Advice on first layer  

RE: Advice on first layer

This looks like a thick layer 1 - Live-Z could be raised a bit to help.  But...

This looks like a drive gear issue: filament is not being extruded evenly: either some teeth are full of debris or the gear isn't aligned with the filament path. Or even just poor QC in the filament diameter... but the change is fast enough it's hard to guess the cause. Could also be some weird resonance with the belt being too loose... again - really tough to tell.

And it MIGHT be underextrusion during fast infill ... but... 

RE: Advice on first layer

Hi Mike, 

Are you using the 7x7 mesh bed levelling or the 3x3 standard mesh bed levelling?

7X7 makes life a lot easier for you!
If you look again at your pictures and click on them,  they should open out to larger pictures now... 

this is because I have clicked theLink to Media File option in the bottom right of the window

Your pictures are showing ripples like the ripples you get in the sand, as the tide goes out... that means that your Live Z setting is too close to the build plate (Too large a negative number)
re run the test piece but reduce the Live Z 20  at a time and watch the printout, when you stop getting ripples, you are about the right level,

regards Joan

RE: Advice on first layer

Joan,

Thanks a lot for your advice (on both the first layer setting and how to better embed images :).  I'm using the standard 3x3 leveling.  How do I change it to 7x7?  That sounds like a great idea!

I suspected it may have been a Z height issue.  However, I don't see it everywhere on my test piece, only in some regions (maybe again pointing to imperfect bed leveling).  That's probably why it's more visible on pieces with a large footprint.  I'll play with the Z and see how it comes out and, if I figure out how, try setting bed leveling to 7x7.

RE: Advice on first layer

Tim,

Thanks for your advice as well.  I'm not sure if this helps to diagnose, by here is a more zoomed out image of the first layer (again apologize that it's not the best picture).  Upper-left seems pretty smooth, while bottom and bottom-right have ripples.  For this reason I don't think it's an extrusion issue as I would expect that to affect the entire layer.

RE: Advice on first layer

Posted by: joan.t

Your pictures are showing ripples like the ripples you get in the sand, as the tide goes out... 

Immediate flashback to the scene in the original Bladerunner movie. "Like tears in the rain..." I'm submitting this for the 3D printing "best poem or haiku" category this year. 

RE: Advice on first layer

Hi mdaneman, 

I had a very similar issue where the first layer was not printing smooth and had waves-like surface. This was not happening on the entire surface though, and I could overcome the issue by releasing the extruder idler screw a little bit (just enough tension to extrude properly). I am assuming that if it's too tight will cause the issue. Now I am having more reliable first layers. I hope this could help a bit. Cheers!

RE: Advice on first layer

It's possible the PEI sheet has surface imperfections from manufacturing -- pressure rollers that apply the PEI sheet to the steel that aren't quite perfect -- a print then having highs and lows that show over extrusion at the peaks left by the roller.  Stranger things have happened.  

You could try the flip side of the sheet to see if the effect remains, or even rotate the steel sheet 180 for a test run to see if the pattern changes sides.

If they are sheet related, perhaps they'll smooth out over time and heat cycles.  

In the Settings menus, look for mesh calibration. You set 3x3 or 7x7 there, along with number of point samples (I use 5), and whether or not the code compensates for magnetic fields.  Try with field correction on and with with off: use the best result.

RE: Advice on first layer

Hi Mike, 
there are a number of factors involved here...

1, use 7x7 mesh bed leveling,

2, sort the middle of the bed using LiveZ,

3, check the perimeter of the bed using the attached file and if problems exist, use 'Bed Level Correction' in the configuration menu... 

to adjust left, right, front, back edge, if a corner is bad, adjust the adjacent sides, unlike like live Z, you can adjust both positive and negative so if the right side is ripply, try changing the right setting more positive to raise the extruder, if the front is not squished enough, try moving the settings for the front edge more negative...

the attached file should print a large hollow square, using concentric infill, let it run a couple of laps, if you can see problems, stop the print and adjust the bed level correction values, then clear the build plate, and run the file again,

regards Joan

RE: Advice on first layer

Thanks for all the advice.  I already made some improvements and will play around with it more this weekend and report back.

RE: Advice on first layer

Hi guys,

Sorry, it took me a bit long than I expect, but I wanted to report back on how I did with the bed leveling.  I have my leveling more or less perfect now.  The key things I change were:

1. Enabled 7x7 mesh bed leveling with 5 sample points.  This improved things but didn't make it perfect.

2. Lowered print temperature to 210C (was previously at 220C which was probably a bit high for my PLA).  This again made things better, but I was still getting some small humps on the lower-right of my bed.

3. Per Joan's advice, I went to "Bed Leveling Correction" menu and raised the nozzle by 30um on the right and 30um on the bottom.  After this the lower-right became pretty good, but I started getting some gaps between the lines in the upper-left.  I then lowered by global Z by 15um and now pretty much my entire bed looks good.

One more note is that I found that just printing a big filled-in square on the first layer showed my problem better than the rectangular pattern that Joan.  This one form thingiverse may work well also, although I haven't tried it: https://www.thingiverse.com/thing:2899815

Thanks to everyone for your advice and I hope my experience can help others.

RE: Advice on first layer

With the smooth PEI steel sheet, I calibrate, and then add a layer of uhu glu stic. No problems with first layer. Glu stic lasts for many prints. Every so often I wash the glu stic off. And start again. I always handle steel sheets on sides with fingertips. Saves a lot of faffle.