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 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.
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'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.
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...
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.
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.
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.
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.
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.
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.
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.
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.
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...
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.
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.
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.
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.
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.
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.
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.
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 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
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.
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.
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.
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 ? :)
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 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.
There would of like to see some tests with 2-part epoxies that would have filled the voids. As I just get into SLA printing I look forward to doing some more experimentation.
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 :-)
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.
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
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 would suggest to make a hole by placing the insert into the 3d model of the test piece and subtracting it. This way you have thr negative of the insert inside the test piece and can press the insert into the part before curing.
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.
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
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.
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.
Great video, my thoughts 💭 is why not using heat set inserts with resin especially for 3d printers parts this will be more convenient of abs or pla parts because the Abs / pla parts not holding the heat inserts well when the parts exposed to heat , I think with resin inserted much more resistant to this application , in my experience with voron parts I need to re print the parts which hold the set inserts time to time because is become loss . And the other solution for using resin parts to put a square nuts if the design of the parts allows this . ☝️
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
Great video. Little sad that after mentioning the different options, didn't have directly screwed or printed threads for PLA for a more complete comparison. You may have done it in a different heat-set insert video, but then it's not all in one place (and my mind just went "wonder if Arachne has made the threads more accurate and thus better for screws"). I'm not a huge fan of needing extra hardware in general when 3D printing parts, but it's probably just because it wasn't until recently that I even had sets of screws/nuts. But it means the few times I've needed screws I just model them into the part (and some finger grips to make it easier to get on), but as I now have some screws, it's crossed my mind occasionally that maybe I can use them. I'll have to check if the other videos contain the comparison and if tapped/heat set from those videos line up in results.
Cured resin will soften at temperature, so it might be possible to place inserts with heat? Still impressed how good (with it's known weaknesses) material PLA is 🤠
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.
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.
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.
You should try to insert the thread just after resin print and before curing the entire piece. In this case, the resin in not hard yet and the thread will melt better. Then hard them together.
Would've been nice to show a nut from behind for comparison. That would show the material's limit and max that an insert thread could take if it was installed in the best way.
I don't have a resin printer (yet?) but I ordered a few parts from the Prusa website and decided to pick up some of your inserts as long as I was placing an order. I'm looking forward to trying them out with my MK3S+ I have a lot of microcontroller dev boards that are just bare pcb's, so I'm thinking of trying to make some enclosures for them.
Hi Stefan, very informative and as always methodological episode - well done. Can you add helicoil inserts and test/ measure them amongst other methods. We have been using them for years together with PolyJet printer and they work well but it would be great to see how are they compare to other solutions. Alles Gute!
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 think you can do even better for tear out with the epoxy with some improved void geometries... so you take your existing improved geometry. then creat a hollow well behind that at the far end of the insert. then before installing the insert you first pre-fill down the hole with enough epoxy to fill that new extra hollow you created. then install the insert. and any excess epoxy should shmooze out in a very messy way. but you can always sand it flush later on. so the epoxy transfer interface zone also has its own anti tearout plug. this is then like a 'double insert' in other words. and you are just applying the same principle twice over you can also experiment with different viscocities of epoxy. to try to find the optimum thickness for easier installation. to be more easy to get into the hole. and be a bit more like the ca glue.
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!!
I'd like to see how a threaded insert, that threads into the resin would work. From your results, you could print in the larger thread and then just thread in the insert. You should get a bit more strength because the insert thread is a lot larger than the threads for the screw.
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.
Looks like limit here is resin part strength. So, smooth sleeve (and glue) will reduce structural tensions and give the better result. Resin are like a concrete. So good for pressure forces, so bad for break forces. Idea of smooth sleeve is reduce pressure, by removing wedge-shaped objects out of resin contour.
Thanks for the great content as always! You should post the results on the page for your items for sale and/or make a page with results and video links to the testing. Having reference material to help make a choice on what inserts to purchase would be very helpful. Thanks and best wishes...
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.
One thought is using the stepped inserts backwards. In other words, the smaller diameter at the top or outer surface. If you were using a conical fastener in a conical hole, you would naturally arrange it so that the cone points in the direction of the pulling force. So why not do this with the inserts?
Standard resin (the elegoo resin here) is always brittle, you get a lot of tough resins like prusas that are only "tough" in the sense of if you drop your model it doesn't shatter like standard resin. A lot of brands do Abs like resin of varying quality. I've come to favour anycubic tough, and anycubic abs like+ resins with tough being resistant to breaking as it is very flexible and abs like+ being generally more resistant to compression and impact... wish I had a test rig like yours to test these 2, alongside a mix of siraya tech blu + tenacious as someone else has wisely recommended.
