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Author Topic: Vacuum Forming Plastics  (Read 3275 times)

johnbentcope

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Vacuum Forming Plastics
« on: June 24, 2014, 12:32:34 PM »
There's been a growing number of makers here doing vacuum assisted thermoforming, and I figure we should pool our resources and knowledge in a thread here.

Here's a great pdf guide I found to the entire process: http://inventionstudio.gatech.edu/wp/wp-content/uploads/2010/11/FormechVacuumGuide.pdf


Here's a great online store to order smaller quantities of polystyrene: http://www.mcmaster.com/#polystyrene-plastic/=sjs2j5


Here's a good instructional guide for making a vacuum table that doesn't look like a pegboard: http://www.instructables.com/id/Make-a-good%2c-cheap%2c-upgradeable-sheet-plastic-vacu/
I like colors.

Gizmo

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Re: Vacuum Forming Plastics
« Reply #1 on: June 24, 2014, 08:39:38 PM »
As far as making our own, I think we should find a way to heat the plastic in-unit. The oven-to-vacuformer sounds tedious and prone to screwup.

Simply7

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Re: Vacuum Forming Plastics
« Reply #2 on: June 24, 2014, 11:22:46 PM »
Here is a nice one that I have been eyeing
https://www.youtube.com/watch?v=7XPeSn23tuE&feature=youtube_gdata_player

Planning on using the broken air compressor tank for a vacum tank. Works much better than a shop vac.

Simply7

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Re: Vacuum Forming Plastics
« Reply #3 on: July 06, 2014, 10:03:21 PM »
Hey Cope. I know you expressed interest  in making a 4 foot platform, but if we cut it down to 35 inches we can move it through a standard door. This would leave us with about ~30 inch work space.  my 2 cents

Gizmo

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Re: Vacuum Forming Plastics
« Reply #4 on: July 06, 2014, 10:16:24 PM »
Could always make something that breaks into a couple pieces, a base and a top unit. If the top unit is thin enough it can be carried through a door vertically, then we get the full size.

williamkeehn

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Re: Vacuum Forming Plastics
« Reply #5 on: August 08, 2014, 09:48:58 PM »
I'm interested in this too.  Last week I purchased the Vacuum Press Kit from veneersupplies.com and have been planning to do the modifications to make it work for a vacuum clamping system for my CNC as well.  In the back of my mind I also had the idea of using it for a vacuum forming table.

Here are some of my thoughts:

1) I like the heater in the unit the way the video had it.  You want the heater elements above the plastic.  I know warm air rises, but hot plastic sags down.  You don't want it to get closer to the heat as it sags.

2) Don't build the frame to an oddball dimension.  Check out common material dimensions available from your preferred suppliers and build to that.  You don't want to have to buy oversized stock and then trim it down.

3) A vacuum tank does work faster than a ShopVac, but only for a limited volume of air.  What I saw in the video was the air under the plastic evacuating quickly and then I heard the vacuum pump running continuously attempting to draw a vacuum on the combined system of the tank and vacuum table.  This means for a minute or two early in the process, the vacuum was much less than it could have been.

A better system is to have a GOOD vacuum motor such as the LH7123-13 for $119 (http://www.centralvacuummotor.com/shopbot.htm) evacuate the air under the plastic and then have the system switch to a vacuum pump after a certain level of vacuum has been achieved.  Both the high volume and high pressure systems can run continuosly.  A check valve allows the vacuum motor to be isolated when the vacuum pump is able to take over.  Under any loss of pressure the system instantly switches back to the vacuum motor to maintain vacuum.

4) I think it would be good if the work holding frame could be divided in half or even in fourths.  A vacuum manifold under the table would let you isolate vacuum only to the area being used.  That way we can do smaller parts and not worry about wasting a big sheet.

5) Pneumatic cylinders are nice, but a manual pulldown system with pulleys and counterweights might work just as well.

6) Add a good box fan to aid in cooling the formed plastic.

7) Consider using heat lamps to heat the plastic.  This may give you better control of the heat distribution and could be easier to repair.

Anyway that's my two cents for now.

