Is this still stringing? PETG

[NickB 2]

So I know stringing this is a common problem with petg but I am not sure this is stringing.

it looks like there are blobs on the side walls. Some of the the begin or end of a string

But on the straight is does not make sens that there should be stringing.

 

So my question is, is this stringing or something else and how can i fix this.

 

I have already made a temp tower (245 was optimal).

I also made some stringing test where I changed the retraction distance but those came out quit good
         -temp: 245        retraction distance 5 7.5 & 10mm        retraction speed 35mm/s

[Oliveros 11]

I'm seeing similar stuff on the PETg I'm printing with.

 

When I'm checking on it, it seems like it's blobbing up on the head, perhaps doing a Z offset would be helpful, I haven't done anything other than increasing retraction distance and speed since it's not a big problem for me, but perhaps that would help.

[geert_2 558]

The PET I have does similar things:

 

- While printing, it accumulates on the nozzle. This goo then gets brown, and sags onto the model, and is deposited as big brown blobs. The brown color is clearly visible on white, but it may not be visible on black. These blobs also tend to cause fine hairs in the print, both when the blob sags from the nozzle, and when the nozzle passes through previously deposited blobs.

- When bridging, it does not pull a nice bridge. But the strand rather tends to snap like chewing gum and fold back onto itself, causing a blob under the nozzle. This is then deposited onto the next wall upon arriving there.

- When traveling through air, the nozzle leaks a little bit (overpressure in the nozzle that is releasing), also causing a little blob or "insect antenna" onto the next wall.

 

It looks quite similar to what you have. Watch carefully while printing, and you can see it happen. Printing slow and cool reduces these effects in my models, but I can't totally eliminate them.

 

[NickB 2]

3 minutes ago, geert_2 said:

It looks quite similar to what you have. Watch carefully while printing, and you can see it happen. Printing slow and cool reduces these effects in my models, but I can't totally eliminate them.

 

So I have been doing test all day and I got rid of most of it by:
-Reducing the flow from 100- 92.5.

-Max retractions from 25-100
-avoid parts when printing OFF

 

I still have a tiny 'antenna' left and a couple of fine hairs but no more blobs.

 

Edited October 15, 2019 by NickB

[Oliveros 11]

Good to hear it improved, do you have a Z offset for your PETG? 

 

Ridgid INK. Matterhackers and some other people highly recommend it, some even require it to print PETG. I haven't done it with my PETG prints but perhaps it would help for you, just offset it by 0.02 MM which will keep the nozzle a little more clear of any already laid down plastic, which in turn should help reduce the blobs.

[NickB 2]

15 hours ago, Oliveros said:

Good to hear it improved, do you have a Z offset for your PETG? 

so I did a test with and without the Z offset and it did not make any visual difference.

 

I did al my tests with a layer height of 0.1mm and these are the settings I got the best results with(on an Ultimaker S5):
     temp: 245/70
     flow: 93.5    
     max retractions: 100    

     avoid parts: ON    

     retraction speed: 35    

     retraction distance: 10    

     coasting: OFF    

     Z offset: 0

And then I changed the layer height to 0.2mm and it came out even better.
Here are some pictures of the tests:
     first pic is best result.
     second is in PLA.
     third is first and last result
     forth is first/worst test result

Edited October 16, 2019 by NickB

[NickB 2]

So now that the smal part are oke I went a bit bigger but then I noticed something wierd.

 

When there are small bits of infill it sort of curl up and does not stick very well to the previous layer.

The bits of curled infill next to the wall get picked up by the nozzle and drops them later on.

 

I lowerd the infill speed so it would have some time to stick to the previous layer.

I dropped from 70 to 50 mm/s but it looks like it does not have very much of an effect.

 

Any ideas on how to fix this?

 

[geert_2 558]

Maybe there are different infill patterns, or infill percentages, in which the nozzle follows a different traject with less starts and stops, and less jumps? I don't know if this is possible, but just guessing. Check this in layer view in Cura, before printing.