3D printed molds

[McCool]

Okay, some of you may have seen my previous contribution in the form of a .stl for the MKVII base shoulder. This is something else. This is what I hope will be an evolution in two major processes of armor manufacture. A handmade fiberglass helmet usually starts out as a pepakura that is then reinforced. While we have some fantastically talented members in 405th, the innately handmade process means that it is always going to be imperfect. A large part of this can be worked out with bondo, rondo, and many hours of painstaking detail work. If you're me, you get through all of that only to realize that it is heavily warped due to a missing strip of paper you didn't glue in right. Another disadvantage of this process is the products we use for finishing, like bondo for example, don't have the same material characteristics of the fiberglass nor the same look. What if you could create a armor piece with the fiberglass weave visible?

On the other hand, you have 3D printing. There is still a lot of post-processing involved but the details are built right into the printed part. The result is much more uniform since most of the forming is done by a computer. The big disadvantage here is the material choice and weight. You can't rely on PLA not to warp in your hot car. PETG is great but it's still heavy compared to fiberglass.

What if you could combine the accuracy of 3D printing with the material advantages of fiberglass?

Hopefully now I have your interest.

Now I can't take credit for the process, I think many people have had the idea. I've seen it implemented in other fandoms but I personally haven't seen it in Halo yet. What I've done:
Make 0cm offset of outer skin of .step file
Make copy of offset
Scale up the copy
Stitch them together
Split into halves
Add flanges
Export as .stl

Start to finish it can be done in 15 minutes, maybe a little longer for larger and more complex pieces.

As of right now, I'm waiting for the first mold to print. I'll update this thread as I make more progress.


I know there are a lot of talented modelers out there. I'd love to see this take off beyond just me. Maybe this could even become a new standard method that 405th caters to like foam, pep, and 'classic' 3D printing. If you have base files that you can make these tweaks to, I'd encourage you to try it out and perhaps we can start building out another type of digital asset repository.

 

[PlanetAlexander]

Printing molds and mold walls (especially for silicone) has been super useful for me, saving a lot of time and allowing me to cast silicone (as a very basic method). So do you plan on coating the inside of the mold with fibreglass?

 

[Off Earth]

The best method would be to 3D Print, post process the print and design a matrix mold for the part. Once you have the piece in silicone, you can cast it in whatever your heart desires (for the most part).

 

[McCool]

Printing molds and mold walls (especially for silicone) has been super useful for me, saving a lot of time and allowing me to cast silicone (as a very basic method). So do you plan on coating the inside of the mold with fibreglass?

Yes, that's the idea. Make fiberglass parts directly from a printed mold thereby skipping the more common method of making a part and then making a silicone mold from that.

 

[McCool]

The best method would be to 3D Print, post process the print and design a matrix mold for the part. Once you have the piece in silicone, you can cast it in whatever your heart desires (for the most part).

I understand that is the more common method, but I want to skip making a part that doesn't get used. So if I print the mold directly and smooth that out, then I can save the amount of work I have to do and reduce waste. I also don't pay for any silicone.

 

[Off Earth]

Yes, that's the idea. Make fiberglass parts directly from a printed mold thereby skipping the more common method of making a part and then making a silicone mold from that.

If you’re making fiberglass casts you’ll be using or should use gel coat.

 

[PlanetAlexander]

That was my original concern too, how will you stop the fibreglass and resin from sticking to the 3D printed mold?

 

[McCool]

That was my original concern too, how will you stop the fibreglass and resin from sticking to the 3D printed mold?

I'll be using a mold release and I'm also printing in PETG which according to a few resources I've seen on the subject doesn't stick well to the resin.

 

[McCool]

Another example where fiberglass is specifically used even though the process and resins are essentially the same for both types of fibers.

 

[McCool]

All right Spartans! I got an update on progress this time because my molds finished printing. One of the key problems I wanted to solve was "How do I make a mold file that can be scaled by the end user and still be put together?" If I were to use screws for example, the screw holes would scale up and down in size with the rest of the mold. That might make it very hard for someone using my files to securely put the molds together because the diameters wouldn't match up well. Sure, I could just make the screw holes super big, but then the fasteners would be expensive. So from my initial concept I thought to use rubberbands. In reality, I don't think a mold has to be super securely put together. It just has to hold it's shape while under typical stress from the attentive armorer using it. So while I don't have a scientific method of measuring the tensile force holding it together, I CAN say that it is surprisingly high and if I needed more, I'd just add more bands. Rubberbands are super cheap, reusable, and they are one size fits all.

