325 limit on home?

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cncsnw
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Joined: Wed Mar 24, 2010 5:48 pm

Re: 325 limit on home?

Post by cncsnw »

If you have space for one, I prefer this style of switch:
https://www.automationdirect.com/adc/sh ... abm6e32z11
Specifically, I like the one-way lever with roller. It is mechanically very reliable, and has reasonably short pre-travel and hysteresis. Usually I provide them with a steel ramp to trip against, but they can operate reliably against a corner of a casting, as in your Y installation.

Yes, CNC12 allows you to have a home switch separate from your two limit switches. However, that will not relieve you of the need to find a switch with low hysteresis.
610Garage
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Re: 325 limit on home?

Post by 610Garage »

cncsnw wrote: Tue May 11, 2021 12:52 pm If you have space for one, I prefer this style of switch:
https://www.automationdirect.com/adc/sh ... abm6e32z11
Specifically, I like the one-way lever with roller. It is mechanically very reliable, and has reasonably short pre-travel and hysteresis. Usually I provide them with a steel ramp to trip against, but they can operate reliably against a corner of a casting, as in your Y installation.

Yes, CNC12 allows you to have a home switch separate from your two limit switches. However, that will not relieve you of the need to find a switch with low hysteresis.
Thanks, I got two of those. I was going to get those originally but I wasn't sure how well they would like the sharp edge. I also have no idea how I will mount them and have the required adjustability. But I'll figure something out. :)

Thanks martyscncgarage for your help as well.
cncsnw
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Re: 325 limit on home?

Post by cncsnw »

I was going to get those originally but I wasn't sure how well they would like the sharp edge.
The steel roller should tolerate the cast iron edge with no problem. Just be sure to position the switch so that, if the axis overtravels and the roller climbs all the way onto the flat surface, it does not (quite) run out of compression in the plunger.
610Garage
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Re: 325 limit on home?

Post by 610Garage »

I got the new limit switch installed on the Z axis and, it still no worky. :( :( It's still throwing error 457 unable to find home. I have no idea where to look for the issue. Especially since it did home before I started to mess with the spindle and calibration. I don't think I made it very far with calibration before I found this issue. The only thing I can think of is that it is looking for an index marker that is failing somehow. :?: :?:

As a refresher, I am using sigma II drives in precision mode. I have also not fully calibrated. I know with the Z axis, a one inch move request equites to a .75" move in the real world. But I wouldn't think that would be enough to mess up homing. And I am using the following switch for the Z axis home switch.

https://www.automationdirect.com/adc/sh ... abm5e32z11
Attachments
IMG_20210510_131003.jpg
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martyscncgarage
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Re: 325 limit on home?

Post by martyscncgarage »

610Garage wrote: Sun May 23, 2021 3:37 pm I got the new limit switch installed on the Z axis and, it still no worky. :( :( It's still throwing error 457 unable to find home. I have no idea where to look for the issue. Especially since it did home before I started to mess with the spindle and calibration. I don't think I made it very far with calibration before I found this issue. The only thing I can think of is that it is looking for an index marker that is failing somehow. :?: :?:

As a refresher, I am using sigma II drives in precision mode. I have also not fully calibrated. I know with the Z axis, a one inch move request equites to a .75" move in the real world. But I wouldn't think that would be enough to mess up homing. And I am using the following switch for the Z axis home switch.

https://www.automationdirect.com/adc/sh ... abm5e32z11
Is the control hitting the switch, and backing off of continue moving and then stop?
IF so, sounds like the control is not finding the index pulse on the encoder.
What make and model drives and motors are you using and please post a fresh report?

Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
610Garage
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Re: 325 limit on home?

Post by 610Garage »

martyscncgarage wrote: Sun May 23, 2021 6:34 pm Is the control hitting the switch, and backing off of continue moving and then stop?
IF so, sounds like the control is not finding the index pulse on the encoder.
What make and model drives and motors are you using and please post a fresh report?

Marty
It hits the switch, backs off until it clears, then I think it tries to move back toward the switch. I was positive till you said something. :) I'll look at the belt directly to make sure that it is moving.

I'll try to generate a report tomorrow. I was going to generate one tonight but my 3 phase generator decided to have a battery cable problem. :roll: I'll also look at PLC Detective to see if it can monitor the index line from the z axis. Not sure if that is possible, but I just thought of it. :)

Z: SGDM-15ADA-V
X,Y: SGDM-08ADA
martyscncgarage
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Re: 325 limit on home?

Post by martyscncgarage »

You should be able to watch the PID screen as you rotate the motor by hand. An asterisk will appear next to the axis number when the index pulse cones around once per revolution.

Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
610Garage
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Re: 325 limit on home?

Post by 610Garage »

Z axis moves toward the switch, trips it, backs off, and clears it. It then, very slowly, continues to back away from the switch. Then the error pops up. Shouldn't it move toward the limit switch in order to find the index?
Also, an index pulse is being captured, thanks for the tip martyscncgarage. There is an asterisk, but only for a split second. Not sure if that is correct or if it matters. I thought it was suppose to flip flop. I wasn't rotating by hand if that matters. Can't on Z axis.
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cncsnw
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Re: 325 limit on home?

Post by cncsnw »

Go to the PID screen.
Press Emergency Stop.
Note the "Abs Pos" value for the Z axis.
Turn the motor shaft one revolution.
Note the new "Abs Pos" value for the Z axis.

What is the difference between the two positions?

If you have more than 16384 counts in one revolution of the motor, then the control may not find the index pulse in what it thinks is the first full turn (first 16384 counts) after it clears the switch, and you will get a 457 error.
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Re: 325 limit on home?

Post by 610Garage »

cncsnw wrote: Tue May 25, 2021 1:57 am Go to the PID screen.
Press Emergency Stop.
Note the "Abs Pos" value for the Z axis.
Turn the motor shaft one revolution.
Note the new "Abs Pos" value for the Z axis.

What is the difference between the two positions?

If you have more than 16384 counts in one revolution of the motor, then the control may not find the index pulse in what it thinks is the first full turn (first 16384 counts) after it clears the switch, and you will get a 457 error.
Thanks again cncsnw. That led me to my problem. Counts per rev in centroid was set to 8192 instead of 32768. So it obviously wasn't rotating the motor a full revolution to trip the index pulse. Changing the CPR value to 32768 corrected all homing issues. I have no idea why, or even when I changed that, but I obviously did. I'll slap myself upside the head at a later date. :)

Thank you martyscncgarage for your help as well.
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