Vacuum forming clear PETG problems
- Thread starter BlindSquirrel
- Start date
I might have to try that. Thanks!
Maybe that's it! I will definitely try that. Thanks!
tictoc
Well-Known Member
I have gotten bubbles or maybe orange peel type imperfections on the corners and edges before. I thought those were due to imperfections (i.e. not smooth enough) on my buck...
What is your buck made of? You might need to make sure it is warm and dry as well. I have only used plaster for bucks and I made sure it is warm and dry before forming. First, I bring it inside the house the day before, then I warm it with a heat gun prior to forming. (Seattle is always lousy with moisture in the air)
I do the same when working with HIPS, ABS and PETG. I also wipe down and then warm both sides of the material I am forming.
Let us know if you find out anything....I am curious and certainly no expert.
What is your buck made of? You might need to make sure it is warm and dry as well. I have only used plaster for bucks and I made sure it is warm and dry before forming. First, I bring it inside the house the day before, then I warm it with a heat gun prior to forming. (Seattle is always lousy with moisture in the air)
I do the same when working with HIPS, ABS and PETG. I also wipe down and then warm both sides of the material I am forming.
Let us know if you find out anything....I am curious and certainly no expert.
I'm happy to report that pre-heating the plastic definitely gets rid of the "stars". I think, thought, that I'm overheating the PETG. What temperature are you supposed to heat it to?
I think I will order some HIPS and give that a try. The pre-heating is a time suck I'd rather avoid if possible.
tictoc, my buck is made from MDF. I've always done it that way and never had a problem with it at all. At this point, it seems to be a plastics issue.
I think I will order some HIPS and give that a try. The pre-heating is a time suck I'd rather avoid if possible.
tictoc, my buck is made from MDF. I've always done it that way and never had a problem with it at all. At this point, it seems to be a plastics issue.
Technically PETG is not hygroscopic (meaning that it absorbs water), but as your having problems it may be wise to dry it in a warm cabinet / oven before forming to drive out any possible moisture in the sheet.
I've seen it go white on our vac former, but it generally meant we'd overheated it.
I've seen it go white on our vac former, but it generally meant we'd overheated it.
Yeah, looks like classic overheating to me. As for temperature... in my experience, vacuum forming is more art than exact science :unsure
As for the fogging, if your dimensional tolerances aren't critical, you should try pulling a "skin" of styrene over your buck first, and then pull the PETG over that. Also, you should wet sand the surface of the styrene skin before pulling the PETG over it - I always started with 320 grit, then 400, and then 600. Anything higher than 600 never seemed to make any difference, in my experience.
Dunno - I've never used HIPS.
LaughingLarry
New Member
You guys are on the right track with overheating or slight moisture problems. I have used PETG and Polycarbonate for years. The polycarbonate must be dried or you get stuff that looks like this.
I formed the wrong sheet (I thought it had been dried).
The moisture turns to steam in the sheet and you get a tons of bubbles.
Regarding temperatures, I agree with D48thRonin that it is a bit of an art. Generally speaking though, they suggest about 5 - 10 degrees above the heat deformation temp of the material. I use the data sheets at my material supplier for getting this info.
Normally, you don't get this with the PETG, but we normally dry it for a little bit just to make sure. I once spoke with a technical guy at Sheffield Plastics in PA about PETG, and he said that they have to dry the resin before they extruded it into sheets.
Still, the PETG is the easiest and best clear material to form. Never heard of the forming over HIS, but we will give that a try.
Thanks for some new ideas.
I formed the wrong sheet (I thought it had been dried).The moisture turns to steam in the sheet and you get a tons of bubbles.
Regarding temperatures, I agree with D48thRonin that it is a bit of an art. Generally speaking though, they suggest about 5 - 10 degrees above the heat deformation temp of the material. I use the data sheets at my material supplier for getting this info.
Normally, you don't get this with the PETG, but we normally dry it for a little bit just to make sure. I once spoke with a technical guy at Sheffield Plastics in PA about PETG, and he said that they have to dry the resin before they extruded it into sheets.
Still, the PETG is the easiest and best clear material to form. Never heard of the forming over HIS, but we will give that a try.
Thanks for some new ideas.
Another tip when vacuum forming clear plastics: Some PETG, Polycarb and Acrylic sheets come with a flexible plastic coating that can be left on when you form it.
I remove it from the top, but leave it on the bottom where the plastic contacts your pattern. It helps to keep the plastic from picking up texture from the pattern.
I remove it from the top, but leave it on the bottom where the plastic contacts your pattern. It helps to keep the plastic from picking up texture from the pattern.
Thanks everyone for the great suggestions. I finally got four good pulls for the robot (after a mountain of FAILS) and that gets me throughout the project.
The RPF comes through again!
The RPF comes through again!
Oh yes, I plan on posting a video showing all it's features including the pulsing colors in his brain!
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