Nozzle Scraping Bed During Probing
I have a support ticket opened for this as well but was wondering if others have/had the same issue. I recently finished my MK3 upgrade to MK4. Sometimes during the point probe step of a print the nozzle drags across the steel sheet. This causes incorrect readings and if I let the print continue, the area it dragged across the bed doesn't extrude because the nozzle is so close.
I normally just stop the print and start again and it works without issue. I have had this happen on both the smooth and textured sheets.
It has happened about 5 times now out of 12 or so prints. It happens at various areas on the bed and nothing seem correlated. I have checked to make sure the hotend it properly secured and inserted all the way. I double checked the bed as well to make sure the screws are all secure.
Only thing left I can think of is maybe one of the z-axis motors is slightly off sometimes? What is more strange is it doesn't happen for the entire process. It scrapes the bed on a few points in a row, then it is perfectly fine for the rest of the points.
RE: Nozzle Scraping Bed During Probing
Your could try doing a Z-axis calibration before doing a prints to rule out the x axis tilt concern. I have this problem sometimes and the doing the calibration usually fixies it.
If doing the calibration does fix your issue, you need to determine which Z-axis assembly is dragging. It is possible that one or both of your z-axis assemblies are dropping when you not using the printed. Both a dragging or dropping z-axis assemble would lead to a non-parallel x-carriage in relation to the bed. This would lead to first layer calibration error and could cause layer shift during the print. But my recommendation would be to do the calibration first before you move on.
RE: Nozzle Scraping Bed During Probing
It happened again last night. I re-calibrated the z last night to ensure both sides are parallel to the bed. The issue doesn't happen after the printer sits, when a print finishes I start another as soon as possible.
It has now sat however for about 12 hours so I will start another print and see if maybe one of the sides has drifted down. The odd part is, if one side is lower than the other I would expect the nozzle to drag across the surface consistently. When it happens it only happens in a small location, and each time it happens in a different area on the bed. Nothing seems corrlated. Sometimes it will be the back right corner, sometimes the middle, sometimes the front left, middle left, etc.
Further adding to the mystery, when it happens I can just stop the print or press the reset button and re-start the print and everything works without issue without me touching anything with the axis.
RE: Nozzle Scraping Bed During Probing
That is weird and obviously frusteratting. The fact that a print restart leads to success make me question the BM, may the load cell is wonky.