Homebuilt Vacu Mold Questions

[Nor Cal Mike]

This is to all of you folks who have been doing vacuum molding. I am contemplating building my on vacuum molding box. I have read some articles on the net and am coming around to building my own vacuum box for making windscreens, fender extensions, interior trays etc. The most common homebuilt type that I have seen is a simple box with a peg board grate for the molding floor and a shop vac attached to the bottom. I have seen various methods for building the frame which holds the plastic sheet material from metal to wood. On home built boxes, it seems that most use an external heating source such as a standard kitchen electric oven to heat the plastic before it is moved over to the box and lowered onto the buck the lid is closed and the the shop vac is switched on.

I have a pretty good idea of how I want to build the box.
1) It would be made of 3/4" plywood scrap.
2) It would have a hole in the bottom which the shop vac would be hard plumbed with PVC pipe. (I have a small spare shop vac which could be dedicated)
3) It would have small vacuum chamber at the bottom which would be topped by a piece of masonite pegboard.
4) It would have two alignment dowels in opposite corners in the interior which would stick up an inch or so above the top of the box.
5) The plastic holding frames would be made of hardwood or metal and would have holes drilled into the corners so that the frames would slip over the alignment dowel and lowered into place.
6) The lid to the box fits over the top of the box and is sealed by weather stripping around its edge.

My wife would have a fit if she caught me heating plastic in her kitchen oven. We do have an ugly 20 year old electric toaster oven which is begging to be replaced. I could get two-fer points by buying my wife a new toaster oven, (happy wife) and a toaster oven (albeit old & ugly) moves to my shop next to the vacu box for heating plastic.

So what do you think? Does my box design make sense? Will the toaster oven work? Is hardwood an adequate material to build the plastic holding frame given that will be going into and out of the oven? Suggestions? Pics of your box?

Thanks!

[ddyke]

Could you post a step by step as you do this?

[Ky.Slot Racer]

Mike,
I`ve had the same idea for awhile, but never proved to myself I needed it enough to dedicate space for it. But I`ve had a idea how I would like to build it. Much like the many you`ve probably research online and like yours. However I was going to attempt a dual hinged top over the main vacuum box. One would hinge off the left or right side of the box and would be the frame to hold the plastic. Another would hinge off the rear of the box and would contain the heating element and would come down atop the plastic frame. I would leave the front of the heat frame open so it would be visual aid for the plastic. just my idea :think:

[Nor Cal Mike]

Sure could Dan. My calendar date for doing this project isn't set yet though. I am only in the information gathering phase. I want it to be simple, not take a lot of space, and most important of all...........................CHEAP :twocents-mytwocents:

[btaylor]

As some of you know, I settled on an old Mattel Vac-u-form machine, it has a 3"x 3" table for the plastic. I dont do whole bodies, but it works really well for windscreens and headlight covers, even small interior trays. I payed $30 for mine off the Auction site,and the pre cut sheets run around 50ct for $7. Overall, thats pretty cheap. But obviously limited to working area. It does not take up much bench space though.

Bob

[Nor Cal Mike]

Mark,
Your's sounds more complicated than mine. It would be a choice set up when completed though.

Since I have you on the line, I think this is something that you could wrap your head around given your many resin and kit builds. On one of my circle track Camaros built from a snaptite kit, I grafted a vacu-formed front end section ) hood, nose & front fenders from a body I got from Smith Scale Raceways meant for a Womp chassis. Being from half way between the scale modeling and the thingie worlds, It is recognizable but it's proportions were exaggerated and wildly out of scale. The project only worked out so, so since I was trying to pull these panels into something of a shape they were clearly molded to do, but it really got me thinking of real race cars and how all of those extended fenders and air dams were really only molded plastic or fiberglass tacked over a stock body. Why can't we do that in the slot car modeling world I asked? Mold panels designed to be tacked onto a specific styrene model kit or slot car body, let's say a Snaptite 78 Camaro. That is some of what I would like to try to do with this vacu thing. Not to mention windscreens, interior trays and whatever else.

