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PETG printing surface

Posted by SupraGuy 
PETG printing surface
February 07, 2018 08:30AM
I am having a frustrating time printing ABS. PETG is supposed to have less issue with warping, but I cannot get a good first layer, which in turn means that everything else is terrible.

I've tried printing on clean glass, hairspray, kapton tape, and unheated on painter's tape.

My printer doesn't like to extrude at more than 230 deg C, so if hotter extrusion will fix it, then I guess I'd better start fixing the *&%#@ firmware.



On the bottom surface, I get ripples and bubbles during the fill process. The plastic is often still fairly soft and flexible when I scrape it up on a heated bed.

The square on the right was particularly bad, here. The centre square is far more typical of the results that I see when trying to print stuff.

This is print on glass with glue. Bed heated to 80 deg C, print chamber is warm, extrusion at 230 deg C.


Prusa i3 / Arduino Mega 2560 / RAMPS 1.4
Kit from a2aprinter
Beltless redesign in progress to move to T8 lead screw drive

MBot3D Printer
Kit from Amazon
Some teething pains, but a reasonably good printer, just missing a heated bed.
Re: PETG printing surface
February 07, 2018 09:24PM
try increasing the Z offset by +0.1 mm and also the retraction length. You can also increase print speed on first layer. I get the same thing with PETG which causes the nozzle to make noise as it scraps across the bumps and it only occurs on first layer the next layers print fine. I think your temp is ok. You can also reduce extrusion multiplier to 0.9 or 0.8 that helped me.
Re: PETG printing surface
February 08, 2018 07:25AM
So what you're suggesting is that it's too much "squish"

I get a very nice first layer in PLA or ABS, so I guess that I expected similar results. I'd be worried about reducing the extrusion multiplier, and getting thin extrusion for subsequent layers. Slic3r has a setting for the first layer, which I'll try adjusting.

I hear people talking about how smooth and nice the finish for PETG is, but so far, every bit of PETG that I've extruded has gone straight from the print bed to the trash bin. It would be nice to get something that I could use.


Prusa i3 / Arduino Mega 2560 / RAMPS 1.4
Kit from a2aprinter
Beltless redesign in progress to move to T8 lead screw drive

MBot3D Printer
Kit from Amazon
Some teething pains, but a reasonably good printer, just missing a heated bed.
Re: PETG printing surface
February 08, 2018 08:25AM
I found that PETG requires a completely different way of approach for the first layer.

With ABS you squish it in, that's for sure, you also squish PLA but a bit less than ABS...

With PETG, almost NONE, LIKE NO SQUISH. I print on PEI sheet and I use a fairly hot first layer and have the tip high enough to just lay it on the bed.
My first layer temp is hot something like 240c if I remember right as I am at work right now, then I drop to I think 230c after that.
My bed temp is about 60c.

Be careful, PETG can stick so well if you get things hot enough and squish too much you will actually pull chunks of bed out when you try to remove it!!!!

The trick to PETG IMO is getting things hot enough that they just lay there and don't get pulled around by the tip.
Think like your pouring a liquid and it does not harden until the tip is away from it.
PETG sticks as it cools, I found when my first layer was stuck too hard I dropped my bed 5c per step till I found my sweet spot for stick.

Takes a little playing around....

Edited 1 time(s). Last edit at 02/08/2018 02:56PM by JustSumGuy.
Re: PETG printing surface
February 11, 2018 01:47AM
Absolutely correct...!...thumbs up

Quote
JustSumGuy
I found that PETG requires a completely different way of approach for the first layer.

With ABS you squish it in, that's for sure, you also squish PLA but a bit less than ABS...

With PETG, almost NONE, LIKE NO SQUISH. I print on PEI sheet and I use a fairly hot first layer and have the tip high enough to just lay it on the bed.
My first layer temp is hot something like 240c if I remember right as I am at work right now, then I drop to I think 230c after that.
My bed temp is about 60c.

Be careful, PETG can stick so well if you get things hot enough and squish too much you will actually pull chunks of bed out when you try to remove it!!!!

The trick to PETG IMO is getting things hot enough that they just lay there and don't get pulled around by the tip.
Think like your pouring a liquid and it does not harden until the tip is away from it.
PETG sticks as it cools, I found when my first layer was stuck too hard I dropped my bed 5c per step till I found my sweet spot for stick.

Takes a little playing around....
Re: PETG printing surface
February 12, 2018 08:58AM
Well, until I do something about the firmware, my printer cannot manage 240 deg C. The normal overshoot range will drive it to it's shutdown point.

I think that I'll have to put off PETG printing until I get my other printer working.
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