Last summer I went tumbling down the rabbit hole of vacuforming (a.k.a. thermoforming, that is, forming heated sheet plastic over a rigid mold using vacuum pressure). After my success with the Robot Rock costume I was looking for an alternative to EVA foam that would be more resilient, repairable and longer lasting. My buddy who runs the paint shop convinced me that plastic was the way to go. If I could figure out a way to form it into a fairly rigid state, he could paint and buff it with automotive paint-a real step up for my costume game.
Initially I was reluctant to get into plastic forming. I had talked with a few folks who had tried it and was told that it is not an easy process and to not expect good results without a very sophisticated setup. I tried contacting some local companies that do thermoforming hoping to make the molds myself and have them professionally formed with industrial equipment (yay!) but could not get anyone to return my calls. In the decade or so that I've been making stuff I've found that larger companies are often not interested in doing small one-off projects.
It appeared I was going to have to do this myself.
I pored over articles and tutorials on the subject until I found a video on YouTube by a guy in the UK who seemed to have figured out a pretty reliable method.
(Here's the link if you wanna check it out. I found it very helpful: https://youtu.be/maH5Ech0wK8)
Armed with this knowledge, I dove feet first into the world of thermoforming. With about 9 weeks to go until DragonCon 2015 (what the hell was I thinking?) I set about constructing my own plastic forming machine and designing/constructing a new Robot costume from scratch. This was gonna be interesting...
*SPOILER ALERT*
It all worked out OK.
BUT...
I learned a great deal about what does and does not work when doing your own plastic forming. Unfortunately I didn't have a lot of time to play around but was able to get some acceptable pieces done to complete the costume in time for the Con.
With DragonCon looming this summer, I decided to get an early start and make some improvements to my vacuforming setup so I can get some better quality pieces. I am planning on redoing the DIsco Roboto suit with some better fitting components and improved designs.
For those of you who may be considering getting into vacuforming, I'd like to share my process with you here and show you what I've done so far. If you're going the DIY route, hopefully this will help. Vacuforming is a relatively simple process (in theory anyway) and a simple rig can be built pretty easily with common shop tools and a shop vac.
Are you ready? Let's get to it!
But first...a word on plastics. Just about any type of sheet plastic can be thermoformed, be it Styrene, ABS, Acrylic, PVC, etc. All plastics have different properties that make them suitable for different applications but it is generally agreed that Styrene is the easiest to work with as well as being pretty resilient for costume applications. Check to see if there is a local plastic supplier as it may be more cost effective to purchase a large 8' x 4' sheet than order smaller sheets via mail. I had a great experience with Piedmont Plastics in Greensboro NC. The salesman was enthusiastic about my projects and took time to walk me through some different materials and offer helpful advice on working with plastic.
Styrene is readily available in a wide variety of thicknesses. For my setup I found the 0.060" thickness to work well for a 1.0" - 2.5" deep draw. Keep in mind that the deeper you draw out the plastic the thinner it gets. Ideally you'd use a thicker piece of plastic for a larger piece but that's when the limits of DIY vacuformers become evident. For a shop vac powered table, 0.080" is about the maximum thickness I think you could pull.
STEP 1 - GET A BOX
The idea is to have a sort of hollow vacuum chamber with many small holes on top and a hole at the bottom to hook a shop vac hose to. The mold is placed on the table and air is sucked out from underneath. When you place a sheet of heated plastic over the top of the table and make a seal, the vacuum pressure draws the softened plastic down around the mold. Simple, right? Good, time to get out the tools...
This is the top surface of the vacuum chamber box. It is a 2'x2' piece of 1/2" MDF. I marked and drilled 1,070 holes. This was super tedious and took several hours. A quality cordless drill really helped here as the cheaper ones tend to overheat during heavy use. I premarked the holes with a spring loaded center punch. This made it easier to hit my mark with the dill bit. I actually considered using pegboard for the table top but thought it would be too floppy and not support the weight of my molds under vacuum pressure. The MDF is much more stable. It was a lot of work to drill all those holes but I'm happy with the result.
