Trying to solve a Z offset

When using ABL I have a Z offset that I haven't been able to sort and could use some advice. When I issue a G28 the X and Y both show 0 with an M114 after the homing command, but the Z shows 2.86. My offset for Z in the ABL is 1.80, so the print is starting way too high. I have tried a G92 to reset zero point for all axis, and then issue a M114 and all axis show 0, but if I home again (whether I use the home button, Z home button, or issue G28) the Z is at 2.86 again. When I reload the stock firmware without ABL, it works fine so it is something I have done to the ABL code. I'm just not finding it. And suggestions would be appreciated.

So your Z offset is 1.8. Do you have a Z_RAISE_BEFORE_HOMING, Z_RAISE_BEFORE_PROBING , or a Z_RAISE_BETWEEN_PROBINGS number set?

Yes I do. Z_RAISE_BEFORE_HOMING 4, Z_RAISE_BEFORE_PROBING 4, Z_RAISE_BETWEEN_PROBINGS 2. And all those settings work, although only the Z_RAISE_BEFORE_HOMING might apply since the offset occurs just with a homing (G28) without the Z probing I think. I'm sure this is a simple offset somewhere, I just can't seem to find it. Doing a find for 2.86 in the configuration.h doesn't turn up any results.

How high does the nozzle end up after a G29?

Thanks for the help Abu, it's really appreciated.

After G28 in Pronterface shows 2.86mm with a measured (manual controls used in Pronterface to desired print height of tight with a sheet of paper) of 1.06mm height. After G29 the M114 reads 3.06mm and measured after manual adjustment of 3.6mm to the sheet of paper. Not sure why the difference between the 2, but I tried several times and the results are repeatable.

I had a similar problem. After a G28, the printer reported the nozzle height as 4mm lower than it really was. When I did G1 Z0, it stopped 4mm above the bed. A G29 reported correctly, though. I never did find out where the bad calculation was.

I know it's something I have done, nothing new there...lol. I just downloaded the DACB fork and am doing a compare now to get my settings transferred and I will give that a try. I would have wound up testing that fork anyway, so probably best just to move on now and eliminate any of my errant mistakes and take advantage of his efforts anyway. I think one thing that made it difficult for me was the difference in the Makerfarm supplied code and the current firmware with so many sections of the code being in a different order. At least for me that made transferring to the newer firmware quite confusing. The DACB fork looks to be very easy to do a compare and most of the settings I had to change for the MakerFarm i3v are already there and I should have an easier time. I'll let you know how it goes.

Just tried it with the DACB fork and the same issue exists. Also tried changing the Z offset at 2.8mm instead of the measured 1.8mm offset that I need with my servo and it made no difference, it was still the same 1.06mm above the desired print height. Very odd that changing the offset had no effect at all in the starting print height. And yet, with the MakerFarm stock firmware it is fine. I'm done for tonight, I'll try again sometime this week.

Do you have the EEPROM settings turned on? It is very possible you have bad Z-Offset numbers stored in the EEPROM. If so, that will over ride whatever number you compile in your Configuration.h file.

Issue is solved. It turned out to be a problem in EEPROM settings. I sent an M502 and then M500 and the issue disappeared. I had loaded default firmware from the LCD control panel several times prior... even with the EEPROM defines commented out in the configuration.h, but apparently that didn't have any effect. The EEPROM settings also had no effect on the stock MakerFarm firmware, which has always worked correctly. So I'm not sure why this behavior happens, I'm just glad I can move on to several other small issues like getting the ABL probing matrix to be more centered on the bed. Right now the right side of the bed is not probing far enough to the right to include enough of the right side of the bed to be as accurate a tool for the entire bed as I would like. But, since most of the parts I'm printing currently are 4" x 4" or smaller it is certainly covering my print area. So a problem for another day. Now I just need to dial in the Z offset to get the proper squish I'm looking for on the first layer. Just glad I finally have a working ABL, and it is really nice to have.