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Making Tires with 3D Printed Molds

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Making Tires with 3D Printed Molds

Old 09-09-2022, 08:42 AM
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Thanks for the input guys, but turns out it was my retraction settings. I'd been using the slicer default settings since I started printing, but I only recently got around to calibrating my e-steps. The unintended side effect of that was increasing my retraction distances enough to start causing problems. I decreased my retractions and now I'm getting good prints again. Took a while, and a good bit of filament, to figure out though
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Old 09-10-2022, 05:04 PM
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I got a chance to try my latest pair of tires the same outdoor dirt track I tested the blue tires on. This time I tested this tire (my tire on the right, a JC DDv2 on the left for comparison):



Like I posted before, these tires weren't as soft as the blue tires I made last week and firmed up a bit more over the last few days. They felt more consistent and predictable around the track this time due to the smaller profile and closed cell insert, but they just didn't have as much grip as the JCs or even my blue tires from last week. I need to go softer for sure.
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Old 09-20-2022, 06:01 AM
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oof, I had a bit of a setback yesterday. I thought resin softened with So-Flex II wouldn't have the demolding problems on a brand new mold. Well turns out I was wrong, it still sticks like glue and now I've got a ruined mold that will take a few days to re-print. Looks like I can't skip the seasoning step even with softened rubber, darn.

I also molded a couple of Mini-B tires using various mixtures of So-Flex II and let them sat for a week to cure. Previously I thought 15% was a good mix based on how the tires felt the day I de-molded them, but now I'm leaning towards somewhere between a 20 to 25% mixture based on how the samples feel after a week.

Also, I've been looking for things that could be mixed into the resin to make the tire grippier. I've found some conflicting sources regarding graphite and graphene's effects on the cured rubber's coefficient of friction. The various sources all seem to use slightly different versions of graphite and slightly different versions of polyurethane rubbers so it's hard to draw any clear conclusions, but a small tube of graphite powder lubricant is cheap enough to warrant testing.
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Last edited by RC10Nick; 09-20-2022 at 07:00 AM.
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Old 09-28-2022, 07:50 AM
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It's been a couple days since my last update and things haven't been going that well for me. I'm running into a new problem now where the resin I use to season brand new molds is sticking too well and causing demolding issues. It's happened a few times now so I know it's not a fluke. I think the problem is my new pressure pot. I can run it at higher pressures than my old DIY'd pot and I think that's forcing the resin even deeper between the layer lines of the print and causing these new issues. I'm going to try printing a new mold and seasoning it at a lower pressure to see what happens.

I also got a small tube of powdered graphite to try mixing into the VytaFlex60 to see how that affects the cured rubber. I'll probably do that tonight using one of the small Mini-B tires molds I have that are already seasoned so I won't have to worry about de-molding issues.
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Old 10-01-2022, 03:44 AM
  #65  
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I decided to work to improve my printer cooling : at this stage, I had still some problems with overhangs and bridges which results some of the spikes being improperly printed for my moulds.
A few prints and test later I'm able to print with overhangs at 70 angles without any issue and with a proper quality and this with a 0.2MM thickness by layer. going down on the thickness per layer should even improve this.

Next is to add some centering plots to my mould and reprint the mold in lower layer thickness than my first print. This will be long prints, but with the quality improvement and lower layer thickness it should be good enough to start with...

RC10Nick , what product do you use to prepare your moulds? Unmoulding agent only or do you do something else in addition?

Thanks
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Old 10-03-2022, 09:24 AM
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Originally Posted by silvertriple View Post
I decided to work to improve my printer cooling : at this stage, I had still some problems with overhangs and bridges which results some of the spikes being improperly printed for my moulds.
A few prints and test later I'm able to print with overhangs at 70 angles without any issue and with a proper quality and this with a 0.2MM thickness by layer. going down on the thickness per layer should even improve this.

Next is to add some centering plots to my mould and reprint the mold in lower layer thickness than my first print. This will be long prints, but with the quality improvement and lower layer thickness it should be good enough to start with...

RC10Nick , what product do you use to prepare your moulds? Unmoulding agent only or do you do something else in addition?

Thanks
I use Stoner E236 Urethane Mold Release.

Funny story, I accidentally bought a can of Stoner Zero Stick Mold Release because I wasn't paying very close attention when I ordered it. Pretty sure that's the reason for my recent mold release problems. I've got a can of the E236 on the way so hopefully that's all my problem was.
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Old 10-06-2022, 11:33 AM
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Brief update today - so far it appears the problems I was experiencing were just a result of using the wrong mold release.

I printed a brand new Mini-B tire mold, coated it with the Stone E236 Urethane Mold Release, injected it with FlexIt 40 resin, let it cure in the pressure pot at 2 bar and the tire popped right out of the mold without any issues.

Dumbest mistake I've made in a while, lol.
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Old 10-06-2022, 03:53 PM
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Originally Posted by RC10Nick View Post
Brief update today - so far it appears the problems I was experiencing were just a result of using the wrong mold release.

