaced material mostly further into the hole. if inserted from the rear (inb4 inappropriate comments) it could/would push the excess in the screw path.
What frollard said is correct, but there's a way around it. I use a slight taper in the holes for the inserts and I often also use a ring cutout at the end of the hole (usually the former is enough). I never have any residue in the screw holes doing this and it is much stronger as you said and also mitigates the risk of ripping out the insert.
I figured it was to present the worst-case data instead of best-case data, but also the hole was modeled cylindrical instead of conical so there might not be that much of a difference.
@@frollard This is true, but I've found it's pretty easy to push that excess out by simply threading the screw in from the back. It takes more time, but is worth it in my opinion.
True, but these inserts are mainly intended for blind holes. For thru holes, a nut on the backside would be stronger anyway.
While pla is common, technical parts are often made of petg or better ASA/ABS.
Maybe it would be good in the future to add at least a couple of samples in ABS/ASA as reference.
For resin prints, just print out threads for the inserts used on wood furniture. Coat the insert with superglue, and install it in the print. You’ll love the results!
Basically the best of all worlds.
I know this video is about heat-set inserts specifically, but where I work we often use "keenserts" to add metal threads to plastic parts. You drill & tap (or print as the case may be) a larger threaded hole, the keensert has an external thread to match, and then you thread it in and drive in a couple of locking pins that are included with the insert. Then the insert has an internal thread at the desired size. Our machinist likes them because they don't involve adhesives or heat, you just drill & tap the external thread of the insert. Would be interesting to see how those compare.
Why dont use wood screws?
Next time someone asks how I placed the inserts in resin I can point them to this video! Thanks for sharing and the shout-out!
If you want higher load you need to use flexible resin. A mix of 95 to 5, which gives you minimal flexibility under load, can hold out more before ripping apart.
One of the proven optimal resins for that would be Siraya Blu (original) for 95% and Siraya Tough for 5%, instead of wasting time and money for some obviously proven inferior crap (in this very video) like that marketing-wanky-named Prusa Anthrashite...
Totally agree, pla and these resins dont compare on the material properties.
@@erikcramer do you think abs-like resin with that 95/5 mix would hold up to similar loads as the pla?
@@jonathancervantes2703 Thats totaly resin brand and mixture dependend.
For my functional resin prints I use a mix of 70% Siraya Tech Blu and 30% Tenacious. I'd highly recommend this mix or anywhere from 50%/50% to 90%/10% depending on the part stiffness requirements.
I seriously start playing with resin mixing at some point!
It's definitely worth it, the high strength resins are strong but brittle, adding something flexible like tenacious makes parts that are much more tolerant to impacts and keeps it from shattering making for a much more useful part
If it’s strong enough to break the part, that’s as good as it can get. And yes inserts makes parts look and function awesome 👍
If tapped or printed threads have great strength already without bonding (which can be very surface prep dependent), print or tap oversized holes and use steel thread inserts. There are so many options to choose from, are easier to put in than heat setting, and can be just as cheap or maybe slightly more expensive. But they extra cost is worth it IMO for not having to mess with soldering irons or glues.
With the super glued resin inserts you should try over drilling the resin, roughing the inside of the hole, then using baking soda and super glue to glue in the insert without using an accelerator. Alternatively try a two part copper epoxy to fix the insert after roughing out the hole.
Accelerators aren't really famous of increasing strength. I would skip it
@@whatevernamegoeshere3644 superglue and baking soda however do seem to make quite a tough bond.
Still it won't do any good if it can't adhere to the surface, so you still need to 'rough up' the edge of the hole. Or just make some kind of rough edges on the resin printed wall surface while printing.
finally a resin oriented study!
Hi Stefan, thank you very for sharing these experiments. I usually manually thread holes into resin parts with Isopropanol BEFORE post UV curing these parts. It is much stronger than doing it AFTER post UV curing like you did.
sounds like tapping it while a bit soft greatly reduces micro-cracks!
I recently tried to add heat inserts into a cast resin version of a 3D printed product I made for a client.
