Vacuum chamber, 2 cup mixing, vibrating table... just about every solution was brought up, but it doesn't solve the efficiency or cost problem. It's just not practical for production, unfortunately. I really hoped it would work.
@@TheFabricatorSeries In our family business in Germany, we also produce PU products in large quantities. To start small, all you need to do is set the mold at a small angle and drill another 2-3 vent holes in the lid. In practice, multi-cavity molds are often used for such small parts to increase efficiency. You could also simply make 20 of these smaller molds and fill them all in one go (with a larger syringe). Otherwise, I think that your method in the moment is not that bad without a dosing system.
Forte plastics!!! They custom build plastic parts for people. Your mold your specification. They run the production and ship it to you. Cherryvale Kansas. I deliver parts for them to dedicated customers and the people and processes are amazing. Might save you some time from reinventing the wheel. Let them do this part for you and you can get back to doing what you do. This is the business tip of the day. Put your time where it is the most valuable. Some days it trouble shooting others it’s covering for someone else. Sitting on a yacht smoking a cigar is a massive expense. There is more reward in walking through the shop seeing everything is taken care of knowing you can move on to your next step. Climbers will always climb. Thank you for sharing your story and insights. Peace be with you.
Great video. I've done a fair bit of machining polyurethane, modifying molded bushings and rod stock. The key is the cutting tool. You need to experiment with the tool shape, feeds and speeds to make decent cuts. Standard metal cutting bits usually don't work well, as you showed,. You need more of a slicing type of cut. You also need to make fairly heavy cuts, including the finish pass. There's no sneaking up on a final dimension like you do with metal.
To remove bubbles: vacuum chamber the mix before injection (can be messy) and/or pressure pot the full mould after injection (probably a better option).
Build your mold 1/4 taller than needed. Once the bushing is removed shave/cut off the bubble portion that will be ususally contained in your 1/4 overage. It is costly, but will work. Good look Sir.
IMO Delrin is a no brainer, if that’s unpopular get abom to make 5x molds that make 10x pieces at a time. Build a vacuum chamber with 2x $100 refrigerant pumps and get a dispenser pump to fill molds. Looking at less than $1k for materials plus atoms fee for the molds and you have your assembly line. You’d easily be able to pump out 1k bushings a day.
In addition to everyone's good suggestion of using a vac pump briefly on the freshly mixed poly, it'd be best to put them in a pressure pot to cure, causing any final bubbles to be microscopic.
I don't know if this would work, but how about using the mixing tubes which come with 2 part epoxy systems. These are ideal for 50:50 mixes. This is supplied as 2 tubes bonded side to side with linked plungers - so equal amount of each are extruded, as the common plunger is depressed. The 2 fluids pass immediately into the mixing/delivery spout (without allowing the introduction of air) and as the fluids pass down the spout, a double helix mixes them together as they are forced down it. The end of the spout is the delivery point where the mixed compound will be injected into the mould (free of bubbles - hopefully). Or possible dispense the mix into a pot from which you can extract with your syringe. Fist CC. from the spout to waste. And also the mixing tube full of compound is waste, so you need to mould a few bushes each time a mix is made. For economic production, I would suggest that you keep stock levels of the popular sizes as low as poss, So when you have to make a single rear bush to order; you can make use of the already contaminated mixing tube, by also filling the moulds for the more popular sizes, without creating stock levels which are inconsistent with anticipated demand.
You need a vacuum pump like everyone else is saying. You will need multiple molds and a peristaltic pump to pump the polyurethane in the mold. The peristaltic pump will allow you to change hose if it gets clogged and you can't remove the polyurethane. It's best to run cleaner through it after each use. It should also not introduce air bubbles if you fill the intake with two-part polyurethane before turning on the pump. You will need to determine the hose to use that will not cause a reaction with the polyurethane. I will send a bill for my manufacturing advice to your office.
Before you suck up the polyurethane into the syringe you should put it under a vacuum it will kill the bubbles off. But it does not speed up the process of producing thousand of them at a time.
Delrin machines crazy well in my experience. In terms of an American supplier you might want to talk to I work with a company called "Trexler Rubber" for my cold isostatic press bags and they can make some wild shapes with polyurethane. Might be work a phone call.
Justin the comment about a vacuum chamber is certainly the correct way to go but you will also need to take account of set up times and also what number of bushings would you seek to produce in each batch. the alternative is maybe a vibrating table fill the mould and stand it on the table whilst it cures. Personally i now use HDPE or Delrin for all my bushings which is quite easy if you have a cnc lathe. Do you have any production facility companies nearby to whome you could contract the manufacture and avoid the massive cost of machines and tooling
Watched this yesterday - and today watched an old episode of Car S O S. Tim went into a business making urethane car bushes. Molds did not have a cover. Mix was just loaded into open topped mold, up to the top. Done by hand with multiple molds in a line all a single assembly. Used some sort of gun to feed the mix - by eye or controlled volume? Not possible to tell, looked like by eye. They were CNC turning the metal insert bushes. Different color (using pigment) for different hardness/compliance.
Justin, if some tools are critical to order fulfilment you need to keep spares. Keep spare band saw blades in house. Maybe spare motor and blade guides. And if that stuff flies, price up an auto feed saw. Or some other coupon maker that can run 24/7 unattended. Not keeping stick is quite efficient, but leaves you venerable to breakdowns and sickness. Quite tough to manage with a small team tho.
Just watched your video Justin, all the urethane moulds I’ve made for my own products I’ve always made an open mold. Leave the top part of your mold off and fill the mold to the top with a cup of urethane not a syringe. Air bubbles will rise to the top and you’ll end up with a smooth finish.
There is a company in Wisconsin that does exactly what you were trying to do with the bushings. A machine shop i worked for would make molds for them. They don't call it "injection molding", they call it urethane casting. You can also put it under vacuum to get rid of the air bobbles before it is cured. If you wanted to get higher volume you would make a mold with more cavities. You would also have a few molds where one is being filled while another is curing.
Just throwing this out there... I've made delrin bushings for jeep lift kits many times and they work fantastic and are basically indestructible. Machine an outer aluminum sleeve and stuff it with a delrin bushing and you can't kill it. Works great, and it's super easy and fast to machine. cuts like butta! Just use insanely sharp cutters and you're good to go.
Have you thought about some kind of vibratory table? For testing purposes, a machine with a flat surface you can pour into and leave the mold there as the machine runs. If it works repeatably then you could, in theory, have a batch of molds made to help it become profitable. Otherwise, great content!
I imagine a split mold out of aluminum with say 2 lines of 2, with removeable cores that are suspended accurately, an input fitting at one end, and a fitting for the vacuum at the other. A large vacuum resevoir has the power mixed resin in a disposable container with a pickup tube hanging at the bottom of the resin. Mix the resin in the disposble container with say a drill motor, place the cup in the vacuum 'vat', put the pickup tube in the resin, put lid on vacuum and draw a vacuum, then close valve on vat. After bubbles are released, open valve at vacuum end of mold also under vacuum, then open valve to vat, allowing resin to flow into mold, by opening vat vacuum valve to ambient. Resin will flow into mold, close vacuum end valve on mold, downstream of a intermediate extra catch container (to protect valve), when resin appears.