I printed a brand new Mini-B tire mold, coated it with the Stone E236 Urethane Mold Release, injected it with FlexIt 40 resin, let it cure in the pressure pot at 2 bar and the tire popped right out of the mold without any issues.

Dumbest mistake I've made in a while, lol.
its those little ones that get you every time,LOL and NOW we know just how important the RIGHT mold release is when working with urethane.. again thanks for being the guinea pig Nick!!
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Old 10-19-2022, 01:34 PM
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I've been working on refining my mold design lately. Specifically I've been re-evaluating how resin enters and and exits the mold cavity.

My current mold design results in lots of resin sprues on the tire that need to be manually trimmed off of the tire after demolding. Another problem is sometimes the sprues do not come out with the tire - rather they tear off and remain stuck in the mold. When that happens I have to clean out all the vents with a drill. It takes a while and isn't fun.

In re-evaluating my mold design I think I've learned a couple of new design tricks and lessons that seem obvious in hindsight but just weren't on my radar when I was just struggling to get all of this to work. I drew up a sketch to show my old vent design vs what I've been testing the last few days:



Basically I realized longer vents give the resin more surface area to stick to, and the more surface area the resin has to stick to the more force is required to pull the resin out of the vents. Conversely, thinner sections of resin will tear with less force. Figuring out those two facts made me realize I need to redesign my vents so they are much shorter and to make the channel the vents open into wider. I've also made the vent hole as small as I can practically make it with my printer right at the mold cavity. The idea is I want the resin to tear right at the edge of the mold cavity so I don't need to do any manual post processing of the tire after demolding it.

I printed out a small mold to test the new vent design and I'm quite pleased with the initial results.



The bottom piece is the final part and the top piece is the the resin that vented out of the mold and gathered in the excess resin channel. The top piece pulled right out of the mold and nothing stuck in any of the vent holes. Also, there were no resin sprues on the final part that needed to be manually trimmed. Even more promising is this batch of resin did not get mixed with the correct ratio of A:B (equipment issue). The resin didn't fully cure and was much softer than usual. This is actually a good thing because resin sticking in the vents has always been more of a problem with softer resins. The new design working as intended with a resin that is far softer than I ever plan on using is pretty exciting. My next concern I need to test is to make sure when the resin sprues tear away from the final part they don't pull chunks out of final part. I'll be testing this with Vytaflex 60 because it has the highest tear strength of the resins I've used so far if there's a problem I'll see it with that resin.
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Old 10-24-2022, 02:54 AM
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A vacuum chamber would probably be a better option than a positive-pressure chamber. Vacuum will cause any bubbles in the liquid rubber to expand until they pop, clearing them out of the way extremely quickly. It will also prevent air bubbles from being trapped on the surface of the mold, avoiding deformation of the tire surface. After the liquid rubber has had all the bubbles evacuated, pressure could be let back into the vacuum chamber to avoid changing the way the rubber cures.
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Old 10-24-2022, 07:44 AM
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I tried putting the mold in a vacuum pot once and it was pretty disastrous. The resin bubbled up so much a bunch of it ended up spilling out of the mold, and that was resin that was already degassed prior to injecting into the mold. It made a mess and there wasn't enough resin left in the mold to make a full tire so I've never tried doing it again.
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Old 11-02-2022, 10:40 AM
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I've got some pretty exciting progress to share today. I took what I learned about vent design from my experiments and re-designed my Mini-B tire mold using those principles. I've spent the last couple days printing, testing, and refining the new mold design and I'm pleased with how much better the new mold design works.

First, here's a tire pulled out of my old mold:


As you can see, it's got long narrow sprues on both sides of the tires that must be manually trimmed after de-molding. These sprues often tear off during demolding and stay stuck to the mold which requires drilling out before re-using the mold.

Taking a look at my old mold design it's easy to see why this happens:


The mold has long, narrow, and completely straight resin ports and vents. It's as if I designed an annoying to use mold on purpose - it goes against everything I just learned in my tests.

Now let's take a look at my new mold design that implements what I learned from my testing:


The ports on the bottom and the vents at the top have very short, deeply angled paths into and out of the mold cavity. This creates a very small cross section of resin at the interfaces to the mold cavity which allows the resin to easily tear away from the tire and allows the excess resin to be easily and quickly removed from the mold for re-use.

Finally, here is what comes out of the new mold without any extra post processing:


The new mold design exceeds my expectations for what I thought I could accomplish going into this. All of the excess resin tears right out of the mold and the tire itself requires much less post-processing after de-molding. I'd estimate it would take me at least 5 minutes to de-mold and clean up a tire using the old mold design and that's assuming absolutely nothing goes wrong. The new mold design is easily less than a minute for the same task. The only downside is the resin waste (resin that goes into the mold but doesn't become a tire) doubled from 3g to 6g. It's a tradeoff I'm perfectly fine with considering how much less frustrating the new mold is to work with.

