Vacuum Former Help

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nathanalaneller

Well-Known Member
I made my first Vacuum Former & it didn't work to my expectations.I need some help or tips on to make a correctly functioning Vacuum Former.Dose the plastic have to be a certain plastic or can you use any plastic sheet form the hobby store?Dose the plastic need to be a certain distance away from the object your forming, as in height or length? Like, should the plastic be wide enough to blanket around the object touching the table, or can the same be a accomplished if the limp plastic is an inch or more hanging over the object on top of a wood square?How far apart do the holes need to be to produce a fare vacuum?
 

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swgeek

Sr Member
As far as materials go, you can vac form acrylic, petg, styrene, and abs. I'm sure there are more, but that is all I can think of right now. The plastic needs to be big enough to drape over the pattern and make a seal with the vacuum table. If there is no seal, there is no vacuum. For the holes, every inch to two inches should work, you could experiment with more or less.
 

cavx

Master Member
RPF PREMIUM MEMBER
The most common issues with vacuum forming fails are heat and suction.

HEAT: Your heater needs to be able to heat the surface of the plastic to at least 130 degrees C. And you need the entire surface at that temp for best results.
SEAL: One you create a seal, you should not be able to break it whilst the vacuum is on. A vacuum cleaner will pull a max of 6"Hg. A vacuum pump can pull 30"Hg.

Raw MDF is a common material to make a platen from, but I discovered it fails at just 6"HG where the air is sucked through the material so I will be fiber glassing mine. I am also working on female tools, but that is another story.

As mentioned, your plastic (and frames) should be larger than the platen itself so that the plastic can make full surface contact with the platen. Adding a rubber seal around the rim can help. What this usually results in is making a smaller platen to economize the plastic being used. Typical sheets are 2400mm x 1200mm (8 x 4 feet), therefore making the rig work with 400mm x 400mm or 600mm x 600mm make more sense.

Foam based plastics like ABS or HIPS are the easiest to form. Perspex is a lot harder and more care is needed during the heating to prevent the plastic from burning.
 

GaryArm

Member
I have used many Vac-froming machines; my favorite material to form in is styrene as it is the most forgiving.
ABS is a stronger plastic but it has a lot of moisture in it that you need to remove before forming as it will leave tiny craters on the surface as the water explodes out of the sheet.
Perspex has a very narrow heat zone to make it pliable and burning.
The use of a vacuum cylinder is one way of pulling the plastic down quickly but I find a slightly slower pull is good to reduce the “webbing” effect (the plastic is pulled down at two points leaving a high point, the plastic then suck together rather than down to your table leaving a rib not intended)
Generally I like to have a space of about 2 inches minimum from your buck to the edge of the frame.
Heating of the plastic is important as a uneven heat will make the plastic stench unevenly and may cause a blow out ( where the plastic has stretched too far and the vacuum pops a hole in it thus losing your seal, causing the entire unit to form incorrectly)
The plastic does not hold its heat at all well so forming must be done quickly.
Although I have tried to reheat some jobs when I don’t get a good pull at one part by carefully using a heat gun , with the vacuum still on
Warning, everytime you heat the plastic it will increase its brittleness so the plastic will deteriorate if you heat it more than once.
 
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Elusiveg

New Member
From what I've been reading HIPS is the most common. Here's some sites I've found, I've used the Online Metal Supply for an order. I was missing 3/4 of the order on the first shipment but they had the missing parts sent out in less then a week with no fuss.
http://www.onlinemetalsupply.com/high-impact-polystyrene-sheet-060-x-24-x-24-yellow-4-pack.html
http://www.amazon.com/Impact-Polystyrene-Opaque-Standard-Tolerance/dp/B00CPREACA
http://www.tapplastics.com/product/plastics/cut_to_size_plastic/styrene_high_impact/560
http://www.usplastic.com/catalog/item.aspx?itemid=22883
 

pielock373

Well-Known Member
What are you using for a vacuume source? Vacuum cleaner or vacuum pump? Do you have a picture of your vacuum former, this could be very helpful to see it. Three critical questions: 1. Is it getting hot enough? 2. Are you getting a good seal? 3. Is your vacuum source strong enough?

Steve
 
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clonesix

Sr Member
The Plastics that you are looking for are called Thermoplastics. They are materials specifically made for heat forming. NOT all thermoplastics are the same. They have different heating ranges, and material qualities. The most forgiving is High Impact Styrene (HIPS).

I order my HIPS online at www.USPLASTIC.COM

The most important issue with vacu-forming as even heating.
 

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nathanalaneller

Well-Known Member
What are you using for a vacuume source? Vacuum cleaner or vacuum pump? Do you have a picture of your vacuum former, this could be very helpful to see it. Three critical questions: 1. Is it getting hot enough? 2. Are you getting a good seal? 3. Is your vacuum source strong enough?

Steve
Old modified oven 13 by 10 & a half.
DSCI0554.JPG


A box made of 2 by 4 & plywood, 15 by 8

DSCI0555.JPGDSCI0556.JPG DSCI0557.JPG
It use to have a vacuum attached to the bottom but it burnt out before I could use it fully. I'm going to modify it to attach another vacuum. ( just the hose part )
 

pielock373

Well-Known Member
Vacuum cleaners do not create enough suction for tight pulls, you need a vacuum pump to get tight pulls. You also need to make sure you have no leaks in that box. Not a big fan of wooden platens.

Steve P
 

cavx

Master Member
RPF PREMIUM MEMBER
Vacuum cleaners do not create enough suction for tight pulls, you need a vacuum pump to get tight pulls. You also need to make sure you have no leaks in that box. Not a big fan of wooden platens.