I went down this road on a similar product. Spincasting was the answer I ended up at. Flash was harder to fight, but otherwise worked to remove the bubbles and increase throughput
I've been messing with silicone molds and resin casts for making clear factory style buttons with very good results. I've seen vacuum degassing suggestions, but haven't seen curing in a pressure pot mentioned. Any remaining air not removed or introduced after vacuuming gets squashed down to microscopic levels when cured under pressure. Essentially necessary for clear parts in a mold. At least with resin and thin parts. I do plan to make my own mounts and bushings in the future.
Great episode! My son and I have a motorcycle parts making business and we have had to overcome a ton of production obstacles but our biggest challenge has been distribution and marketing which seems like two things you got covered. Would really like to follow along as you go down this path so please post more videos of the process.
I know you're just prototyping but you need a polyurethane with a longer working time so you can vacuum degas it before pouring it. A 3 minute open time just doesn't give you enough time to degas. Then put it in a pressure chamber so that any leftover bubbles collapse and become microscopic. For production you'll need a multi-cavity mold with runners so you can do a single pour.
Just watched the video to the end. Yes Delrin , I have used Detroit Speed bushings but nobody has them for aftermarket mustang 2. They need to have a spiral grove for grease
You can get the bubbles out with vacuum. Put the filled molds in a vacuum bell jar, and pull a vacuum (HVAC vacuum pump). Maybe you can design a cap for the mold that your put on after filling and connect your vacuum pump. Commonly used for resin casting, wood working glue-ups, etc.
Solution for the bubbles...either going to have to get slower setup poly, mix up the solution, inject in the smaller mold, then put the entire mold inside a vacuum pot at pull all the air out of the liquid...going to be messy as hell, then let it setup...you might also put the mix cup in the vacuum chamber, foam it out, then inject (but that might cause air to be pulled into the solution) Very awesome idea on molds...I wonder if a 3D printed with ABS or PETG and then smoothed (layer lines in the bushing would suck) but since it doesn't get that hot when curing, you could rapid prototype a mold w/o spending a crapton on machining...and cool shout out to Abom79!
Justin, look up skateboard wheel fabrication process. There are a couple methods. Batch processing is the most economical. For machining polyurethane stock on the lathe, you need a cutting tool with a radial edge. Full round carbide insert works at high speed... To avoid air bubbles, there are a couple ways. Vacuum degassing the liquid prior injection helps, but having a mold with aguaranteed high spot to allow the bubbles to congregate. same idea as the 'rise'r in metal casting. however allowing the urethane to cure in a pressurized environmont, like a painter's pressure pot, you will eliminate the bubbles compleyely.
The max producing part, is actually an easy fix, and at the same time we'll solve the bubble issue too. For mass production, your mould doesnt hold 1 bushing. You need to machine a mould, that can do many many bushes at once. You want a single big fill point, this can even be a part of the large top piece, and has the runners everywhere as needed. At the same time, have extra small breathers every where. Build the mould big enough, that it will fit into a vacuum chamber, just a home hobby variant for now. When you build the mould for multiple units, additionally add a few routes through it, than can be used for coolant later on. The coolant part is for when you start wanting to really turn them out. But in regards to the breathers etc, take a look at nost plastic enclosures, youll start being able to spot the fill and breath points by those tiny little flat circles. Not to mention, the "whiskers" tyres have, theyre from all the breather points. But to make sure you get the air out of the poly, vacuum chamber. But for efficiency, its all in scaling the mould up to hold many all at the same time. :) PS, a local University/College may even help you automate it a little bit as a team project. So multiple bright students bringing their robotics mind in, and typically youd be the one to help fund the supplies to build the jig, which you get to keep. They also get to bring their ideas to you first, and youll get to help teach upcoming engineers how to think about real world issues too :)
14 дней назад
If the bubbles are strictly at he top surface, Angle mold at 45 degrees with vent at highest point and fill from bottom and allow a percentage of flow through the mold.before setting mold flat.
You need bigger modules with many individual units. Multiple of these allow you to keep the injection unit busy. Get rid of bubbles by using pressure, heat or lower density resin.
You need a urethane with longer working time, preferably a lower viscosity as well. And as many others have mentioned, vacuum chamber then move it to the pressure pot. You could figure out an efficient way to make short production runs in house. The properties of the material matter too.
Another great video👌 3D printed molds for poly bushings are also a good option, it wil take some trial and error to get the dimension where you want them to be but if you got it it’s just print and repeat, also works great to make double flanged bushings since you can spit them along the axis, and just use a simple hoseclamp to hold them together. Cheers!
That's exactly how most poly bushings are made. Process slowness is due to inperfection in your technology chain. First of all - mould design! Current mould is ok for prototyping and it's cheap, but for mass production you need something better. What do I mean when I say better: you need a batch type mold. For example one mold fo 10 bushing - such a way you can mix one batch and immediately pour full mould giving you like x10 bushings at a time. Next you need to think about quick assembly and unmoulding process - it should be like quickly push bushings out of the mould and immediately be ready for a new batch. Next part is bubbles. There are two main sources of bubbles: air trapped pockets in mould and air trapped in polyurethane. You can solve first problem by fixing the mould design - just think how liquid urethane fills the mould and where you'll get a trapped air - just add a riser hole at that spot. You have a flat top - just tilt your mould to have a one top spot. Next is air trapped in urethane itself - you need a simple pressure pot to pressurise your parts while urethane is curing. Urethane likes to bubble in contact with moisture (moisture ib air is enough to make it bubbly) so pressure pot is like a must have with urethane. Using multiple moulds in parallel will make it work. Perfectly worker should demould and repour one mold while other is curing. Lets say you have only one 10 position mould and a really slow worker that can refill mould each 30min- it's 160 parts per 8 hour work day. This number is if you have a really turtle-slow worker. Perfectly your should use multiple moulds and single mould repour cycle should be around 10-15min.
To get the bubbles out build a small vacuum chamber 1 cubic foot should be about right and use a shop vac to pull the vacuum. For proof of concept you'll be ok, for production your going to invest a lot of money in tooling, injection dies are not cheap. Multiple cavity dies for each particular size desired will be needed. Once you have the tooling you could find a company to do the molding for you and that cost will depend a lot on quantity. May be more cost effective to find an existing source for the bushings in the short term. Good luck I hope you succeed.
I do car restoration work, replacement bushings are a huge problem for me. I've never used delrin for bushings but if the price is comparable to PE I'd be very interested.
As a small business owner also, you hit the nail on the head describing my days. It's funny when I get asked what I do, and then the folks asking hear that I own the business - they think I'm rolling in the dough and do nothing all day long. Could not be further from the truth. On your process, you could outsource to a low cost manufacturing facility (think overseas), but I know you want to do sourcing here. Going to be hard to do without significant resources. Oh, stay away from venture capitalist money. Trust me on this one.
i use to do lots of 2 part liquid polyurethane mould pours, we would line up our moulds and pour 30 at a time or more, you can get longer cure time urethane's we used electric mixing paddles on a drill press. A vacuum pump is a must have, or your wasting your time.. We used a large electric pizza oven to speed up cure time's and warm our moulds before the pour .. any bubbles the did come to the surface after filling we use a small blow torch to get rid of them..