I didnt quite expect the powdery results I got, I went to recasting the piece and then drilled and glued the inserts into the design. Thankfully the part did the job it was intended.
I do still worry that the mechanical fixing of the resin and insert are not as strong as the insert and the 3D printed parts.
PLEASE READ IT, STEFAN! I may have an explanation for why the resin prints underperformed so much and why they exploded so easily.
The devil's in the detail. In the jig to be specific. You use PLA holder with PLA plates. But you also use PLA holder for resin plates. With PLA+PLA combo, you see significant deflection in the holder. It's not critical since the PLA plate also has as much elasticity. For the resin plates, however, because of the holder deflection, most of the force on plates is on the edges, resulting in bending forces rather than thread shearing. For real-life strength approximation, you could be testing plates and holders from the same material (as you mostly print all the mating parts from the same printer), but for more universal results and thread testing strictly, the holder should be from something more rigid (like aluminum - you can cheaply order such a part online).
Great insights, as always, Stefan! Your videos are the best out there on 3d printing. One or two of them combined usually have a similar scope of testing to the engineering thesis I review.
Good point. Might update my test setup!
What a thoughtful, interesting video, as always. It seems there is some opportunity for someone to make something like an “E-Z Lok” style insert specially tweaked for plastic applications.
Ive been using them in my resin parts. You just use a little resin around the outside of the part and uv and it works great...especially when, like me, you use translucent ABS-like resins for parts. If i design the parts my resin prints have threads, if someone else designed it for these... I use em. Works fine as long as you drill it just barely oversize, then resin, then uv pen or rig your curing light to be on.
Honestly if you want a truly "tough" resin, use anycubic abs like plus or abslike v2. Both are good and strong and i used them for my voron parts
Great video. I hope someone is inspired by this and finds the perfect solution for threaded inserts with resin. Loved seeing you dip your toe into resin printing again (I laughed out loud), and always love your unique subscribe segments.
Inserts or no Inserts in 3D prints - What's your opinion?
I have never tried them
A friend of mine used these in non-3D-Printed plastic parts and he saw some really impressive durability increases, specifically it was for RC Car Wheels and it prevented the screws from coming loose, he saw I think it was 4-5x more usage on those wheels
Inserts for machine screws. Un-tapped pilot holes for coarse thread wood/sheet metal screws. Both FDM.
Using inserts in PLA and HTPLA, especially in fixtures needing frequent cycling of the fasteners. Your videos are a huge help! Your work is inspiring and educational. Thank you for investing so much time capturing details and wonderful editing.
finde die aktuell noch eins der besten lösungen für verbindungen die unter dauerbelastung sind im sinne von rein und raus schrauben.
nutze sie für die meisten parts oder auch für cosplay sachen, wo man sachen einfach schnell wechseln soll.
inserts work very well in resin prints in situations where screws have to be screwed in and out many times. The insert is then saved by the thread in the resin or the hole in which the screw is placed.
It is best to place the inserts immediately after printing the object, before washing it in alcohol. They may not provide the force of your test, but they will protect the printed hole from the screw that will be screwed in.
I've been using inserts in resin glued with epoxy glue into backwards papered holes so even if the epoxy doesn't bond properly it can't just pull out.
Tough my applications aren't high force normally. But they do want to be able to be disassembled and assembled regularly.
I recently made a new carriage for my Ender 3 that is cast from polyurethane resin and has the inserts directly molded in. Making the mold was difficult, but it was fun figuring out the silicone mold design.
While I don't have a resin printer I do use heat set inserts in my FDM prints all the time. I love them!
This application really depends on the amount of times the part is expected to be accessed and taken apart. Has a hard-core scale RC geek, I will print undersized holes into the part if it is part of something that likely will not be touched again for a long while. But, for things like receiver boxes, where access is likely, a threaded brass insert is perfect.
I use a hex recessed hole for the nut and bolt through load bearing parts, just like standard model parts for 90s helis and model cars. No insert needed and rely on compression strength.
I tried numerous ways with resin, including 2000 degree C heat (not pretty), and in the end I just use epoxy. (Shown in my Universal Atari Keyboard video.)