-Bill




Simply7

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Re: Vacuum Forming Plastics
« Reply #6 on: September 15, 2014, 09:48:02 PM »
Here we go. They show a good basic setup here.

http://youtu.be/5eZmxTerat4

Ben2

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Re: Vacuum Forming Plastics
« Reply #7 on: September 18, 2014, 06:14:33 PM »
I've worked with Thermoforming plastics for the past 7 years, if there's anything anybody wants to know, just ask, I've probably done it.

BTW, the "pegboard box" technique works, and I can't take that away from it, but it's not optimal.

It's a bit hard to describe, but basically you just need 2 metal frames made from 1"x3/16" steel flat bar, welded into two matching rectangles...
Pinch the sheet of plastic between the frames
Hold the metal frame - plastic sheet - metal frame sandwich clamped together with metal spring-clamps.
Cook the sandwich in an oven
When plastic is heated and starts to sag, remove from oven with thermal gloved hands
Your "fixture" consists of your mold/pattern shape to thermoform which you then place on top of a rectangular platen of plywood with one hole cut in the middle of it (to suck the vacuum)
The plywood platen is slightly smaller than the inside dimension of the metal frame
When you pull the plastic down over the pattern, pull it so that the metal frame goes down past the plywood platen (this is hard for the plastic to do so it forms a tight seal against the plywood instead), this creates a tight seal where the molten plastic hits the sharp plywood edge.
Apply vacuum.
Allow plastic to cool. 
Trim plastic with a utility knife while it's still very warm, if possible
Remove waste plastic from metal frames, and re-use metal frames.

Basically if you have a baby shop-vac, a few pieces of plywood, just a few pipe fittings, and several sizes of rectangular metal "picture frames" welded up, you can thermoform anything.

Simply7

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Re: Vacuum Forming Plastics
« Reply #8 on: November 14, 2014, 01:09:24 PM »
I've  been working with Doug to get this built, we welded up the frames using steel channel like in the video above.  For the main rails that guide it vertically I have some aluminum channel that I plan to use.  Doug routed out some half inch mylar that we found at the lab to use as slides on the aluminum.  For what we are doing, the little friction there is should not be a problem.  I just cut the backings that mount the  mylar to the steel frame  but forgot the camera so pictures will have to wait. 

Simply7

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Re: Vacuum Forming Plastics
« Reply #9 on: November 23, 2014, 02:25:25 PM »
So I'm looking at how to wire up the vacuum forming table and came across some information.  Documented  on this website  http://www.tk560.com/vactable4.html.

The details are here, where they discuss the wiring setup and keeping the resistance to a minimum by running the heating coils in parallel

http://www.tk560.com/vactable4ovenwire.html
http://www.tk560.com/wiringdiagram.jpg

Anyone have experience or advice on how to set this up?   The heating bed will be 2 x 4 feet.

Details for the nichrome wire
http://www.infraredheaters.com/nicrcoil.html

Simply7

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Re: Vacuum Forming Plastics
« Reply #10 on: May 18, 2016, 10:42:13 PM »
Okay, all the mechanicals are in place and working on the vacuform table. Now there are a few things left

- The pedastal that the parts stand on, which is mostly done, just need to make standoffs

- The electrical wiring, which a quick trip to Home Depot should take care of.

- And purchasing a vacuum pump.  Might need some help with this bit $150.


http://www.amazon.com/Mastercool-90066-A-Vacuum-Pump/dp/B0021UMFF0?ie=UTF8&psc=1&redirect=true&ref_=ox_sc_act_title_2&smid=ATVPDKIKX0DER
$12.31

http://www.amazon.com/Mastercool-90066-A-Vacuum-Pump/dp/B0021UMFF0/ref=sr_1_1?s=automotive&ie=UTF8&qid=1463624034&sr=1-1&keywords=Mastercool+90066-A+Vacuum+Pump
$137.71

bradsilcox

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Re: Vacuum Forming Plastics
« Reply #11 on: May 24, 2016, 03:14:11 PM »
Rick, are both of those links supposed to be the same?  I assumed at 12.31 that was hose or something else we needed...