Plywood Cube, bed leveling error, Z axis movement problems


#1

I’ve just built the plywood kit, and have completed my first few prints with it.

I’m having a little trouble with bed leveling. The routine runs as expected, and most of the PLA comes out the correct height, but in the left rear, the bed seems to sit a little low, and I get poor/no print adhesion in that corner. I can fudge it a little by decreasing the Z offset parameter, making the printer squish the rest of the print in order to get a Z height in that corner that still works, but this is obviously not the ideal situation. I’m not sure what I’m doing wrong here, but maybe the solution will be to finish the adjustment that I started as below.

I don’t mind fine-tuning leveling the bed myself, and not depending on software, but I was under the impression that the machine should handle doing this itself so long as values were reasonable, without intervention.

I had some initial problems with setting the Z offset, and Z movement as well. With Slic3r set to give me 0.25mm layers, I’d get extremely little or no movement at all in the Z axis over the span of the print, which resulted in a big mess. I found that bumping up the Z acceleration to ~1300 (Just what I spun the dial up to, no particular reason for that number. I’ll probably change it to the 2000 figure that the X and Y axes use later though) solved that problem, and made the Z offset calibration work better and more consistently as well. Still not perfect (As stated above) but I’ve got some nice prints now. Anyone else experience this?


#2

is ti possible to sent picture of part?
what type switch using on z axes mechanical , proximity ?


#3

Do you mean the switch/sensor, or the printed mess?

The Z probe is a microswitch attached to the print head. I don’t have a picture handy, but it is firmly mounted and is consistent in its results when homing the printer. I get the same height every time, once the Z acceleration is set higher. It is just off towards the back left corner, maybe .1-.15mm or so. enough to cause problems with print adhesion on the bed.


#4

Well, I’ve determined the source of the problem. The build platform is warped, so that the sensed location of the front right is a slight amount lower than the actual plane of the bed.

In the short term, I’ve got a shim on the bed, which makes for workable results.

longer term, I plan on implementing a heated build platform, which will require that I make it from something other than acrylic, so I can correct for the error in flatness at that time. I suppose that I could plane the existing platform to bring it back to true, or I could (carefully) heat the whole thing, and flatten it on a smooth surface, like the top of my tablesaw. I’d like to keep the original platform if I can, but as it sits, it’s not very useful.

I drew up a model of the platform which I’ll be working with to add in a 220X275mm aluminum heated build plate. The build plate is 3mm in thickness. My thought is that I can include this in one of 2 ways: Either cut a 3mm depth slot into my replacement platform, or just add it on top, and increase the Z offset to take it into account. I think that the first option is more elegant,and will allow for me to add a glass sheet to the top. Easier if I had a CNC router, which I haven’t finished yet, but I can manage that easily enough with a hand router and a jig.