Homebuilt Vacu Mold Questions

[Nor Cal Mike]

What I mean when I say reduce the base size is this. Suppose you built 12"X12" vacuum box but you only want to do a run of 3"X5" parts. You could build what is very similar to is a restrictor plate that fits inside the 12"X12" box. Its outer dimensions would be 12"12" and would bedesigned to seal the entire 12 X12 area. But it would have a 3"X5" area with vacuum holes so a smaller plastic frame would be installed.

[chappy]

Yes your right, that is one way to accomplish it.
However if you take a piece of neoprene 12x12 and cut a 3x5 hole in the middle, and place it over the 12x12 vac plate, same thing happens, it seals all but the 3x5 area.
This way you could have several pieces of neoprene with different size holes cut in each one for a different purpose.
The neoprene would act as a sealer for the vac plate, and the smaller frame you place on top.
Hmmm food for, thought.
Bob C

[Nor Cal Mike]

Thanks Bob C things are starting to clear up. As mentioned before, I would like to vacuform small parts but wouldn't preclude something larger such as a whole body or items for my G scale model train club. It would be great to make a vacu bed large enough to do bigger things but be able to restrict it down for smaller items. What are the most common sizes of plastic materials available in affordable sized packages of let's say about 6"X 6" and 12"X12"? Can you recycle used vacuformed packaging material for consumer items? I mean the flat part rather than the molded part.

[chappy]

Mike I have heard of people using recycled packaging the flat parts.
Also pop bottle parts for canopies for airplanes and such.
I dont really know about small pieces as I have only used the 8x11 which isnt that cheap.
I tend to, use the 4ft x 8ft sheets and cut them to, size, but I Think Bob T and Dave have mentioned getting smaller sheets in 50 packs .
They would be better to answer that I think.
Bob C

[Nor Cal Mike]

I asked about the used plastic because we go through a lot of the vacu packaging used for salad mixes sold in the supermarkets. Every one of those lids would make a 5X7 sheet.

I just checked out the HP of my spare small shop vac. It is a 2 horse. Is that totally out of the question for thinner materials such as we would use for slot cars? I have a bigger shop vac too which is about a 5 horse or so. I am just trying to find a use for that little shop vac before I throw or give it away.

[Kemtronracer]

I built my vacu-form from scratch a few years ago. I use an electric BBQ heater for the heating element. Initially I had the heater box next to the vacuum box and used a hinged setup to flip the heated plastic onto the vacuum. I found it better to mount the heater overhead and have the plastic drop down instead. My small shop vac wasn't strong enough to do the job for anything other than polystyrene. So I now use a larger shop vac. I'm using PET-G for making clear bodies. I found it is best to research the available sizes of the sheet plastic before building the vacuum table. That way you can determine what size your table should be and minimize your waste. I found 12"X12" plastic online, so I cut those in half and designed my unit to hold a 6"X12" sheet of plastic and made the table just small enough to fit inside the frame that holds the plastic. Here's a pic of my unit:



You can see in the pic there are two bucks sitting on the vacuum table. Above that is the frame that holds the plastic - it's resting on a ledge until the plastic is hot enough. On top is the heater and an aluminum heat shield. It works like a charm.

[chappy]

I think Mike the little vac may be too small depending on the size of the plastic and the thickness.
But you never know until you try it.
The salad flats aren't really thick, so they may work with a smaller vac.
but a little practice with the heat may help you avoid thin spots or melt throughs.
Thats a nice looking unit you have too Kemtron.
Reason I went to 10 x 10 plate is I can often do 3 or 4 cars at a time.

Bob C

[Nor Cal Mike]

OK It will be the larger vacuum then. I like the idea of having the heat overhead. How far away is the heating element from the plastic sheet while heating it up? As to learning the right temperature, I saw a tutorial that described looking for a certain amount of sag in the plastic that will tell you the right temperature has been reached. I suppose how much sag depends on the size and thickness of the of the material being used. Practice makes perfect in that regard I suppose.

[dreinecke]

Here's mine - simple and works perfectly. Depending on what I'm doing I can normally do 8-10 parts on the frame.

[chappy]

Nice one Doc, looks like a 5hp vac for suction.
Mike the overhead heat is not bad, most of the commercial, units use it.
If you can find an electric bbq element they work fine.
I couldnt find one up here so went with the single burner.
My small one has an overhead.
For Sag on my 12 x 12 frame I go for 1.5 to 1.75 inches
on the little one usually about 1.25 inches.
Keep us updated on your plans and progress.
Lots of sealant, works good lol
Bob C

[Nor Cal Mike]

Thanks again Bob.

David, what are using for heat? Seeing those windows that you have on your machine is getting me excited about making clear glass for some of my old old mid 90's Scalextric black window T Bird Nascars. I have always admired those bodies but the black windows have turned me off to using them.

[Nor Cal Mike]

The one in this video is a pretty cool set up. http://vacuum-forming.com/

[chappy]

http://www.micromark.com/do-it-yourself ... ,7566.html


Nice one Mike, Micro Mark have abook on building and using Vacuum formers .
It talks and gives examples of vacuum systems and other resources.
I don't think it was costly about $15.00.
l found a link and put it above
it also compares materials and different plastics and sources.
There are some plans, and more available depending on how big you want to go.
Bob C

[Nor Cal Mike]

I found this one for a very simple box. http://www.largescaleplanes.com/tips/Ra ... umform.php

I like his idea of butting metal mesh over the pegboard to distribute the vacuum better. He uses his kitchen oven for heat. I really want to keep my process totally in my shop so I will have to come up with a heat source of some kind. I will look for a hot seat or a heating element of some kind. I think I will use that flip over design to bring the plastic frame from the heat over to the vacuum chamber that was shown in the video.

[chappy]

Another good idea Mike.
looks simple to make too.
Bob C