I’ve been experimenting with 3d printing and vacuum forming for a few years now. I think I have it down really well. I showed some pics to Paul Emmerson, Circuit Flyer / Climb and Dive creator. He suggested I post some info on how I’ve been doing this here on Stunthanger. Paul’s timers are great by the way. They’re all I use anymore.
Unfortunately, the DYI vacuum formers that use a shop vac really can’t draw good enough to produce good quality results. I built this machine back in 2020. There are plans available online for sale of a very similar machine. I didn’t buy them, but I took a good look at it and adapted the design to fit the parts and materials I wanted to use.  I 'll go into how I make the bucks using a 3d printer in the next post. I want to see if I am getting the pictures attached before I proceed.

Here’s a solid canopy in case I decide to go without a pilot. The next is the cowling buck. When 3d printing bucks, they need to be able to stand up to the heat and pressure of vacuum forming over it. These bucks have 8 side layers and 10 top layers. If you plan to form clear parts, the buck has to be perfectly smooth. If there is even a tiny line in it, it will show in the clean plastic. PLA or PETG are difficult to sand perfectly smooth. To make it easier, I sand the buck to get a lot of the layer lines out with 60 and 80 grit on an orbital sander.  Then I form oner it with .020 HIPS (high impact polystyrene). Then I will glue that to the buck. Then sand it smooth with 240, 320, and 400. The HIPS sands faster and cleaner than 3d print filament.  Also note the small holes in the areas that have a tight angle. I'll post more later, with a little more advice on how to make a successful buck and what are the best materials to use. 

That's an impressive machine and awesome work. How many inches Hg of vacuum can that pump attain?  I'd like to hear more of the details about the materials you have found that work the best.

Very nice work. What are the weights of those formed parts? 
HIPS (high impact polystyrene) is around 66lbs a cubic foot.

Thanks so much for the details!

I hope to build one about the size of a shoe box (I fly 1/2A). Your notes provide enough detail so I can replicate in miniature. I hope to use a freon or propane tank for my vacuum storage.

Given the size I hope to build, this places my heated size no bigger than a large counter top toaster oven.

Unfortunately, the DYI vacuum formers that use a shop vac really can’t draw good enough to produce good quality results. I built this machine back in 2020. There are plans available online for sale of a very similar machine. I didn’t buy them, but I took a good look at it and adapted the design to fit the parts and materials I wanted to use.  I 'll go into how I make the bucks using a 3d printer in the next post. I want to see if I am getting the pictures attached before I proceed.

     Those parts look amazing, I would never even try to do anything like that!

     While I know other people who have success, I have had nothing but frustration trying to vacu-form things, or even work with pre-made parts. As you note, the home job systems are generally awful and I don't have the space to make a dedicated machine.

    What always frustrated me when making parts or complete models using vacu-form is that the parts, at least those made from styrene, tended to fail or split along stretch marks or grain lines. Is that just because it's styrene, or is there some other issue?  Some rocket kits back in the late 60's/early 70s were nearly impossible to build as supplied just because every time you tried to cut out, glue, or bend the  vacu-form, it would split or the cut would take off in another direction.

     Brett

   

Another thing to keep in mind, when these parts are painted there is no grain to be filled. It usually only needs a single coat of primer. There is no primer on the pilot/cockpit.
I haven’t had any issues with cracking or grain lines. If you try to use too thin of material it will tend to crease or crack, but for the most part I haven’t had that happen.
The material I like to use best is High Impact Polystyrene (HIPS). PETG is good as well. PETG is tougher. It is hard to crack it. Locally it is only available in clear. It doesn’t pull as easily as HIPS. It has a smaller temperature range to get the best results. HIPS isn’t as tough, but it sands easily and is very forgiving with forming. Both materials have a much greater tensile strength than balsa parts. It glues to balsa and ply with CA and has a good bond. I find that most parts can be pulled from 0.030 or 0.020 thick sheets. The hatches and canopy are all pulled from 0.030” stock. The pilot is 0.020. The cowling was actually 0.060. It is a tall part to pull. By the time it is pulled, it’s around .020” thick at the base. It’s more like .035 at the top. It was a challenge to get it right. I started with .040 stock, and it would web badly. Once I got it dialed in, I was able to make multiple cowls. The buck is taller than the finished part. This is because when the part is taller than it is wide the plastic sheet will tend to web in the corners. This is because the sheet stretches when it is first pulled over the buck. When vacuum is applied there is too much excess plastic. As it is pulled tight to the buck the material will fold. If the buck is taller than the finished part the webbed portion can be trimmed off. It was a learning experience to get quality parts. I found a lot of good information on the internet and trial and error. Now I feel I can produce quality parts. I’m working on making them lighter. In a future build I am going to do an all HIPS skin with a laser cut balsa skeleton. The trouble is I have a least 5 designs I want to build that are more conventional construction. I’ve gone on way too long for this post but if anyone wants to know some good points on how to 3d print the bucks I can ramble on that too.