I solved my stepper reverse motion problem. The reason it wouldn’t move in reverse is that it was checking for the state of the endstop. The endstop was not connected and the pull-up resistors were not active. This should have been pretty obvious because the Sprinter firmware even warns you about this in the comments around the endstops, but I still missed it. Just to temporarily get by placed a jumper between the signal and ground for the Y min endstop. I also turned on the endstop pullups and set the inverting to true:
//// Endstop Settings#define ENDSTOPPULLUPS 1 // Comment this out (using // at the start of the line) to disable the endstop pullup resistors// The pullups are needed if you directly connect a mechanical endswitch between the signal and ground pins.const bool ENDSTOPS_INVERTING = true; //set to true to invert the logic of the endstops
After that I tested things with the scope again. Now everything works fine! (Except I will need to get some real endstops in place.) Below you can see the pulse traces from both the forward (top) and reverse (bottom) movements.
I went on to making some real endstops. I scavenged some opto-interrupters from some scrap machines. These particular ones needed a 2.2k ohm resistor tying the Vcc wire to the signal wire. I spliced the wires and soldered in the resistor before making up the crimp ends for the connectors. I threw some small heat shrink tubing around the outboard end of the Vcc wire and a larger tube around the whole setup.
I used some SteelTec pieces and strips of steel shipping straps (from the crate of my Smithy 3-in-1 delivery) to make some flags. The one below is for the Y-axis.
These endstops had a threading bushing pressed in them. I wanted to mount the Y-Axis sensor to the t-slot extrusion. At first I was thinking about drilling out the M3 threads so I could pass an M4 or M5 screw through it. Instead I used a Dremel cutoff disk (the thin one) to make a slot at the end of the M3 screw. Now I had a place to turn it with a slotted screwdriver. I put a #6 washer on the screw then threaded it from the bottom up into the sensor, leaving a bit of a gap underneath the sensor base. Then I slid the assembly onto my t-slot extrusion and used a screwdriver to finish snugging up the inverted M3 screw. Remember: lefty-tighty.
For the X-Axis I also used some SteelTec brackets to mount the sensor. I found some random round bushing that was about the right height I needed and put that in place as well. Later I’ll print myself some nicer brackets.
To guide the wires for the Y endstop I decided to run them in the bottom of the Y Makerslide extrusion. I needed to find something quick to push the wire in the lower t-slot so I wrapped some extra toolbox lining material around some pieces of coathanger. I also tried a few other materials such as the more smooth foam toolbox liner, but this grippy one seemed to work the best.
I also tried making some little dots out of hot glue. They seemed to work ok, but they took much more time to make than I thought they were worth. I had to constantly rotate the glue until it cooled down or else it would just spread out.
Now it was time to get to printing. I didn’t feel like complicating my workflow with CAM tools to generate my machine’s G-Code, so I sketched a simple image out on some graph paper and gave it coordinates. I then manually wrote all the G-Code to make the moves. After remembering to remove the top to the marker, everything worked! The extra tall H below was because I didn’t re-zero the machine as I thought I did when I went to write the upper image. Although, the machine did follow the first path very well.
Here’s a video of the action:
[youtube https://www.youtube.com/watch?v=GkJNYom9nwA]