I use them as a glued in place nut. I make the big hole on the back side of the part and a smaller one on the front, that way when you tighten the screw it pulls the insert into the part, not out of the part.
Oh boy this is exciting! My experience with threading blind and through holes on resin prints have always resulted in disaster! Great video!
4:08 thermoset resin doesn’t mean it doesn’t melt enough to apply an insert. That’s precisely how I do it. In paper yes it’s thermoset and on paper no it doesn’t melt depending on your definition but for your use case, “melt” is an inappropriate benchmark. You mean soft enough to insert and allow the resin to harden around it. That you can achieve with heat. What you show at the timestamp also doesn’t satisfy the amount of heat needed given you’ve indirectly heating the resin. The part won’t pass enough heat off to effectively soften the surrounding area. So it’s essentially a false positive based more on confirmation bias. You are applying a lot of heat to one local area . Of course that will crack it. Do you have a heat chamber? I use an old mini fridge I sealed shut and removed the electronics then heat on a spinning tray for 10 minutes with a small heater inside the unit. THEN try the insert way with your soldering iron and adapter. Or Use a heat gun and monitor carefully applying heat to the full surface for a few minutes and then apply the insert adapter and insert
I don't know much about Resin printing, but couldn't you push them in before you cure the resin? Isn't it fairly gummy before curing?
Other resins may be different but that's never been my experience. They're more brittle before curing, you're more likely to shatter everything before you could push something in
Stefan - thank you for this interesting data. However, there’s a flaw in you testing setup in that your jig is not rigid enough… One can see it bend as the force on the insert increases. This would cause bending of your test piece as well, which in case of brittle resin prints explains the catastrophic failures. So the test results are not only influenced by the pullout strength of the inserts, but also on the rigidity and flexibility of the test piece. You could fix that by inserting a thick steel washer (or a few of them) between your test piece and your test jig!
I have used inserts but I added an undercut on the insert and made it alingn with an undercut on the resin printed part and then I put the epoxy on both the hole and undercut and the insert and its undercut... these hold magnificently, they are as strong as the part itself. In reality this should be a kit available for resin prints...
...last week I had a costomer who wanted a SLA Print whith a m5 Tab. To this time I didn't know that heatinserts didnt behave like in FDM print...and now I see this Tutorial...damn
Dang, I was going to look at threaded inserts on McMaster-Carr but seeing you're selling on Amazon, I'll go there.
Protip from Franlab: Rotate the screw backwards until you feel it find the old threads when screwing back in to self tapped plastic
Great tip and something everyone should know!
In the setup the resin test plates break at the given pull force, because it is brittle and the holder has not the dimensional/flatness stability in the range of pull forces. That makes it more of a break test than the pull force needed to pull the insert out of the hole.
A 5mm thick steel plate with a 10mm hole on top of the test plates in the holder would give more accurate results.
Big thumbs up for this laboratory testing effort though, and have a center of discussion. Love it! Thank you.
For resin prints you should use left turned incerts perhaps with a locking notch.
Very interesting comparison yet I see a major fault in the test methodology: the fixture used to hold the samples is prone to bending leading to stress the the less flexible resin samples until they shatter . The load values seems more related to the destruction of the resin samples than the failure of the screw/insert. I would use a more rigid fixture with a smaller pass-through hole to contain the stresses only on the screw/insert section. Maybe for the next chapter it would be very interesting also to see how the situation changes upon temperature and applicable torque.
5:10 Keep in mind some tests have shown accelerated superglue to not be as strong as without.
10:00 Since the resin has to at least partially absorb the UV for it to be cured, this might be dependent on the shape of the part. E.g.: on a corner, or as part of a wall, parallel to it, it might fare better. And maybe increased curing time.
could you possibly test the differences in performance for standard resin vs water soluble resin? like is there even a good reason to use standard resin when its so much easier and less toxic to use water soluble resins?
I find that water soluble resin doesn't clean up as well and you have basically no options for engineering resins for functional parts. Water soluble resins are also still very toxic.
