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noah@noahsart.co.nz
06-16-2004, 03:41 AM
Does anyone have experience of bending right angles in 6mm black ABS plastic? Hows it done? When I use the "element in a channel" system that we all know and love (Works well for acrylic) it fries the surface before it softens the plastic.

artisan
06-16-2004, 08:21 AM
This is just an educated guess....try "cold" bending it on a metal brake.....this works for polycarbonates (lexan etc.). ABS has some built in resistance to bending that is inherent to it's design as a tough ding resistant plastic, but should be able to take the bend in a brake, though I have NOT tried it myself with ABS....D

Brady Watson
06-16-2004, 12:27 PM
You also may want to try relieving the angle by running a V-bit down the length of the inside corner and then heat and/or bend in the brake.

Not sure what adhesives will work with ABS, or if it is only weldable.

-Brady

gerald_d
06-16-2004, 12:38 PM
If the surface fries before the rest softens, doesn't this mean that the heat must applied slower? ie. The wire must be further away, or the channel must be deeper? (Have never done it myself)

stevem
06-16-2004, 01:35 PM
Gerald,
Yes. Reduce the heat and increase the cycle time.

Brady,
ABS cement used for glueing ABS pipe.

johnny_s
06-19-2004, 01:27 AM
Simon, try here:
http://www.ipscorp.com/wo_html/weldonhome.shtml
If you want to v-groove, then bend. Use the glue to strengthen the mitre.

I bend abs with my wire element all the time. I have a variarc on it and have had no problems. The setups are super easy to make, just a variac, channel and nichrome wire. I put some ceramic blocks with tension springs on the ends.

simon
01-12-2005, 03:22 PM
Happy new year everyone.

I need to rejuvinate this old post because I am having further problems with ABS bends.

I have a new contract making up trays from quarter inch black ABS. These vary in size, but on average are are about 20 inches square, with three edges bent up 90 degrees, one inch from the edge.

I have been getting great looking bends using the wire in a channel. EXCEPT... the bends this close to the edge tend to banana in an outward direction. This distorts the flat base and it becomes unacceptable to the client.

I have tried reducing the width of heat all the way down to a quarter inch and up to one inch. I have varied the time of heating, and the heat applied using a variac. I have tried heating one side, both sides, cooling while clamped, cooling by dumping in water, cooling slowly.

I think I have tried everything I can think of, but I cannot seem to get rid of the distortion.

Suggestions anyone?

Ken Brisk (Unregistered Guest)
01-13-2005, 12:00 AM
Hi Simon,

We bend a lot of ABS and if I understand you correctly I would make a jig to hold the edge while you bend it upward. The jig would be made from wood with a 1/4" + groove running down the center and the inside edge would have a radius on it to accomodate the inside edge of your bend. You should leave it on until you cool the peice. If you are using "regrind" ABS that maybe the problem. Virgin grade is much easier to work with. Hope this helps.

simon
01-13-2005, 12:44 AM
Ken
Yes I am using the wood with the quarter inch groove to make the bend Actually it is a bit of wood with two inch square pcs screwed on with a quarter inch gap between them.
I do not heat it with the groove on, I slip it on once it is heated. The groove does not grip the material, it only loosely slips on for the bend. I have tried leaving the groove on, and also taking it off and forcing the tray against a right angle with a ledge to hold the tray down.
I have no Idea whether it is regrind or virgin, as I get the sheets from the customer. As a matter of fact I didn't know there was a choice. It has a leathergrain side and a smooth side if that says anything.

Ken Brisk (Unregistered Guest)
01-13-2005, 07:32 AM
Simon,

The leathergrain is what they call "haircell" and is avaiable in both virgin and regrind. We primarily use regrind, it's much cheaper. To make a 90 degree bend in a piece we use 110 V strip heaters. The electrod sits in a 1/2" wide teflon trough. This will yeild a 1/2" radius on the part while keeping the rest of the plastic cool. They are controled by a reostat. We do not do any V-cutting in the peice prior. No force is needed to bend the part when it is heated up properly. Use your jig only to hold the part in the finished position. Tempature and the time that the part sits on the heater are key. For 1/4" thick material we place it on one side for aprox. 45 seconds and flip it and do the other for about the same time and than flip it again for about 30 seconds on each side. Time and temp is purely trial and error so use a scrap piece. ABS is somewhat tougher to form compaired to many other plastics but with a controled setup you should end up with a good part. The corners will roll outward slightly but hopefully it won't be too noticable. If it is you can reduce the tempature a little and flip the part more frequently.

simon
01-13-2005, 03:17 PM
Ken
I never thought of teflon...duh!
Is the plastic in contact with the teflon? I am not sure if teflon is available here in new zealand. Does it come in sheets?
My heater is made from a half inch aluminium channel, and I can 'close the doors' using a fibre-cement building product called hardieglaze laid over the top, but this damages the abs if it actually contacts when hot, thus I have to keep the abs at some distance. Maybe there is heat leakage either side of the heat band.

gerald_d
01-13-2005, 03:45 PM
Simon, this (http://www.abbeon.com/tools/ftmcompt.html) may interest you. I would be very surprised if you guys don't have Teflon there in KiwiLand.

Ken Brisk (Unregistered Guest)
01-13-2005, 04:20 PM
Simon,
Here is the link for the type of heater we use. http://www.thefabricatorssource.com/products/03freeheat.htm

As you will see by their picture, the electrode sits in the trough and the teflon on each side of the electrode is a little higher. The object is to lay your plastic flat on the top of the "tray" and the electrode will only heat the plastic that is exposed to the plastic. Thus, a 1/2" wide trough yeilds about a 1/4" radius with regars to the bend. Although these "trays/strip heaters" heaters are kinda of expensive ($250-tray & $125-reostat US) I think you'll find it much more economical than purchasing teflon sheet. In our area a 1/2" x 12" x 48" peice of Virgin Teflon runs about $275 US.

Whenever we make bends that are parallel to the edge of the material we build a fence (usually a small peice of scrap lumber)that runs a long side of our heater. We space it so that the edge of the fence is the exact distance to the center of the electrode that we need for our bend. This technique will keep everything square when you are flipping the plastic and all your bends will be the same length.

Good luck and please let me know how you make out.

Ken