Steve P
A vacuum cleaner will pull about 6"Hg at best. A vacuum pump will pull 28"Hg (it is not worth the time to get a full 29.5" or true vacuum for vacuum forming).
Also be aware that MDF is air porous at 6"Hg. In other words, it leaks air through its cross-section and is therefore not ideal for a platen or the box that holds that.

Having said that, it is perfect for making tools (both male and female) where you can't drill a hole (or holes) for air evacuation. There is no need if your system can pull greater than 6"Hg (and every vacuum pump will do that) as the air will be sucked out right through the material.

Laminated MDF on the other hand will handle suction up to 20"Hg (that is all I have tested to) so might be better for building the box, but you will still need to seal it properly and I would suggest a few layers of fibre-glass is best for this. This is where I am right now on my rig. I spent extra on laminated MDF only to find my joins leak like a siv. In the end, I probably should have just used raw MDF and fibre-glass to make a box that can be 100% sealed.
 

nathanalaneller

Well-Known Member
I don't have the money to buy a vacuum pump. I have to make due with a vacuum cleaner.
I do have a air compressor, (2HP, whatever that means). It dose have an air intake, would that work?

DSCI0558.JPG
 

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slicerd

New Member
Hey Nathan, I am pretty new to prop making and just recently built myself a vacuum forming rig with just a normal (decently powerful) shopvac and an patio/shop heater. I am working on a Ghostbusters Proton Pack and I have been very pleased with my results so far. Here is a link to the instructable that I used as a guide to make my vacuum forming setup. It it a little different than the conventional builds and gets around a few problems that I have seen with the cheaper homemade versions.

Here and here are links to my pretty simple setup. It will pull 16x24" sheets of plastic I used board that was already laminated but you could easily just add plastic to you own board to get the same effect. Then i just made a single hole and sealed it to the metal drain flange like in the instructable above then used a series of adapters to get to my large shopvac hose. The shelf brackets are used to make sure I pull the hot plastic straight down and onto the seals. I dont have a picture of the frame the holds the plastic but it's super simple just 1x2" joined together to made a perfect 16x24 frame and then I use plain old tan masking tape to attach the plastic.

Here are some pics of my pulls the detail is pretty good and webbing isn't too bad. I am sure if I had a $1.5k setup it would be better but my $40 setup works pretty good so far. Here is a link to my whole build it has it's ups and downs but I am getting closer each week.

I did a lot of research and viewed a lot of tutorials and youtube videos about simple diy solutions. I should probably make a quick video featuring all the smaller things that I have learned but I just wanted to share because it's easy to get discouraged.
 

cavx

Master Member
RPF PREMIUM MEMBER
slicerd, your form looks good and the pulls look amazing. I noticed that you had to break a few to get the buck out. I am sure you worked it out by now, but there are a few reasons why this happened.

Your buck is quite tall in places and those parts have vertical sides. As the plastic cools, it tends to pull down onto the buck and when you have tall vertical parts, it can be challenge to get the buck out.

- - - Updated - - -

I don't have the money to buy a vacuum pump. I have to make due with a vacuum cleaner.
I do have a air compressor, (2HP, whatever that means). It dose have an air intake, would that work?
2HP = 2 horse power.
 
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slicerd

New Member
@slicerd, your form looks good and the pulls look amazing. I noticed that you had to break a few to get the buck out. I am sure you worked it out by now, but there are a few reasons why this happened.

Your buck is quite tall in places and those parts have vertical sides. As the plastic cools, it tends to pull down onto the buck and when you have tall vertical parts, it can be challenge to get the buck out.
Yeah I had some broken molds and broken hearts in the beginning. I fixed it in multiple ways first i separated the pieces of the model and them screwed them back together this way I can assemble the buck make my mold then remove the screws and then individually remove each piece. Also like you said there are some tall pieces and while they look pretty vertical some are a little rounded causing some undercutting so I sanded the sides to try to angle them just enough to make removal easier. And finally I bought some mold release which does seem to held to remove the parts that really stick into the mold.

I still need to build a 24x24" setup to do the upper sections because my first pulls had some paper thin areas.
 

cavx

Master Member
RPF PREMIUM MEMBER
I never heard of mold release being used for Vacuum forming. What is happening is the plastics shrinks as it cools and can shrink wrap itself on the buck. Not sure what you paid for your 'release agent". but a jar of Vaseline will work just as well to provide a slippery surface to prevent any sticking.

Given the height of the parts, maybe a female tool version would be better for a couple or reasons -

1. As the plastic cools, it still shrinks, but now pulls away from the tool, so making removal easier.

2. You can use thicker plastic and not have paper thin walls. With a female tool, once you get a seal and suction starts, you add more heat as go with a heat gun inside the tool. Ultimately, you do want a vacuum pump to get up to 28" of suction.

3. Female tools give tighter pulls because the plastic pulls into the corners, not over the corners. It is said that they can look as good as injection molded parts.

4. You will never get webbing with female tools.

5 Female tools may be a bit harder to make (because you work and build in reverse), but are much easier to store.

6. As mentioned, with MDF, if you ever move up to a vacuum pump and so long as you seal the edges of the MDF, you don't even need to drill holes in the tool. The air will sicked right through the side walls/base).

7. Time is not really a factor either. Once a seal is made, you can even let the part cool and reheat under suction.

There are more reasons and I need to fibre-glass my rig so I can make some cool plastic stuff.
 

division 6

Master Member
You can get extremely sharp pulls with a shop vac especially if you fill the canister with bricks. Instead of a fixed size table use a piece of plywood with 1/2" thick neoprene laminated to it with a 2" opening in the middle with an elbow on the bottom that the vac hose attaches to. place 1/4" thick spacers under the edges of the buck and wet down the neoprene for a solid seal with your plastic holding frame (sheet rubber won't work)
 

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