Axis Over-ride switch not working.

All info relating to the Denford Triac series of CNC milling machines

Moderators: Mr Magoo, Martin, bradders, Steve

Post Reply
MAX THE MILLER
CNC Apprentice
CNC Apprentice
Posts: 90
Joined: Tue 23 Aug , 2011 18:25 pm
Hardware/Software: Denford Triac PC. VR Milling 5.51.0.616

Axis Over-ride switch not working.

Post by MAX THE MILLER » Tue 03 Jul , 2012 15:51 pm

Triac PC running VR Milling 5.

I've adjusted the 'Z' axis limit switch actuating bar to prevent the cutter going through the table if an offset is set up wrongly.

Machine in jog mode. Head jogged downwards until it trips the Z axis limit switch, everything stops and "Emergency Stop" is displayed. Normal operation I assume?

Press the axis over-ride button. After a few seconds machine seems to activate and "Machine Ready" is displayed. Continue to hold down button and attempt to jog head upwards. Nothing happens. Machine stays still.

Sometimes I can get out of this by clicking on the home all axes button. At other times even this doesn't work and I have to open the cabinet and release the Z axis limit switch manually. I've never suceeded in jogging out of the situation though.

My background is in electronics, so I'd have no problem tracing the wiring from the switches back to the control cabinet. Thought I'd ask here first in case I'm doing something wrong though.

Thanks.

User avatar
Denford Admin
Site Admin
Posts: 3588
Joined: Fri 10 Feb , 2006 12:40 pm
Hardware/Software: Go to User Control Panel > Profile
Enter as much information about your CNC hardware and software as you can - it makes it easier for everyone to know what you're talking about then.
Location: Sunny Brighouse
Contact:

Re: Axis Over-ride switch not working.

Post by Denford Admin » Tue 03 Jul , 2012 16:53 pm

That limit switch sounds to be working OK.
I believe it's just in series with the Emergency stop push button, so in effect hitting the limit switch is like hitting the big red button.
The override pushbutton you're holding in, should be wired in parallel to the limits, so that when you press it, the emergency stop 'line' is energised again (as long as e.stop button is also out)

It's just occurred to me what's happening: when the control is e.stopped, the axis counters are reset to 0.000
This means that if the Z+ve limit (in parameters) is set to 0.000 then the machine will not jog +ve after an e.stop...you'll probably find you can jog the Z downhill (-ve) but not up :shock:
Homing out all axes after an emergency stop is the only solution.

MAX THE MILLER
CNC Apprentice
CNC Apprentice
Posts: 90
Joined: Tue 23 Aug , 2011 18:25 pm
Hardware/Software: Denford Triac PC. VR Milling 5.51.0.616

Re: Axis Over-ride switch not working.

Post by MAX THE MILLER » Tue 03 Jul , 2012 19:01 pm

Thanks. I'll check the actual wiring of the switches against the diagram and proceed from there.

MAX THE MILLER
CNC Apprentice
CNC Apprentice
Posts: 90
Joined: Tue 23 Aug , 2011 18:25 pm
Hardware/Software: Denford Triac PC. VR Milling 5.51.0.616

Re: Axis Over-ride switch not working.

Post by MAX THE MILLER » Tue 03 Jul , 2012 23:39 pm

I don't think this is a hardware problem. As Denford Admin stated, all the limit switches and the Emergency Stop Button are NC types wired in series with the coil of the ESR Relay. Operating any limit switch releases the ESR Relay. The axis over-ride switch (NO) is wired in parallel with all the limit switches. If a limit switch operates and releases the ESR Relay, then pressing the axis over-ride switch will energise it agian.

If I switch on the control cabinet and operate a limit switch I can hear the ESR relay drop out. It pulls in again if I release the limit switch. If I hold the limit switch depressed, then pressing axis over-ride energises the ESR Relay again.

This is all exactly as expected.

With VR Milling running, the Z axis is jogged until it operates the limit switch, which releases the ESR Relay and displays "Emergency Stop". At this stage pressing axis over-ride operates the relay again. Machine Ready is displayed, but jogging is impossible. The Z axis co-ordinate is displayed correctly. It doesn't revert to zero.

The only way out of this situation is to diconnect from the real machine and then reconnect. The machine can then be homed by pressing the axis over-ride switch and pressing the homing button on the PC screen.

This seems to be at variance with the user manual which suggests that with a limit switch operated and axis over-ride activated it should be possible to jog the Z axis.

Martin
CNC Guru
CNC Guru
Posts: 1678
Joined: Fri 24 Feb , 2006 17:09 pm
Location: Brighouse

Re: Axis Over-ride switch not working.

Post by Martin » Wed 04 Jul , 2012 6:47 am

If the axis activate a limit switch the software should see it as a emergency stop & therfore will need to be homed again while the Axis Limit Overide is pressed in.

Post Reply