Heat bending acrylic / cast plexiglass

[PeterT]

I want to make a simple 'L' bracket from plastic & have this stuff coming. The strip will be 2.5" x 8" but the bend will be across the 2.5".
The plan was clamp it to an MDF base with a radiused edge, use my heat gun on the joint basically persuade it around the corner. Sound like a plan or any input if you've worked with the stuff?

 

[PeterT]

Like so but with a rounded corner.

 

[DPittman]

I've done a bit of bending with my metal brake and did it room temperature and it worked great. I thought it would break (no pun intended) but it did not.

 

[Perry]

I second the metal brake. I bent up some plexi and it turned out really nice.

I have tried the heat method before. If you heat too fast you can have gas bubbles form in the plexi. From what I understand that can be caused by the moisture content of the plexi. If you preheat the plexi in an oven it will dry it out before you try to heat and bend it. With better results.


Using a brake does leave the corner with a cloudy appearance if that is a concern for your project.

 

[Dabbler]

I've bent a lot of ABS, and a fair amount of acrylic panels - a lot of years ago. If you use heat (my preferred method), you have to be patient, go slow and only heat the plastic enough to make it almost pliable. There if a very fine line betwen getting it hot enough to bend and distorting the rest of the plastic you want to remain straight.

Acrylic is hygroscopic, so it absorbs moisture from the air. The longer the protective film is off the panel, the more moisture it contains until saturation. By heating the acrylic too fast, it cannot release the moisture fast enough and bubbles begin to form. I have found using desiccants to not help hardly at all.

An up-to-date article on polymers and moisture can be found here:

Resins: Hygroscopic or non-hygroscopic

There are two groups of polymers: hygroscopic and non-hygroscopic. Each has with a set of processing characteristics and an attraction to moisture.

www.plasticsnews.com

The most successful pros only heat the bending zones, and then with minimal temperature rise. Some home shop guys have been successful just using the sun in summer to warm the plastic enough.

 

[trevj]

The guys I saw doing stuff like Restaurant Menu Holders and the like, used a hot wire in a slot in the base board of their heater, so when you laid the material over the wire, you could accurately align it. The slot was not much more than a couple saw cut kerfs, so all the heat was held in the limited volume once the work is placed.

I would have thought a cheap and cheerful setup like this would be a great addition, and not take up too much shop space when not in use.

They were using AutoTransformers (expensive!) to vary their temperature, but I think you could put together a dimmer circuit for quite a bit cheaper, or use a variable Solid State Relay (couple bucks on Ebay/amazon/etc.)

 

[Garyt]

I don't think that you could bend acrylic that on a brake (polycarbonate maybe). You would ha e to heat it to be successful.
There is a lot of good information on the net about forming acrylic.

 

[Johnwa]

There are a few bender examples on instructables. This one looks pretty simple

DIY Acrylic Plastic Bending Machine

DIY Acrylic Plastic Bending Machine: As a DIYer it's always fun to fiddle with small yet handy projects. Last weekend I decided to use my scrap particle board to make a small plastic bending machine with as fewer parts as possible. finally I managed to make a small 11 by 9 inch Book sh…

www.instructables.com

 

[PeterT]

Material arrived, that was speedy. The bending was pretty straightforward with my heat gun & blocks of wood.
But... its a design fail. Too much weight for 3mm plastic to cantilever. I should have guessed that. I need to tie the rear end into the rear plastic tab maybe like a much shallower 'U' (red).
But it just has one cheesy screw holding the trigger housing to the motor can. Maybe the rear motor end bell itself.

 

[PeterT]

The material actually cuts & drills pretty decent. Might come in handy for other projects.