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Vac forming

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Martin McIntosh02/01/2017 16:41:08
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2484 forum posts
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I need some canopy vacuum forming material in at least 12 1/2" by 16 1/2" to fit my moulding box but the only stuff available from all suppliers I have tried is A4 which is too small. Any ideas out there please?

Philip Ogden02/01/2017 16:50:45
64 forum posts

Try these people, **LINK** or **LINK** .

Martin McIntosh02/01/2017 16:55:35
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2484 forum posts
947 photos

Thanks Philip, I shall give them a try. That must be S.H. Grainger, didn`t know they were still around.

Barry Meredith02/01/2017 17:00:39
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1 forum posts

Try Barkston plastics in Leeds.

The supplied me with PETG in around 2 meter by any legth you require.

Richard Norman02/01/2017 17:02:17
9 forum posts

My material of choice is for canopies is PETG sheet. A Google search for that should provide a fair amount of choice.

For example:

http://www.ebay.co.uk/itm/CLEAR-PETG-Sheets-1250mm-by-2050mm-Cut-to-Size-All-Thickness-PLASTIC-SHEETS-/201518059054?var=&hash=item2eeb698e2e:m:mPCsatOvbpdjiH9jhSJ4D_g

http://www.plasticstockist.com/PETG-Sheet.aspx

https://www.simplyplastics.com/catalog/sheet/petg-sheet/clear-petg-sheet/c-24/c-89/p-254

As it is widely used you may even find someone able to cut to size locally and save delivery.

Hope this helps.

Richard

Denis Watkins02/01/2017 17:08:59
2899 forum posts
141 photos

School Technology suppliers do every size and colour

Martin McIntosh02/01/2017 19:00:16
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2484 forum posts
947 photos

Thanks very much guys, lots to go on now.

Martin

ROSS MANSELL 114/02/2018 12:17:39
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7 forum posts

As of 14 FEB 2017

. A4 PET 1mm thick TRENT PLASTICS (uk..CHECK Google). 0.64p for an A4 size inc vat. 10 sheets postage was £2.99. 1.5mm thixk A4 is 0.96p both prices inc vat.

As I use a dental vac I buy 5" x 5" plastic from Aliexpress..free postage but prices vary with thickness and number of sheets per box (some have 20 sheets others 30). so be careful!

(The dental vac does a good job). Prices vary and they can occasionally be picked up less than half price (I paid £38 for mine ex Amazon returned item!!! bargain of the centruy!!

..Check their Open Box section for anything....

Both worth checking out.

Martyn K14/02/2018 14:22:54
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4611 forum posts
3217 photos

What thickness is recommended for a largish (20" long) caopy?

Martyn

Denis Watkins14/02/2018 14:47:18
2899 forum posts
141 photos
Posted by Martyn K on 14/02/2018 14:22:54:

What thickness is recommended for a largish (20" long) canopy?

Martyn

It is actually the depth too Martyn, for example 20" by 1/2" depth could be very thin plastic

A canopy 20" by 4" deep would work with 1 mm plastic

Martin McIntosh14/02/2018 16:01:10
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2484 forum posts
947 photos

How do you actually intend to form it? I have done a few but with only about a 10% success rate. Lots on Youtube but they all seem to have the same problem, creasing from the corners of the box. Have tried acetate and PETG with A4 and A3 size boxes, grill and heat gun methods, vacuum or not, run out of ideas.

Denis Watkins14/02/2018 16:09:17
2899 forum posts
141 photos
Posted by Martin McIntosh on 14/02/2018 16:01:10:

How do you actually intend to form it? I have done a few but with only about a 10% success rate. Lots on Youtube but they all seem to have the same problem, creasing from the corners of the box. Have tried acetate and PETG with A4 and A3 size boxes, grill and heat gun methods, vacuum or not, run out of ideas.

If you are lucky, a vac forming machine is really easy to use, but is aided by getting the whole of the sheet so hot

That it sags under its own weight and it smells hot

The same process without a machine

In the oven, so hot that it begins to smell, or with a heat gun, used with hand protection

On a former the vacuum is introduced or the plastic pulled just long enough until it cools

Martyn K14/02/2018 17:10:36
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4611 forum posts
3217 photos

Thanks Denis. At least I know what to buy..

