Random roughness in print and other issues
So many problems I don't know where to start. I have worked really hard to calibrate and the skew is good. I am now using glass cleaner on the bed between prints, because that seems to work much better than 99% isopropyl alcohol. But even still, I'm having a hard time getting the prints to work cleanly. There are random perturbation during the streaming PLA. You can see in the bottom layer image how the stream is often getting disrupted. But then after the first layer it smooths out and goes very well. I'm convinced this is something to do with the bed. The bed feels smooth and I've tried to be very careful about cleaning the print nozzle.
As it printed, problem #1 emerges. I've seen this a few times. The material seems to warp away from the print bed. See how it beds up? It wasn't like that for the first 25%, but then later, I suspect as it cooled, it began to warp.
Anyway, the print was continuing ok, but as it got to the very top layer, the roughness emerged again and the edges got messed up and eventually, while I was asleep, it must've broken free from the print bed, because the lines were streamed randomly over the top for just one layer.
Please help.
Re: Random roughness in print and other issues
You need to adjust your Z offset - the first layer is clearly not squished down onto the bed adequately. If any part of a print ever starts to lift up off the print bed, you might as well quit the print right away and start over. Getting good adhesion to the bed requires proper cleaning (you are probably doing that), the right temperature (you probably are doing that too) AND good "squish". If your Prusa model has "Live Z" adjust (I think they all do) then use that to adjust the Z offset. Ideally, at the end of the test pattern, when it prints the 1cm square, the square should be well adhered to the bed and the top surface should be smooth.
Re: Random roughness in print and other issues
Clean your print bed with a drop of no-additive dish soap, hot water, and clean paper towels. (see https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/newly-assembled-mk3s-issues-z-leveling-enforced-an-t29012.html#p137810 )
IPA and windex will not be effective at removing finger oils from the bed, which causes the prints to lift.
Also, see https://shop.prusa3d.com/forum/assembly-and-first-prints-troubleshooting-f62/life-adjust-z-my-way-t2981.html for a better way to calibrate live Z than the built-in Gcode, it has a much larger print that makes it far easier to see what is going on.
Start from the bottom up, problems lower down in the print will continue to exhibit further up, so start by rectifying the "lower" ones (live z, bed adhesion) first before fixing any other issues that manifest later on.
Re: Random roughness in print and other issues
Thank you both! So it sounds like I need to more thoroughly clean the oils off the bed and squish it more. I've used various calibrations, including that one you linked to. Maybe the bed just wasn't clean enough when I squished more. I'll try again and report back.
Re: Random roughness in print and other issues
I used the 75x75mm calibration (v4) that @vintagepc mentioned. I've used this in the past. Results are confusing. I cleaned the bed well. Check out the image named "0413192240.jpg" it shows the result, which printed from right to left. Notice how it started out (on the right) really nicely! It feels nice too, very smooth and very nicely connected, doesn't pull apart at all. I checked thickness with calipers and it measures consistently at 0.1mm thick.
Then you can see about 25% across (diagonal) it starts to not be as smooth and you can see through. Note that I did not change any settings at that point, it just started stranding on it's own. The starting Z adjust was -0.,615mm. At the half way diagonal (where the first black dot is), I adjusted the Z to -0.650mm. After a bit more printing it looked the same. So at the next (left most) black dot, I further adjusted to -0.675mm. The final thickness was 0.2mm thick.
Given that I moved the print head closer, I'd have thought it shoudl be thinner? But given the stranded effect it seems like it was actually too high (and as such thick).
Does this mean the printer is warped vertical along the y axis? EIther way, what to do about this?
Re: Random roughness in print and other issues
The picture suggests your bed and print head may not be co-planar.
Re-run your Z calibration, and check carefully for junk/stray filament between your build plate.
Try using a metal straight edge to see if there is warp to your bed, and double check your y/x assembly for alignment issues.
What firmware are you running? If anything other than 3.7, upgrade as it has 7x7 bed levelling which will significantly help here.
Re: Random roughness in print and other issues
The picture suggests your bed and print head may not be co-planar.
Re-run your Z calibration, and check carefully for junk/stray filament between your build plate.
Try using a metal straight edge to see if there is warp to your bed, and double check your y/x assembly for alignment issues.
What firmware are you running? If anything other than 3.7, upgrade as it has 7x7 bed levelling which will significantly help here.
Thank you for continuing to help vintagepc! I have the i3 MK2, the latest firmware is v3.1, which is what I'm running.
I used a metal straightedge and it seems pretty straight, but there may be a very slight dip in the center of the bed, less than a millimeter. I can see a slight bit of light coming from under the center.
Finally, I'm not sure which calibration details are relevant so here are all of them:
Y distance from min:
Re: Random roughness in print and other issues
Ah, nuts. Sorry, my bad; I just browse "unread posts" and occasionally don't see what category something is in.
Does your firmware have Z level correction? If so, you can try playing with that in order to get a nice even first layer:
https://help.prusa3d.com/article/TPGip0OmaP-bed-level-correction
For this, I'd recommend finding a 3x3 grid of small squares as a first layer pattern (e.g. https://www.thingiverse.com/thing:2840705 )
and use that to dial in correction values for each of the four regions to get them all as uniform as possible. Note your live z value should be set so the center of your bed is good, and then use the values do adjust the perimeters up/down.
Note the center squares on each edge will be the most useful; the zones are slightly tricky because they overlap - e.g. the front left corner is affected by both the 'front' and 'left' correction values.
You may still have some issues in the very corners if your bed is very uneven,but hopefully you can get a far better improvement.
Alas the Mk2 bed is not as easily adjustable, IIRC, but when I had the same issue I did what's called the "nylock" levelling mod that lets you correct for this sort of thing. Then shortly after the 7x7 mesh firmware came out and made that almost unnecessary. If you're not adverse to running third party firmware it might be good to seek out whether anyone has implemented a similar higher-density bed levelling for the Mk2 and save yourself a lot of fiddling.
Re: Random roughness in print and other issues
And once you get the bed level, your part is also warping as it prints.
A warp pulls the print loose from the bed and causes other problems you see. A clean bed is essential to prevent warpage. Another way to reduce warp is to raise the bed temperature from 60c to something higher, around 70c.
You can also try slowing the print fan to 50% or less (your part doesn't have any overhangs that need 100% fan).