Saturday, May 25, 2013

Z-Axis Endstop, Micrometer Head Adjust

I was still not having good luck consistently getting the z-axis endstop to zero my MendelMax 1.5 rep rap Z-axis in the right place. Using a 4/40 or M3 screw just didn't provide the vertical resolution that I needed to really zero in the axis. So, I decided to really do it right and use a micrometer head to provide extremely fine adjustments.

I found this great Mitutoyo micrometer head on e-bay- a $150 unit for $20, shipped. Second hand industrial surplus is great.

Mitutoyo 148-811 Micrometer Head
So, instead of trying to fumble with turning a unlocking nut, then a screw only a couple degrees, then locking the nut again- all you have to do is twist the dial and watch exactly how far you move the tip up or down. Very easy.

I updated the Z-axis screw holder to accommodate the new micrometer head and printed it out.

Mount for Micrometer Head
 Everything seemed to fit well, and I uploaded the finished design to thingiverse, download the files here

Everything Mounted and ready to go

Front view

So far it seems to work great- it's a lot easier to dial in the nozzle height. Some people claim that adjusting this in software is easier, but for me twisting a knob and immediately running the program again is the most convenient way to go.

To give it a try I ran the old standby- the 5mm calibration object pyramid. It looks better each time. I'm still puzzling at how to get the top block square, and the bridging tests aren't super clean. (visible on the back of the pyramid)

5mm calibration object test

Back of Pyramid
Maybe adding a fan would clean up the bridging and some of the odd sidewall shrinkage?

With the hot-rodded printer, I designed and printed a replacement part for the swiffer. The piece that connects the handle to the mop head broke. It's a challenging part- it has a large internal ACME screw thread to join it to the handle. To my amazement it threaded right on, no cleaning of the threads needed. So far it seems to work just like the "factory" part. Download this part here. 

Swiffer with new head mount

Closer view

Wednesday, May 1, 2013

Z-Axis Endstop Switch Update

I'm still having a challenge getting the nozzle height correct for prints- and part of it seemed to be some inconsistency in the Z-axis homing / endstop. The stock Z-axis endstop switch is a standard microswitch. Doug suggested that I remove the spring arm from the switch. Doing this should remove at least some variability from the Z-axis homing cycle.

Z-Axis endstop microswitch with metal spring lever attached

Spring Lever "Removed"

Switch back in position and ready to go
So far no definitive data on if this actually improves anything, but I don't see how it can hurt.