Thread: Bending perspex

For a simple bend make a form for it too shape too then heat it with a heatgun, gravity will do the work.
Heat it gradually and watch for hot spots otherwise it will melt/discolour.

Heat Gun


Ross

That was quick!

Haven't got a heatgun, time to go tool shopping I think

How about heating up a wire option? Anyone done this?

I have used the kitchen oven to heat larger sheets.Place the perspex on a form to cool. Google can tell you what temperature to use. Just be aware that the perspex shrinks a little, and that it is better to wait for SHMBO to leave the house.

Regards,

James

Yes I did in high school plastics, it had an element like a bar heater(not as hot!) it was pretty limited on what you can do compared to using a heat gun.

Some tips.

• If you buy a heat gun see if you can get one with a hot air constrictor attachment and or temp control. Some airguns will heat too wide an area and any bend you made will be a wide one. With a constrictor you can heat a narrower strip of perspex and make sharper bends. With a bit of practice you can bend with a hot air gun with one setting but I like one with a range.
• Make sure you heat both sides of the bend by sweeping the air gun, don't let its sit on the same spot for too long.
• I start by heating the outside of the bend, then the inside and the go back to the outside and keep heating sweeping the air right across the bend while applying light pressure to form the bend.
• If it does not want to bend repeat the previous step until it does
• If you mark the bend line with a felt tipped marker be aware that the ink will infuse into the perspex and cannot be removed afterwards. Inscribed lines need to be deepish or they can melt away.
• If you want to hold one side of the perspex in a vice be aware that a metal vice will draw heat away from the perspex. I use a wooden jaw vice to do this and make the bend about a cm or two above the jawline
• Experiment with a piece of perspex and get a feel for how hot it takes to get get it to bubble.
• When it starts to bubble the perspex is decomposing this is not good and you should not heat it this far.
• While heating look for a slight change in the transparency, this is the right temperature.
• One the bend is made, rather than immediately removing the heat, pull the air gum back 5 cm or reduce the heat on the air gun and heat in on low for a minute or two so that relaxes into that position. If you don't do this it can spring back and you will lose some of your bend.
• An alternative is to over bend and let it shrink/cool into the right shape. This takes practice.
• if you have to do multiple bends plan the bending sequence so you don't get trapped into a situation where it is harder to make a bend
• Either way you need to practice. The longer the bend the harder it is. I use two hot air guns when the bend is longer than about 50 cm.

Good luck

Tap Plastics in the US have a series of instructional videos on plastics including how to bend sheet plastics.

http://www.tapplastics.com/info/video.php

I hope this helps

if you want a sharp clean bend you will need to use a strip heater.....thats what the commercial buys use.

these things are realy simple and crude items.

it is simply a single strand of straight or coiled nicrome wire in a housing.

it needs to be in a proper housing because if run on 240 mains the wire will be live.

there are a couple of how to make a strip heater articles arround.

be aware that they are designed arround US voltages and building one is electricians work.

cheers

Originally Posted by soundman

if you want a sharp clean bend you will need to use a strip heater.....thats what the commercial buys use.
these things are realy simple and crude items.
it is simply a single strand of straight or coiled nicrome wire in a housing.
it needs to be in a proper housing because if run on 240 mains the wire will be live.
there are a couple of how to make a strip heater articles arround.
be aware that they are designed arround US voltages and building one is electricians work.
cheers

I made several of these benders in the 1980's including with built in adjustable width heat shields, angle benders and clamps to hold large sheets, and water cooled jackets. I found the easiest source of heaters was to use elements from domestic ovens. In the end I dumped everything except the frame and the adjustable width heat shields because I got skilled enough with a heat gun or even 2 heat guns to do the job. The adjustable sheet metal heat shield was used to narrow the heated gap to double the thickness of the material. This would make sharp corners that were always a bit more brittle than more rounded corners.

Hi guys,

I started out making acoustic covers for computer printers and these cabinets had a pespex lid which was bent . I have bent 100s of sheets of pespex and I remember when making the prototype resorting to the heat gun, heating the sheet in an oven etc with only limited success.

The main problem with the heat gun was that it didn't localise the heat enough. You need to heat a 10mm wide strip across the width of the sheet and the only way to do this is to use an infrared heating element with a thyristor control and a water jacket to localise the heat.

Now this may sound complex and for one bend in one sheet of perspex it is defintely not an option but as for so many things it is hard to a good job without the correct tools eg.If you want to saw a piece of wood you need a saw and we can justify the expense because we can use it on lots of projects. If you make a perspex bender then maybe your creativity will lead you to make other items.

My perspex bending jig was not expensive and consisted of 2 x 25mm sq ali tubes with spigots welded in each end, an old washing machine pump + bowl to hold the water to be recycled throgh the tubes to provide the localised cooling. Some mdf to make the bench, asbsetos sheeting to sit the element on, all sitting on a metal frame.

Worked like a charm for 11 years. Having just reread the post so far its as clear as mud so if anyone is really interestd in making one then I vae included a couple of quick drawings that hopefully make some sense.

I forgot it needs to have a sign attached warning of 240v and moving water so use at your peril!

We are talking about bending rather than forming arent we? Forming which involves complex curves etc is extremely hard without the right (and expensive) machinery.

Using the above heating bench and some simple geometry allowed me to make any lid upto 800mm (Width of the heating element) x 2400mm (length of the sheet) with a bend anywhere along the length at any specified angle.

The bending jig is so simple as it is just a flat bench with two adjustable stops across it .


The process was to:

1. Measure where you want the bend and mark on the perspex (leave the protective paper on).
2. Put on the heat bench and leave until the heated area allows the perspex to bend easily but before the internal bubbles start to appear (used take about 3 to 8 minutes)
3. Set up the forming bench with the stops set to the previously calculated distance apart
4. Put the heated pespex on the bench inside the stops and the angle will be as calculated
5. I would then have a bucket of cold water and a cloth an cool the perspex Takes 5 mins
6. The whole exercise would take about 15 minutes

Any questions will try to answer.

jeff.........