Thanks @jazozaya for the advice, as well as your colleagues who have helped.
In your machine, is the nozzle contacting the bottom Z switch in the center of the cylinder or off to a side?
The nozzle contacts off to a side. In fact during the probe, ink, and solder steps, I think the nozzle contacts the bottom Z switch in slightly different locations. I'm not certain about this because I haven't compared photos, but I wonder if it's intentional that the tip contacts in semi random places in order to avoid build up of residue?
Can you confirm your print height is 0.100 mm?
Yes, I confirm it is .1 mm. I've done almost nothing with the configuration to try to solve the bent nozzle tip problem. Once I experimented with the height for a unrelated reason (to learn) but I've since clicked 'restore defaults' at least on two occasions to be sure.
I changed the backlash value out of desperation but have since reset backlash to zero because any other value caused poor alignment.
It seems the list of bent tip causes is quite long:
- A dirty bottom Z axis switch.
- A dirty gold pad (X and Y switches)
- A substrate that wasn't clamped down properly
- Removing and replacing the cartridge lid cap
- Particle in the ink or paste blocking the nozzle
- Prefabricated PCBs with varying PTH and pad heights
- Working too fast to excercise extreme caution
...and my gut feeling is that there might be a few other causes. I've implemented about half of a dozen ideas which your colleague offered by phone. It seems that some (or one?) of them helped a little. Probably slowing my work (like making dozens of photos at several steps) has helped too.
It just takes 1/10 millimeter of error for the tip to strike substrate or metal, which is a key thing to keep in mind.