Originally Posted by
Roxy
That is one of the big benefits of the Bed Level Topology map. If you have the bed orientated the same way you have the #define's setup... You should be able to look at the topology map and picture that over your bed. If one corner is higher than the others, lower it and re-run the test. You will get a feel for how it zero's out. The biggest problem is if you correct one corner the right amount, the other corners sort of 'float' and it will be closer, but it won't be right. You keep getting closer and closer, but you never quite get there. And with a Standard Deviation of .02 for the Z-Probe measurements, you won't ever get it flatter than that. For the first couple of iterations, you can just use G29 n 2 T to get the readings quicker.
OK. There is another place we can try. Or... If it is behaving rationally, we can just leave it. I was thinking a little bit more on the problem. The nozzle has to raise enough to have clearance, but it has to raise even more because your bed it tilted. If you measure a low spot, and raise it enough to have clearance, what happens if you move the nozzle to a high spot? You will scrape the nozzle. Raising it 4 or 5 mm above the bed might not be a bad thing to do in general.
And switching topics... I don't know which axis (X or Y) is the one that the nozzle is moving on. But if you do a set of M48 commands at both sides I bet you see a noticeably difference. My guess is doing an M48 x 25 y 25 n 10 v 4 is probably going to give a noticeably smaller Standard Deviation than doing a M48 x 175 y 175 n 10 v 4 If that is really true, the extra amount of error is coming in because the Z-Axis height is only set on the one side. My guess is adding the L 6 parameter to add legs of travel in X & Y might also show up on the far side. But if you do that, you have to be far enough away from the very edge that it can sweep out arcs. It won't go past the edge of your bed, but you will lose some of the legs of travel between moves if it tries to head off the bed.
Because of the design of the machine, there isn't really an easy way to improve that (if this assertion is true). But it is still worth while to know because what it will mean is you can print with higher accuracy closer to the Z-Axis support than on the far end of the X (or maybe it is Y) Axis.