Imo if you get a decent set up for recycling your alcohol there's no reason to use water washable resins
@@noobulon4334 you can recycle alcohol!?
@@lnfotron set it out in the sun in an airtight container, this will cure the resin diluted in the alcohol which then will fall out. After that you can shake it up to break up the particles and run everything through a filter.
Also don't let it get too dirty or it will not break up and it'll just kinda turn into a blob
Seems to me that threaded inserts like the ones used for MDF furniture, where the outside is threaded as well, would be the ultimate. Just model the threads and maybe a touch of CA to stop them from coming out. They normally have a recessed allen key head for convenient insertion.
They are still limited by the strength of the resin printed threads. The only thing I can see them or helicoils helping with is how long they last screwing and unscrewing the bolts.
@@conorstewart2214 The threads are bigger than the target bolt and seem to cut deeper into the material, so it could have more strength for the same sized bolt.
I'm not sure about the resin you are printing in, but it seems very brittle. With many years of experience using a Formlabs printer, I can say their fiber reinforced resin (Rigid 10k) holds inserts very well. We would print them with a 0.003" to 0.007" interference fit, with the insert being pressed in from the opposite side from the screw. This would allow for a small lip, or big lip depending on geometry, for the insert to press against. The inserts we used had no taper to them and a very precise flat bottom. We would then put a little CA glue on both the insert and inside the hole and press in insert into place. Never had any pull out, pull through, nor break. Our application was over-molding PCBs with thermally conductive encapsulant for use in tools for oil well drilling.
Hmm... Given the relatively good results from printed helical threads, I bet helicoil-type inserts would work well. Or, for that matter, the inserts intended for wood that have huge aggressive external threads.
I've had good luck using slightly undersized holes with a heated press fit using elegoo water washable resin. It seems to soften when heated, but not melt.
I never used inserts but I have installed/ glue nuts on the backside of the prints. So it’s squeezed the two pieces together. You should try a test to see what it would take to pull a nut thru the resin print in you imbedded it on the backside. Love your RUclips channel.
not really a resin guy. but i do plan on using inserts on some of my PLA projects. not fro strength as much as reliability. thanks Stephan really helpful.
Very interesting. One thing to note, when it comes to small bolts and machine screws people often exceed the rated torque values by as much as 300% because "it just feels right". Which is why they often strip threads in softer materials.
50 kg is WAY more than you will need in practical situations. Nice vid!
No doubt!
Imho why would anyone expect only 1 small M3 thread into a plastic part to hold over 40kg.....in most of your tests you are at about that weight with brass inserts...plenty strong enough for 99% off applications.
Cause Terrence "1×1=2" Howard Said it would
Can we appreciate how pixelated and crisp that print looked in the into? The mini Stefan
Component parts review request.
Thoughts on using 'compression limiters' along with the threaded inserts on plastic parts. This would be to avoid plastic part damage in higher component part stress applications.
--- Compression Limiters --- threadless sleeves installed into mating parts where threaded inserts are used for attachments. They stop the mating plastic part from being damaged from excess screw torque/pressures and stop pullout of threaded insert through aggressive assembly torqueing of screws.
When you cure resin, only part that is outside will be cured properly. It is not because of its color but simply because UV doesn't have enough penetration. Even transparent resin is not transparent for UV. The reason you are able to create resin prints is the fact that UV light doesn't penetrate it very deep (not deeper than 0.2-0.5mm), otherwise you'd just cure one single block of material continuing from buildplate to the top of the print if it was the case.
Similar with CA activator, you supposed to cover one part with activator and another with glue. Otherwise activator only works for outer layer.
This makes me wonder if thick-walled resin-prints are even cured througout or if they only have a hard shell and are liquid or gooey inside…
@@rynnjacobs8601when you print with resin, UV lamp under screen cures resin just fine, there's no issue here
@@shadyb But Stefan had the problem, that the resin he used to glue the insert in, does not cure completely? 8:06 and 9:45
@@rynnjacobs8601 he did what I said he shouldn't have been doing in comment. It is not resin that was inside print, it is resin he put there to mount insert.