You need a vacuum chamber and a riser tube and reservoir and always have it overfilled so when you vacuum it and release the vacuum it gets filled. Keep in mind that when vacuuming it usually bubbles and rises at least 30% extra volume. And your mould should probably also have some tooling to easily get it apart
Well your video maybe makes me understand why when I order something that says, "Ships the next day" but it takes a week for me to get a tracking number that it is not the shops fault but instead it UPS or FedEx. In the future I'll be a little more patient. Not talking about your shop, you guys are always pretty prompt. I'm not an expert but I have poured a little bit of concrete and of course bubbles are an issue. That's why they have "vibrators' to work the bubbles to the surface. I think you had the right idea with shaking them but that will never equal what vibrating could do. Keep up creating ideas. You will eventually find a solution. Thanx.
To move into higher numbers, prob eventually do a multiple mold process. Vacumm before pour, and pressure pot during set up. Just ideas, i do like this vid style as well, because Im in a similar mind set. Constantly brainstorming and solving etc. Great job as usual.
Vacuum degassing is the next step if you want to get perfect results with minimal investment. The pumps and pot can be had on Amazon these days for way cheaper than in the past. You probably already have a vacuum pump if you ever did your own AC work. I used to make custom mounts years ago and this was the easiest and cheapest method for quality production level results. Get a longer cure poly, degass after you mix and pour your production run. Its not much more in terms of money or steps. A lower viscosity poly will naturally degass much faster. BTW Is that a welded up Luxor on your front desk?
A vacuum chamber and multi-part mold with sprues on the top would be the way to go. Since you don't high temperature/pressure to mold it, you can prototype with 3d printed or silicone molds.
I make a few custom urethane parts and Delrin bushings. Most all the Delrin is for road race cars - to harsh for street cars. For the urethane I put the mold in a vacuum pot. My vacuum solution, which works great, is a cheap pressure cooker from Amazon and an old R12 vacuum pump. When you vacuum, apply it gradually and don’t take it over 20 inches or it can foam by pulling the bubbles out too quickly. I had read about vacuuming the mixture before injecting, but have not tried it - concerned about the material setup time.
I used to work as Millwright at a plant that injected silicone and then vulcanized, our moulds had a 2 mm vacuum channel around all mating surfaces. Maybe this at the very top plate would work or injecting from the bottom like Cosworth did with aluminum.
Build yourself a mixing machine that A. Has a batch capacity enough to do a bunch of bushings, B. That you can stir the batch rapidly, (but not vigorously, C. Can be sealed closed to pull a vacuum on to remove bubbles, then pressurize to push the urethane into the molds, D. Has a drain port at the bottom for transfering the urethane to the mold so any remaining bubbles do not get moved to the mold, E. Has a cone shaped bottom going down to the drain port to minimize the urethane wastage while decanting bubbles out of the urethane charge, F. That has a viewing port in the top cover so you can check on bubble removal and also monitor remaining batch charge.
Makes me wonder what it would take to make Heim joints. Delrin bushings sound cool but that oughta be really well field tested, hot and cold environments, high impact situations like rallycross that type of stuff.
First of all, you did a proof of concept. Second you can do the injection in a vacuum chamber with lines going thru the vacuum pot and be able to make the part. Another option is to make the part a tiny bit over sized and cut off the porous excess after curing. I think youve got a great idea going on, just keep after it
Try filling it with the lid off, going a little high, then put the lid on and see if that removes some of the bubbles. Also add two more holes in lid adding a chamfer to the holes toward the bottom could help let air out.
More molds would help to increase quantity. Vacuum the mixture before injection or use vacuum chamber for injected molds can help get rid of the bubbles. Perhaps a vertical container (old gas bottle or sth) could be an option. Add a filling gap for poly and an inlet for vacuum and air pressure. Underneath the bottle an outlet with a valve. You mix the poly, pour it in the gas bottle, close the filling gap, open vacuum valve (i think for trying out an car engine oil extractor system could work) for some time, then close the vacuum valve and open air pressure valve (use a common regulator to adjust and keep the airpressure inside the container constant). If molds are ready open the valve in the bottom of the bottle and through an hose fill all the molds. Excess poly discard in some waste bucket so that the system vill be empty and ready for next run. Just an idea.... perhaps even plausible if poly don't stick too much to the conteiner wall or lower valve/hose etc.
The bubble issue is the same as when working with silicone, you need to use a vacuum chamber after mixing it. I personally wouldn't use Delrin bushings it easy to machine though.
Cut it in pieces to see where the bubbles are piling in, i.e., if only towards the top or through the whole piece. If just on the top, then the upper portion needs to be open to release the gasses from the mixture.
That cup your using has a teflon coating. It could be reacting since it is such a thin coating and not covering enough to see red right thru it. Practically comes off wi5h milk let alone a chemical compound
I learned 25 years ago that stuff doesnt machine. One of the first things i ever came up with was an improved racing steering shaft and "column". Instead of the typical slightly oversized 3/4 rod end over pipe i made a column from 1-3/4 and made poly bushings from 2" round poly stock. That sucked. Btw for poly prototyping grab a product called "window weld". Same thing squeezed from a caulking type tube with less to zero bubbles lol. Definitely not for production. But great for testing.
I would get a polyurethane with a longer pot life. Mix it in one cup, then pour that in a second cup and mix again. This prevents sticky spots. The resin needs to be degassed. You'll need a vacuum pump. I've had great luck with Just Better brand pumps, which are made for AC repair, but work as well as a lab pump. Then you'll need a vacuum chamber. At the very least, degas the resin while it is in the cup. If you still get bubbles, degas in the cup, then fill the mold with the top off and degas the mold. Careful, it'll expand a lot at first. Then add the top. Check the data sheet for the polyurethane, it may want to be heated in an oven, which is something not to short cut.
If you are not going to vacuum it (which you should), you will have to flow more material through it to purge the air out. That or drill more bleed holes.
Just like alot of people have been saying vacuum camber but also different molds with multiples could be yours answers for upscaling production. Used to do something very similar for resin reproduction taillights and markers lights covers
What about casting the polyurethane in place in the bushings? You could make a fixture plate with a circular indentation to hold the outer shell of the bushing, and a pin in the center to align the inner sleeve. If you make the centering pin undersized, you could have a selection of adapter sleeves made to fit multiple inner bushing sleeve sizes. As others have said, vacuum degassing will solve the bubble problem. You can get a small metal can/bowl/pot that the disposable cups fit in and a thick piece of acrylic as a lid. For testing with a small chamber you could use one of those hand vacuum pumps for bleeding brakes. It may help to apply and release the vacuum a few times to work all the bubbles out. If the casting in place works, you could scale up with a larger fixture plate and a non-manual vacuum pump.
