Z homing issues and random stoppages

[snowdenworkshops]

I've been running my Carve King for 6 months using both Fusion 360 and VCarve 10.  Recently I've been having UGS lock up in the middle of a carve. I've tried using a new computer, new gcode files, and a new USB cable.  It seems pretty random when it stops too. its never in the same place when using same Gcode.  After a few hours of trouble shooting,  I noticed that the z axis was not always reaching it's respective homing switch during every time i homed the machine. I did some on reading about random induced voltages or EMF causing the CNC shied to think a homing switch had been made. I have tried my best to separate anything that might be inducing voltage, however I am still having the same issue.

I've got another ardunio and CNC shield on order to see if that could be the issue. Looking for any suggestions or ideas.

[Derek the Admin]

Good troubleshooting. It's electrical interference. The factory default is that $21 (hard limits) is equal to 0 (off). If it's on then it will often trip randomly. Are you getting a hard limit or a control reset?

[snowdenworkshops]

In real life I am an Automation Engineer, so troubleshooting is nothing new.

I did get the hard limit alarm once.

[snowdenworkshops]

Most of the time UGS just stops with no with alarm. UGS kind of freezes.

What is the purpose of the hard limits?

[Bruce]

github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration#21---hard-limits-boolean

$21 - Hard limits, boolean
Hard limit work basically the same as soft limits, but use physical switches instead. Basically you wire up some switches (mechanical, magnetic, or optical) near the end of travel of each axes, or where ever you feel that there might be trouble if your program moves too far to where it shouldn't. When the switch triggers, it will immediately halt all motion, shutdown the coolant and spindle (if connected), and go into alarm mode, which forces you to check your machine and reset everything.

To use hard limits with Grbl, the limit pins are held high with an internal pull-up resistor, so all you have to do is wire in a normally-open switch with the pin and ground and enable hard limits with $21=1. (Disable with $21=0.) We strongly advise taking electric interference prevention measures. If you want a limit for both ends of travel of one axes, just wire in two switches in parallel with the pin and ground, so if either one of them trips, it triggers the hard limit.

Keep in mind, that a hard limit event is considered to be critical event, where steppers immediately stop and will have likely have lost steps. Grbl doesn't have any feedback on position, so it can't guarantee it has any idea where it is. So, if a hard limit is triggered, Grbl will go into an infinite loop ALARM mode, giving you a chance to check your machine and forcing you to reset Grbl. Remember it's a purely a safety feature.

[Derek the Admin]

We could try replacing the board if you aren't getting anywhere with it.

[asumasensei]

It sounds like a combo of problems with interference being the main issue but UGS freezing too. It started happening to me during especially complicated or long runs but has become such a problem for me I'm moving away from UGS entirely. Nothing like managing handheld dust collection (for my dust collection boot) for 2 hours only to have UGS freeze up so I have to start all over lol

I bought some shielded 18-4 on Amazon and I'm just going to rewire everything with it but in the meantime I only replaced my Z & X homing switch wires (separate runs) and it solved the alarm issues for me.

[snowdenworkshops]

Feb 8, 2020 4:05:35 GMT asumasensei said:

It sounds like a combo of problems with interference being the main issue but UGS freezing too. It started happening to me during especially complicated or long runs but has become such a problem for me I'm moving away from UGS entirely. Nothing like managing handheld dust collection (for my dust collection boot) for 2 hours only to have UGS freeze up so I have to start all over lol

I bought some shielded 18-4 on Amazon and I'm just going to rewire everything with it but in the meantime I only replaced my Z & X homing switch wires (separate runs) and it solved the alarm issues for me.

I was thinking about running some shielded cable and actually grounding the control system some how. 

[snowdenworkshops]

Feb 4, 2020 16:17:22 GMT Bruce said:

github.com/gnea/grbl/wiki/Grbl-v1.1-Configuration#21---hard-limits-boolean

$21 - Hard limits, boolean
Hard limit work basically the same as soft limits, but use physical switches instead. Basically you wire up some switches (mechanical, magnetic, or optical) near the end of travel of each axes, or where ever you feel that there might be trouble if your program moves too far to where it shouldn't. When the switch triggers, it will immediately halt all motion, shutdown the coolant and spindle (if connected), and go into alarm mode, which forces you to check your machine and reset everything.

To use hard limits with Grbl, the limit pins are held high with an internal pull-up resistor, so all you have to do is wire in a normally-open switch with the pin and ground and enable hard limits with $21=1. (Disable with $21=0.) We strongly advise taking electric interference prevention measures. If you want a limit for both ends of travel of one axes, just wire in two switches in parallel with the pin and ground, so if either one of them trips, it triggers the hard limit.

Keep in mind, that a hard limit event is considered to be critical event, where steppers immediately stop and will have likely have lost steps. Grbl doesn't have any feedback on position, so it can't guarantee it has any idea where it is. So, if a hard limit is triggered, Grbl will go into an infinite loop ALARM mode, giving you a chance to check your machine and forcing you to reset Grbl. Remember it's a purely a safety feature.

So basically $21 =1 enables the homing switches or does it use the homing switches only, disabling the soft limits.                                         

[snowdenworkshops]

Feb 6, 2020 0:12:57 GMT Derek the Admin said:

We could try replacing the board if you aren't getting anywhere with it.

Been out in the field all week. going to looking into it more today.   Going to set $21 to 1, look for ways to ground the circuit, and maybe replace the homing switch wiring with a shielded pair. 

I have a new ardunio and cnc shield on hand just in case.

[snowdenworkshops]

Just wanted to say thanks for all the help!

[Bruce]

Homing is controlled by parameter $22. Type $22=1 to enable it, $22=0 to disable it. Homing can be triggered by typing $H.
github.com/gnea/grbl/wiki/Set-up-the-Homing-Cycle

You will want to disable both hard limits-$21=0, and soft limits-$20=0 for now. You may never really need them.

[jms]

If you have a spindle only ground the VFD end. This is what I have been told. in Fact a friend of mine that installs big ass fans told me they had a problem with grounding both ends that actually caused the ball bearings to arc and ruin the motors. So they had to come up with a new design.

[mguyre]

Feb 4, 2020 0:45:17 GMT snowdenworkshops said:

I've been running my Carve King for 6 months using both Fusion 360 and VCarve 10.  Recently I've been having UGS lock up in the middle of a carve. I've tried using a new computer, new gcode files, and a new USB cable.  It seems pretty random when it stops too. its never in the same place when using same Gcode.  After a few hours of trouble shooting,  I noticed that the z axis was not always reaching it's respective homing switch during every time i homed the machine. I did some on reading about random induced voltages or EMF causing the CNC shied to think a homing switch had been made. I have tried my best to separate anything that might be inducing voltage, however I am still having the same issue.

I've got another ardunio and CNC shield on order to see if that could be the issue. Looking for any suggestions or ideas.

I have the exact same issue on the z-axis of on my Carve King. Did you ever figure it out?