Calibrated extrusion multiplier, yet still have gaps

[kartcrg]

Since I switched to the V4 and a new roll of the same filament I have been using (matchbox 1.75 black PLA), I haven't been able to have smooth top surface finishes without boosting the extrusion multiplier. Calibration cubes lead me to a multiplier of .93 yet I can see light through a two layer flat print. It takes a multiplier of 1.00 to get a flat, gapless surface finish. Filament measured in multiple places and entered in Simplify3D at 1.76. .35 nozzle with .4 extrusion width set, .2mm layer height.

Here you can see .93 vs 1.00 multipliers.




Am I missing something?
Thanks!

[Tim]

The several things that come to mind are (1) There is much more difference to be seen in a small bed-to-nozzle distance difference than in a small difference in extruder multipliers. (2) It may take some time to condition the new nozzle. I often have problems like that for the first print or so after swapping out a nozzle, or running a different filament type through the nozzle, depending on the filament. (3) Every roll of filament is different. (4) The extruder multiplier is a fudge factor that covers a large number of things that are difficult to impossible to predict.

So, no, I don't think you're missing anything, but with a new hot-end and a new roll of filament, you've changed a lot of variables. Be wary of effects due to the first layer height. Otherwise, 1.0 may be your new normal.

[Jules]

Agree with tim's first premise....it looks like a gap problem. (Nozzle is too far away from the bed. You're having to over-extrude with a multiplier of 1.0 to compensate.)

Might want to take the bed just a little bit closer to the nozzle for the first layer (decrease your Z-offset by -0.03 mm or so) and re-run your calibration squares. (Particularly the ones for height of the cube.) Keep doing that until you wind up with a square that is exactly 2.0mm tall.

The gap has a huge effect on the surface quality of my prints. Even a difference of .01 mm can mean the difference between a gappy surface and a smoother finish.

[kartcrg]

Thank you so much for the insight guys. The thing is, even if I squish the first layer flat and put tons of layers on top of it, the top layer finish still has gaps. I've always calibrated the first layer height by how it looks going down but double checking with the calibration cube, the height is dead on.

Anyway, I'll keep messing with it and find a happy medium. Thanks again!

[insta]

Thank you so much for the insight guys. The thing is, even if I squish the first layer flat and put tons of layers on top of it, the top layer finish still has gaps. I've always calibrated the first layer height by how it looks going down but double checking with the calibration cube, the height is dead on.

Anyway, I'll keep messing with it and find a happy medium. Thanks again!

Make sure your nozzle diameter is set to 0.35 in your slicer, and try another nozzle if you can. This sounds like a clog.

Alternately, check that your extruder is perfectly vertical relative to the bed. Sometimes a good whack will spin it in the holder (especially with the V3b) and you'll end up with weird behavior like this.

[kartcrg]

Make sure your nozzle diameter is set to 0.35 in your slicer, and try another nozzle if you can. This sounds like a clog.

Alternately, check that your extruder is perfectly vertical relative to the bed. Sometimes a good whack will spin it in the holder (especially with the V3b) and you'll end up with weird behavior like this.

Head is trammed. Z height is calibrated. Cleaned hotend and swapped the nozzle. Still need an extrusion multiplier of 1.00 for nice surface finish which I'd rather have than an accurate calibration cube. So be it I guess.

[Matt_Sharkey]

have you played with the different thicknesses? I found that changing the top layer thickness can have dramatic effects on the top finish.

[willnewton]

My feeling is that the behavior in a two-layer print is going to be a bit different than a calibration cube. Funky things happen at the interaction of the bed and the first layers and in your search for a setting that works everywhere may lead to lots of frustration. At some point, you might just have to say, this is a good two layer FFF setting, save it, and move on.

I might try a .12-.15 layer height to see if things improve. Possibly adjust your first layer height settings a percent or two.

I wonder if this is caused by S3D not liking the way the numbers work out. There is an odd bug in S3d that can cause issues when the layer height math works out the wrong way. You can fix it by changing the layer height from .2000 to .2010 or .1990 or by changing the first layer height % from 100% to 99% or 101%. It's a bit of a shot in the dark, but might rule out a software bug.

[kartcrg]

My feeling is that the behavior in a two-layer print is going to be a bit different than a calibration cube. Funky things happen at the interaction of the bed and the first layers and in your search for a setting that works everywhere may lead to lots of frustration. At some point, you might just have to say, this is a good two layer FFF setting, save it, and move on.

I might try a .12-.15 layer height to see if things improve. Possibly adjust your first layer height settings a percent or two.

I wonder if this is caused by S3D not liking the way the numbers work out. There is an odd bug in S3d that can cause issues when the layer height math works out the wrong way. You can fix it by changing the layer height from .2000 to .2010 or .1990 or by changing the first layer height % from 100% to 99% or 101%. It's a bit of a shot in the dark, but might rule out a software bug.

Hi Will,

Thanks for the input man - I'll definitely do some experimenting with these settings for the two layer print. On taller prints, I had to go back to the .93 multiplier as I was over extruding (very evident on the perimeter layers). Taller prints now look fine at .93, (even top layers), weird...