Triac loosing Z datum
Moderators: Martin, Steve, Mr Magoo
- Roy
- CNC Expert
- Posts: 104
- Joined: Tue 30 Jan , 2007 20:20 pm
- Hardware/Software: 1986 Triac modified & running Mach 3
- Location: Bucks, UK
Triac loosing Z datum
A small problem sometimes occurs with my '86 Triac in that it looses its Z datum occasionally this happened once last Friday whilst milling some slots and twice yesterday whilst drilling and profiling.
What appears to happen is when it moves in the + direction away from the job it looses its zero, so next time it go's in the - direction it is deeper than intended. When milling some slots last week it came up from the job in rapid to what was supposed to be Z20, but when it plunged into the next slot it was about 3mm deeper and machined into the fixture plate
Any ideas why this loss or movement of the Z datum is occuring? could it be the drive board??
Thanks, Roy
What appears to happen is when it moves in the + direction away from the job it looses its zero, so next time it go's in the - direction it is deeper than intended. When milling some slots last week it came up from the job in rapid to what was supposed to be Z20, but when it plunged into the next slot it was about 3mm deeper and machined into the fixture plate
Any ideas why this loss or movement of the Z datum is occuring? could it be the drive board??
Thanks, Roy
- Denford Admin
- Site Admin
- Posts: 3634
- 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:
- Roy
- CNC Expert
- Posts: 104
- Joined: Tue 30 Jan , 2007 20:20 pm
- Hardware/Software: 1986 Triac modified & running Mach 3
- Location: Bucks, UK
Will Have a look at the Gib tonight, although I think this should be ok as I checked everything when I got the Machine in March.
I don't think its a Lubrication problem as there is plenty of oil getting to the slide and ballscrew.
With regard to only having problems recently, I have only recently being using the machine reguarly (Since last month), So could it be now that this is showing up some electrical probs? Just a thought?
Will advise outcome of Gib, Thanks Roy
I don't think its a Lubrication problem as there is plenty of oil getting to the slide and ballscrew.
With regard to only having problems recently, I have only recently being using the machine reguarly (Since last month), So could it be now that this is showing up some electrical probs? Just a thought?
Will advise outcome of Gib, Thanks Roy
Hi,
Sorry I don't know how you change the speed or if its possible on the PNC 3. I am sure someone else will know though.
If it had been running on VR Milling then the parameters are easy to change.
I would still look to the mechanics though as it will have run at that speed when new so something must have changed.
Good Luck.
Sorry I don't know how you change the speed or if its possible on the PNC 3. I am sure someone else will know though.
If it had been running on VR Milling then the parameters are easy to change.
I would still look to the mechanics though as it will have run at that speed when new so something must have changed.
Good Luck.
- Roy
- CNC Expert
- Posts: 104
- Joined: Tue 30 Jan , 2007 20:20 pm
- Hardware/Software: 1986 Triac modified & running Mach 3
- Location: Bucks, UK
Matt, 1000 mm/min is the rapid speed (G00), not feedrate!
I have investigated the Gib adjustment and this seems fine.
I wrote a little programme just moving the z up and down in rapid to try and observe whats happening. I notice when it starts to move in the Z+ direction there is a little 'knock' sound. This gets me thinking perhaps there is some backlash in the ballscrew, so I will try and look into this tommorow night.
Any tips on this one?
Cheers Roy
I have investigated the Gib adjustment and this seems fine.
I wrote a little programme just moving the z up and down in rapid to try and observe whats happening. I notice when it starts to move in the Z+ direction there is a little 'knock' sound. This gets me thinking perhaps there is some backlash in the ballscrew, so I will try and look into this tommorow night.
Any tips on this one?
Cheers Roy
- Triac whizz
- CNC Expert
- Posts: 238
- Joined: Mon 17 Jul , 2006 21:48 pm
- Location: France
Hmm, any backlash wouldn't acumulate. something loose maybe but still won't give 3mm of error - other than a pulley loose, also check the tightness/state of the belt & while you're there make a note of the size for future reference.
Self Catering Lodges in Central France with covered pool & large grounds
www.la-coterie.com
www.la-coterie.com
- Denford Admin
- Site Admin
- Posts: 3634
- 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:
- Triac whizz
- CNC Expert
- Posts: 238
- Joined: Mon 17 Jul , 2006 21:48 pm
- Location: France
Have you tried with a DTI? do a prog
G00 Z0
Z-100
Z0
Z-100...etc
then finish with Z-101 so that it kisses the DTI (which you've previously setto zero.
If it don't work at rapids try feedrates just to see if you can make it work.
I'm sure I've heard that those drives do that when they start going duff, but don't quote me on it
G00 Z0
Z-100
Z0
Z-100...etc
then finish with Z-101 so that it kisses the DTI (which you've previously setto zero.
If it don't work at rapids try feedrates just to see if you can make it work.
I'm sure I've heard that those drives do that when they start going duff, but don't quote me on it
Self Catering Lodges in Central France with covered pool & large grounds
www.la-coterie.com
www.la-coterie.com
- Triac whizz
- CNC Expert
- Posts: 238
- Joined: Mon 17 Jul , 2006 21:48 pm
- Location: France
perhaps it's your code
Self Catering Lodges in Central France with covered pool & large grounds
www.la-coterie.com
www.la-coterie.com
- Denford Admin
- Site Admin
- Posts: 3634
- 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:
This may be a long shot, but it could be electrical noise from the spindle.
I've have seen it where step pulses are "added" to the drive step input purely by noise coming from the spindle drive / motor wires - especially if the earthing and shielding isn't right.
Try run your test with ths spindle running, and try put load on it somehow (hold a plank of wood against it - at your own risk of course ! - I didn't recommend it - don't blame me etc....)
I've have seen it where step pulses are "added" to the drive step input purely by noise coming from the spindle drive / motor wires - especially if the earthing and shielding isn't right.
Try run your test with ths spindle running, and try put load on it somehow (hold a plank of wood against it - at your own risk of course ! - I didn't recommend it - don't blame me etc....)
If you take the program with the problem and run it first without the spindle running. (delete the M03's) and check if there is any loss of position.
If not add the M03's back in and try again. If still no problem then try while cutting.
If you have coolant it may be a noise problem with the coolant switching on and off so try with and without coolant.
You could put a clock on the spindle and then just start and stop the spindle. If there is a problem with noise it will occur on the accel and decel of the spindle which is the period when the current is highest.
You need to find the point where you have a stall and then work out what else is happening at that point.
If not add the M03's back in and try again. If still no problem then try while cutting.
If you have coolant it may be a noise problem with the coolant switching on and off so try with and without coolant.
You could put a clock on the spindle and then just start and stop the spindle. If there is a problem with noise it will occur on the accel and decel of the spindle which is the period when the current is highest.
You need to find the point where you have a stall and then work out what else is happening at that point.