I have decided that my first goal is to replace my X-Gantry using the gantry I found on thingiverse. The X-Gantry I have chosen is from Proto-Plastik and is part of his A5-1Z upgrade to the TwoUp 3D printer. This X-Gantry seems to most closely match my goals for a replacement part, and supports an Anti-Sag truss to help fix the sag due to the long moment-arm of the current gantry.
Because of the limitations of my printer, remember I can only use the left 50-70mm reliably, I must take care to rotate the parts and force them to the edge before printing them. In addition, I have learned from my calibration cubes to leave enough room on the left side to allow a skirt around each object so the filament starts flowing well before each part begins. Fortunately, the parts of the X-Gantry have a cross-section of 50mm or less, so should print well.
X-Gantry Left and Another Surprise
I decided to bite the bullet and print the most complex part of the new gantry first so I started with the X-Gantry Left. I loaded the image into Repetier-Host and sliced it with Slic3r. I then re-zeroed my print head, started to print the part, watched it begin the first layer and then switched over to a game to occupy the next few hours while it printed.
After an hour or two (my wife calls them programmer minutes) I thought to look at the object and noticed it looked a little odd. I watched it as it continued to print for a few minutes before I finally figured out what was wrong with the object. For some reason, the seat for the acme threaded retainer was printing on the wrong end of the part.
After stopping the print and analyzing the situation for a while, it finally occurred to me that the Y-axis was moving in the wrong direction. I had noticed some issues zeroing the print-head in manual mode, specifically that my opinion of positive motion and the printers disagreed. However, I had learned to compensate for the issue while zeroing the print-head and assumed that it was and issue with the UI manual mode.
Based on previous experience with stepper motors I knew I could reverse the connector on the stepper motor controller board to reverse the motors direction. After moving the connector, I printed out a few more cubes, which all looked pretty good. As an added bonus, in addition to fixing the Y-Axis of the print-head, this also got rid of a startup noise that I had mistaken for the printer checking for an end stop.
X-Gantry Left again
I restarted the X-Gantry Left part and watched it a little more closely this time. When I could see the first layer of the object looked like what I was expecting, I switched back to my game for a few more hours. When it finally finished, I snapped the part off the painters tape and removed the small lip at the base using a sharp knife. Besides the lip, I noticed some small ripples on the vertical sides, but that is something for a later time.
This is obviously going to take a few more nights…
X-Gantry Upgrade Part 2