# Correct Setup of Dual Extruder with BLTouch Autobedleveling

i have installed a MK8 Dual Extruder on my 3D Printer. Now i have some short problems to get the autobedleveling working.

The distance between the nozzle is 35mm so i have setup the nozzle offset as follows:

EXT0 = X0, Y0

EXT1 = X35, Y0

The firmwareconfiguration tool generate 5061 stepps as offset. This could be right. After homing xaxis the head drives 35mm to the right side and there is set the point 0.

Is there a difference between my setting and the settings i read in the manuel?

EXT0 = X0, Y0

EXT1 = X35, Y0

and

EXT0 = X-17,5, Y0

EXT1 = X17,5, Y0

Okay. The next step is the BLTouch sensor. The correct offset position i measure is:

Z-Probe offset:

X17,5

Y59,75

Now to my problem. I get error in coordinate dimension if i start the leveling.

I have a real printable Bedsize of XY: 275, 395

On real startpoint xy = 0 the nozzle is on the bed at front left. The BLTouch is behind the nozzle at 17,5, 59,75 (real position)

to measure the real 0 point it is nessessary to drive in negative area. So i have change the position of y endstop at front left about the maximum posibile position (50mm). I have set Y-min endstop to -50. In this case i have raise the Y-lengh value about 50 up to 445 because i have see the printer dosnt drive over the point 345 after change.

Now at home the BLTouch must be a real position of x17,5 and y9,75.

i have try to setup the A/B/C coordinate for the measurement grid, but the error stay. what is wrong? Can somebody help me to get my parameters work?

A: X -35 , Y 9,75

B: X 275, Y 9,75

C: X -35, Y 335

Thank you very much in advanced

Mr Zortrax