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Workbench Creations

Workbench Creations is the place for conversation and discussion about do-it-yourself (DIY) projects. This DIY blog will feature projects completed by its owner as well as projects completed by other do-it-yourselfers. Workbench Creations is the place where DIYers can discuss ideas, learn about what others have done, and share their expertise.

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8 comments

DIY Vacuum Forming Machine

Posted March 05, 2008 12:00 AM by frankd20

Sometimes even my projects have projects, this was the case with one project that I have put on hold temporarily. I need one particular plastic part that isn't just available anywhere. Instead of trying to find a place to make this part for me, I decided to build a tool to make it myself; hence was born my plastic vacuum molding machine.

I decided that if I was going to build it, I was going to build it the best I could since I could use it for other things. The design is based off of the parts I liked from a few other people's designs I found online.

The principle is simple, you heat a sheet of plastic which is held in a frame. When the plastic is soft you place it on top of a mold. The frame which the plastic is held is sealed to the table that the mold is on and you pull a vacuum to suck the plastic onto the mold.

I made the table, commonly called a platen, out of 3/4" MDF board, which I purchased from the hardware store. In the center of this board I drilled a 1 ¼" hole and bolted on a ¾" pipe flange fitting onto this hole, sealing it with calk. I connected a PVC right angle corner on this flange and glued-in a shop vac hose, which I cut to fit into the pipe fitting.

I used some right angle aluminum sections to make a frame above the flat side of the table to which I connected a heater at the top. I made a frame out of the same aluminum material that would slide up and down in this frame. I also made a frame to hold the plastic sheet out of aluminum, and some flat aluminum pieces; this would make so that it would form a seal on the table. I inserted the holding frame inside the frame that slides up and down.

I wired in two light switches and two outlets that would connect to the heater and vacuum. For my heater, I used an electric grill which has a square heating element. I used aluminum roasting pans, one with holes in it, to both focus and diffuse the heat onto the plastic. For the vacuum I used a small shop vac, which I have had.

The process of molding a part is done by placing a piece of plastic in the frame and sliding it up just below the heater. When the plastic becomes soft, I turn on the vacuum and quickly slide it down until it makes a seal with the table. As soon as it creates a seal, the vacuum pulls the plastic onto the mold and I let it cool.

I am still learning how to improve my plastic molding skills, but I can already tell that this tool will allow me to make many unique plastic parts as the need arises.

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Guru
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#1

Re: DIY Vacuum Forming Machine

03/05/2008 2:51 AM

Hey that's great. I may be wrong but I think the bed usually has a grid ov small holes, this bay give a more even pull down?

Years ago we had a craze at work fro radio controlled cars, I scratch built a a nice off roader. I made a wooden 'Jeep' style body form and took it to the vac form machine we had in the workshop... it was pretty good, but they only had thin ABS material which was a tad flimsy.

Del

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Guru
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#2
In reply to #1

Re: DIY Vacuum Forming Machine

03/05/2008 10:31 AM

The bed with a grid of holes is usually used when you form more than one part at once, so that each part gets a vacuum. For my use the single hole in the center which the part sits over has worked fine. I have thought about using peg board with a boarder to sit on top of the current bed for making multiple parts, but I haven't needed it yet.

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#3
In reply to #2

Re: DIY Vacuum Forming Machine

03/05/2008 4:11 PM

Nice idea! I need to form a cone shaped nose (think front of a torpedo!) for project X! It's about two foot long by a foot and a half in diameter! To get the thickness I want (for strength ) after forming, I'm looking at using 8mm ( Yes I know I'm bi-unit but WGAFFA!) That's quite a lot of plastic and quite a lot of forming! So, I either stick it in an industrial bread oven to get pliable, then, use a version of your machine or use a former with bags of sand hanging off its edges! Would your machine have the guts to form 8mm sheet plastic? Any other ideas on how to do this? The material I can get hold of is 8mm or 6mm ( I think this will end up about 3mm thick, which is pushing it a bit close to the limit!) clear Plexiglas or perspex!

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#4
In reply to #3

Re: DIY Vacuum Forming Machine

03/05/2008 5:41 PM

I don't think my machine could form something that big or thick, but ive never tried. I ended up buying PETG plastic sheet for my project, and it was much easier to form then plexi. It is the recommended plastic for forming. I did form a piece of regular window plexi glass (1/8" thick I think) I got from the hardware store, and pulled it on a 4" depth piece and it worked ok, but thats as deep a mold as ive done. In the future I was thinking of adding a place to connect a refrigerator compressor to pull a better vacuum.

I found that PETG plastic would form a decent cone shape without the vacuum machine. I wasn't able to regulate the shape well this way, but this may work for you. I cut a hole in a piece of sheet metal and put the PETG plastic over it, and put this in the oven. I then let gravity do the work for me and let the plastic sink down into the hole, I just had to stop it at the right moment. It was hard to control the shape, but the clarity was very good with this method. If all you need is a cone shape this should work great. For kicks I did this with a 1 foot square sheet, and let it sink into a cone shape about 1.5 feet deep, and it worked ok. The PETG plastic was reasonably priced, I ordered it from a place called industrial plastic supply

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Guru

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#5
In reply to #4

Re: DIY Vacuum Forming Machine

03/05/2008 11:16 PM

You can add a tank to accumulate a vacuum before you hit the valve. That way you can get a bigger volume of suction so there is no delay in pulling down the plastic. Then it doesn't matter much the size of your compressor unless you are wanting to do production volumes.

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#6
In reply to #3

Re: DIY Vacuum Forming Machine

03/06/2008 9:55 AM

Aren't 'nose cones' usually blow molded as opposed to vacuum? That has been my experience as a 'rocket scientist'

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Associate

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#7
In reply to #3

Re: DIY Vacuum Forming Machine

03/06/2008 9:59 AM

I've just supplied a client Tubular elements, hot air fans (same one's used in domestic ovens), and solid state relays for his second vac forming machine. This particular one has 21 off 2500W 2215mm long, 4.7w/cm2 Tubular elements spaced 85mm apart-if you want the bed size or to calc the required wattage per sq meter.

His client is going to vac domestic baths from 8mm material-I havn't a clue how thin the material will be eventually. His tank is approximatley 1200x2000x30mm, the vac pump I think-is 4.5HP. Problem is, he wont tell us the material-cant blame him.

In my experience it's best to use elements rated 4.7w/cm2 together with small circulation fans and solid state relays and not contactors to get an even heat over the material.

I suggest for your application, cutting a few sections of plywood either with a jigsaw or get them lazer cut, space them 100-150mm apart and cover the inside with fiberglass and resin from which you should get a pretty good molded shape.

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Anonymous Poster
#8

Re: DIY Vacuum Forming Machine

08/06/2010 3:25 PM

this is something I'm contemplating at the moment. but I'm wondering about the risks of fumes from heating acrylic sheets! will I need some kind of ventilation system rigged up to extract anything potentially toxic fumes?

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Users who posted comments:

Anonymous Poster (1); Del the cat (1); frankd20 (2); Hellcat (1); Mr. Truman Brain (1); rcapper (1); Ryan (1)

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