I then cut out two additional 2'x2' sheets of MDF for the middle and bottom layer. For the second layer I cut out a square in the middle so I was left with a 1.5" border around the inside of the box. I then bored a hole in the bottom piece to fit a shop vac hose.
Here's a diagram of the three pieces that make up the vacuum box:
OK, so once I had my 3 layers ready, I assembled them with wood glue and screws. Here is a shot of the underside of the vacuum box. Notice the hole for the vacuum hose. If you look closely you can see the top layer with the small holes.
* I also added some weatherstripping around the edge of the table top to help get a good seal.
STEP 2 - A FRAME TO HOLD THE PLASTIC
I've seen several different approaches to this and I guess it depends on how you're heating your plastic. A metal frame would be ideal if heating the plastic to a very high temperature or if using an enclosed oven. Since I elected to go with the heater box as detailed in James Bruton's YouTube video from earlier I figured MDF would be adequate. I cut out two frames out of 1/2" and 1/4" thick material and drilled holes all the way round to screw them together.
What I ended up doing was placing a 2'x2' sheet of Styrene under the top half of the frame and drilling holes through the plastic to match those on the frame. I then secured the frame closed with wingnuts. In retrospect this was a a bit silly as it took a good five minutes to prepare one sheet of plastic for forming. It worked OK but I have something else in mind for the future-more on that in a bit.
STEP 3 - A HEAT SOURCE
As in the video I used a Quartz patio heater laid on its side. This was placed in a plywood box with sloping sides lined with aluminum foil.
*A quick note on the heater - These units are not designed for laying down flat as pictured nor for working inside an enclosure. If you plan on using one of these, you will have to bypass a couple of safety features, namely the tipover switch and the thermostat. THIS IS POTENTIALLY VERY DANGEROUS AND SHOULD BE DONE WITH THE UTMOST CARE. As always, be safe and keep a fire extinguisher handy. Don't say I didn't warn you.
STEP 4 - BUILD YOUR MOLDS
Now that I had my vacuum table, frame and heating element ready, it was time to make my molds. Ideally they should be heat resistant and strong enough to resist vacuum pressure, so again I went with MDF. I also felt the smooth surface (no grain) would be good for molding.
I cut these out with a jigsaw and finished the edges with a plunge router. Light sanding and a bit of Bondo smoothed out some of the rough spots.
STEP 5 - GET EVERYTHING READY
In this photo we're just a few minutes away from a vacuum pull. Notice the styrene is beginning to soften up a bit. With this setup it took about 4-5 minutes to achieve the "droop" that tells you it's time to set the plastic down on the mold.
If you haven't witnessed this process, it's really freakin' cool! I would start the shop vac just before removing the plastic from the heater box and quickly transfer the frame over the the vacuum table. Once the frame contacts the table and makes a good seal, the vacuum pressure almost instantly draws the hot plastic around the mold. The plastic cools very rapidly and is ready for removal in 30 seconds to 1 minute.
Here are some finished pulls:
Not too bad!
I was generally pleased with how these came out, but I had a lot of issues. Only about 1 of every 4 pulls came out OK. It was frustrating to see time and money being wasted with every attempt.
A few observations on the limitations of this setup:
- Heating element is too small for a 2'x2' sheet of plastic. The edges never really got hot enough and I ended up having to massage the plastic with a heat gun while still pulling vacuum. This caused some distortion and in many cases the plastic got too hot and melted through without warning, effectively ruining the piece!
- Transferring the frame from the heater box to the vacuum table was a bit clumsy. The plastic begins to cool the second it is removed from heat and it was tricky getting the frame to line up squarely with the table. Sometimes I did not get a good seal and was not able to get a full draw over the mold.
- The MDF frame was too flexible and not heavy enough. Made it difficult to achieve a good seal on the table. Again, you only really get one shot to get it right.
I've been thinking about how to improve the functionality of my setup and I've had a few (hopefully good) ideas.
Planned fixes for Version 2:
- A larger heating element. Using two quartz heating elements side by side to heat a larger area.
- Engineering a sliding carriage system to carry the plastic from the heater (mounted above) down to the table. This is based on some really well made professional vacuform tables I've seen.
- A heavier/more rigid frame (steel) to hold the plastic sheet