CPE / PETG terrible first layer & surface quality

[Smithy 1,144]

Hi

I aborted yesterday a print with Ultimaker CPE because the first layer was really bad. I had a lot of crumbs on the top of the first layer. I searched the forum and found some others with the same problem, but without any useful solution. I have to say, it was the first time I printed CPE with the 0.4 print core, before with the 0.8 print core it was ok or not so much that I had to abort the print.

 

Then I thought, maybe the spool got too much moist in the last days and repeated the print now with a fresh spool Colorfabb XT - but its the same.

 

What is it? Bed was leveled before print with auto leveling. Is it an over extrusion on the first layer(s)? Or is the nozzle too near at the bed?

 

Here some pictures from the Colorfabb XT, the CPE yesterday had more crumbs and bigger crumbs.

 

Thanks!

Edited August 26, 2018 by Smithy

[StephanK 30]

I just ran into the same thing, first print using CPE on my UM3 and my first layer looks the same. Two ways to go about this usually:

a) increase the nozzle <> bed distance, but so far I haven't found a good way to do so on the UM3 with active levelling turned on. (ActiveLeveling is setting the nozzle too close consistently imo)

b) reduce flow% - there's even a initial layer flow% now that should work well to fix this. (just about getting ready to try it here)

Your blue tape is probably not helping here, either, as it further reduced the gap between the nozzle (or was it on there during Active leveling?). May I ask why the tape? Bit of gluestick or magigoo or printafix works really well for adhesion..

 

[Smithy 1,144]

I have played in the meantime with the temperature, default was 245° and I decreased it to 235°, which helped for the second layer. But you are right, the Initial Layer Flow setting would be better. How much have you reduced the flow?

 

And yes, the blue tape makes the distance between bed and nozzle even more smaller. It was there during the leveling, but I have the tape only in the center of the bed, so leveling was done outside without tape.

 

Maybe for CPE no blue tape is needed, I haven't tested it yet without, but the Colorfabb XT which is quite similar, didn't stick on the bed without. I tried normal glue stick before, but had no luck. But good to know, the next print will be with glue stick only.

 

Thanks!

[Smithy 1,144]

I have to print now 5 pieces of the same object and I have to print them with UM CPE light grey - good test for various settings.

 

The first one was printed with default settings, just with 90% Initial Layer Flow. That was not really better, same result on the first layers, but ok afterwards.

 

Second try now runs with 80% Initial Layer Flow and -10° print temperature because I have the feeling that the default profile for CPE prints a little bit to hot. I had some stringing and some crumbs on the inside walls of the object, so lets try if a little bit cooler is possible and give better results.

 

And @StephanK you are absolutely right, UM CPE sticks well on the glued glass bed, no need for blue tape. Colorfabb XT which is also PETG doesn't work with only glue on the bed.

Edited August 26, 2018 by Smithy

[Smithy 1,144]

The first layer with a lot of crumbs are nearly gone with 80% Initial Layer Flow and -10° temperature. But the crumbs on the inside are still there. I am also not sure if I see under extrusion on the walls with the crumbs or is it something else?

 

The outside wall looks also a little bit strange, first I thought over extrusion, but must something else.

 

For the next part, I still use 80% flow for the first layer, but with default temp for CPE, but now with lower speed of 40mm/sec instead of 60mm/sec.

 

Does it make sense to play also with the general flow setting?

 

[Smithy 1,144]

Printed now with the settings from my previous post, so mainly slower. The result was, that the outer wall was nearly fine and smooth. But the inner wall has still these crumbs. Additional due the higher temp again (default temp) there is a little bit of stinging, but not too much and I read that stinging with CPE/PETG is quite normal when not too excessive.

 

I assume, that these crumbs inside are rest of the end of a layer and that these crumbs are not stick enough to the bottom layer, before the head travels away. The extruded filament is still hanging on the nozzle and therefore some small chunks are missing in the wall and hanging as crumbs around.

 

So thats my presumption, but I don't know how to fix it. Any Ideas? Or does someone have a general advise how to print with Ultimaker CPE successfully?

