Any luck printing transparent polycarbonate?

[strantor]

I've burned through 2 rolls of Overture PC Professional trying to get results like these:

But the closest I've gotten is this:

That looks almost acceptable but my typical result is more along the lines of this:

I followed the instructions in the link as a starting point but they are for PETG which behaves much differently than PC. I've tried all manner of ratios between layer height and width, all kinds of infill, nozzles of 0.4mm, 0.6mm, .8mm, both normal and CHT variety. Speeds from 20mm/s to 500mm/s, hot end Temps from 250C to 350C, build chamber temp from ventilated to 65C, tuned input shaping, tuned pressure advance, all kinds of stuff.

I can get it clear as glass as you look down through the top, down a column of stacked perimeters, up to an inch thick or more. But No matter what I do, the separation between columns, and the layer lines, form "walls" inside the part that obstruct the view. The layer lines can be removed from the outside by machining, sanding, and hitting them with a heat gun to make them clear in through the sides, but that's too much work and too risky. Too much heat gun and the part warps. The line between when it gets glass clear and when it turns into a Pringle is very fine.

I am going to try Polymaker Polylite in the morning, but if that doesn't work I'm giving up. That is, unless one of you fine folk can suggest something I haven't tried.

 

[Firstram]

Try flame finishing with a small Butane torch. The quick licks with the torch don't heat the whole part and shouldn't warp it. If it does heat soak stop and let it cool. You will probably get slight soot staining from the Butane but. it's worth a try.

We used Hydrogen and Oxygen in a plastic fab shop I worked in for the clean burn.

 

[strantor]

Try flame finishing with a small Butane torch. The quick licks with the torch don't heat the whole part and shouldn't warp it. If it does heat soak stop and let it cool. You will probably get slight soot staining from the Butane but. it's worth a try.

We used Hydrogen and Oxygen in a plastic fab shop I worked in for the clean burn.

I tried my "MAPP" ("MAP pro") torch first and found it to be even more of a crapshoot than the heat gun; that's why I started using the heat gun. With the torch, something like 400 milliseconds of direct blast takes it from translucent/rough surface to a crystal clear polished surface, while 600 milliseconds results in a yellowed bubbly surface with charred corners. The heat gun can be adjusted for a certain temperature that can give nearly repeatable results. Just sucks that the warpage is as repeatable as the surface finish.

But I do think that there could be more to this. Your oxy-torch "clean flame" comment has me wondering if there is some kind of oxidation component to it, and it does seem intuitive that an extremely hot flame to quickly melt the surface without soaking heat into the part, is the way it should be done. I have an oxy acetylene torch, I will try that and see what happens.

Thanks for the insight.

 

[strantor]

Look at this, you can see straight down through 2" thick of the stuff, as if it weren't even there, from the right angle. I'm betting you'll be able to see through 5" thick of it just as easily once these prints are done.

But from any other angle...

I'm going to sand and flash burn these with acetylene and then we'll see what we see. Sure would be nice if they could just come out of the printer clear though.

 

[Firstram]

I tried my "MAPP" ("MAP pro") torch first and found it to be even more of a crapshoot than the heat gun;

MAPP is too hot, use the Propane in the blue can. I think the blue is the cleanest of the gasses.
You have to wave it by at just the right speed. If you miss a spot, wait until the part has cooled or you'll burn it!

ut soaking heat into the part, is the way it should be done. I have an oxy acetylene torch,

I'm going to sand and flash burn these with acetylene

Not Acetylene, it's nasty and sooty. We were set up to use Hydrogen and Oxygen!

 

[strantor]

MAPP is too hot, use the Propane in the blue can. I think the blue is the cleanest of the gasses.
You have to wave it by at just the right speed. If you miss a spot, wait until the part has cooled or you'll burn it!



Not Acetylene, it's nasty and sooty. We were set up to use Hydrogen and Oxygen!

You said not to use acetylene but I did anyway, just to cross it off the list. You were right about propane being the best gas to use. Here are the test results from the parts I was printing earlier; propane vs MAP vs acetylene vs heat gun. Each part was sanded with 320 to remove high spots and surface imperfections prior to surface melting. I saved the worst looking part for heat gun to make sure my results weren't biased towards what I already thought was best.

Propane:

MAP:

Acetylene:

Heat gun:

Heat gun was the clearest part and also the most warped. Propane #2 and also warped. MAP and acetylene both scorched but it took several passes with MAP before it looked like what the acetylene did in a single glance. MAP and acetylene neither warped.

Propane and heat gun warp:

MAP and acetylene no warp:

You have to wave it by at just the right speed. If you miss a spot, wait until the part has cooled or you'll burn it!

Now I know what you're going to say, but... it just didn't work that way. I tried going over the part with propane at various speeds, to melt just the surface without heating the part. It didn't work. I gave it due diligence, many passes followed by cool-downs even though it didn't seem to be having any effect. Spent a few hours doing this, quick passes at first, then getting progressively slower, towards the end finally stopping on top of the part and heating one spot until surface melting was observed.

That's only way it seems to work. Whether heat gun, propane, or whatever, you have to get the surface to melt, and that only seems to happen with heat intense enough to cause charring, or duration long enough to cause warping .

 

[Firstram]

That's why Hydrogen and Oxygen works so well. It's incredibly hot and clean burning so the surface melting happens quickly without the soot.

Have you tried wiping with Acetone?

 

[Firstram]

Is that a Bernzomatic torch head on the mapp tank The torch on the blue bottle isn't very good at making intense heat. As thin as that part is, flame finishing without warpage might not be an option.

Your next acrylic project should work out well though!

 

[strantor]

That's why Hydrogen and Oxygen works so well. It's incredibly hot and clean burning so the surface melting happens quickly without the soot.

Well I never thought that building a "HHO Generator" would be on my to-do list but here we are...

Have you tried wiping with Acetone?

Yes it doesn't respond like ABS. There is a reaction but it's different. I have found that if I sand with 320, 600, 1000, and 2000, then wipe it with a blue shop towel (the ones on the roll) that was recently wet with acetone but half-way dried out now, it turns like glass. But if the rag is too wet or too dry it doesn't work. If you brush it on, something weird happens. It's like a new substance is formed. Some kind of boogery white stuff and the surface of the polycarbonate turns milky and worse than before. The process is too labor intensive (all the sanding) and unpredictable.

Someone on the internet said PC is dissolved by MEK like ABS is dissolved by acetone, but I haven't tried MEK yet.

 

[Firstram]

I know wiping PC with Weldon #4 acrylic adhesive does a fair job but, you would still have to sand it flat.