Poor first layer quality with PETG

[bitskrieg]

All,

Pulling my hair out trying to figure out what's wrong with my first layer when using Raise3D PETG:

If you'll notice, the raft below it looks perfect, and the shell looks ok too - it's just the infill that is the problem. I've quadruple-checked my slicer settings and I just cannot figure out what is causing it. The extrusion widths, percentages, print speeds, etc. are consistent, but I am getting radically different results as you can see. I used nearly identical settings for ASA (minus temps, fan speeds, etc.) and I didn't have any issues like this.

The follow-on layers are totally fine (minus the initial weirdness of filling in the gaps created by the first layer). I know it looks like under-extrusion, but I don't know why I don't have that issue on the other layers that use the same settings if it was truly under-extrusion.

When I look at the slicer preview, it looks totally fine as well. No idea what's causing it. Any ideas?

Using a Pro2 Plus, 1mm nozzle, .6 mm first layer height, .7 mm follow-on layer height.

Edit: I know that the z gap is necessary because of the raft and it has impact on first layer quality, but this is significantly worse than what I was experiencing with ASA.

[Steven@Raise3D]

All,

Pulling my hair out trying to figure out what's wrong with my first layer when using Raise3D PETG:

IMG_20210726_114917.jpg

If you'll notice, the raft below it looks perfect, and the shell looks ok too - it's just the infill that is the problem. I've quadruple-checked my slicer settings and I just cannot figure out what is causing it. The extrusion widths, percentages, print speeds, etc. are consistent, but I am getting radically different results as you can see. I used nearly identical settings for ASA (minus temps, fan speeds, etc.) and I didn't have any issues like this.

The follow-on layers are totally fine (minus the initial weirdness of filling in the gaps created by the first layer). I know it looks like under-extrusion, but I don't know why I don't have that issue on the other layers that use the same settings if it was truly under-extrusion.

When I look at the slicer preview, it looks totally fine as well. No idea what's causing it. Any ideas?

Using a Pro2 Plus, 1mm nozzle, .6 mm first layer height, .7 mm follow-on layer height.

Edit: I know that the z gap is necessary because of the raft and it has impact on first layer quality, but this is significantly worse than what I was experiencing with ASA.

Typically when using large size nozzles we do no suggest using a raft as it is very difficult to get the settings dialed in correctly? If you print this same model without a raft do you notice the same affect on the first layer?

[svandru]

I too have struggled to perfect printing PETG with a large nozzle. I think your issue is caused by the raft gap and the behavior of PETG. When printing on a raft, you under-extrude the first layer. The nozzle is at a layer height of 0.6 + [raft gap] but the extruder only puts out enough filament for 0.6mm. I don't think your shells really look better than the infill, though. When I zoom in on your photo, it looks to me like the shells are as much under-extruded as the infill and have a pretty big gap between them.

As to why it is different that the same object printed in ASA, I think that is due to the material properties. I have not printed ASA, but PETG behaves very differently than the PLA. TPU, NGEN and Nylon that I have printed, especially with a with a large nozzle. The beginning of a PETG line does not want to start, then it doesn't want to stick to the bed, often curling up and sticking to the nozzle. I think you can see at the beginning of your infill lines there is a gap before the filament starts to flow, especially on the shorter segments at the bottom.

The infill at the top of the photo looks quite acceptable to me, it is much better than farther down. The bed may not be perfectly level (trammed).

I suggest the following:

• Level the bed.
• Do away with the raft. Instead (if needed) use glue stick, Magigoo, etc. on the build plate, or try a PEX flex surface from WhamBam (that is what I use). Without a raft, you might want to print the first layer really slowly.
• Reduce print speed on the infill.
• Adding some Extra Restart Amount can help fill in some of those empty spots at the beginning of a line if you are using retraction on infill (maybe only on that first layer).
• Reducing acceleration on infill can also help with the empty spots (again, only on that layer if you happy with the others).
• If the Raise3D firmware offers it, adjusting linear acceleration or junction deviation for PETG can also help fill in those starting gaps. Those values will be quite different than for ASA.

I hope something above is useful.

