Success with 3D printing of door hardware; continuing on 1053 typewriter restoration

THE MAGIC WORD IS Z OFFSET

I discovered an important setting for the printer, in addition to bed temperature, extrusion speed and extruder temperature. There is a parameter called Z Offset, which determines how high the extruder nozzle actually sits above the bed. Once the leveling is complete and the auto-leveling takes place as printing starts, the difference between the bed level determined by the leveling sensor and the tip of the nozzle is the offset.

The printer moves left and right on the X axis, forwards and back on the Y axis, while it moves up and down on the Z axis. After the auto-level completes it has a mesh of offsets from the presumed home level of Z=0, since it tests sixteen points across the bed to compensate for tilting and warping of the bed. To that we have to add the Z Offset to place the nozzle the ideal height above the bed. That is a tad less than the thickness of a sheet of printer paper, to produce the best results.

I experimentally determined the offset, set it in the software and immediately achieved successful printing of both the bottom mount and the pivoting side parts. I am delighted with the quality of the parts and can't wait to print the second set of parts and install it on the rear cover. No issues at all with adhesion, nothing fancy needed. 

Side pivot parts as they come off the printer

TYPEWRITER WRESTLING CONTINUES

I discovered a broken part on the side of the 1053, the cord self-tensioner. Two cord are used, to haul the carrier to the right and to wind the mainspring when the carrier does a carriage return to the left. The cord that pulls to the right is routed around a pulley with a strong spring, called the self tensioner. The purpose of this part is to absorb slack as the cords stretch with age and usage. 

The self-tensioner part can be made with plastic, but those parts are famous for cracking with age (and abuse as it is sticking out on the right side). 

Damaged tensioner from 1053

Luckily the parts donor machine I bought had a good tensioner - one that was made with metal instead of the plastic used in the 1053s. It is stronger than the original part, therefore.

Donor part now installed on the 1053

Getting the two cords installed on the machine is trickier than I expected. I need to end up with the cords wound over the drums on the mainspring axle with just enough tension to partially compress the self-tensioner. My first attempt resulted in cords that were too short to even reach the tensioner.

This cord fit on the 1053 when it arrived, presumably, so there is some trick to installing it that I haven't yet found in the several IBM manuals covering the printer. I will keep at it until the cords are installed with a proper position on the self-tensioner. Once that is done, I can wind up the mainspring and that part of the restoration will be complete. 

I am still looking into the failure to fully reset the latches for the rotate selection at the end of a print cycle. My objective is to ensure reliable printing of characters which depends on all the settings for tilt, rotate and print shaft timing. I don't want latches that are left over from a prior print operation to cause the printing of the wrong character.