What is causing my bottom layers to have large gaps?  

Re: What is causing my bottom layers to have large gaps?

First layers do look good.

What's your print temperature and what material did you print before the PETG? It could be a partially clogged nozzle, too low a temperature or something else. If you printed with something like flexible filament before I find running some PLA through at 240-250 helps clear it out since the PLA is much stiffer than the PETG which may jam. Some cold "Atomic" pulls couldn't hurt either.

For PETG I use 240-260 nozzle and 85-90 bed temp. Anything lower and you risk it jamming/clogging when you move away from the bed (the heat from the bed helps it keep its temp better). Also, do a PID tune just in case your nozzle is dropping down to 220 if you set it at 230.

Re: What is causing my bottom layers to have large gaps?

Thank you for your thoughts.

I don't think the nozzle is clogged, but I'll try a cold pull just to be sure. I printed the silver Prusa PLA that came with the printer before the PETG, nothing fancy.

For temperature I've been using the default temps from Slic3r Prusa Edition, 230 for first layer then 240. I'll try raising the temp a bit and see what changes.

So far what I've been doing is raising the Live-Z by 1/100th of a mm a time, and checking the difference.

The top one is the first print from my previous picture, Live-Z at -0.975. Then follows from top to bottom Live-Z at -0.965 and Live-Z at -0.955.

Re: What is causing my bottom layers to have large gaps?

If you use Prusa Slic3r, it may be due to over extruding. I had similar problems and especially when I used infill Honeycomb and PETG.
It just smelt the pattern together.
The problems disappeared when I started to use Simplify3D as a slicer.
The FFF profile "Prusa Research Original Prusa i3 MK3.fff" worked better than "Original Prusa i3 MK3 v2.fff". Both are available here on the forum.

Re: What is causing my bottom layers to have large gaps?

Thank you for your thoughts.

I don't think the nozzle is clogged, but I'll try a cold pull just to be sure. I printed the silver Prusa PLA that came with the printer before the PETG, nothing fancy.

For temperature I've been using the default temps from Slic3r Prusa Edition, 230 for first layer then 240. I'll try raising the temp a bit and see what changes.

So far what I've been doing is raising the Live-Z by 1/100th of a mm a time, and checking the difference.

The top one is the first print from my previous picture, Live-Z at -0.975. Then follows from top to bottom Live-Z at -0.965 and Live-Z at -0.955.

The live z adjust won't affect layers after the first. If your solid 5 layers on the bottom are fine then you don't need to adjust it.

Re: What is causing my bottom layers to have large gaps?

The live z adjust won't affect layers after the first.

If the first layer is squished, it can become uneven. Couldn't that affect following layers?

If your solid 5 layers on the bottom are fine then you don't need to adjust it.

But they aren't, only my first layer is?

Re: What is causing my bottom layers to have large gaps?

I had a similar problem when I tried PETG (Inland brand, not Prusa). My solution was to raise the print temperature to 250.

Re: What is causing my bottom layers to have large gaps?

I'm trying to print PETG from Prusa, and while I can get my first layer to stick to the bed, I'm having trouble with the subsequent layers. They clump together in some places.

There are supposed to be five full layers - including the first layer - before the infill pattern starts. Four of those layers have clumped together in places, allowing the first layer to peek through.

Does anyone have a hint to give as to what I'm doing wrong?

Had the same exact issues and I just resolved it. Had to lower first layer print speed to 15mm/s and raise Z by .20 mm.

Re: What is causing my bottom layers to have large gaps?

I'm trying to print PETG from Prusa, and while I can get my first layer to stick to the bed, I'm having trouble with the subsequent layers. They clump together in some places.

here are supposed to be five full layers - including the first layer - before the infill pattern starts. Four of those layers have clumped together in places, allowing the first layer to peek through.

Does anyone have a hint to give as to what I'm doing wrong?

are you running any fan? it looks like the nozzle is dragging the last layer with it in those spots. normally because it has not cooled enough, so 20% fan or so and you should be perfect.

Re: What is causing my bottom layers to have large gaps?

I'm trying to print PETG from Prusa, and while I can get my first layer to stick to the bed, I'm having trouble with the subsequent layers. They clump together in some places.

here are supposed to be five full layers - including the first layer - before the infill pattern starts. Four of those layers have clumped together in places, allowing the first layer to peek through.

Does anyone have a hint to give as to what I'm doing wrong?

are you running any fan? it looks like the nozzle is dragging the last layer with it in those spots. normally because it has not cooled enough, so 20% fan or so and you should be perfect.

Re: What is causing my bottom layers to have large gaps?

Ok, so here's how I resolved my issue which looks exactly like your issue.

First, I had to raise my Z by .20mm
Then I lowered the default slic3r nozzle temps to 220c
I lowered first layer speed to 5mm/s.... slow... so slow.... but it prints perfectly and everything sticks

Lowered the following settings:

Infill: 75mm/s (was set to 200)
Solid infill: 75mm/s (200mm/s again)
External Perimeters: 25mm/s
Small perimeters: 20mm/s

Lowering the speeds drastically improved print quality and the parts sticking to the bed properly. I kept having the nozzle move so fast when printing details that the end of the filament would be stuck to the nozzle and would pull away the part with travel.

Hope this helps!

Edit: running the new X axis parts and infill speed is still too high at 75mm/s. I lowered it to 45mm/s and it really helped. I noticed that if you print PETG too fast it doesn't get a chance to cool properly and it looks really bad. All of the fine details really came out at lower speeds

Re: What is causing my bottom layers to have large gaps?

Nvm to the above. Printing petg has been a hair pulling adventure.