And as a final bonus I made the new mold design more material efficient. It uses about 30% less material to make and prints about 30% faster.
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Old 11-02-2022, 11:55 AM
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Originally Posted by RC10Nick View Post
I've got some pretty exciting progress to share today. I took what I learned about vent design from my experiments and re-designed my Mini-B tire mold using those principles. I've spent the last couple days printing, testing, and refining the new mold design and I'm pleased with how much better the new mold design works.

First, here's a tire pulled out of my old mold:


As you can see, it's got long narrow sprues on both sides of the tires that must be manually trimmed after de-molding. These sprues often tear off during demolding and stay stuck to the mold which requires drilling out before re-using the mold.

Taking a look at my old mold design it's easy to see why this happens:


The mold has long, narrow, and completely straight resin ports and vents. It's as if I designed an annoying to use mold on purpose - it goes against everything I just learned in my tests.

Now let's take a look at my new mold design that implements what I learned from my testing:


The ports on the bottom and the vents at the top have very short, deeply angled paths into and out of the mold cavity. This creates a very small cross section of resin at the interfaces to the mold cavity which allows the resin to easily tear away from the tire and allows the excess resin to be easily and quickly removed from the mold for re-use.

Finally, here is what comes out of the new mold without any extra post processing:


The new mold design exceeds my expectations for what I thought I could accomplish going into this. All of the excess resin tears right out of the mold and the tire itself requires much less post-processing after de-molding. I'd estimate it would take me at least 5 minutes to de-mold and clean up a tire using the old mold design and that's assuming absolutely nothing goes wrong. The new mold design is easily less than a minute for the same task. The only downside is the resin waste (resin that goes into the mold but doesn't become a tire) doubled from 3g to 6g. It's a tradeoff I'm perfectly fine with considering how much less frustrating the new mold is to work with.

And as a final bonus I made the new mold design more material efficient. It uses about 30% less material to make and prints about 30% faster.
Fantastic work! I really like the design improvements!
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Old 11-16-2022, 07:07 AM
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Check this out:

+ YouTube Video
ERROR: If you can see this, then YouTube is down or you don't have Flash installed.


I've seen this guy post on rctech before and he's one of the first guys who made me think all of this was possible. He's been posting videos lately showing his method for making tires. It's worth a watch to see what he's doing - his mold design is pretty different than what I'm doing but it looks like it works pretty well. He's also using a resin printer to make his molds and the resulting tires look really nice.

Speaking of resin printing, I found a local guy with a nice msla machine to print one of my molds for me. It's a bit of a mixed bag - the prints themselves were not the greatest. They had warping issues, there were some soft/sticky spots on them, and the tread pockets in the mold cavity weren't fully cleaned out. He also broke one of the parts before delivering it to me. Frankly, if it was me I'd have been too embarrassed to deliver that as a final product to a paying customer (to be fair he did knock the price down, and it wasn't a part that really needed to be resin printed anyway). So off the bat I knew any tires made from this mold would be unusable to start with. But I tried the mold anyway, and despite the obvious flaws related to the poor print quality the tire itself was rather nice. The surface finish was really good and the tires in no way looked like a 3D print. But after a bit of research it seems like despite their ability to reproduce very fine details, resin printers are not the most dimensionally accurate machines and the process of resin printing will inherently create warping issues in the models it prints. Also, the cured rubber stuck really hard to the mold even with a good coat of mold release so I'm not sure what's up with that.

I was looking at picking up a resin printer on Black Friday but now I'm looking at ways I can improve the quality of the molds made on my E3V2. I've experimented with some slicer settings and a smaller nozzle and I think I can print some high quality molds with my E3V2 that will result in tires that look much less like they were printed, but the downside is the huge print times. A single mold piece that takes 4 hours to print with my current slicer profile will take 14 hours with the new profile, but the test prints I've done using the new profile look really good, like you have to use a magnifying glass to tell it was printed. I also have a roll of matte pla filament on the way, too, because I'm curious to see what effect that will have on the finished tires.

So for now that's where I'm at and what I'm experimenting with.
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Old 11-19-2022, 10:21 AM
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Here's my first test tire using the new slicer profile I've been playing with along with the matte PLA filament.



This tire was cast with half of an old mold and half of a new mold. I think the differences are subtle but also easily noticeable. The treads from the new mold have sharper, more defined corners and the carcass has much less visible layer lines and less of a glossy sheen to it. Finally, and what I was really hoping to solve with all of this, there is no more visible z-seam. The tire half that came out of the new mold is uniform around the entire circumference. That's a huge win for me.

You've probably figured this out by now, but the left side is the old mold and right side is the new mold.

Here are the changes I made to my printing profile: I went from a 0.4mm nozzle to a 0.25mm nozzle, 0.2mm layer height to 0.125mm layer height, randomized Z-Seam alignment, and enabled fuzzy skin with a really high frequency and really low thickness.

The mold piece I printed is a 4 hour print with my old slicer settings and took 10 hours with the new settings. The extra time is definitely worth the improved appearance of the tires and all of my molds will be printed like this moving forward.
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