Vacuum Former


#1

On World Create Day, I started work on something that’s been swirling around in my head for a while.

By leveraging tools that we already had, I figured it should be possible to build a small vacuformer very very quickly…

@rsim very kindly sketched up a box with a tilted false floor in Fusion 360, and I laser cut it up and woodglued it all together. I also cannibalised a space heater that VHS no longer needed for melting materials.

A couple weeks later, I brought in an 1/8th inch tube, fixed it in place with the finest sealant around (hot glue), and did another pass of woodglue to seal up all the gaps in the box.


(Top panel not shown)

The idea behind this is that it can be hooked up to our vacuum chamber, which can provide a quick shot of suction, a lot cleaner and more steady than a vacuum cleaner (of which we don’t reliably have in good order).

With some added fittings, that becomes a reality.

With a good vacuum in the tank and the pump completely off, it’s actually powerful enough to hold itself up with a sheet of acrylic for a good twenty seconds.

While asking the VHS hive mind where to get sheets of styrene (a common material used for these), @SeanPo suggested old CD cases, which is exactly the kind of free/recycling source that appeals to me.

So I laser cut a frame to adapt them to the machine.

Seems to clamp on okay.

Along with @toma’s help, we determined that the space heater is not hot enough to melt the styrene - more research needed, I think it can work. Instead, it was helped along with a heat gun for now.

And, finally, first pull:

Yeah, it’s not great.
As we were heating it, the left side of stock in that image shrunk/pulled out of the frame, and probably ruined the good vacuum seal required.

I then made an attempt to grab the edges of the polystyrene better using the heads of woodscrews.

Different, but still poor results.

The issue here might have been uneven heating with the heat gun due to impatience, and then the material stock rippled in a weird way.

I also attempted to break off the raised edges of the CD case to flatten the frame somewhat.

This was a victim of the same rippling effect.

You can see that overheating put a hole in the material, also causing issues with pulling a vacuum.

So that’s where it currently stands. This could be a pretty capable rig after the process is tweaked.

Improvements that might immediately fix everything could be:
Better / larger styrene sheets
Better frame or clamping method
Better heating (fix space heater?)

But I’ve spent my standard 3 evenings on this, I am shelving it for a long time, or maybe forever. If anyone else would like to take it from here, or play around with it, that’d be pretty amazing!


#2

Awesome work Jarrett. Could it be that the thickness of the CD cases is giving you some of the grief coupled with the Heat gun as a heat source?


#3

The CD cases are easy to heat but still rigid, so I think they’re a good thickness. The heat gun is definitely a bad method to use, the uneven heating is an issue. Low and slow is probably ideal, which the heat gun can’t do.


#4

This is one of the most awesome hacks!
Can a heated dryer which is used for drying floors and rooms or Space Heaters replace a Heat Gun?


#5

Yes, I have taken apart a space heater and removed the safety components. It doesn’t currently blow hot enough, but that should also be fixable.


#6

Whats the usual melting temp for vacuum forming?

Only thing I’ve ever seen used is a heater element. I think maybe because any blowing air during the heat up phase would cause the plastic to bend prematurely and unevenly. Just a guess.

I have a thought. Would a steel plate on the top that heated with an upside down induction pot heater? No idea if it would work, just an idea.


#7

Would something like this do the trick:


$80 Infra-Red Space Heater @ Rona


#8

The usual DIY elements for these come from toaster ovens, though I don’t know what sort of temp them get to. I suggest bolting the plastic to the wood, it’d be tough with a cd case, but some bolts at the edges would stop it from pulling inward. You also need to probably heat it slower and longer, wait for it to get saggy and soft before doing your pull.


#9

Yeah, it sounds like the plastic is not getting hot enough. The vacuum force is not going to be sufficient to tug the plastic out of the frame if the plastic is pliable enough. You should be able to get away with firmly clamping it in the frame. Once vacuum is compromised it goes all to hell instantly if there are not large volumes of cfms to overcome the seal breach, it’s for this reason that I have never liked vacuum clamping on cncs. Have you tried the same method but using a shop vac instead of a vacuum pump? Would have more tolerance to leaks.


#10

Just had another thought. Maybe a slight modification to the process? Try placing the tray and plastic over the form and begin heating it against the form to start. Then as it is almost sagged down and hot you force the frame against the box to create the seal. This would require that the form be heat tolerant like metal or silicone, etc.


#11

It was uneven heating that tugged the plastic out of the frame, before the vacuum was involved. Just not enough material being clamped due to the styrene sheets not being wide enough really. Could make a frame with a smaller ID to get more clamped material, or a better anchoring system.

Definitely

The advantage of this isn’t the vacuum pump, it’s the large volume of vacuum already pulled, so you have more force (initially) than a shop vac can provide.


#12

Here’s some inspiration for a design if anyone wants to take this up.

Based on watching that, even heating seems critical, as well as secure holding all around the edge of the plastic. Note that the clamping surface is quite nice on that machine, and the heating element is very even.