frustrating first layer problem w/photo

I'm suddenly having some difficulty with sections of my first layer "bubbling." (see attached photo) At first I thought it was a bed leveling issue, but I dialed it down to the point where the nozzle was starting to gouge the blue tape and the same problem results. It never seems to be in the same spot either. If the bubbling is minimal, the rest of the layers and model print perfectly. If this was something I was printing for myself I wouldn't care, but I sell these and to have the bottom looking all scratched up and gouged (which is what the bubbling looks like from underneath) is going to cause customer complaints. Below are my settings, which haven't failed me until now -

Software - Simplify3D
Filament - PLA 1.75 mm
Temp - 205, bed at 50
Surface - Blue tape on glass
First layer - 250% height, 30% speed (normal print speed is around 55 mm/sec)

Given that this doesn't seem to be a bed leveling issue, the only thing I can think of is I've got a weird batch of PLA or a "bad" roll of blue tape. Any other ideas?
Attachment 3224

Looks like you are over extruding the first layer. Why the 250% first layer height? Might have your initial nozzle clearance too close.

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Originally Posted by jfkansas

Looks like you are over extruding the first layer. Why the 250% first layer height? Might have your initial nozzle clearance too close.

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Based on experience mostly. I was having trouble getting my prints to stick to the 3M blue tape I have and S3D mentioned in their tech blog that increasing the layer height to 200 or 300% was sometimes helpful in getting the first layer to stick. I played around with it and found that 200 - 250 seemed to give me full "stick" 99% of the time. Maybe it's something about this particular model design and that first layer height. I'll try dialing it down a bit to see if it improves.

200-250% raises the distance between the extruder and build plate. The default 90% makes the first layer smash into the build plate a little more. 200-250% may not "smash" at all.

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Originally Posted by jfkansas

200-250% raises the distance between the extruder and build plate. The default 90% makes the first layer smash into the build plate a little more. 200-250% may not "smash" at all.

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Yes, but I believe at 200% it also extrudes 100% more filament than at the normal level, right? That's what it looks like and that was the impression I got from the S3D blog. They said that higher layers like 200-300% were especially useful when printing at fine layer heights because the "extra thick" first layer helped to even out bed alignment issues and give the model a nice cushion to build on. I just know that it fixed issues I was having with first layers sticking...at least until now.

I prefer to print 4-6 floor layers. Than one big thick one.

If the print head is too close to the print surface it will do that. It's being blocked as it travels.

Is the first layer starting distance the same thing?
I have been trying to get an ABS print started and the raft cross layers are not even sticking to one another very well, I am using S3D , the nozzle temp is up to 240C and I have slowed the speed to 2400 mm/s

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Originally Posted by LakeDuck

Is the first layer starting distance the same thing?
I have been trying to get an ABS print started and the raft cross layers are not even sticking to one another very well, I am using S3D , the nozzle temp is up to 240C and I have slowed the speed to 2400 mm/s

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Lower the heat, 240c is too hot really unless its wood or flex filament. 230c should be fine, any hotter and it will melt the top layer because its lingering there too long. Too slow, and the same thing happens.

If the first lines being laid down are not close together, as in enough to touch eachother, the build plate needs levelling again.

200% is fine for a first layer but only necessary of you build plate is not flat. s3d does increase the extrusion amt when you increase the first layer height to still keep your extrusion width in spec. if your build surface is flat then just keep it simple and have your first layer at 100%. if its not too flat then increase to 150 and maybe 200 but dont go over that. as geoff said it could be that your too close to the sureface. it could also be that your surface isnt clean. looks almost like there could be some contamination there and in certain areas the plastic isnt sticking to the tape. did you wipe the tape with anything before you printed on it?

if you're using s3d - it's actually easier to add an extra process and print the first few layers at 0.3 mm and then increase resolution for the rest of the model in a second process.
That way you're not screwing with the extrusion rate.

And maybe think about adding an actually flat bed to the machine. I use an extra 3mm aluminium plate, but glass is also popular.
And try switching to duck brand blue tape. Everything sticks to that stuff !
Often more than I'd like :-)

s3d also daoes a nice raft that can be used for compensating for unlevel bed.

I seem to have discovered the fix. I lowered the first layer height back down to 100% and it printed just fine. Clearly I need to stop screwing with that. I think aardvark's advice is probably what I'll follow in the future...just print the first few layers thicker and not mess with the extrusion rate.

As far as build surface, I'm using the thick glass plate that's sold by FF. I love it! I just wish I could get PLA to stick directly to it. That's one of those things that eluded me for so long I finally just gave up trying. I now use 3M blue tape which is excellent. Once the model cools it will, more often then not, pop off the bed on its own. I have to remind myself to change the tape once in a while because it'll last that long. For the problematic prints I have a roll of some generic blue tape from the local hardware store. PLA sticks to the stuff like cement. But the problem is that it sticks so well that the blue tape gets ripped to shreds pulling the print off as well as leaving bits of blue tape embedded in the model that are sometimes impossible to remove.

you can get round the over stick with blue tape. By not heating the bed - at all.

I find that with room temperature prints the pla sticks well but comes off fairly easily.

If I heat the bed - it just sticks like superglue.

I use 60C on the glass plate, and I have the 6mm glass. PLA sticks very good to it.

If I run lower than 50C I have problems with it sticking, at no heat on the bed it won't stick at all and just oozes around the extruder :P

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Originally Posted by roykirk

I seem to have discovered the fix. I lowered the first layer height back down to 100% and it printed just fine. Clearly I need to stop screwing with that. I think aardvark's advice is probably what I'll follow in the future...just print the first few layers thicker and not mess with the extrusion rate.

As far as build surface, I'm using the thick glass plate that's sold by FF. I love it! I just wish I could get PLA to stick directly to it. That's one of those things that eluded me for so long I finally just gave up trying. I now use 3M blue tape which is excellent. Once the model cools it will, more often then not, pop off the bed on its own. I have to remind myself to change the tape once in a while because it'll last that long. For the problematic prints I have a roll of some generic blue tape from the local hardware store. PLA sticks to the stuff like cement. But the problem is that it sticks so well that the blue tape gets ripped to shreds pulling the print off as well as leaving bits of blue tape embedded in the model that are sometimes impossible to remove.

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I don't think it is ever a good idea to go over 100% even if the extruder compensates by pumping out more filament. You want that first layer to smash a little more into whatever adhesive, tape, or slurry you have applied to the build plate.

When set your z axis gap in several spots using a piece of paper that isn't the starting point of the print for the zaxis. It will move down .2mm x (first layer height percent). So .2mm x .9 = .18mm, subsequent layers will be .38, .58, .78, etc. This can all be read when looking at the Z moves in the gcode.