Needed bushes for a Datsun Stanza about 30 years ago, OEM not available. Friend of a friend produced bushes for me, think they were turned from generic or larger after market poly-urethane bushes. Not done by a machinist but just a hobbyist. Bushes were perfect and worked 100%. How did he do it?
Holy crap!! When you were talking about not being able to lathe poly I immediately thought Delrin. Then right at the end you said it. You heard me days before I thought it I am so good !!
I have run my own business for over 50 years and the pace never changes. I still would not have it any other way. Try a vibratory against the table to remove the air pockets.
Without using a vac chamber, even if you get the bubbles to the top in the mold,they can lay on the service between the mold and the liquid, causing a divit on the surface.
Longer pot time product and use a mix container or a small vacuum chamber that you can pull a vacuum on for a minute or two before filling the syringe.
I made delrin bushings for my 89 Shelby CSX. It's easy to machine and they work well. I'm not sure about the durability compared to poly, but for the miles I put on it, they will be fine. In regard to your poly method, have you thought about a vacuum chamber to get the air out? That is how the epoxy guys deal with bubbles for the most part.
Hi Justin, Î’m not an expert in fabrication but I tried a few delrin bushings for trailer bearings. I suggest you try a 6PA or other fiber added polycarbonate as Delrin will wear out very fast by itself if used as a load bearing
Learned a long time ago if you want to make money you have to spend money. Should have at least two saw blades on hand. We used to check inventory every week for commonly used material ,tooling etc.
1 Yes for more content on this stuff 2 yes for the Delrin 3 yes this is a great idea to expand weld metals and I have a feeling it will work out the way you think it will once you get these small issues sorted. I know I will definitely buy some from you! Thanks Justin
You need to inject under pressure in order to eliminate the bubbles for production purposes. For that you need an injection machine. You can find them in all sizes and also used. Syringe is fine for prototyping, but don't think of it as adapting to production. Also, you need a discharge area where the bubbles are ejected from the product mold. If you had pressure and a place for the bubbles to go, you would get a better product. Thanks for sharing.
Slower curing urethane that allows time for a vacuum chamber and you can do a larger mixing pot. Then several molds being poured and onto a vibrating table, think 40 at a time. It might take 20 to 30 minutes to get that all done. I would think 10 minutes on vibration would be sufficient
Hi Justin I have had a bit of experience with machining delrin in a bar fed twin spindle lathe doing 1st and 2nd ops same program one method was to up the feed rate to get the plastic to chip like steel the other was to to use live tooling to mill a slot as close to finish diameter as possible then turn as per normal plus i was using carbide tips designed for brass with a 0.2mm radius. hope this info might help
Echoing others here. Delrin machines well. For poly I would look into a lot of the tools that epoxy workers use. 1:1 pumps, vacuum chambers, etc. Also does the top have to be put on. If you could have a 'baking sheet' of mold blanks that sit in a pressure pot, leave the tops open ended then just chop the top off for your flat/size consistency?
Vibrating with a sander, yeah, like it in a cap section steel pot grill and tapped for figment to an A.C. vacuum pump, let it setup while under high vacuum. Or if that method negatively affects its density, pressurize it during setup
i'd try letting it rest with a few washers underneath on one side so the air makes it to one corner of the mold , you can see it's traped evenly and can't make it's way out to the ejection breather holes.
Honestly for the poly bushings just contract them from prothane. They probably make all the sizes you want already but don’t let you search the OEM parts by dimension. And that has the added benefit of being able to figure out the oem application if you want to use the same size bushing in rubber, for like an engine mount or a control arm where you don’t want the extra friction of poly. Don’t do this on delrin. The only reason to make fabbed arms with delrin bushings is if your racing class rules forbid rodends or other full metal joints. Delrin almost always overconstrains the joint and causes binding or causes the delrin to get wallered out.
Keep it flowing Justin, business and how2s work, as far as the injection molding the pressure chamber works but maybe if you buy the resin in bulk with disposable tips you might cut cost if you revisit this idea, good luck man.
I think efficiency would come with a high volume design. Abom has that big CNC machine, could set up a design that would mold 10-20 bushings at a time. Vacuum pull the two part mix into the mold. Maybe mold the bushing slightly long and use essentially a forstner bit with a centering dowel to trim to final dimension. Finishing op should be down to seconds to be profitable. Built right, the same mold should be usable if switched to Delrin. This would be a big leap/risk of course, but it feels like you are super close. Figuring out the finishing may help decide.
vacuum is inefficient for mass production the problem is if you lay the mold flat the bubbles are trapped on the top tilt the mold few degrees and leave the hole at the higher point so air can escape also a slower setting pu would help a lot
To degas with a syringe, just fill the syringe half way, block the end, then pull the plunger back all the way to pull a vacuum from the silicone in the chamber.
Personally I'd be cool with either material for bushings; however, I’m also the kind of guy who would just make his own so I'm probably not the best person to ask. I also just spent 3 months working with injection molding machines and while I can attest they are very cool and you can get some of the older machines for cheap and I would love one. It's a deep rabbit hole… And also still wouldn't solve the problem of needing multiple molds. As much as I hate people giving me advice, here's what I think you should do. Weld together a box and fill it with as many single piece open molds as you can. Honestly it could just be some various sizes of pipe. Then just put a lid on said box and pull vacuum from it. Hopefully a larger batch size solves the efficiency problem and in my opinion degassing urethane in the mold as opposed to beforehand separately is so much easier. I'm not sure if that would put you over budget but It seems like that kind of stuff you might just have lying around :)
@abom79 Vids
Part 1 - ruclips.net/video/xyf0zzCUVF8/видео.html
Part 2 - ruclips.net/video/s06Zh1MX06A/видео.html
@ArtByAdrock Casting Freddy Kreuger - ruclips.net/video/O2VHWmxbKAQ/видео.html
Any shop project is good in my book. You either teach us something we might have not known or learn something yourself in the process. Win win.
Justin, you really do need to get a vacuum chamber to evac bubbles for any kind of potting process.
Was just coming here to say this
X3. Been doing a lot of epoxy, poly and vinylester work lately. Vac chamber has been great.
Or a pressure pot.
Came here to advocate for debubbling in a vacuum chamber also
Same. You can even build your own with the compressor from an old refrigerator and a pressure cooker
If you stick your injection mold into a vacuum pot that'll help pull those bubbles out. I do that stuff at work.
Grate video!!
Vacuum chamber, 2 cup mixing, vibrating table... just about every solution was brought up, but it doesn't solve the efficiency or cost problem. It's just not practical for production, unfortunately. I really hoped it would work.
@TheFabricatorSeries That makes sense
@@TheFabricatorSeriesLast possible solution would be to increase the length of the mold and cut the end where the bubbles form off....
@@TheFabricatorSeries
In our family business in Germany, we also produce PU products in large quantities. To start small, all you need to do is set the mold at a small angle and drill another 2-3 vent holes in the lid. In practice, multi-cavity molds are often used for such small parts to increase efficiency. You could also simply make 20 of these smaller molds and fill them all in one go (with a larger syringe).
