This was the most tedious step in the whole project. Took me about complete 8 hours to complete with the help of an advanced craftsman (Father).
The plate of the printer which supported the print head and rod was excessively treated with my beloved metal saw.
I had to cut out pieces of the L-profile to get room for the stepper.
In the original printer structure there was a DC motor where now the stepper resides. Often (hopefully) the washer of the stepper, which is from the same printer, has the same spacing so it fitted nicely into the DC hole.
The rod on which the led the print head carrier had some decentered metal nobs on it. They could we easily removed by twisting them and pulling them off with a plier. They revealed very nicely centered metal tips.
I used two T-profiles and drilled holes in them. So I could just plug the tips from both end through and mount both profiles on the L-profile. This step needs to be precise as possible as later on the y-axis might drift off. This might distort the whole drawing/lasering process as the Y-axis isn’t right-angled to the X-axis. Use a caliper is a must. Drawing by eye, too.