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Plasticman · Expert Joined: 08 Jul 2006 Posts: 109

I managed to find some "smooth both sides ABS", and made a first pull tonight. Some things I noticed.

1. ABS takes a long time to heat up. I let th oven pre heat for 15 minutes and once I put the ABS on it, it took 14 more minutes to get a 4 inch sag out of it.

2. it stinks really bad compared to Styrene, almost toxic, cough, cough. definately do it in a highly vented area.

3. Its way stronger than Styrene and can be man handled more to remove from the mold. Of course I went from 0.060 Styrene to the 0.093 ABS so...go figure.

4. Its more apt to getting deformaties in the finish. I have small bubbles and a cold spot on my pull, even after heating the oven all that time!

The good news, (I think) is that I probably can sand out the bubbles and the cold streak and nuvus it back to a high luster. I didnt pre dry the ABS, so that may be a problem. Gotta figure that one out.

All in all I'd say the first pull went well.

Questions:

Am I heating it too much? Do I need the sag like styrene does? Maybe it got too hot and that is what caused the bubbles? Should I preheat my molds? Is .125 Styrene as strong as this too??

crashmann · Guru Joined: 27 Sep 2005 Posts: 501

Cool! And yes, that ABS is some nasty smelling stuff compared to HIPS. I have not found any conclusive evidence as to what causes the pitting. I suspect too much heating in the oven and moisture trapped in the plastic. It probably does not need as much sag as HIPS. However, if it's not sagging, then it's not as pliable - and there is the reason you need a high vac setup to make successful pulls with ABS.

This also demonstrates an advantage of the flip flop design versus over under. With an over under, you provide all the pressure pushing down on the plastic holding frame. A flip flop has a hinge, and you can press all of your weight on the opposite side. The hinge will assist you with sealing the plastic to the table (and there's no danger of burning off your eyebrows Wink

)

Try another pull, and heat it for a shorter time. You may need an assistant to encourage the plastic to seal around your molds.

Charlie
TI-386

remarque · Posted: Wed Apr 25, 2007 8:26 am Post subject:

How well did the plastics take the detail of your mold? I've tried 0.060 haircell ABS when I first started vacuum forming, but by the time I got it out of the oven and onto former it had cooled and the mold only formed half way.Good job though.

Plasticman · Expert Joined: 08 Jul 2006 Posts: 109

It took on the shape really well. I have a robinair 15600, so vacuum is no problem. I was pulling 27 inches of vacuum for this pull. I have the flip flop design too. It seemed like it sealed better than the Styrene. I am going to try cutting down the heating time and preheat the oven for 25 minutes this next time. I agree with crashman that the ABS is getting too hot and too close to the coils. I was looking at the flash that I cut off and there is no pitting anywhere but near the center where it got closer to the coils. So next time less sag.

cod · Posted: Thu Apr 26, 2007 2:41 pm Post subject:

Stomper · Posted: Fri Apr 27, 2007 8:01 pm Post subject:

It seems to me that you have to look at this like you would cooking a thick-cut steak... lower heat for a longer amount of time so you don't burn the outside, while the inside gets cooked enough (I like mine medium rare, BTW) You may have to actually heat it longer at a lower heat level for the "whole sheet" to get pliable enough. Perhaps placing it slightly further above your heating elements so that "sag area" in the middle won't get bubbly and pitted while the outer edges get warm enough.... just a thought. Wink

_________________
Tony Krewson
FEAR... is not my god!!

drcrash · Posted: Sat Apr 28, 2007 8:47 pm Post subject:

harley guy · Novice Joined: 25 Nov 2005 Posts: 71

i form 1/8 abs all day long. takes 3-1/2 minutes to heat a 24x36 sheet for forming. i have a flip flop design. you have to make a adjustable oven so you can change the heights. not all abs will heat up the same so you wil have to adjust the oven height. make the oven be able to rasie and lower. make the oven shroud adjustable to. so when you lower your oven, you can raise your shroud to meet with the plastic holder. if you need pics, search my flip flop design rig.

Plasticman · Expert Joined: 08 Jul 2006 Posts: 109

I will check that out.

Also just noticed that I had a broken coil on the outer ring for that pull. Smile

That might be it...... Embarassed

cod · Posted: Wed May 02, 2007 5:05 pm Post subject:

Plasticman · Expert Joined: 08 Jul 2006 Posts: 109

I just twisted it back together. Ive broken the coils now a couple of times. they are very brittle after they have been heated up. i am glad I kept the extra wire. The resistance does change, but in my case thats good because I made the outer coil a little to long anyway. Now maybe it'll heat a little better.