During printing UV light cures layers thoroughly because layer height is only about 0.05mm which is less than what UV able to penetrate through.
Careful when using the CA kicker so it doesn't skew the results. When kicker is added, the CA bond is brittle compared to normal. If you want to test the bond as strong as possible, use baking soda.
Try eyelet inserts for tear out strength vs normal holes printed in parts. It's an idea I've had and implemented but don't have any data to backup if it's any stronger. The idea is the eyelet fused around the entire hole opposed to having pressure applied to just the weaker points of the holes connection.
Always love your comparisons. Thank you for sharing.
I wonder if you were to model the insert more precisely so that it fits the hole like a glove if you'd get even more strength.
If it improves strength, you could have 3d models of the inserts you sell differentiating them even further from other sources. A one time investment of modeling time could pay off long term. I know it would affect which inserts I would buy if it came with models that I could use to directly create precise holes.
Really good information, as always. Ever since I saw heatserts used (I think, actually, in one of your or Thomas' videos) I bought a small assortment pack and use them wherever it makes sense. Just a simple little thing that makes such a difference to projects.
Your timing is great... I'm just starting out with resin again =)
So I am relieved, that my method of modeling the threads in cad, is actually the best method for ultimate strength. But I wonder how thread repair kits would perform. U know, those inserts with a m3 internal thread and a m4 or m5 external thread.
i would really go for undercut stepped holes in resin, you can make the "positive" shape of the cavity as a component in your CAD program, and just paste it wherever you need a hole, then a cut-combine / subtract command would give you the perfct holes with undercut features for extra grip!
It is better to redesign the insert specifically for resin to avoid crack formation. The sharp edges on the default insert do not help.
Since resin tends to shrink when curing placing the inserts before curing might make a okay interference fit.
Maybe even put relief slots around the insert location to reduce the force the inserts put on the part as a whole.
Hello, this won't work. The hole gets larger after being cured since the resin shrinks, which lessens the material at the hole, hence decrease in diameter.
Great video - very thorough and professional.
Glad you liked it!
I don't think it is ideal to compare a M3-screw to a M3-threaded insert, because for the insert you need a bigger hole and therefore you have a larger surface area. A better comparison would be a M4-Screw vs a M3-Insert resulting in a smaller difference for PLA parts and strong win for directly printed SLA-threads.
With epoxy, having a surface for the epoxy to "grab onto" for both sections being glued is key. Really rough surfaces or hard undercuts is a great thing for strength. I would be using an epoxy more like JB Weld or better yet PC-7 two-part reinforced epoxies, as they have proven themselves to me to be a winner for such type applications as holding dissimilar materials solidly in place with great strength. I do not like the "paste" type versions, but the two-part in different containers. Threaded inserts will always have their place, but a person can never expect the force required to break the insert loose be more than the parent strength of the material they are inset into. The situation is great if you even achieve that level of adhesion. Off topic, I wonder why no-one has designed a new type of FDM printer that uses chemical set two-part epoxy. Some of the thicker consistency epoxies, such as PC-7, should lay down a nice strand through an extrusion process and would make extremely tough plastic parts where layer separation would be a thing of the past. JB weld would probably be too thin, but some of the reinforced epoxies would definitely be thick enough. Instead of using a hot-end, you would use a replaceable mixing tip like used on some epoxy caulking guns. Could be tube fed using the same principle as a caulking gun by hydraulic pressure using a refillable set of tubes, and a "gun" pressed by two stepper motors driving feed screws, one for each tube. A thought I have been kicking around.
Threaded rivet nut inserts are by far and away the better solution, and are way stronger than heat-set inserts even in FDM prints. It's worthwhile designing out blind holes to use them.
Guter Test! Wenn ich sie mal benötige, hole ich die Teile in deinem Shop. Danke für die großartige Arbeit!
Vielen Dank, freut mich zu hören.
I really like the proper extruder, I'm strongly thinking about getting one
Build one! I think his design files are available.
