How do I account for belt driven reduction and multiple pulses per rev

All things related to the Centroid Acorn CNC Controller

Moderator: cnckeith

Post Reply
Justin2200
Posts: 8
Joined: Mon Nov 02, 2020 6:46 pm
Acorn CNC Controller: No
Allin1DC CNC Controller: No
Oak CNC controller: No
CNC Control System Serial Number: none
DC3IOB: No
CNC12: No
CNC11: No
CPU10 or CPU7: No

How do I account for belt driven reduction and multiple pulses per rev

Post by Justin2200 »

So here's how things are setup.

PM940V conversion running Acorn into a Delta VFD-E. The base specs on this motor are 0-1390 RPM and I have Acorn currently configured to this.
The spindle itself is driven by a belt from the motor with two possible pulley arrangements. The low gear arrangement is approximately 1:1 However, the high gear drive is 1:3.75.

So, if I tell my VFD to run at 1000 RPM, it drives the motor to 1000, and in high gear, this drives the spindle to 3750. Furthermore, the spindle has a 24V hall effect sensor which reads the spindle RPM and sends it to Acorn. However, this particular spindle reads FOUR pulses per rev instead of one.

Is there a way to account for both of these in CNC Mill 12 so that I can put actual spindle RPM in my Fusion toolpaths and Gcode instead of having to manually calculate for the speed multiplier?

Basically, I want the Mill software to be able to read 3750 RPM in the Gcode and send a 1000 RPM frequency signal to the VFD, as well as show me 3750 on the RPM readout instead of 15000.

Hardware: PM940V with Acorn Rev4, spindle motor 0-1390 RPM. 1:3.75 pulley ratio to spindle with 4 pulse/per rev hall effect sensor
Software: CNC Mill 12 Pro, Fusion 360 CAD/CAM.

Have attached a photo of the belt drive and motor assembly for reference. Also attached is current Report
Attachments
report_0035FF621168-1202204167_2022-01-03_13-25-56.zip
(604.84 KiB) Downloaded 39 times
20220103_131606.jpg
cncsnw
Posts: 3765
Joined: Wed Mar 24, 2010 5:48 pm

Re: How do I account for belt driven reduction and multiple pulses per rev

Post by cncsnw »

Basically, I want the Mill software to be able to read 3750 RPM in the Gcode and send a 1000 RPM frequency signal to the VFD,
The only way to make that happen is to tell the PLC which position the belt is in. That is typically done either with:
1) A switch or sensor on a PLC input (easier to implement on a back gear lever than a belt)
2) A VCP button to indicate high range vs. low range
3) M functions (e.g. M41 / M44) you have to execute at MDI or in your program

Once the PLC knows what position the belt is in, it can set SpindleRange_W to either 1 or 4, which will then trigger code that uses Parameter 65 to compensate speed commands and, if necessary, direction.
tblough
Posts: 3072
Joined: Tue Mar 22, 2016 10:03 am
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
CNC Control System Serial Number: 100505
100327
102696
103432
7804732B977B-0624192192
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
Location: Boston, MA
Contact:

Re: How do I account for belt driven reduction and multiple pulses per rev

Post by tblough »

https://centroidcncforum.com/viewtopic.php?f=63&t=1650 tells how to calibrate your VFD.

Parameters 65-67 control the spindle gear ratio settings. I believe there is also a setting in the Wizard for this.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
Justin2200
Posts: 8
Joined: Mon Nov 02, 2020 6:46 pm
Acorn CNC Controller: No
Allin1DC CNC Controller: No
Oak CNC controller: No
CNC Control System Serial Number: none
DC3IOB: No
CNC12: No
CNC11: No
CPU10 or CPU7: No

Re: How do I account for belt driven reduction and multiple pulses per rev

Post by Justin2200 »

tblough wrote: Mon Jan 03, 2022 3:19 pm https://centroidcncforum.com/viewtopic.php?f=63&t=1650 tells how to calibrate your VFD.

Parameters 65-67 control the spindle gear ratio settings. I believe there is also a setting in the Wizard for this.
That describes how to get your VFD to spin your motor at the commanded speed. The motor IS spinning at that speed, but it's driving the spindle through a belt which has a multiplication factor.
tblough
Posts: 3072
Joined: Tue Mar 22, 2016 10:03 am
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: Yes
CNC Control System Serial Number: 100505
100327
102696
103432
7804732B977B-0624192192
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
Location: Boston, MA
Contact:

Re: How do I account for belt driven reduction and multiple pulses per rev

Post by tblough »

You don't tune the VFD for the motor speed, reading carefully, the document tells you how to get the SPINDLE to spin at the commanded speed. You tune if for the spindle speed when in high range. You then use the gear ratio parameters for the other ranges.

If you only have one speed and no others, then it's just a matter of tuning the VFD for the correct spindle speed.
Cheers,

Tom
Confidence is the feeling you have before you fully understand the situation.
I have CDO. It's like OCD, but the letters are where they should be.
Post Reply