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Hitch
Senior Member
Joined: 16 Jan 2006
Posts: 2436
Location: Somerset
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 Posted: Mon May 01, 2006 6:37 pm Post subject: Bending Perspex/Acrylic |
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Chez,
I have read the bit about working with perspex...
Is it possible to bend it cold, 90deg bend with a 4mm internal radius without damaging?
Or would it need to be warmed? Im only talking about 3/4mm thick. Would that thickness be quite rigid over about 200mm?
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ultimatehandyman
Site Admin
Joined: 16 Jul 2005
Posts: 9321
Location: Darwen, Lancashire
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| Posted: Mon May 01, 2006 10:16 pm Post subject: |
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Hi Hitch,
You have no chance of bending any thickness of perspex at 90 degrees unless it was a very large piece and had a huge radius on it. You would need to heat it up for sure, but there is the chance that it will craze and so it may even need annealing afterwards!
A 90 degree bend on 3 or 4mm perspex should be quite easy to acheive once it has been heated and should not craze, it is normally thicker sheet which crazes!
Perspex is the trade name for net market acrylic sheet, which is used for some glazing and lots of signs/furniture making.
Lucite is the name of sanitaryware perspex which contains a chemical that means you can mould it and shape it more easily, such as for baths etc. Without the need for annealing afterwards, the only problem is that Lucite does not cut as well as Perspex and can chip when cutting!
So if you ever need to bend acrylic sheet (it will still require heating) you are better off using Lucite as it will bend and mould a lot easier. You can get clear Lucite as well as the normal sanitary ware colours. But 3 or 4 mm should bend with little difficulty when heated.
A 200mm piece of 3 or 4mm would be quite rigid!
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Gadget
Jack Of All Trades
Joined: 18 Dec 2005
Posts: 3459
Location: Whitley Bay
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| Posted: Mon May 01, 2006 10:35 pm Post subject: |
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Iv'e never tried to bend Perspex, but getting a 4mm radius bend would need it to be very hot. So hot, and I reckon it would almost melt.........just a thought guys!!
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ultimatehandyman
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Joined: 16 Jul 2005
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Location: Darwen, Lancashire
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| Posted: Mon May 01, 2006 10:55 pm Post subject: |
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No, It won't melt!
You can heat it up to 200 degrees C in the correct type of oven and it won't melt.
You have to remove the masking first though or that will bubble and melt.
Once you have heated up perspex to a suitable temperature (140-170 degrees C) it is like a piece of rubber, in fact if you had a piece of 5mm rubber sheet and a piece of 5mm heated perspex the perspex would be more maleable, until it started to cool!
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Gadget
Jack Of All Trades
Joined: 18 Dec 2005
Posts: 3459
Location: Whitley Bay
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| Posted: Mon May 01, 2006 11:07 pm Post subject: |
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Like I said, I've never tried bending the stuff!!.. 
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ultimatehandyman
Site Admin
Joined: 16 Jul 2005
Posts: 9321
Location: Darwen, Lancashire
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| Posted: Mon May 01, 2006 11:14 pm Post subject: |
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It's not something that can be done easily, without an expensive oven or line bending machine and there is not much call for it.
Some of the items made from acrylic though are cool, but some of the designer stuff costs mega bucks. |
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Hitch
Senior Member
Joined: 16 Jan 2006
Posts: 2436
Location: Somerset
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| Posted: Tue May 02, 2006 5:09 am Post subject: |
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Nice one. Cheers men.
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honeymonster
Senior Member
Joined: 17 Jul 2005
Posts: 406
Location: Newcastle
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| Posted: Tue May 02, 2006 11:20 am Post subject: |
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| ultimatehandyman wrote: |
It's not something that can be done easily, without an expensive oven or line bending machine and there is not much call for it.
Some of the items made from acrylic though are cool, but some of the designer stuff costs mega bucks. |
WOW I have just been to the acrylics section
http://www.ultimatehandyman.co.uk/acrylic_sheet.htm
And checked out the links on the Google ads, there are some very cool products made from Acrlic. Some of the furniture is out of this world, glad I am not paying for it though
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diysurgeon
Junior Member
Joined: 10 May 2006
Posts: 4
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| Posted: Wed May 10, 2006 8:35 pm Post subject: |
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| Use a line bender or strip bender. Heat up slowly and keep turning the plastic over so heating both sides. This allows the heat to penetrate the plastic without over heating - thats when it bubbles or crazes. Then bend using a wooden jig. Did this frequently in school technology workshop when I was a DT teacher. |
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Hitch
Senior Member
Joined: 16 Jan 2006
Posts: 2436
Location: Somerset
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| Posted: Wed May 10, 2006 10:51 pm Post subject: |
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Hello Surg,
Done it from metal, seems like a bit of a ball ache to bend plastic to me 
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Stoday
Electricity economics consultant
Joined: 20 Jan 2006
Posts: 3085
Location: Sitting on the Bog
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| Posted: Fri May 12, 2006 2:52 pm Post subject: |
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You can use infrared to heat acrylic safely. The wavelength is best between 1.5 and 2.2 micron because acrylic is only partly transparent at these wavelengths.
If it absorbs all, you have to heat slowly to heat through the thickness; if it's transparant, most goes through & dosn't heat the inside & you get surface heating.
You can use ceramic IR heaters or metal sheathed heating elements underrun so they don't glow.
Here's a graph of IR transmission: http://www.fresneltech.com/graphs/acrylic_graph.html |
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doc
Junior Member
Joined: 25 Jul 2007
Posts: 1
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| Posted: Sun Jul 29, 2007 11:00 am Post subject: |
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what can you use to bend acrylic if you have no speciallist tools?
will a paint gun do? |
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ultimatehandyman
Site Admin
Joined: 16 Jul 2005
Posts: 9321
Location: Darwen, Lancashire
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| Posted: Sun Jul 29, 2007 12:55 pm Post subject: |
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| doc wrote: |
what can you use to bend acrylic if you have no speciallist tools?
will a paint gun do? |
Yes you can use an electric heat gun to bend acrylic.
Don't leave it in the same place for too long or else it could bubble.
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Edz
Senior Member
Joined: 10 Oct 2006
Posts: 163
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| Posted: Wed Sep 19, 2007 9:36 am Post subject: |
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Lot's of interesting stuff in this post.
Obviously too late in the day now but you could use PETG. It is clear like acrylic and you can bend it through 90 degrees in a bench vice. I've done it. It needs no heating and you can buy it from most plastic sheet stockists. |
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Stoday
Electricity economics consultant
Joined: 20 Jan 2006
Posts: 3085
Location: Sitting on the Bog
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| Posted: Thu Sep 20, 2007 12:37 am Post subject: |
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Hitch was talking about 3/4mm thick perspex.
According to the data sheet, cold bending is not advisable for thicknesses over 2.5mm.
NUDECPETg sheet can be bent and folded with a small radius by first heating a thin strip on each side of the sheet using a resistance wire. When the sheet reaches the correct temperature (just above 105°C) and a slight resistance to folding can be noted, it can then be easily bent.
If an attempt is made to bend the sheet before it is sufficiently hot, stress is caused which could be make the part brittle; if , on the other hand, it is overheated, bubbles can appear along the bent section.
Thickness of up to 2.5mm can also be cold bent |
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