It's not pretty, but it's functional. You can see the scars from the support material, but it doesn't matter. It's what's on the inside that counts. I'll be coating the inside of the mold to make it nice and smooth like a Venus commercial. Maybe I'll use gel coat, seems pretty common.

But another benefit of this kind of mold is the amount of space it takes up. With no silicone to worry about damaging and the ability to very easily make multi-part molds that can break down, I imagine I'll save quite a bit of space. While I don't have a wife to complain about the space I take up, I'm sure it would make her happy. I'm sure plenty of you out there have a similar experience with an SO.

 

[McCool]

Not a substantial update in the way of photos and such. Sometimes the most work is the research end of things. In this vein, I've gone through a lot of resources showing processes similar to what I'm going for. The 'best' process would probably be to put on a layer of gel-coat, after application I'd sand it to a high polish. Then, I could apply PVA mold release and proceed with the fiberglass layup.

I'm not doing that.

I've seen other people do filler/primer instead of gelcoat, sand, PVA, fiberglass.

Not doing that either.

I did do an application of polyurethane finish as a sort of sealer, at least, that's the intention.

The reason I'm not doing any of those more proper steps is I know that there are a lot of people who will try to skip it. So, if the process works for the worst case scenarios then it would have to be pretty robust.

However, it seems plenty of people have had success without any kind of surface treatment. So maybe my polyurethane is even overkill.

I have some PVA release agent on its way in the mail. It will get here around December 8th. Obviously, I'll be busy around that time.

Once I have it, I can get going on the fiberglass layup.

 

[McCool]

Okay, I now have my first attempt at molding done. I learned a lot from this. Biggest thing I learned is the value of having the right tools for the job, because I didn't. I've used fiberglass one other time on a pepakura helmet years ago. I forgot how thick the resin is and was trying to use a foam craft brush to apply it. This did not work well at all. So with that in mind, I think this turned out really good in spite of me. Next time, I will use a proper brush so that I can really push it into the nooks and crannies as well as properly saturate the fibers.

There are quite a few successes here though. I used aluminum foil as a cheap alternative to a peel ply. I haven't gotten it all off, but it won't ever be visible either, so for cases where it just doesn't matter and you just need a barrier, foil seems to work.

The mold itself performed admirably. It survived, for one. And for two, the details that were properly coated in resin are wonderfully transferred. That said, I'm going to trim away a lot of the lip of the mold. That will make it a lot easier on my next attempt to access everything, coat it, and seal it.

This test part is 2 layers of fiberglass, I think for a finished product I want more. I used a foodsaver as a cheap vacuum bagging solution and I think it did a pretty good job.

 

[McCool]

Alright, I'm really happy with what I have to show today. The first image shows the upper section of this MKVII shoulder in a foodsaver bagging system that I am using as a cheap option for vacuum bagging. There are some tradeoffs compared to a more professional vacuum bagging solution. First, I can't control how much of a vacuum I pull and I don't have any confidence that it is a particularly good vacuum. Second, you are limited by the bags that you can use. Third, if you do this a lot, this will probably be more expensive than doing a bulk buy of all the proper equipment. That said, for one-off pieces this does provide an excellent way of compressing your parts to get a more consistent result. When you let it cure inside the bag, you don't have to worry about it lifting up or moving around. You can also see in the photo that you can get it to conform pretty well to the details of your part.

The process is not perfect with the foodsaver, the grey areas on the part are some filler being used to patch some voids that did still result. I think this could be mitigated by doing a thick resin layer, letting it cure, and then doing fiberglass. Though, that would be an inefficient use of material relative to their strengths.

I should also note that the part has been lightly sanded (which explains the white areas, these are not exposed fibers), the surface quality was originally much better. In my excitement, I neglected to capture a photo.

Overall, I am extremely pleased with this result. At the very least, this shows that high quality fiberglass armor pieces can be made from 3D printed molds. Better yet, they can be done for pretty cheap and for much fewer man hours that the old school pepakura route.