I have been using the stock thread minor hole diameters in SolidWorks, starting with the correct tap size drill in a drill chuck without the drill by hand. This normally removes only a bit of material as the holes print just a bit undersize. Then I use the drill chuck holding the correct tap and turn by hand or use my tapping jig tool. DO NOT use a drill motor: it creates too much heat and either melts the plastic or the tap trashes out way too much material. On my Ender 3 V2, I printed a 50mm dia x 40 mm long cylinder with a 5mm wall thickness split in half with a female recess and a flange both with 1/2 wall thickness 2.5 mm tall and thick, in PLA each half printed with the cylinder end down. The dims printed less than 0.5mm with the two halves fitting into each other perfectly with NO allowance made in any way as a test in SolidWorks. FYI. Will be starting to use the brass inserts as you demonstrate; great work on the videos, super informative.
1 Put the inserts upside down so the widest point is at the bottom (this would work for glue and resin) which would make it easier to flow material around the fitting, allow light to transmit deeper around the fitting and when cured would provide a more mechanically retentive layout.
2 Use translucent resin and a stronger UV light source (dental unit would work sweet)
3 Use a duel cure light-cured resin. Common in dental industry
Would it be possible to make a machine that tests thread strength until a certain load, then backs off, and then measures how much "slack" was created? Perhaps only strength isn't enough of a metric for this. Initially I was blown away by the strength rating of the tapped PLA but your explanation makes a lot of sense.
I would have been interested in seeing how they performed glueing them into the screwed in holes with printed threads, combining the 2 best performing methods if you will :-)
I still think that inserting regular nuts or square nuts is the better solution for prints. Especially when dealing with vibration. Over time I've seen any type of insert vibrating out of the parts. But having a clipped in nut with a drop of Loctite on the screw, they hold much better and are stronger as they sandwich both plastic parts between each other.
Regards,
Etna.
I've used a few different styles of E-Z Press branded press-in threaded inserts. They're specifically manufactured for use in thermoset plastics. They work well enough for my application. I wonder how they would perform in the pull tests. A quick tip though, I used 2 different versions of the E-Z Press inserts. The ones with the slot through the opening where you insert the bolt were too deformed to thread in a bolt easily. The version with the slot on the side of the insert that gets pressed into the material first we're way easier to thread into. That may effect the pull out strength though.
Try to use a mix of sodium bicarbonate with superglue, you gotta move pretty fast or it will cure before you are ready, so go small batches as for one insert only at the time, also make some circular channels around the insert in the resin to create more groves of glue plus bicarbonate to hold into.
Would it be possible to print the negative of a threaded insert and use those in resin instead? The kind designed for wood tend to have wide ‘blades’ that allow them to spread any force on the threads through quite a bit of wood. I’m wondering if printing the negative of that in resin so that you could screw in a wood insert would be much stronger than more typical plastic heat set inserts.
I’m also curious if ultrasonic installation of heat set inserts (generally how they’re installed industrially as far as I can tell) would allow the part to be stronger.
I tested printing threaded holes in PLA and PETG. I was surprised to find out my Prusa MK3s was able to print M3 size that still worked well (but was a bit tight). Larger sized like M4 were very smooth. That is something one can try out and see how it workes. Often I need screws just to keep a lid closed or similar situations where printed threads can work just fine.
Sure, if it is something you open and close multiple times (like a battery compartment), inserts are better and will not wear like plastic probably will in time.
I've got no resin printer and no experience how well printed threads work or not in those type of prints.
what about superglue and baking soda (and other material/powders) for threads?? make a oversize hole, put in bolt, fill with baking soda and superglue. bolt unscrews and viola you have a threaded part. please test this out!!
