More Noob questions: My BRIM is curling and tolerance problems:

Prokktor

Hello,
I printed for a week now and I still have problems getting my brim (PLA) to stick to the bed, the edges start curling up from the inside or outside and 50% of the time this ruins the whole print.

What I did so far:
- Mesh Bed leveling while bed is hot, we can consider the whole thing leveled.
- bed heat at 60 to 70 degrees, confirmed with a thermocoupler
- PLA Temps from 190 to 230 degrees C (confirmed with tc)
- print speeds as low as 8 (Cura)
- Cura Flow rate reduced to 90%, this made it worse (not curling but the brim was totally inconsistent now)
- I clean the bed with alcohol and a "glasses towel" before every print

The best results I achieve when printing the first layer with speed 8, PLA at 230 C, bed at 70 C. After the first layer i continue to print at 190 C, speed 30/60, full fan. But even that does not work all the time.

I printed a temp tower from 230 to 190 C I saw no difference whatsoever between the temps, even printed it a seconde time to confirm it actually did print at different temps...

My other problem (maybe even related) are tolerances, I printed https://www.thingiverse.com/thing:2975429 a few times.
(0.2 layer thickness) it failed 80% of the tolerance test (no clear gaps) while the rest is ok i think.
I reduced Flow Rate (Cura) to 95% and then 90% as advised in a youtube video, this improved the tolerances a lot, but now the large curved tower ended at angle 70 (95%) or even 60 (90%) and the rest of the print was a blob of plastic hanging from the top of the unfinished tower.

I there a way to improve tolerances without attracting those new problems?^^

kind regards,

Martin

Samuel Pinches

Hi Martin,

What is your first layer height?
Have you tried cleaning the bed with isopropyl alcohol?

I don't have much advice on tolerances.... if fine tolerances are important to you, maybe you will want to purchase Simplify 3D? Makers Muse also has a few videos comparing alternate slicers - some do better on tolerances than others.

Cheers,
Sam

Prokktor

My first layer height ist 0.3, I tried 0.2 but that was worse.
I clean with alcohol before every print.

Hmm ok I will try another slicer, maybe there will be new options I can try.

Samuel Pinches

I would recommend 0.1mm for the first layer. Then, I suggest to adjust the bed height slightly until it is perfect.

Prokktor

Ok I will try that after insulating my heat bed this evening.

Prokktor

Ok I insulated the Bed, that works great!
I also added M420 S1 after G28 in the start GCode to make sure the mesh gets used.
Then I tried a 0.1mm first layer.
The Brim now consisted of individual lines with more gaps then lines...
So I increased the flow rate for first layer to 200%, the brim now worked, but the print was warped, probably because the real 1st layer was way overextruded and there is no brim flow in cura, only 1st layer flow^^
Then (about 10 prints into the 0.1 1st layer I found the culprit:
If I press babystep Z- arround 8 times right at the start of the print I get a great brim even with 150% 1st layer flow (probably even lower, have to wait...)
There is a save button in the babystep menu, but it does not help, I have to press every single print 8 times...

So the Mesh gets used (else I would have to press baby z+ because the insulated bed is a little higher) I meshed at the exact same temps I am printing at, using a metal 0.2mm "feeler gauge" (or whatever thats called in english^^) I baught for this reason alone.  How can it be that my extruder is consistently 0.2 mm to high?

Samuel Pinches

If there is individual lines, then the nozzle is too far from the bed. I would suggest redo the mesh with a sheet of paper. I think 0.2mm feeler gauge is too thick, in my opinion.

Prokktor

Ok no problem I also have a .15 a .1 and a .05 mm gauge, which should i use?

Samuel Pinches

I think perhaps try the 0.1mm, and if that doesnt work try the 0.05mm.

Also, for the first layer height, try 0.12mm, rather than 0.1mm.

Prokktor

Ok before I do that I have some more questions... :-)


I fear my nozzle might hit the print bed when moving so close to the bed.
The Mesh Leveling function does not raise the nozzle while moving and it always uses the z value of the previous point instead of the previous value of the mesh point. (as far as I know)
Also it moves in a zig zag line so I cant simply make x0 and y0 the highest point on the bed and then fix that with the mesh.
I will probably raise the z endstop by another .5 mm.

Does the standard bed level function use the mesh?

Samuel Pinches

No, the buttons on the normal LCD bed level simply move the head to 5 preset points via gcode commands, and they do raise the head substantially between points. 

The mesh levelling function does seem to raise the head for the first point, but I agree that it does not raise it much. If you keep the paper sheet between the nozzle and the bed, that will help protect the bed from damage between movements.

Prokktor

Ok I releveled the bed with 0.1mm gauge... first the bed then the mesh at printing temps...
Now around 10 prints later I am at
G29 S4 Z-0.275
so I moved the mesh .275mm down across all points and now I can print without Babysteps...

Why that is so is beyond me, I would need a negative 0.175mm gauge to reach that config without g29 s4 z shifting... which is a physical impossibility^^

But thanks again and again for all your help, my prints really look much better now :-)

Samuel Pinches

I can’t explain it sorry, but glad to hear it.