Otherwise, I think that your method in the moment is not that bad without a dosing system.
Yup, you beat me too it.
Forte plastics!!!
They custom build plastic parts for people.
Your mold your specification.
They run the production and ship it to you.
Cherryvale Kansas.
I deliver parts for them to dedicated customers and the people and processes are amazing.
Might save you some time from reinventing the wheel. Let them do this part for you and you can get back to doing what you do.
This is the business tip of the day. Put your time where it is the most valuable.
Some days it trouble shooting others it’s covering for someone else.
Sitting on a yacht smoking a cigar is a massive expense.
There is more reward in walking through the shop seeing everything is taken care of knowing you can move on to your next step.
Climbers will always climb.
Thank you for sharing your story and insights.
Peace be with you.
Great video. I've done a fair bit of machining polyurethane, modifying molded bushings and rod stock. The key is the cutting tool. You need to experiment with the tool shape, feeds and speeds to make decent cuts. Standard metal cutting bits usually don't work well, as you showed,. You need more of a slicing type of cut. You also need to make fairly heavy cuts, including the finish pass. There's no sneaking up on a final dimension like you do with metal.
To remove bubbles: vacuum chamber the mix before injection (can be messy) and/or pressure pot the full mould after injection (probably a better option).
Probably need some sort of vac chamber to make sure its clear of bubbles.
Build your mold 1/4 taller than needed. Once the bushing is removed shave/cut off the bubble portion that will be ususally contained in your 1/4 overage. It is costly, but will work. Good look Sir.
As soon as you said "bubbles", I started shouting "vacuum chamber!" at the screen. No less than 10 times, at that.
IMO Delrin is a no brainer, if that’s unpopular get abom to make 5x molds that make 10x pieces at a time. Build a vacuum chamber with 2x $100 refrigerant pumps and get a dispenser pump to fill molds. Looking at less than $1k for materials plus atoms fee for the molds and you have your assembly line. You’d easily be able to pump out 1k bushings a day.
In addition to everyone's good suggestion of using a vac pump briefly on the freshly mixed poly, it'd be best to put them in a pressure pot to cure, causing any final bubbles to be microscopic.
I don't know if this would work, but how about using the mixing tubes which come with 2 part epoxy systems. These are ideal for 50:50 mixes. This is supplied as 2 tubes bonded side to side with linked plungers - so equal amount of each are extruded, as the common plunger is depressed. The 2 fluids pass immediately into the mixing/delivery spout (without allowing the introduction of air) and as the fluids pass down the spout, a double helix mixes them together as they are forced down it. The end of the spout is the delivery point where the mixed compound will be injected into the mould (free of bubbles - hopefully).
Or possible dispense the mix into a pot from which you can extract with your syringe.
Fist CC. from the spout to waste. And also the mixing tube full of compound is waste, so you need to mould a few bushes each time a mix is made.
For economic production, I would suggest that you keep stock levels of the popular sizes as low as poss, So when you have to make a single rear bush to order; you can make use of the already contaminated mixing tube, by also filling the moulds for the more popular sizes, without creating stock levels which are inconsistent with anticipated demand.
You need a vacuum pump like everyone else is saying. You will need multiple molds and a peristaltic pump to pump the polyurethane in the mold. The peristaltic pump will allow you to change hose if it gets clogged and you can't remove the polyurethane. It's best to run cleaner through it after each use. It should also not introduce air bubbles if you fill the intake with two-part polyurethane before turning on the pump. You will need to determine the hose to use that will not cause a reaction with the polyurethane. I will send a bill for my manufacturing advice to your office.
Before you suck up the polyurethane into the syringe you should put it under a vacuum it will kill the bubbles off. But it does not speed up the process of producing thousand of them at a time.
A mold that can make multiple bushings at once would be ideal. Most people don't bake cookies one at a time.
Definitely need to try it in a vacuum chamber before changing materials.
Delrin machines crazy well in my experience.
In terms of an American supplier you might want to talk to I work with a company called "Trexler Rubber" for my cold isostatic press bags and they can make some wild shapes with polyurethane. Might be work a phone call.
Justin the comment about a vacuum chamber is certainly the correct way to go but you will also need to take account of set up times and also what number of bushings would you seek to produce in each batch. the alternative is maybe a vibrating table fill the mould and stand it on the table whilst it cures. Personally i now use HDPE or Delrin for all my bushings which is quite easy if you have a cnc lathe. Do you have any production facility companies nearby to whome you could contract the manufacture and avoid the massive cost of machines and tooling
Watched this yesterday - and today watched an old episode of Car S O S. Tim went into a business making urethane car bushes. Molds did not have a cover. Mix was just loaded into open topped mold, up to the top. Done by hand with multiple molds in a line all a single assembly. Used some sort of gun to feed the mix - by eye or controlled volume? Not possible to tell, looked like by eye. They were CNC turning the metal insert bushes. Different color (using pigment) for different hardness/compliance.
Justin, if some tools are critical to order fulfilment you need to keep spares. Keep spare band saw blades in house. Maybe spare motor and blade guides.
And if that stuff flies, price up an auto feed saw. Or some other coupon maker that can run 24/7 unattended.
Not keeping stick is quite efficient, but leaves you venerable to breakdowns and sickness. Quite tough to manage with a small team tho.
Just watched your video Justin, all the urethane moulds I’ve made for my own products I’ve always made an open mold. Leave the top part of your mold off and fill the mold to the top with a cup of urethane not a syringe. Air bubbles will rise to the top and you’ll end up with a smooth finish.
There is a company in Wisconsin that does exactly what you were trying to do with the bushings. A machine shop i worked for would make molds for them. They don't call it "injection molding", they call it urethane casting. You can also put it under vacuum to get rid of the air bobbles before it is cured. If you wanted to get higher volume you would make a mold with more cavities. You would also have a few molds where one is being filled while another is curing.
Yes I would like more content like this..
Just throwing this out there... I've made delrin bushings for jeep lift kits many times and they work fantastic and are basically indestructible. Machine an outer aluminum sleeve and stuff it with a delrin bushing and you can't kill it. Works great, and it's super easy and fast to machine. cuts like butta! Just use insanely sharp cutters and you're good to go.
Have you thought about some kind of vibratory table? For testing purposes, a machine with a flat surface you can pour into and leave the mold there as the machine runs. If it works repeatably then you could, in theory, have a batch of molds made to help it become profitable.
Otherwise, great content!
I imagine a split mold out of aluminum with say 2 lines of 2, with removeable cores that are suspended accurately, an input fitting at one end, and a fitting for the vacuum at the other.
A large vacuum resevoir has the power mixed resin in a disposable container with a pickup tube hanging at the bottom of the resin. Mix the resin in the disposble container with say a drill motor, place the cup in the vacuum 'vat', put the pickup tube in the resin, put lid on vacuum and draw a vacuum, then close valve on vat. After bubbles are released, open valve at vacuum end of mold also under vacuum, then open valve to vat, allowing resin to flow into mold, by opening vat vacuum valve to ambient. Resin will flow into mold, close vacuum end valve on mold, downstream of a intermediate extra catch container (to protect valve), when resin appears.
