For some reason G20 is Centimetres

[VanCnc]

Hey there everyone,

I've just started working on an old Makino with a Fanuc 0M controller and for some reason when in G20, the machine is using centimetres instead of inches....? Does anyone have any idea as to what could be causing this? Is there a parameter in the machine that could be changed to correct this? I'd like to get the machine back to "normal", though it's been this way since I started at this shop a few months ago.

I called Fanuc, but the service tech seemed very uninterested in giving me any worthwhile advice over the phone.

[dcoupar]

Are all the position displays in MM, or just the Machine Position display?
If it's only the Machine Positions, check parameter #0063 bit 0.

[VanCnc]

Thanks for the reply dcoupar

G20 should be displaying inches, though it actually uses centimetre positioning (the machine does display inches for positioning and for feeds, but I've confirmed the positioning is actually centimeters with a test piece I milled) ....which is very very very strange to me.


G21 won't even function properly because of this since it will convert everything by multiplying by the factor of 25.4 to change to millimeters, and when it does this it's obviously giving me positioning that is way off of what it should be.

[dcoupar]

If you program the following move, how far does the machine physically move?

G20
G01 G91 X-10. F10.

[VanCnc]

The machine would move negative 10 centimetres if I were to program that.

[dcoupar]

On the settings, is INCH: set to 1?

[VanCnc]

I believe it was, but I'll have to double check on Monday since I'm not at the shop right now.

[Dan Fritz]

Has anyone messed around with the parameters for DMR (detect multiplying ratio) or CMR (command multiplying ratio) ? These parameters determind how far an axis moves relative to the pulse coder feedback.

If you have an original parameter list from Makino, check to see if paramters 004, 005, 006, and 007 are set correctly. Also check parameters 100, 101, 102, and 103. If any of these vary from the original factory settings, you could get axis motion that does not agree with the display.

Also, check parameter 035, bit #7 (the bit on the far left). It should be set as Makino delivered the machine.

If an original parameter sheet can't be found for this machine, you'll have to calculate these parameters the hard way. To do that, you'll need to know the pitch of each axis ballscrew, the number of pulses per rev. of the pulse coders, and any gear or belt ratio between the ballscrew and the pulse coder.

There is also a parameter (somewhere) which can change the G-code table. It's normally set so that G20/G21 is inch/metric. It may, however, be used to change the inch/metric G-codes from G20/21 to G70/71. You may want to try to execute a G70 and see what happens.

[VanCnc]

I can't thank you guys enough for all of this help and can't express how frustrated I've been over the last little while trying to figure out what's going on.

The shop unfortunately purchased this machine sight unseen from a place in the states that was selling off their machinery due after closing their doors - no inspection, no verification of working condition (other than an email that basically said "Yep, it works good). They got the machine over here sometime in Feb 08, and I've only started working there, so it's entirely possible that someone has gone and mucked with the parameters either prior to or after it's arrival here.

This is actually my first foray into troubleshooting a machine as the shops I've worked for in the past have been large and would just call in a tech - so I'll probably have a lot of questions haha

I've just been working around this problem by converting everything I do into centimetres, but it'd be nice if I could just have a normal machine to work on instead of wasting time/productivity like that.

Where would I find DMR or CMR settings? I'll have to go through all of the documentation that came with the machine on Monday to see if there's a Makino parameter list.

[VanCnc]

Well I ended up getting an original parameter sheet from Makino, and solved my problems. It turned out being in parameter 1 bit 1 or 0 I think. I think it was SCW that was turned on if I remember correctly.

Thanks again for all of the help guys.