Hi stephan, i guarantee that your undercut idea will improve the pullout force a fair bit. Any chance of releasing a follow up video? I know its a bit different but i do design work with composite sandwich panels and we use undercuts with adhesive to glue mechanical inserts in place. The idea being that the adhesive glue fills a groove around the exterior of the insert, then also an undercut underneath the composite ply face, and you are trying to shear the adhesive material iself to remove the insert, not separate a bond line! currently you are relying on the bond line to the material to withstand the pullout force on your adhesive tests, and on the tapped tests, the tapping is damaging the material so the threads are weak as you say. With your pla prints you are relying on a mechanical gripping force directly using the material strength. if you make these undercuts, it will be more of a similar idea to the pla prints, but what would be better is if you can get inserts that have a groove around them instead of knurling!! Great video.
i would wonder about using a locking screw, like a grub screw to hold the inserts, flood the hole with loctite or glue, shove in a grub to press against the insert
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.
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 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?
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'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.
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.
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.
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.
finally a resin oriented study!
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.
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.
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.
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.
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.
While I don't have a resin printer I do use heat set inserts in my FDM prints all the time. I love them!
Oh boy this is exciting! My experience with threading blind and through holes on resin prints have always resulted in disaster! Great video!
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 you should use left turned incerts perhaps with a locking notch.
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...
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 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.
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.
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.
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.
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.
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.
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.
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 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
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.
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!
Dang, I was going to look at threaded inserts on McMaster-Carr but seeing you're selling on Amazon, I'll go there.
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
Great video - very thorough and professional.
Glad you liked it!
50 kg is WAY more than you will need in practical situations. Nice vid!
No doubt!
Your timing is great... I'm just starting out with resin again =)
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.
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.
The durability of the blue and red parts is impressive
Just simple PLA 😉
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 ? :)
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.
For epoxy, try one made to bond well to low surface energy plastics. Thixo is a good example.
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.
You should try 2 Part MMA adhesive. From my experience the adhesion is unmatched, and remains more flexible compared to CA glue or Epoxy
There would of like to see some tests with 2-part epoxies that would have filled the voids. As I just get into SLA printing I look forward to doing some more experimentation.
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 :-)
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.
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
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.
You can incorporate T nuts into the print design.
Drop in, 1/4 turn to lock and viola!
Great video, thank you very much. Surprised to see you got that much strength out of resin.
I would suggest to make a hole by placing the insert into the 3d model of the test piece and subtracting it. This way you have thr negative of the insert inside the test piece and can press the insert into the part before curing.
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.
Great research and results, thanks!
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
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.
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.
Great video, my thoughts 💭 is why not using heat set inserts with resin especially for 3d printers parts this will be more convenient of abs or pla parts because the Abs / pla parts not holding the heat inserts well when the parts exposed to heat , I think with resin inserted much more resistant to this application , in my experience with voron parts I need to re print the parts which hold the set inserts time to time because is become loss .
And the other solution for using resin parts to put a square nuts if the design of the parts allows this . ☝️
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
I would like to see you do this with the Siraya Tech Blu resins, since they are meant to be used in engineering applications.
Great video. Little sad that after mentioning the different options, didn't have directly screwed or printed threads for PLA for a more complete comparison. You may have done it in a different heat-set insert video, but then it's not all in one place (and my mind just went "wonder if Arachne has made the threads more accurate and thus better for screws"). I'm not a huge fan of needing extra hardware in general when 3D printing parts, but it's probably just because it wasn't until recently that I even had sets of screws/nuts. But it means the few times I've needed screws I just model them into the part (and some finger grips to make it easier to get on), but as I now have some screws, it's crossed my mind occasionally that maybe I can use them. I'll have to check if the other videos contain the comparison and if tapped/heat set from those videos line up in results.
With parts which shattered, I am not sure if you tested the heatsert stength, or actual strength of the material itself.
Cured resin will soften at temperature, so it might be possible to place inserts with heat?
Still impressed how good (with it's known weaknesses) material PLA is 🤠
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.
Seems like this type of comparison should include a typical nut and clearance hole, or a nut in a nut trap. Still, great video!
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.
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.
I think they need something along the lines of a Heli-Coil where it threads into the part with deep threads and offers metal thread for reuse.
It is better to redesign the insert specifically for resin to avoid crack formation. The sharp edges on the default insert do not help.
You should try to insert the thread just after resin print and before curing the entire piece. In this case, the resin in not hard yet and the thread will melt better. Then hard them together.
