I’ve had this happen several times. I’ll start jogging the machine with the keyboard, or be in the middle of jogging with the keyboard (bluetooth keyboard), and all of a sudden the y has lost it’s position. Here’s a screen shot of Mach 4 when it happens. The real position is in the front, but the machine suddenly thought it was at the max y, as shown in the DRO (set to machine coordinates).
What in the world could cause this to happen? It has me really worried.
Everything in both boxes can cause a lot of noise. The VFD can for sure, but the steppers are driven by high current square wave pulses, and there are very large switching power supplies in there too. They are all designed to reduce the effects, but if things are not properly connected it could be a problem. I’m not saying this is your problem, just that pretty much everything in a CNC is a high noise device.
The thing I don’t understand: isn’t this a software problem? Something is telling Mach that the y-home location has changed. I wonder where that happens, and if I could back-trace it from that location.
I can reproduce this on a wired keyboard; it is just harder to make happen due to no latency. I think it is a software bug in Mach 4. Could someone else try to reproduce it? @jjneeb or @Eric
Keyboard jogging turned on.
Home Machine (front/left)
Shift-Up arrow for a short bit to jog towards Y+ (away from you)
Shift-Down arrow, and immediately after the jog starts hit the up arrow, while still holding down shift and the down arrow. As soon as you add in the up arrow it will reset the home position, and jogging stops because it is now at a soft limit.
It might take a few tries…but this happens nearly every time for me. It doesn’t happen when doing it in the opposite direction.
I can make a video if you all want to see it in action.
Yep, I can reproduce it too. Happens about 80% of the time. Seems to be the specific combination of a rapid negative jog and then hitting the positive jog at the same time. Most people don’t hold down the opposite jog direction arrows at the same time, so they wouldn’t notice. What were you doing that you ran across this?
Awesome! It’s good to know I’m not crazy. I was just rapid jogging back and forth to see how the machine moves. Second time it happened I was demo’ing the rapid rates to someone. That got me worried…so I had to figure out what was happening.
The work around is easy:
Me: “Doc it hurts when I do this!”
Doc: “Well, don’t do that!”