I went down this road on a similar product. Spincasting was the answer I ended up at. Flash was harder to fight, but otherwise worked to remove the bubbles and increase throughput
I've been messing with silicone molds and resin casts for making clear factory style buttons with very good results.
I've seen vacuum degassing suggestions, but haven't seen curing in a pressure pot mentioned. Any remaining air not removed or introduced after vacuuming gets squashed down to microscopic levels when cured under pressure. Essentially necessary for clear parts in a mold. At least with resin and thin parts.
I do plan to make my own mounts and bushings in the future.
Great episode! My son and I have a motorcycle parts making business and we have had to overcome a ton of production obstacles but our biggest challenge has been distribution and marketing which seems like two things you got covered.
Would really like to follow along as you go down this path so please post more videos of the process.
I know you're just prototyping but you need a polyurethane with a longer working time so you can vacuum degas it before pouring it. A 3 minute open time just doesn't give you enough time to degas. Then put it in a pressure chamber so that any leftover bubbles collapse and become microscopic. For production you'll need a multi-cavity mold with runners so you can do a single pour.
Camera de vacuum sau masa vibratoate.
Felicitari pt tot ce faci!
Respect de la Stelian din Romania !
We vacuum the potting mix before we pour it at my work and it takes care of a vast majority of the bubbles. But also delrin could be an option
Just watched the video to the end. Yes Delrin , I have used Detroit Speed bushings but nobody has them for aftermarket mustang 2. They need to have a spiral grove for grease
You can get the bubbles out with vacuum. Put the filled molds in a vacuum bell jar, and pull a vacuum (HVAC vacuum pump). Maybe you can design a cap for the mold that your put on after filling and connect your vacuum pump. Commonly used for resin casting, wood working glue-ups, etc.
Heat the mold with a blow torch straight after injecting and the bubbles should pop. Like they do with resins. Awesome video Justin. Keep em coming..
I love this content. I like seeing the real life of this industry.
Solution for the bubbles...either going to have to get slower setup poly, mix up the solution, inject in the smaller mold, then put the entire mold inside a vacuum pot at pull all the air out of the liquid...going to be messy as hell, then let it setup...you might also put the mix cup in the vacuum chamber, foam it out, then inject (but that might cause air to be pulled into the solution)
Very awesome idea on molds...I wonder if a 3D printed with ABS or PETG and then smoothed (layer lines in the bushing would suck) but since it doesn't get that hot when curing, you could rapid prototype a mold w/o spending a crapton on machining...and cool shout out to Abom79!
Justin, look up skateboard wheel fabrication process.
There are a couple methods. Batch processing is the most economical.
For machining polyurethane stock on the lathe, you need a cutting tool with a radial edge. Full round carbide insert works at high speed...
To avoid air bubbles, there are a couple ways. Vacuum degassing the liquid prior injection helps, but having a mold with aguaranteed high spot to allow the bubbles to congregate. same idea as the 'rise'r in metal casting.
however allowing the urethane to cure in a pressurized environmont, like a painter's pressure pot, you will eliminate the bubbles compleyely.
The max producing part, is actually an easy fix, and at the same time we'll solve the bubble issue too.
For mass production, your mould doesnt hold 1 bushing. You need to machine a mould, that can do many many bushes at once.
You want a single big fill point, this can even be a part of the large top piece, and has the runners everywhere as needed. At the same time, have extra small breathers every where.
Build the mould big enough, that it will fit into a vacuum chamber, just a home hobby variant for now.
When you build the mould for multiple units, additionally add a few routes through it, than can be used for coolant later on. The coolant part is for when you start wanting to really turn them out.
But in regards to the breathers etc, take a look at nost plastic enclosures, youll start being able to spot the fill and breath points by those tiny little flat circles. Not to mention, the "whiskers" tyres have, theyre from all the breather points. But to make sure you get the air out of the poly, vacuum chamber.
But for efficiency, its all in scaling the mould up to hold many all at the same time. :)
PS, a local University/College may even help you automate it a little bit as a team project. So multiple bright students bringing their robotics mind in, and typically youd be the one to help fund the supplies to build the jig, which you get to keep.
They also get to bring their ideas to you first, and youll get to help teach upcoming engineers how to think about real world issues too :)
If the bubbles are strictly at he top surface, Angle mold at 45 degrees with vent at highest point and fill from bottom and allow a percentage of flow through the mold.before setting mold flat.
Filling the mold from the bottom, letting the air escape from the top, might work. A similar principle is used when filling boat lower units with oil.
You need bigger modules with many individual units. Multiple of these allow you to keep the injection unit busy. Get rid of bubbles by using pressure, heat or lower density resin.
You need a urethane with longer working time, preferably a lower viscosity as well. And as many others have mentioned, vacuum chamber then move it to the pressure pot. You could figure out an efficient way to make short production runs in house. The properties of the material matter too.
Another great video👌 3D printed molds for poly bushings are also a good option, it wil take some trial and error to get the dimension where you want them to be but if you got it it’s just print and repeat, also works great to make double flanged bushings since you can spit them along the axis, and just use a simple hoseclamp to hold them together. Cheers!
You can shake it really good with a reciprocating saw (no blade inserted)
That's exactly how most poly bushings are made. Process slowness is due to inperfection in your technology chain. First of all - mould design! Current mould is ok for prototyping and it's cheap, but for mass production you need something better. What do I mean when I say better: you need a batch type mold. For example one mold fo 10 bushing - such a way you can mix one batch and immediately pour full mould giving you like x10 bushings at a time. Next you need to think about quick assembly and unmoulding process - it should be like quickly push bushings out of the mould and immediately be ready for a new batch.
Next part is bubbles. There are two main sources of bubbles: air trapped pockets in mould and air trapped in polyurethane.
You can solve first problem by fixing the mould design - just think how liquid urethane fills the mould and where you'll get a trapped air - just add a riser hole at that spot. You have a flat top - just tilt your mould to have a one top spot.
Next is air trapped in urethane itself - you need a simple pressure pot to pressurise your parts while urethane is curing. Urethane likes to bubble in contact with moisture (moisture ib air is enough to make it bubbly) so pressure pot is like a must have with urethane.
Using multiple moulds in parallel will make it work. Perfectly worker should demould and repour one mold while other is curing. Lets say you have only one 10 position mould and a really slow worker that can refill mould each 30min- it's 160 parts per 8 hour work day. This number is if you have a really turtle-slow worker. Perfectly your should use multiple moulds and single mould repour cycle should be around 10-15min.
To get the bubbles out build a small vacuum chamber 1 cubic foot should be about right and use a shop vac to pull the vacuum. For proof of concept you'll be ok, for production your going to invest a lot of money in tooling, injection dies are not cheap. Multiple cavity dies for each particular size desired will be needed. Once you have the tooling you could find a company to do the molding for you and that cost will depend a lot on quantity. May be more cost effective to find an existing source for the bushings in the short term. Good luck I hope you succeed.