[P3D 46]

I have the same problem (crumbs and holes) with black CPE, especially when printing multiple parts. Anyone printing successfully willing to share their CPE settings?

[IRobertI 520]

Have you tried letting it keep printing? How the first layer looks doesn't really matter in 99% of cases since it immediately gets hidden by the rest of the print. To me it looks like the first layer is slightly too close which causes some plastic to squeeze out on the side of the nozzle. I would try going back to defaults and letting a whole print complete (you can print something smaller obviously to not waste too much plastic) just to check if the other print issues stay or go away with the defaults.

[Smithy 1,144]

Yes I did, when the bottom is thicker than it doesn't matter, but it needs 3-4 layer until the crumbs are totally hidden, so it is not just the first layer. I could improve it with setting 80% initial layer flow, then it is still a little crumbly but so not much that will not hidden by the next layer.

 

But and this is my bigger problem, that the final print is also not really beautiful. Look at the images in my previous post here.

The outside of the object was better (no picture) after slowing down to 40mm/sec, but the inner side of the object is still terrible and I have currently no more idea how to fix it. I suppose that the small junks inside (see picture) are the end of the layer, plastic is extruded, put an the layer and then the head move away and pulls some of the freshly layer away. Because nearly at every crumb there is also a hole. But could be also some other reason.

[Smithy 1,144]

Printing currently the next part (good that I need 5 of them) and I analyzed the travels in Cura. There are no travels away from the wall, so my assumption that some layers is pulled off at travel begin was wrong, there are no travels away from the object.

 

I am printing with Fast profile (0.2) and changed only first layer flow to 80% and reduced speed to 40mm/sec. All other settings are profile defaults.

 

But I observed the print some time now and I think it comes from the infill. So the crumbs inside the object is plastic from the infill which is not clean printed. Maybe due the very small object wall. I have just 1-2 mm infill and therefore it is not clean placed in this small space.

 

Next part will have more infill (currently 20%) or try another infill pattern. Maybe also slow down the infill speed a little bit (currently 40mm/sec)

 

But for initial layer crumbs, the setting 80% flow for the first layer helps a lot.

Edited August 27, 2018 by Smithy

[Smithy 1,144]

OK, no change, I still have the crumbles inside the object.

 

I come to the conclusion, that CPE is not really good to print. I have no issues with warping or that it is not sticking to the bed, absolutely no problem, but the quality of the printed object is not good. Most of the issues can be "repaired" in post processing, but sometimes I have black dots in the surface of the light gray filament, maybe a burnt piece of plastic. 

 

I am also wondering, that there is so low feedback to this topic, I assume that there are not a lot of people printing with CPE, maybe they know why ? 

 

I have also a black spool of CPE and will try if it is better, maybe its the spool itself or the color that makes problems. Read that white should be generally more bad than other colors. But I think I will not buy more CPE material, the frustration is much higher than the benefit of the material. I have also printed with Colorfabb XT and there are also some crumbs but the surface quality is much better. 

 

Is someone has some tipps how to get a beauty surface with CPE and want to share the secret of his settings, you are welcome!

 

 

 

 

[P3D 46]

I'm currently running a temperature test tower with 5°C increments, but so far there doesn't seem to be much difference between the temperatures. It's a pity, with XT I get a lot of blobs/zits on the surface, which is also annoying, but not as bad as the crumbs with CPE. Seems PETG is not the "wonder material" that some people claim it to be.

 

[Smithy 1,144]

I tested a bit with the temperature, but the effect was always there. With lower temperature I had less stringing, but this is not annoying, can be easily removed. But the crumbs and are sticking well on the surface and when removed it leaves a viewable mark on it.

 

 I have no more idea how to get a smooth surface. I tried to print slower, which helped a bit (40mm/sec) but no difference to 30mm/sec. Played with infill, thought that could be caused by travels of the head, but nothing.

 

For me, CPE is only workable for functional parts, that are not really visible, because of the bad surface.

