Any luck printing transparent polycarbonate?

[7milesup]

Acetone will cloud PC.

Might want to check this web page out.

Polycarbonate Chemical Compatibility Chart

www.calpaclab.com

 

[strantor]

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

Thanks, never heard of it. Just ordered some. Will see how it goes.

 

[strantor]

I will do whatever post-processing is required but I really would like to solve this at some point before the part gets printed, and I had an idea about that. I started to type this up but thought toddler illustrations would be more effective.

As long as I print the part with aligned layers (aligned rectilinear infill or solid part made of nothing but perimeters), it is ultra clear from top to bottom, through those narrow channels that are created when the extruder lays down layer after layer of the exact same pattern on top of the last. But it is ONLY clear from that orientation.

I think that if I could stagger the perimeters by making the outer perimeter of every-other-layer be half-width, these problematic holes would be filled in for the most part.

But there is no option to do this in slicer, so here is my idea: I edit my model to create a repeating pattern that matches the layer height I slice at, having protrusions that are half the width I extrude at, to trick the slicer into doing what I want:

This is not a feasible solution for clear parts, always needing tedious modifications to the 3D models and post processing, but it is a proof of concept to see if I am on the right track. If it works as I envision it, then I can look for a permanent software solution that does what I want.

 

[Flyinfool]

another thought, try printing with either a slower head sped or faster filament speed to have the material available to fill those corners.

I do not know if is applicable to PC but look up vapor polishing, it is used on ABS to smooth the surface.

 

[strantor]

another thought, try printing with either a slower head sped or faster filament speed to have the material available to fill those corners.

I do not know if is applicable to PC but look up vapor polishing, it is used on ABS to smooth the surface.

Yeah I've tried everything from full turtle to full rabbit and it didn't make much difference regarding filling in the gaps. Most manufacturers of PC filament recommend 50mm/s or lower and right now I'm running about 18mm/s, but with a 0.8mm nozzle, 0.64mm layer height, and 2.4mm line width to keep my extruder maxed out at around 30mm³/s volumetric flow so prints don't take all day long.

These super thick and fat lines result in much better "corridors" or "light pipes" through which one can see.

These super thick and fat lines one would also expect to result in much larger "holes" as I circled in red earlier, but I did also try the super fat lines with much lower layer height and this didn't seem to improve the result at all. Not sure why. I think I need to look deeper into that. Maybe shorter layers was the right direction to go, but I saw no improvement due to some other setting I was experimenting with at the time.

So many variables! This business of trying to find the right combination of variables X, Y, Z, E, T, and C is most frustrating. It feels like 2011 again, when slicers didn't come out of the box with default profiles that worked. I thought all this was behind me, and I guess it would be if I stuck to the beaten path, but the physical properties that Polycarbonate offers are things I just can't get from the usual suspects.


On that topic, I have good news. A rather large investment of time and Overture PC Professional polycarbonate was lost sometime last night (the bad part of the good news):

This was due to dribble that PC seems to exhibit no matter what. It builds up in certain spots and forms obstacles for the print head. As a result of this failure I switched over to Polymaker Polylite PC and what a difference! Very little dribble! The dribble is nonexistent for most of the print, but when it does happen, it's so insignificant that it gets buried in the layers and doesn't build up. Very smooth top on all layers, no nasty crunchy dragging sound during travel moves. Mucho more gooder.

The Polylite doesn't seem any more or less clear than PC Professional, and exhibits the same refraction through layer lines.

 

[ttabbal]

Interesting problem. I honestly think this part is too thick to get good transparency from FDM. The layer lines work against you for that, as you're discovering. I think it would be far easier to get a solid piece of PC or Acrylic and machine it, then polish the tool marks off, finished with flame polishing.

You might make spots over the LEDs with a hole and thin lens at the end. Or, if you can convince the slicer to do it, spiral patterns to build a sort of light pipe. Then the last bit would act as a diffuser to spread it out. Maybe 100% concentric infill?

I have no idea if it would be better or worse, as I don't work with PC on printers. No reason, just never needed to. What about the trick people are using to heat treat parts? Bury it in fine salt, put it in an oven at about the glass transition temp for a few hours. The idea is to melt the layers together better. The salt forces the part to keep it's shape. It does leave surface imperfections from the salt, but you would machine/polish those out. It might help make the internal layers more consistent for light to pass. It might also be a huge waste of time, I'd try it with a small test part first.

 

[Lo-Fi]

Are you 100% sure it's not a bit of under extrusion? Looks suspiciously like you're not fully filling the gaps.

Apologies for not replying to your other thread yet. Time has been short and it requires more thought than a quick response!

 

[pdentrem]

 

[strantor]

Are you 100% sure it's not a bit of under extrusion? Looks suspiciously like you're not fully filling the gaps.

Yes I am sure. It is very hard to see if the gaps are filled, even with the thing in your hand. This "quasi clear" stuff causes optical illusions. But I have enough failed prints to have gotten tired of breaking parts "for science." They break as if they were molded parts. They do not come apart at the seams.

There are some gaps in tight corners, but those gaps exist in the slicer too. It is because I am printing such wide lines with such a fat nozzle.

Apologies for not replying to your other thread yet. Time has been short and it requires more thought than a quick response!

No worries! Nobody under any compulsion to reply. Thanks!

 

[strantor]

Interesting problem. I honestly think this part is too thick to get good transparency from FDM.

You're probably right but I think it is possible to get nearly there. My staggered line slicer test that I described in post #13 yielded promising results. I will post about that later after I post process it but for now here is the "before" pic:

The clarity is much better but still you can only see through it well from one perspective.

The part is 3/4" thick and here's how it looks from the side:

The layer lines work against you for that, as you're discovering. I think it would be far easier to get a solid piece of PC or Acrylic and machine it, then polish the tool marks off, finished with flame polishing.

You're absolutely right but chunks of polycarbonate in the dimensions i would need to machine are incredibly expensive. The idea here is to 3D print the chunk with already 90% of the machining not needed, and lighter than it would otherwise be, because of infill.

You might make spots over the LEDs with a hole and thin lens at the end.

not sure what you mean. I'm not doing anything with LEDs. The parts I've shown thus far in this thread are slewing ring bearings with 10" OD and swivel vacuum fittings flanges with 6" OD.
EDIT: oh yeah, and some bike pedals.

Or, if you can convince the slicer to do it, spiral patterns to build a sort of light pipe. Then the last bit would act as a diffuser to spread it out. Maybe 100% concentric infill?

I'm basically accomplishing this already, using 100% perimeters as 100% infill.

I have no idea if it would be better or worse, as I don't work with PC on printers. No reason, just never needed to. What about the trick people are using to heat treat parts? Bury it in fine salt, put it in an oven at about the glass transition temp for a few hours. The idea is to melt the layers together better. The salt forces the part to keep it's shape. It does leave surface imperfections from the salt, but you would machine/polish those out.

no i have not tried that. Heard about it, but seems labor intensive. I will try it though,, if nothing else pans out.