Homing -- No pull off

flytyree

FlyTyree
The machine goes to the homing position and properly sets the homing sensors but does not pull off.

What am I missing?

Thanks
 

breezy

Arie
Staff member
What pull off distance have you set in the Homing screen?

Is MASSO displaying Ready in the top "Indicator lights"?

Are you using Auto Tool zeroing?

All these things can affect Homing.

Regards,

Arie.
 

flytyree

FlyTyree
What pull off distance have you set in the Homing screen? 0.2 inches

Is MASSO displaying Ready in the top "Indicator lights"? All homing sensors indicate "red"

Are you using Auto Tool zeroing? Don't know what this is.

All these things can affect Homing.

Regards,

Arie.
 

evermech

evermech
Hi @flytyree might I suggest taking all of the pull off settings away and see if you can get it to home without any alarms. Then you can gradually work on the pull off settings once you can get it to home.

Guy
 

flytyree

FlyTyree
Thank you Sir. I will try that first thing in the morning. It is a little late here; 9:55 PM. I appreciate you contact.
 

breezy

Arie
Staff member
What is your homing speed? Try slowing it down.

What is happening is that the Z axis is over shooting the limit switch and when it pulls off, the limit switch is still operated, hence the alarm.

I sometimes have an hard limit alarm on the X or Y axis and just pulling the relevant axis (they are belt driven) off the switch and rerunning the homing fixes it.
Quote from evermech on August 16, 2019, 3:46 am

Hi @flytyree might I suggest taking all of the pull off settings away and see if you can get it to home without any alarms. Then you can gradually work on the pull off settings once you can get it to home.

Guy,

I disagree here, you need some pull off to allow for the hysteresis in the limit switch, sometimes set pull off to a large value and then work to reducing it. But I agree that homing is a combination of speed and pull off.

Regards,

Arie.
 

evermech

evermech
Hi @breezy

is it possible to pull off in the wrong direction or is it always opposite of direction of homeing? Yah I usually blame feed rate and distance to prox first.

Guy
 

breezy

Arie
Staff member
Quote from evermech on August 16, 2019, 4:43 am

is it possible to pull off in the wrong direction or is it always opposite of direction of homeing? Yah I usually blame feed rate and distance to prox first.

When I set up homing, I have the machine sitting in the middle of its axis and set the homing sequence to individual homing moves so that I could stop homing if the axis moved in wrong direction. The first time I homed the machine I had the homing speed set same as rapid speed and the machine slammed into the end of the axis, I quickly adjusted the homing speed down to a crawl. Then I worked the speed and pull off until I was happy the homing speed was as high as possible and the pull off was as short as possible. (Why waste axis travel).

Pull off is in the opposite direction to the homing direction.
Quote from ECS on August 16, 2019, 4:50 am

It won't pull off if you have your coordinates wrong. I had that problem at one stage.

If your homing position is not the 0,0,0 position, then you have to set the coordinates so that when you issue G0/G1 X0 Y0 Z0 it will travel to the machines 0,0,0 position. And those coordinates need to match or be less than the values set in each axis travel settings, else you will get soft limit alarms and homing failures. How do I know, because that happened to me. So now I home to the 0,0,0 position.

Regards,

Arie.
 

evermech

evermech
@breezy

thanks for the explanation on how the homing cycle works. I don't use any pull off at all, and I am cycling to home position every 30 seconds. Must be a tight and solid axis I guess, no hard limit alarms as of yet.

Guy
 

masso-support

MASSO Support
Staff member
There is a limited distance (about 10mm) the axis will back off a sensor and if it cannot clear it in that distance it will give a homing alarm. This initial distance is not the pull off distance. The pull off distance is the additional distance it backs off after the sensor or switch goes low.

As Arie says speed is the main cause of these issues and causes the axis to overshoot by a distance that will not allow the sensor to clear in the initial back off.

In extreme cases it will overshoot a sensor and actually clear the sensor entirely causing it to go low so it doesn't need to do the back off but when it starts to do the pull off it trips the sensor and you get the hard limit.

Hope this helps

Cheers

Peter
 

breezy

Arie
Staff member
Quote from MASSO Support on August 16, 2019, 10:12 am

There is a limited distance (about 10mm) the axis will back off a sensor and if it cannot clear it in that distance it will give a homing alarm. This initial distance is not the pull off distance. The pull off distance is the additional distance it backs off after the sensor or switch goes low.

Peter,

Based on that I will test it on Monday at the Men's Shed.

Regards,

Arie.
 

flytyree

FlyTyree
Gentlemen. Thank you for your input.

The pull-off is now working. I slowed the rate down but I think the biggest issue was I had a "-" in front of the pull off values. Bad move. I removed the "-" from the Z axis and the Y axis and left the "-" in front of the X axis. Z and Y pulled-off. The X did not. Changed the X axis by removing the "-" and then all three axis function properly.

My bad. Again thank you for your input.

Clifford
 

breezy

Arie
Staff member
Quote from FlyTyree on August 16, 2019, 4:46 pm

The pull-off is now working. I slowed the rate down but I think the biggest issue was I had a "-" in front of the pull off values. Bad move. I removed the "-" from the Z axis and the Y axis and left the "-" in front of the X axis. Z and Y pulled-off. The X did not. Changed the X axis by removing the "-" and then all three axis function properly.

My bad. Again thank you for your input.

Clifford

Sometimes a photo will tell us more than alot of words.

Regards,

Arie.
 

breezy

Arie
Staff member
Quote from Breezy on August 16, 2019, 12:03 pm

Quote from MASSO Support on August 16, 2019, 10:12 am

There is a limited distance (about 10mm) the axis will back off a sensor and if it cannot clear it in that distance it will give a homing alarm. This initial distance is not the pull off distance. The pull off distance is the additional distance it backs off after the sensor or switch goes low.

Based on that I will test it on Monday at the Men's Shed.

Well I tested this and here is what I found.

Set back off to zero and homed the machine. It backed off the sensors and stopped as the sensor went low, but this left the sensor in a flickering state when watching the MASSO homing inputs. So when returning to MCS 0,0,0 position 9 out 10 times it would trip HARD LIMIT alarm.

I just needed to set back off to 0.1mm to prevent HARD LIMIT alarm from occurring when returning to 0,0,0 position.

Final back off was set to 0.5mm just be sure.

Regards,

Arie.
 

flytyree

FlyTyree
Arie, thank you very much for your effort. I have mine set on 0.1 " (.254 mm). Mine is working well on the 0.1" offset.

Clifford
 
Top