[Smithy 1,144]

Here some pictures from another part printed with CPE - same problem:

 

But interesting, the top layer is perfect ?

 

I am really interested if this is normal for this material, then ok - lessons learned, or if there is something working with the setup.

[P3D 46]

Did you already try switching to another infill type? One suggestion I heard is also to disable combing... if I get around to do it, I'm gonna run some test parts, checking some of these things out.

BTW, here is the temperature test tower - encourages me to actually print hotter instead of cooler, contrary to the typical PETG advice.

[Smithy 1,144]

No, I haven't changed the infill type, just reduced the speed of the infill. Combing is interesting, I will try it with the next part.

 

Yesterday I also thought, that I could try to print a little bit hotter, because I just tried to print cooler and maybe this could really help when I look on your temp tower. Per default it prints with 245 I think, so 250 or 255 could be worth to try.

 

I printed yesterday some parts that were straight objects like boxes, no overhangs not curved or something like that and the quality was quite good.

Edited August 29, 2018 by Smithy

[P3D 46]

So I did some test parts - and I think I have identified the culprit. See for yourself- first with combing enabled: 

 

And the same part, with the same settings (Standard CPE profile, 0.2mm layer height)., but with combing disabled: 

 

To be fair, there was quite some stringing with the combing disabled (I removed some of the strings manually before taking the photos), but you can remove the strings quite easily using a heat gun. Personally, I'd choose stringing over those strange crumbs and holes every time.

 

 

 

 

Edited August 30, 2018 by P3D

[Smithy 1,144]

Looks good, stringing is easy to remove and leaves no much defects in the skin. The crumbs are terrible, I post processed now 9 parts from the last days and tried with blade knife, finger nails, etc. to remove most of the crumbs. Problem is, that the holes are still there of course.

 

If combing off is the solution, then the reason must be, during combing and traveling within the object, that there is not retraction. As far as I know, there is only retraction when traveling outside with combing off. PETG is known to stick well everywhere, so also at the nozzle, maybe the last few mm of a layer are sticking to the nozzle and is pulled off to end in a crumble. Who knows, but it could be possible.

 

Thanks for your tests, I will try it with the next CPE part and have hopefully the same results.

[P3D 46]

Speaking of retraction, I found a setting to enable retraction for combing. When enabling this ("Max Comb Distance With No Retract" = 0.1mm), there is less stringing this way, while maintaining the good inner surface of the part. The outer surface seems to be just a bit worse, so I'll probably stick to just disabling combing.

[Smithy 1,144]

Ok, but maybe, depending on the part, worth to try.

I have to print today another part in PETG (Colorfabb XT, not CPE), so maybe I try there the CPE settings we found. XT is also a bit crumbly but not so bad with normal default settings as CPE.

[P3D 46]

I tried XT too. I never had crumbs with XT, but I could never get rid of those small blobs/zits on the walls, so I decided to try CPE - and now that I've got rid of the crumbs, I'll probably stick to it.

[Smithy 1,144]

Have your tried combing off with XT as well ?

[P3D 46]

Yes, I have, but it didn't seem to make much of a difference. It doesn't hurt to turn it off probably, if you're Ok with some stringing. 

[Smithy 1,144]

I am currently running a job with white Colorfabb XT and is fantastic. No crumbs and no stringing so far with default CPE material settings. I just lowered the speed to 40 and changed the initial layer flow to 80% to get a clean first layer without crumbles. 

 

But lets see when the print has finished, still 6 hours to go, then I can say if the surface is fine.

[Smithy 1,144]

Print finished and it looks great. No stringing, no crumbs, perfekt skin. So after using both CPE and XT, I like XT much more. Only annoying issue is, that CPE stick well with glue stick on the bed and XT not. But I will try it again with just glue, because the blue tape is also not the best solution. XT sticks too good on the tape and after each part I also have to renew the blue tape.

 

I am now printing another part with XT but with layer height 0.2 and default speed of 60mm/sec and I can see now more crumbs and stringing, so I think best is 0.15 and slower for XT.