Would've been nice to show a nut from behind for comparison. That would show the material's limit and max that an insert thread could take if it was installed in the best way.
CA accellerator spray can cause the glue to be a somewhat weaker joint btw
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 don't have a resin printer (yet?) but I ordered a few parts from the Prusa website and decided to pick up some of your inserts as long as I was placing an order. I'm looking forward to trying them out with my MK3S+ I have a lot of microcontroller dev boards that are just bare pcb's, so I'm thinking of trying to make some enclosures for them.
Hi Stefan, very informative and as always methodological episode - well done. Can you add helicoil inserts and test/ measure them amongst other methods. We have been using them for years together with PolyJet printer and they work well but it would be great to see how are they compare to other solutions. Alles Gute!
I wonder if it would make any difference to print the threads and THEN tap, just to clean it up. I wouldn't expect much, but it might be fun to test.
Could add a knurled resin printed hole oversized then using the epoxy would give added grip surface.
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.
Loved this video. Keep it up, you're doing great!
Thanks!
i think you can do even better for tear out with the epoxy with some improved void geometries... so you take your existing improved geometry. then creat a hollow well behind that at the far end of the insert. then before installing the insert you first pre-fill down the hole with enough epoxy to fill that new extra hollow you created. then install the insert. and any excess epoxy should shmooze out in a very messy way. but you can always sand it flush later on.
so the epoxy transfer interface zone also has its own anti tearout plug. this is then like a 'double insert' in other words. and you are just applying the same principle twice over
you can also experiment with different viscocities of epoxy. to try to find the optimum thickness for easier installation. to be more easy to get into the hole. and be a bit more like the ca glue.
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!!
Standard Formlabs resin does soften with higher temperatures
Never thought to use heat inserts in resin prints. Been using them alot lately with my FDM parts.
I'd like to see how a threaded insert, that threads into the resin would work. From your results, you could print in the larger thread and then just thread in the insert. You should get a bit more strength because the insert thread is a lot larger than the threads for the screw.
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
Looks like limit here is resin part strength.
So, smooth sleeve (and glue) will reduce structural tensions and give the better result.
Resin are like a concrete. So good for pressure forces, so bad for break forces.
Idea of smooth sleeve is reduce pressure, by removing wedge-shaped objects out of resin contour.
You could try stepped holes BUT insert heat-sets BEFORE curing process
Thanks for the great content as always! You should post the results on the page for your items for sale and/or make a page with results and video links to the testing. Having reference material to help make a choice on what inserts to purchase would be very helpful. Thanks and best wishes...
Thanks for the idea!
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.
One thought is using the stepped inserts backwards.
In other words, the smaller diameter at the top or outer surface.
If you were using a conical fastener in a conical hole, you would naturally arrange it so that the cone points in the direction of the pulling force. So why not do this with the inserts?
Try 3d printed threads with a threaded exterior insert!
Standard resin (the elegoo resin here) is always brittle, you get a lot of tough resins like prusas that are only "tough" in the sense of if you drop your model it doesn't shatter like standard resin. A lot of brands do Abs like resin of varying quality. I've come to favour anycubic tough, and anycubic abs like+ resins with tough being resistant to breaking as it is very flexible and abs like+ being generally more resistant to compression and impact... wish I had a test rig like yours to test these 2, alongside a mix of siraya tech blu + tenacious as someone else has wisely recommended.
Hi stephan, i guarantee that your undercut idea will improve the pullout force a fair bit. Any chance of releasing a follow up video? I know its a bit different but i do design work with composite sandwich panels and we use undercuts with adhesive to glue mechanical inserts in place. The idea being that the adhesive glue fills a groove around the exterior of the insert, then also an undercut underneath the composite ply face, and you are trying to shear the adhesive material iself to remove the insert, not separate a bond line!
currently you are relying on the bond line to the material to withstand the pullout force on your adhesive tests, and on the tapped tests, the tapping is damaging the material so the threads are weak as you say. With your pla prints you are relying on a mechanical gripping force directly using the material strength. if you make these undercuts, it will be more of a similar idea to the pla prints, but what would be better is if you can get inserts that have a groove around them instead of knurling!!
Great video.
How about thin CA gluing helicoil inserts into modeled threads? That should provide the best insert to plastic joint.
I had no clue that Resin did not melt, I figured it was still a type of plastic and so one just had to add more heat.
i would wonder about using a locking screw, like a grub screw to hold the inserts, flood the hole with loctite or glue, shove in a grub to press against the insert
For the through holes, I would melt in one of the tapered inserts on the far side.
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.