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Home Switch Repeatability
- Thread starter TomS
- Start date
But I still like my floating home position
Wow! Lot's of good advice. Thanks guys. I too like to ability to shut down at the end of the day then be able to restart the next morning, home the mill, then key in the work offsets. And, if for some reason I run up against a limit switch re-homing gets me back to my starting point/work offset. Items 1 and two that jbolt mentioned are one's I use to make sure I haven't set myself up for a crash.
All that being said I went back and reduced my homing speed to 5% as Jim suggested. The X axis now repeats within +/- .0005". I'm happy with that. The Z axis repeats within +/- .001" with a little help from me. Evidently my gib is a bit on the tight side so if I put some body weight on the head I can pull it down a few thousanths. I'll readjust the gib and that should cure it. The Y axis is another story. For some unknown reason the Y comes up against the limit, stops, but does not reverse. If I hit the jog button (opposite of the homing direction) it trips the limit. Not sure what's causing this but I just did a rewire of my limit switches from individual inputs to wired in series. The switches worked fine before the rewire. I'm going to wire the Y switch to a separate input and see what happens. If this doesn't work out could it be noise? My limit switch wiring is not shielded but has been working flawlessly for nearly two years. I can rewire the circuit with shielded cable if necessary but would like to rule out other causes first. How about a bad limit switch? Anyone have these symptoms and traced it to the switch? Could it be Mach3? I had a homing problem when I first got my machine running where it would blast through the switches and crash when I attempted to home the machine. I reloaded Mach and the problem went away.
I've got a few things to work through but am always open to criticism and different ideas.
Tom S.
All that being said I went back and reduced my homing speed to 5% as Jim suggested. The X axis now repeats within +/- .0005". I'm happy with that. The Z axis repeats within +/- .001" with a little help from me. Evidently my gib is a bit on the tight side so if I put some body weight on the head I can pull it down a few thousanths. I'll readjust the gib and that should cure it. The Y axis is another story. For some unknown reason the Y comes up against the limit, stops, but does not reverse. If I hit the jog button (opposite of the homing direction) it trips the limit. Not sure what's causing this but I just did a rewire of my limit switches from individual inputs to wired in series. The switches worked fine before the rewire. I'm going to wire the Y switch to a separate input and see what happens. If this doesn't work out could it be noise? My limit switch wiring is not shielded but has been working flawlessly for nearly two years. I can rewire the circuit with shielded cable if necessary but would like to rule out other causes first. How about a bad limit switch? Anyone have these symptoms and traced it to the switch? Could it be Mach3? I had a homing problem when I first got my machine running where it would blast through the switches and crash when I attempted to home the machine. I reloaded Mach and the problem went away.
I've got a few things to work through but am always open to criticism and different ideas.
Tom S.
- Joined
- Feb 1, 2015
- Messages
- 9,994
Tom,
The fact that the y axis homing stops indicates that the switch is tripping.
You might try temporarily switching the x and y wiring to see if the problem stays with the y axis or moves to the x axis. That should tell you if it is a switch/wiring problem or Mach 3 or the controller.
The fact that the y axis homing stops indicates that the switch is tripping.
You might try temporarily switching the x and y wiring to see if the problem stays with the y axis or moves to the x axis. That should tell you if it is a switch/wiring problem or Mach 3 or the controller.
- Joined
- Feb 27, 2014
- Messages
- 2,274
just to weigh in on the "To Home or not To Home" conversation. I am with Jim on this one. I can and have "Homed" my mil and even used work offsets but 99% of the time I do not Home the mill but just Zero on the appropriate place for the job I am doing. Most of the time I am doing one-off parts anyway. I even feel confident to turn off my Mill at night and come in the next day without re-zeroing if I am on a longer run. Usually though I move the tool to X=0, Y=0 and Z=2 before shutting down so I can verify that all is good the next day. When I have used Homing and work offsets it has been when I had a long run of a part and expected to want to do other non-related work during the run. i.e. take a break from the run of 50 widgets to make a specific part and then go back to the widgets. Although I am not sure it would really save time unless I was going to interrupt a long run many times. It only takes me 5 min or so to home X,Y&Z and as a hobby, Time is cheapest part of my investment.
I tried a few things and still no luck with Y axis homing accuracy. First thing I did was reload Mach3 version 066. When I first started my machine a couple of years ago I couldn't get the mill to home. When I pushed the ref all button the mill would blast past the limits and crash. After reloading Mach all was well. I next took the Y axis out of the series wiring circuit and connected it to pin 13. No luck again. When homing the accuracy is erratic, as much as +/- .020", or it trips the limit switch.
I'm not convinced it's a switch problem because it does trip when it reaches the machine's limit. I'll troubleshoot it some more and see where it leads me.
Tom S.
I'm not convinced it's a switch problem because it does trip when it reaches the machine's limit. I'll troubleshoot it some more and see where it leads me.
Tom S.
Maybe it's a sticky switch. It would still work, but not be accurate. I would try swapping with the X axis switch and see what happens. Maybe a squirt of contact cleaner would be helpful.
I agree, it's the switch. Ran a few more tests and the motor reversed a few times. When it did reverse the dial indicator readings repeated within +/- .001". I also ran two more tests; one test using the ref all button and the other test using the ref Y button. I first homed the axis and set my DI to zero as the basis point then ran ten repetitions. Using the ref all button my DI readings varied between +.001" and -.015" with the switch tripping twice. Using the ref Y button my readings varied between -.001" and -.012" with the switch tripping twice. All of my testing and what others have said leads me to believe it's the switch and not Mach3.
The switches are rated IP67 but I'll try the contact cleaner and see what happens. Whether I free up the existing switch or buy a new one I guess I won't know if my homing is accurate until I scrap a part.
Tom S.