contact surface quality issue  

Re: contact surface quality issue

The most common causes are contaminants on the bed - yeah, a fingerprint will ruin a print; and improper Z-Layer calibration (your Z looks a bit too low, but good enough). A third less common problem is the filament can be contaminated with finger oils by improper handling. But I've seen all three issues several times in the past six months (including a spool of Prusa filament). You can spot filament contamination by running 50mm through while watching the nozzle: if the filament comes out and expands, you have bad filament: oils or moisture content. I've had to strip the entire first layer off of spools to get to clean filament.

If you have ever handled the print sheet with bare hands, you need to wash it thoroughly. PLA and hand oils are not compatible. The process is quick and simple:

1) Wash & Dry hands.
2) Wash bed using a few drops of Dawn dish soap, hot water, and a paper towel to scrub.
3) Handling by the edges, dry with a fresh paper towel (do not use cloth towels that have been through the wash machine - they usually have brighteners and softeners that recontaminate the bed).
4) Seat the bed, handling only by the edges, then wipe the bed with 91% alcohol (Everclear is not recommended).
5) Sometimes you'll still have a spot where PLA won't stick. Burned on oils, I suspect. They will need cleaning with Acetone.

Many first timers don't believe the lore and fail to wash the bed. Some even resort to sanding the bed. But for whatever reason, PLA just loves to find the spots where you've pried a part up and then not stick. I now use alcohol every few prints, with an occasional acetone wash when a spot shows up (usually looks like a white spot under the first layer) - these are likely places I got too close when removing a part.

This all said, PLA is nice, but requires a super clean bed. On the other hand, PET sticks so well that you need a dirty bed to get parts off. So we add gluesticks or let Windex dry and even intentionally rub hands all over the bed. Go figure.

ps: One other remote possibility is the idler tension is too loose and you have a feed issue. If you hear the extruder clicking that's another sign.

Re: contact surface quality issue

Armin,

to me, it looks like your liveZ is too low, causing the first layer to form ripples,the extrusion lines should be parallel, yours have kinks where the extruded filament is misplaced...

have you done live Z adjustment, and bed level adjustment?

regards Joan

Re: contact surface quality issue

Hello,
thanks for your help. I will adjust Z a little bit higher, and care fore more cleanness.
But just one more question :
The areas, where the quality is not OK, are areas, where different printing zones touch each other. Due to the holes, the printing areas are segmented.
Is there a way to print the first layer, by not linear, but a lets say hazardous movement?

best regards

Armin

Re: contact surface quality issue

I am not sure what you mean by print zones; do you mean your part has multiple shells? Or do you mean the holes in the part?

And I'm also not aware of any method to make layer print differently except to change the infill angle; or, perhaps use a different slicer that may have more control, like concentric or hex pattern infill.

Back to the ugly fill: there seems to be a pattern to the ugliness that suggests the extruder isn't providing continuous flow. Either a skip along the way or a burp happens as the nozzle accelerates from an edge (extrude speed isn't linear). Also, to Joan's point, the connection points at the perimeters look "too good," as if you are over extruding (too low or flow > 95%). Not sure that's causing the "buckling" but would cause layer 2 to be visibly bumpy with excess material.