[bitskrieg]

All,

Pulling my hair out trying to figure out what's wrong with my first layer when using Raise3D PETG:

IMG_20210726_114917.jpg

If you'll notice, the raft below it looks perfect, and the shell looks ok too - it's just the infill that is the problem. I've quadruple-checked my slicer settings and I just cannot figure out what is causing it. The extrusion widths, percentages, print speeds, etc. are consistent, but I am getting radically different results as you can see. I used nearly identical settings for ASA (minus temps, fan speeds, etc.) and I didn't have any issues like this.

The follow-on layers are totally fine (minus the initial weirdness of filling in the gaps created by the first layer). I know it looks like under-extrusion, but I don't know why I don't have that issue on the other layers that use the same settings if it was truly under-extrusion.

When I look at the slicer preview, it looks totally fine as well. No idea what's causing it. Any ideas?

Using a Pro2 Plus, 1mm nozzle, .6 mm first layer height, .7 mm follow-on layer height.

Edit: I know that the z gap is necessary because of the raft and it has impact on first layer quality, but this is significantly worse than what I was experiencing with ASA.

Typically when using large size nozzles we do no suggest using a raft as it is very difficult to get the settings dialed in correctly? If you print this same model without a raft do you notice the same affect on the first layer?

Printing without a raft seems to be fine - it's just when using a raft that I have issues with the bottom fill on the first layer. I've had some success with adapting the raft settings to work with a 1 mm nozzle with other thermoplastics, maybe this one just needs to be tweaked a little more.

[bitskrieg]

I too have struggled to perfect printing PETG with a large nozzle. I think your issue is caused by the raft gap and the behavior of PETG. When printing on a raft, you under-extrude the first layer. The nozzle is at a layer height of 0.6 + [raft gap] but the extruder only puts out enough filament for 0.6mm. I don't think your shells really look better than the infill, though. When I zoom in on your photo, it looks to me like the shells are as much under-extruded as the infill and have a pretty big gap between them.

As to why it is different that the same object printed in ASA, I think that is due to the material properties. I have not printed ASA, but PETG behaves very differently than the PLA. TPU, NGEN and Nylon that I have printed, especially with a with a large nozzle. The beginning of a PETG line does not want to start, then it doesn't want to stick to the bed, often curling up and sticking to the nozzle. I think you can see at the beginning of your infill lines there is a gap before the filament starts to flow, especially on the shorter segments at the bottom.

The infill at the top of the photo looks quite acceptable to me, it is much better than farther down. The bed may not be perfectly level (trammed).

I suggest the following:

• Level the bed.
• Do away with the raft. Instead (if needed) use glue stick, Magigoo, etc. on the build plate, or try a PEX flex surface from WhamBam (that is what I use). Without a raft, you might want to print the first layer really slowly.
• Reduce print speed on the infill.
• Adding some Extra Restart Amount can help fill in some of those empty spots at the beginning of a line if you are using retraction on infill (maybe only on that first layer).
• Reducing acceleration on infill can also help with the empty spots (again, only on that layer if you happy with the others).
• If the Raise3D firmware offers it, adjusting linear acceleration or junction deviation for PETG can also help fill in those starting gaps. Those values will be quite different than for ASA.

I hope something above is useful.

This was helpful, thank you. I think there are a conflation of factors causing this - part of it is that I think PETG is just less tolerant of uneven beds than other thermoplastics - it just wants to stick to everything (nozzle, itself, silicon shroud, etc.) and I think an uneven bed is exacerbating it. I'll do a nozzle height test and a full bed leveling today. Part of the reason I use a raft is to kind of hide those issues so I can focus on printing instead of tweaking the level every 20 seconds, but that may be counterproductive at this point.

I'll also tweak some stuff in ideamaker based on your comments and see what I can come up with - thanks!

[bitskrieg]

After doing a nozzle height calibration and a full leveling of the printing surface, the issue has mostly gone away. I think PETG is more temperamental than other thermoplastics regarding nozzle/bed gap, and the > .02 mm physical nozzle distance plus the extra z-height that is included right after the final layer of the raft plus the extra height included inherently because of the large nozzle size was just too much and was the root of the issue.

tldr; level your bed if you're having problems with PETG and large nozzle sizes.