Centroid Community CNC Support Forum

Recently I got help from the forum to get my M3 and M4 macros running correctly on my turret mill (thanks Keith, Marty and Swissi amongst others). These are working fine now so the machine switches automatically between high and low spindle ratio depending on whether the demanded spindle speed exceeds a threshold (currently 1000rpm).

The issue I have now is that I need to notify the controller when the low ratio is engaged so that it can provide the correct control voltage to the VFD. When the low gear is engaged, the PLC needs to run the motor faster to account for the reduction ratio (1:0.167). This functionality is catered for in the CNC12 PLC but according to the CNC12 4.14 manual, the gear range signals are expected on INP63 and INP64. On my machine, they already come in on Acorn inputs 1 & 2 (high ratio engaged = #50001 and low ratio engaged = #50002).
Is there a simple(?) way to connect INP64 to INPUT2 on the Acorn (aka #50002)? My machine has only high (1:1) and low (1:0.167) ratios, so all the required information would appear to be contained in #50002. INP63 doesn't change unless you are using the intermediate "medium low" and medium high" ratios which my machine does not possess.

Hope this makes sense but currently when I select a low spindle speed, the VFD runs the motor at that speed AND the low ratio is engaged. It barely creeps along.

The references to INP63 and INP64 are archaic information, left over from CNC7 and CNC10 (for an earlier generation of hardware). They do not apply to CNC11 or CNC12 and should be removed from the manual.

Your PLC program should have some type of logic to set a variable named SpindleRange_W to either 4 (high) or 1 (low) based on your switch state.

Standard PLC logic which follows will handle looking at Parameter 65 and adjusting spindle motor RPM.

Thanks for the direction, cncsnw - I'll have a look into that and see if I can figure something out. This will be a bit of a step in the dark for me...

Hi cncsnw - in the end I went back through your recent posts and came across this one which pretty much addresses the exact same issue. viewtopic.php?f=60&t=3026&start=10

I installed the revised Acorn PLC source template used by the wizard, then changed Input 1 to "Backgear" in the wizard - and Bob's your auntie!

Now, the high or low gear are automatically selected by my modified M3 and M4 macros, the VCP correctly displays "Spin High" or "Spin Low" and the spindle actually spins at the correct speed.

What isn't quite right is the spindle speed display in the main screen. It always says "0 A", where I assume the A stands for Automatic. Obviously it would be nice to display the spindle speed here - any idea what I'm missing? I was testing this by issuing S1200 M3 etc from MDI.