SKR e3 mini v3.0 - BLTouch inaccurate..

[Yves]

I recently bought two SKR e3 mini v3.0 and tft35 to upgrade my existing Ender 3 Pro. After the switch and upgrading the firmware to the latest available that when i print i'll have issues with z-offset accuration. The printer is a standard Ender 3 with dual z-axis connected to the two Z-axis ports on the board.

When i start the printer and start "auto home" it runs normaly - at least it seems so. after starting a simple bed leveling testprint i have a lot of inaccuration with ubl activated and a freshly generated mesh. Even when i restart the printer a few times it is inaccurate. When i calibrate z-offset and store the settings in eeprom and restart the printer, do a "auto home" it isn't accurate anymore.

When i test the probe with M48 Probe Accuracy Test i have a inaccuration of 2.7mm instead of the normal 0.001-0.004mm i have on the stock ender 3 pro with the Creality board. Interesting is that some measurments are accurate then a few not. i can visible see that bltouch is having contact (as it changes color from blue to red) but z-axis are moving down instead of stopping and going back up for the next measurement. The same bltouch mounted on the creality printer with stock mainboard is accurate (<0.004mm) in M48 and homing.

I first thought it could be a wiring issue. i've tried both ways direct 5-pin dupont and the probe/z-stop pinning. the issue is the same. i also switchted the board (as i bought two) but have the same symptoms. i then tried to build my own firmware as i use it on the stock ender 3 with latest marlin bugfix-release but the issue still persist. I've also switched the bltouch 3.1 with a new one but that also didn't resolve the issue.

Any idea what could be the reason? Open for any inputs :)

[BTT Tony]

Hi, it may be that the distance between your nozzle and probe is not set correctly. You need to measure according to the actual situation and then modify the reference of the firmware. NOZZLE_TO_PROBE_OFFSET