I do car restoration work, replacement bushings are a huge problem for me. I've never used delrin for bushings but if the price is comparable to PE I'd be very interested.
As a small business owner also, you hit the nail on the head describing my days. It's funny when I get asked what I do, and then the folks asking hear that I own the business - they think I'm rolling in the dough and do nothing all day long. Could not be further from the truth.
On your process, you could outsource to a low cost manufacturing facility (think overseas), but I know you want to do sourcing here. Going to be hard to do without significant resources. Oh, stay away from venture capitalist money. Trust me on this one.
i use to do lots of 2 part liquid polyurethane mould pours, we would line up our moulds and pour 30 at a time or more, you can get longer cure time urethane's we used electric mixing paddles on a drill press.
A vacuum pump is a must have, or your wasting your time..
We used a large electric pizza oven to speed up cure time's and warm our moulds before the pour .. any bubbles the did come to the surface after filling we use a small blow torch to get rid of them..
You need a vacuum chamber and a riser tube and reservoir and always have it overfilled so when you vacuum it and release the vacuum it gets filled.
Keep in mind that when vacuuming it usually bubbles and rises at least 30% extra volume.
And your mould should probably also have some tooling to easily get it apart
Well your video maybe makes me understand why when I order something that says, "Ships the next day" but it takes a week for me to get a tracking number that it is not the shops fault but instead it UPS or FedEx. In the future I'll be a little more patient. Not talking about your shop, you guys are always pretty prompt. I'm not an expert but I have poured a little bit of concrete and of course bubbles are an issue. That's why they have "vibrators' to work the bubbles to the surface. I think you had the right idea with shaking them but that will never equal what vibrating could do. Keep up creating ideas. You will eventually find a solution. Thanx.
To move into higher numbers, prob eventually do a multiple mold process. Vacumm before pour, and pressure pot during set up. Just ideas, i do like this vid style as well, because Im in a similar mind set. Constantly brainstorming and solving etc. Great job as usual.
Vacuum degassing is the next step if you want to get perfect results with minimal investment. The pumps and pot can be had on Amazon these days for way cheaper than in the past. You probably already have a vacuum pump if you ever did your own AC work. I used to make custom mounts years ago and this was the easiest and cheapest method for quality production level results. Get a longer cure poly, degass after you mix and pour your production run. Its not much more in terms of money or steps. A lower viscosity poly will naturally degass much faster.
BTW Is that a welded up Luxor on your front desk?
Keep these coming. Planning to start my own business soon!
A vacuum chamber and multi-part mold with sprues on the top would be the way to go. Since you don't high temperature/pressure to mold it, you can prototype with 3d printed or silicone molds.
I make a few custom urethane parts and Delrin bushings. Most all the Delrin is for road race cars - to harsh for street cars. For the urethane I put the mold in a vacuum pot. My vacuum solution, which works great, is a cheap pressure cooker from Amazon and an old R12 vacuum pump. When you vacuum, apply it gradually and don’t take it over 20 inches or it can foam by pulling the bubbles out too quickly. I had read about vacuuming the mixture before injecting, but have not tried it - concerned about the material setup time.
I used to work as Millwright at a plant that injected silicone and then vulcanized, our moulds had a 2 mm vacuum channel around all mating surfaces. Maybe this at the very top plate would work or injecting from the bottom like Cosworth did with aluminum.
Build yourself a mixing machine that
A. Has a batch capacity enough to do a bunch of bushings,
B. That you can stir the batch rapidly, (but not vigorously,
C. Can be sealed closed to pull a vacuum on to remove bubbles, then pressurize to push the urethane into the molds,
D. Has a drain port at the bottom for transfering the urethane to the mold so any remaining bubbles do not get moved to the mold,
E. Has a cone shaped bottom going down to the drain port to minimize the urethane wastage while decanting bubbles out of the urethane charge,
F. That has a viewing port in the top cover so you can check on bubble removal and also monitor remaining batch charge.
Great advice right here.
Makes me wonder what it would take to make Heim joints. Delrin bushings sound cool but that oughta be really well field tested, hot and cold environments, high impact situations like rallycross that type of stuff.
First of all, you did a proof of concept. Second you can do the injection in a vacuum chamber with lines going thru the vacuum pot and be able to make the part. Another option is to make the part a tiny bit over sized and cut off the porous excess after curing. I think youve got a great idea going on, just keep after it
Try filling it with the lid off, going a little high, then put the lid on and see if that removes some of the bubbles. Also add two more holes in lid adding a chamfer to the holes toward the bottom could help let air out.
More molds would help to increase quantity.
Vacuum the mixture before injection or use vacuum chamber for injected molds can help get rid of the bubbles.
Perhaps a vertical container (old gas bottle or sth) could be an option. Add a filling gap for poly and an inlet for vacuum and air pressure. Underneath the bottle an outlet with a valve.
You mix the poly, pour it in the gas bottle, close the filling gap, open vacuum valve (i think for trying out an car engine oil extractor system could work) for some time, then close the vacuum valve and open air pressure valve (use a common regulator to adjust and keep the airpressure inside the container constant). If molds are ready open the valve in the bottom of the bottle and through an hose fill all the molds. Excess poly discard in some waste bucket so that the system vill be empty and ready for next run.
Just an idea.... perhaps even plausible if poly don't stick too much to the conteiner wall or lower valve/hose etc.
The bubble issue is the same as when working with silicone, you need to use a vacuum chamber after mixing it. I personally wouldn't use Delrin bushings it easy to machine though.
Cut it in pieces to see where the bubbles are piling in, i.e., if only towards the top or through the whole piece. If just on the top, then the upper portion needs to be open to release the gasses from the mixture.
That cup your using has a teflon coating. It could be reacting since it is such a thin coating and not covering enough to see red right thru it. Practically comes off wi5h milk let alone a chemical compound
I learned 25 years ago that stuff doesnt machine. One of the first things i ever came up with was an improved racing steering shaft and "column". Instead of the typical slightly oversized 3/4 rod end over pipe i made a column from 1-3/4 and made poly bushings from 2" round poly stock. That sucked.
Btw for poly prototyping grab a product called "window weld". Same thing squeezed from a caulking type tube with less to zero bubbles lol. Definitely not for production. But great for testing.
I would get a polyurethane with a longer pot life. Mix it in one cup, then pour that in a second cup and mix again. This prevents sticky spots. The resin needs to be degassed. You'll need a vacuum pump. I've had great luck with Just Better brand pumps, which are made for AC repair, but work as well as a lab pump. Then you'll need a vacuum chamber. At the very least, degas the resin while it is in the cup. If you still get bubbles, degas in the cup, then fill the mold with the top off and degas the mold. Careful, it'll expand a lot at first. Then add the top. Check the data sheet for the polyurethane, it may want to be heated in an oven, which is something not to short cut.
You can use flat tray and the flame before you fill up a syringe. You can also buy a pressure/vacuum pot and let it cure inside. Don't give up.
If you are not going to vacuum it (which you should), you will have to flow more material through it to purge the air out. That or drill more bleed holes.