Martin McIntosh14/02/2018 20:15:11
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2484 forum posts
947 photos

Thanks Denis, but tried all of that. Along with all of those Youtube guys I must still be doing something very wrong since many products these days are packaged in this way. Anybody know of a video which shows how to do it properly? I mean with a home built set up of course, not a professional machine.

Denis Watkins14/02/2018 20:30:57
2899 forum posts
141 photos
Posted by Martin McIntosh on 14/02/2018 20:15:11:

Thanks Denis, but tried all of that. Along with all of those Youtube guys I must still be doing something very wrong since many products these days are packaged in this way. Anybody know of a video which shows how to do it properly? I mean with a home built set up of course, not a professional machine.

Sorry Martin, I just read your creased corners comment

It sounds like you have built a frame with a vacuum

OK, the former is important, timber is best, totally smooth, with no undercuts, and bees wax rubbed in or furniture polish

This gets warm and becomes a release agent

If you can, bore tiny holes right through the thick part of the former to allow air out

Now creased corners are one or more of the following

former too deep, drill holes

Sheet not hot enough right to the edges

Sheet too thin, as it gets stretched it gets thinner, so start off with thick sheet

Make sure you are using thermoplastic as some plastic is already at its limit

Warm the sheet until it smells

Keep asking

ROSS MANSELL 115/02/2018 10:05:09
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7 forum posts

A recently viewed a  video on YOUTUBE   which showed   simple vac forming using plastic picnic plates obtainable usually from supermarkets  ( I have seen some in a UK supermarket).... Quite thin and cheap. Might be worth a punt. They may need a rim cut off but they appear ok for small size moldings.

Go here https://www.youtube.com/watch?v=oJVFxK5pseA&feature=youtu.be

This video is 1 of a series of 3 also shows a small vac forming box , made very cheaply.....details of which are mentioned in the US Model Airplane News website (search) and also the video mentions a couple of sites showing the plans for the box.  (a small version of the plans  is shown on the MAN article,....)

By the way..ref my earlier re plastic sheets.

RAPID  have some white sheets ( Plasticard).. 457mm x 254 @ £10 for 10 sheets  at this price I snapped up 20 sheets for stock!     p&p £2.99. delivered next day by courier!   Other colours ( inc clear)  different price s.

Edited By ROSS MANSELL 1 on 15/02/2018 10:11:21

Edited By ROSS MANSELL 1 on 15/02/2018 10:25:20

Edited By ROSS MANSELL 1 on 15/02/2018 10:27:38

Martyn K15/02/2018 10:31:36
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4611 forum posts
3217 photos

This makes it look so easy

Martyn

Martin McIntosh15/02/2018 11:00:24
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2484 forum posts
947 photos

Thanks for your suggestions. The methods shown in the videos are exactly what I have tried and my vacuum boxes are about identical. Huge sag in the acetate/PETG but the corners still crease. Vacuum is variable speed so have tried it high and low. Will just have to try again but already got through an 8x4ft sheet of PETG to get five forms for my Lanc. Those guys really do make it look simple.

Denis Watkins15/02/2018 11:22:07
2899 forum posts
141 photos
Posted by Martin McIntosh on 15/02/2018 11:00:24:

Thanks for your suggestions. The methods shown in the videos are exactly what I have tried and my vacuum boxes are about identical. Huge sag in the acetate/PETG but the corners still crease. Vacuum is variable speed so have tried it high and low. Will just have to try again but already got through an 8x4ft sheet of PETG to get five forms for my Lanc. Those guys really do make it look simple.

You will hit the " sweet spot " soon Martin, it takes a couple of 8 x 4s to learn. When you get the rhythm, then follow that always.

Now a new tip

The sheet is clamped and tight and hot

Flick it, and if too cool it will sound like a drum, as it gets hotter it will sag and no longer drum

Vacuum at this point

If a sheet is not too badly distorted, it will reheat and go again

Allow a sag of only 1/4 inch to start with

Trouble is different colours and materials do react slightly differently, but not much

Martin McIntosh04/03/2018 15:49:25
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2484 forum posts
947 photos

Got one done at last using a rather long winded and unconventional technique. I made a plaster of Paris cast from the original ABS. This kept cracking so I coated it with GF, sanded down and applied three coats of release wax. I then slowly heated it to 180C and pulled the framed acetate over it. This took several reheatings, finishing off by pushing a ply former over it and applying a heat gun and vacuum. Where there`s a will there`s a way.

Thanks for the tips.

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