Bob,
Your's is a handy tool I am sure. I'd certainly use one if I had one at hand.

[chappy]

http://www.micromark.com/compact-vacuum ... 11244.html


Mike here is my small one, or at least the store model.
It works for smaller items, quite well and will do up to 30th PETG (Vivak).

I will send you pics of my larger one on an email, as I always have trouble posting here.
When you get them feel free to post on here, it is nothing fancy, but works very well.

I send an explanation to you aswell.
Bob C

[chappy]

Ok Mike you should have 4 emails with pics.
Let me know if it came through alright.
Feel free to repost .
Bob C

[Nor Cal Mike]

[waaytoomuchintothis]

I have the same vac platform that Bob does, but when I tried to make windshield replacements for a bunch of us last year, it failed miserably. I have found since then, that what was wrong was the high quality clear material I bought for the project was at the limit of what that box can handle, and it needs a lot more powerful vacuum than the extra large Shop Vac I tried to use. If I heat the white styrene, I can get a decent molding froma little Shop Vac meant for car interiors. The difference is the material. I may order some thinner clear one day and make things with it, but for now, I cut out the shape of the winshield I need from that thick stuff and heat it with a small hair dryer, then shape it with my hands in cotton gloves. I have a lot of this expensive thick stuff, so I'll be using it exclusively for a long time!

Also, I used a small pizza oven for mine, and it worked great. But the door was solid glass, and eventually, it was scratched and the next time it was heated up, it shattered all over the place, so it is strictly indoor use now (I have my orders). But those 5th burner things are dirt cheap, and they put out amazing amounts of heat, so you don't need an oven anyway.

[chappy]

It does take a lot of playing around with heat and vacc , and also, the plastic you use.
Type and thickness, just to get things right.
My shop vac is a 4.5 hp, but I have a 6hp incase.
I use the petg made by Vivak as it forms better at lower temps, and gives great detail.
I did a small old Hornby mini as a test, and it even got the windshield wipers, and that was 30 th.
Petg is funy though, it has to be kept in a dry environment.
The singlre burner unit above was about $25.00 Cdn.
The heat box is old pine for the bottom braces, with reynolds tinfoil covered cardboard around it.
The front folds down so, you can access the burner and also see the sag in the plastic.
The side posts are round abs plastic tube, 9inches tall, and suppoert the plastic and frame which is held on with big binder clips. The sealer around the surface of the vacc pad and the frame rest below the vacc pad is just that peel and stick insulation stuff for doors. The overall table is 12 x12 but the vacc chamber is 10 x 10. My biggest issue is having to cut the 8x4 sheets into 12 x 12 squares.
But it works , not fancy but does the job. The little one cost over twice as much but is great for 5x5 items like windshields or headlight lenses or even driver inserts.
Bob

[Nor Cal Mike]

I was hoping to use my small shop vac because I wanted to do a dedicated set up. I'll have to dig it out to see how many hp it has. I do have a larger one that is about 5 hp that I could use. Could efficiencies be gained by using chamber base plates (the thing with the holes that the buck rests on) with holes only as large as the work being done? For instance, if you are using only 5X5 stock, you only use a base plate that is about that size?

[Nor Cal Mike]

[btaylor]

I just posted this pic for Todd, but this is how small my vac is. not to good for many things.I did just pop him out two windscreens though! Your idea is much better, I like Chappy's unit!

[chappy]

Thanks Bob, it does the job, so thats all that really counts.

Mike you can use any base plate you want to reduce the size of the vacuum area as long as it dosent leak vacuum. But you would have to make mods to the plastic frame so it doesn't waste more than the
required plastic, ie more frame and less plastic, but the clips likely wouldnt work on the plastic so you may need to make a frame like Daves, but it would work.
You bucks should be put on a pedestal, that is wider at the bottom so it makes for easier extraction.
also watch for, under cuts.
Bob C