Just like alot of people have been saying vacuum camber but also different molds with multiples could be yours answers for upscaling production. Used to do something very similar for resin reproduction taillights and markers lights covers
What about casting the polyurethane in place in the bushings? You could make a fixture plate with a circular indentation to hold the outer shell of the bushing, and a pin in the center to align the inner sleeve. If you make the centering pin undersized, you could have a selection of adapter sleeves made to fit multiple inner bushing sleeve sizes.
As others have said, vacuum degassing will solve the bubble problem. You can get a small metal can/bowl/pot that the disposable cups fit in and a thick piece of acrylic as a lid. For testing with a small chamber you could use one of those hand vacuum pumps for bleeding brakes. It may help to apply and release the vacuum a few times to work all the bubbles out. If the casting in place works, you could scale up with a larger fixture plate and a non-manual vacuum pump.
It's eerie how much this guy reminds me of my friend who ran his own business, but ended up losing everything from his coke habit
He does have a frantic tic that made me immediately think he's got a substance issue.
Needed bushes for a Datsun Stanza about 30 years ago, OEM not available. Friend of a friend produced bushes for me, think they were turned from generic or larger after market poly-urethane bushes. Not done by a machinist but just a hobbyist. Bushes were perfect and worked 100%. How did he do it?
Holy crap!! When you were talking about not being able to lathe poly I immediately thought Delrin. Then right at the end you said it. You heard me days before I thought it I am so good !!
I have run my own business for over 50 years and the pace never changes. I still would not have it any other way. Try a vibratory against the table to remove the air pockets.
Without using a vac chamber, even if you get the bubbles to the top in the mold,they can lay on the service between the mold and the liquid, causing a divit on the surface.
I have had several ingersoll Rand tools, air and electric, I think they are the best.
Longer pot time product and use a mix container or a small vacuum chamber that you can pull a vacuum on for a minute or two before filling the syringe.
I made delrin bushings for my 89 Shelby CSX. It's easy to machine and they work well. I'm not sure about the durability compared to poly, but for the miles I put on it, they will be fine.
In regard to your poly method, have you thought about a vacuum chamber to get the air out? That is how the epoxy guys deal with bubbles for the most part.
Hi Justin,
Î’m not an expert in fabrication but I tried a few delrin bushings for trailer bearings. I suggest you try a 6PA or other fiber added polycarbonate as Delrin will wear out very fast by itself if used as a load bearing
I have the bigger 3/8 gun and I absolutely love it. Also my battery last a long time.
Learned a long time ago if you want to make money you have to spend money. Should have at least two saw blades on hand. We used to check inventory every week for commonly used material ,tooling etc.
Lots of high performance bushings nowadays are made with Delrin/Acetal. It's pretty well accepted. Would be much easier to handle manufacturing.
1 Yes for more content on this stuff
2 yes for the Delrin
3 yes this is a great idea to expand weld metals and I have a feeling it will work out the way you think it will once you get these small issues sorted. I know I will definitely buy some from you! Thanks Justin
You need to inject under pressure in order to eliminate the bubbles for production purposes. For that you need an injection machine. You can find them in all sizes and also used. Syringe is fine for prototyping, but don't think of it as adapting to production. Also, you need a discharge area where the bubbles are ejected from the product mold. If you had pressure and a place for the bubbles to go, you would get a better product. Thanks for sharing.
Loved this episode!
Slower curing urethane that allows time for a vacuum chamber and you can do a larger mixing pot. Then several molds being poured and onto a vibrating table, think 40 at a time. It might take 20 to 30 minutes to get that all done. I would think 10 minutes on vibration would be sufficient
Hi Justin I have had a bit of experience with machining delrin in a bar fed twin spindle lathe doing 1st and 2nd ops same program one method was to up the feed rate to get the plastic to chip like steel the other was to to use live tooling to mill a slot as close to finish diameter as possible then turn as per normal plus i was using carbide tips designed for brass with a 0.2mm radius. hope this info might help
Echoing others here. Delrin machines well. For poly I would look into a lot of the tools that epoxy workers use. 1:1 pumps, vacuum chambers, etc. Also does the top have to be put on. If you could have a 'baking sheet' of mold blanks that sit in a pressure pot, leave the tops open ended then just chop the top off for your flat/size consistency?
Vibrating with a sander, yeah, like it in a cap section steel pot grill and tapped for figment to an A.C. vacuum pump, let it setup while under high vacuum. Or if that method negatively affects its density, pressurize it during setup
i'd try letting it rest with a few washers underneath on one side so the air makes it to one corner of the mold , you can see it's traped evenly and can't make it's way out to the ejection breather holes.
Honestly for the poly bushings just contract them from prothane. They probably make all the sizes you want already but don’t let you search the OEM parts by dimension. And that has the added benefit of being able to figure out the oem application if you want to use the same size bushing in rubber, for like an engine mount or a control arm where you don’t want the extra friction of poly.
Don’t do this on delrin. The only reason to make fabbed arms with delrin bushings is if your racing class rules forbid rodends or other full metal joints. Delrin almost always overconstrains the joint and causes binding or causes the delrin to get wallered out.
Keep it flowing Justin, business and how2s work, as far as the injection molding the pressure chamber works but maybe if you buy the resin in bulk with disposable tips you might cut cost if you revisit this idea, good luck man.
I think efficiency would come with a high volume design. Abom has that big CNC machine, could set up a design that would mold 10-20 bushings at a time. Vacuum pull the two part mix into the mold. Maybe mold the bushing slightly long and use essentially a forstner bit with a centering dowel to trim to final dimension. Finishing op should be down to seconds to be profitable.
Built right, the same mold should be usable if switched to Delrin.
This would be a big leap/risk of course, but it feels like you are super close. Figuring out the finishing may help decide.
vacuum is inefficient for mass production the problem is if you lay the mold flat the bubbles are trapped on the top tilt the mold few degrees and leave the hole at the higher point so air can escape also a slower setting pu would help a lot
To degas with a syringe, just fill the syringe half way, block the end, then pull the plunger back all the way to pull a vacuum from the silicone in the chamber.
Came for the S13 content. Stayed for the welding. Happy to see a return to form.
You need to inject the poly in a lot slower, and I would have had more holes in the mold to allow the air to come out.
Personally I'd be cool with either material for bushings; however, I’m also the kind of guy who would just make his own so I'm probably not the best person to ask. I also just spent 3 months working with injection molding machines and while I can attest they are very cool and you can get some of the older machines for cheap and I would love one. It's a deep rabbit hole… And also still wouldn't solve the problem of needing multiple molds. As much as I hate people giving me advice, here's what I think you should do. Weld together a box and fill it with as many single piece open molds as you can. Honestly it could just be some various sizes of pipe. Then just put a lid on said box and pull vacuum from it. Hopefully a larger batch size solves the efficiency problem and in my opinion degassing urethane in the mold as opposed to beforehand separately is so much easier. I'm not sure if that would put you over budget but It seems like that kind of stuff you might just have lying around :)
If you put the mold into a vacuum/degassing chamber after you pour, the bubbles should come out better.