so depending in the resin the properties change drastically. Not to mention tough means different things for different manufacturers. That being said you can heat set without glue. At least I've managed to do that in the resin i use which is a 25% Sirayatech Blu in clear, 25% tenacious clear yellow and 50% Anycubic Standard+ in clear. But you need to preheat the entire part. Like I put it in an insulated heated chamber for like an hour at around 90C. I haven't tested the strength but since i'm not really creating load bearing parts i'm not worried and it hasn't failed so I'm happy and it works at least for me
What about a vacuum chamber ? Certainly not for all of us, but some like you might try that :) Printing under low atmospheric presure means less air in the gaps in the end, and you could heat it in an oven to help shrink the gaps. Something to try for science, maybe ? :)
I use the UV resin pens with the wee UV light attached to the pen for repairs in resin as it cures really strong in the wash and cure station to the wee uv light on top of the pen! They are a brilliant must have for any 3D printing I say! Give it a try as it actually cures into the teeth amd grooves unlike super glue you need an activator that fast cures it but also turn it brittle
How about testing the strength of PLA parts after electro plating the part with copper or nickel? That would be a good video to watch
I used inserts with success in the past with transparent resin and curing them with a violet laser, the laser has more penetration and cures instantly
So far I have only worked with FFF, not resin but I would think this method would work similarly.
I like to design a hole just wide enough for the bolt to fit easily and run it all the way through the part. Then I put the wider area for the heatset insert on the opposite side of the part from where the bolt is going in.
This way any pulling on the bolt has to pull the insert further in and all the way through the part instead of just out the side it was inserted. I'd love to see you run that test!
You have to be more careful this way about not filling the hole with molten plastic. Often for that I will actually run an extra-long bolt through the part and screw it part way onto the back of the insert before I set it so that plastic cannot get into the hole. Sometimes a little plastic even squeezes into the gap between the bolt and the hole, forming into threads giving the bolt even more to lock into.
I guess with Resin printing it would be glue or resin runnig into the bolt hole, not molten plastic but same situation.
Seeing the nut for comparison would be great, and idea with printing the notches seems very interesting
Adorable Stefan. Thank you for threading my day :)
It would be interesting to see how strong a through hole is. Put the bolt through and thread a nut on the back. For the resin prints, maybe it wasn't the joint between the insert and the print failing, but the material itself failing. If you got similar results with just a through hole, you could assume it was the material.
Great video, thank you very much. Surprised to see you got that much strength out of resin.
This one was - again - excellent.
Thanks for the hint with your shop! I'll buy all my threaded inserts now there. Even if they cost a little more than in china. But they're then more reliable, tested, well made and help you. That's actually very satisfying :-)
Thanks! Highly appreciated.
I don’t know why but I really like the way you say hoop.
I usually use sheet metal or wood screws and they seem to work best and are easy to do you make the holes the same size you would drill into wood or sheet metal (self tapping screws)
It was nice to see your face at the end! Thank you and have a great day! Danka! Auf Wiedersehen!
Great research and results, thanks!
Apart of why resin broke completely might be that the mounting jig flexed, while the resin print is rigid, resulting in force redistribution where the jig is applying force on the edges, with the screw in the middle. It becomes a doubly supported beam, not just strength of the insert mount.
I use helicoil inserts. I've never tested the strength as my prints don't require the strength, but do require repeated screw cycles.
What is the likelihood that it isn't the insert, rather, the PLA-holder combined with the brittleness of the SLA/resin part that is the real limiting factor?
Look at 7:13 (freeze-frame). The blue PLA part is able to arch when loaded, as it is relatively thin-walled. The "DUT" is then no longer loaded in the middle, rather at the sides. This shall put a bending load on the SLA/resin part, causing it to explosively fracture at the weakest point (around the point where the insert is, well, inserted).
In that sense, a steel "blue frame" (or anything else that is orders-of-magnitude stiffer) shall give an apples-to-apples comparison between PLA and SLA/resin, IMO.
With parts which shattered, I am not sure if you tested the heatsert stength, or actual strength of the material itself.
thought: what about making the stepped hole so the threaded insert is inserted from the back of the part, and held in place with CA or thickened epoxy (if epoxy than additional ridges to increase bonding area). This way you are pulling on the part not on the bond as your primary source of resistance.
For epoxy, try one made to bond well to low surface energy plastics. Thixo is a good example.
Super glue kicker quickens the bond, but it's weaker than letting it set on its own. I think one of the woodworking channels tested many different glues and that was one of the conclusions. I don't know whether it would change much on such a small contact area.