Spindle Motor Recommendations

All things related to the Centroid Acorn CNC Controller

Moderator: cnckeith

jpmsteadi
Posts: 45
Joined: Fri Feb 19, 2021 5:51 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F1121A-1204204111

Spindle Motor Recommendations

Post by jpmsteadi »

Hi all!

I have been very happy with running my CNC mill these last couple of month and have been cranking out parts I have designed, but the big bottleneck in my mill currently is the spindle motor. From the factory the Precision Mathews PM-728VT comes with a 1hp brushless DC motor for the spindle. This allows them to do variable speed cheaper than a VFD and three phase motor, which is great, but comes at the expense of torque, especially at higher RPM in the high speed pulley range.

As I am doing mostly aluminum and smaller parts this is starting to really fight what I would like to do. I have ordered new, nicer bearings (all NSK, and high precision for the angular contact) for the spindle to be confident in spinning it faster, but am still searching around for a motor to use.

I would love a motor in the 1.5-2hp range, preferably aluminum for weight, and ideally happy (bearings wise) to spin at 6-8K rpm using a VFD.

Based on the great video series by Marty I have been looking at the TopTech motors (he is using one on his newest build it seems) and have found this particular motor: https://www.caldwellmotors.com/products ... hase-motor

Still debating 2 pole vs 4 pole as well. Most of the stuff I have read seem to indicate that 4 pole is the way to go, especially with a VFD as you can always overdrive it, but given that 99% of my machining is going to happen over 3600 rpm, it seems like 2 pole might make more sense for me.

Just wanted to tap into the hive mind here and see if anyone had any thoughts on this as I move forward!

Thanks in advance!

-jpm
jpmsteadi
Posts: 45
Joined: Fri Feb 19, 2021 5:51 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F1121A-1204204111

Re: Spindle Motor Recommendations

Post by jpmsteadi »

Just to double post here:

I have been doing research all morning and I stumbled across another clearpath servo on ebay that took me down quite the rabbit hole. I am now also considering going this route: https://www.teknic.com/model-info/CPM-M ... =230VAC1ph

It won't spin as fast, but has way more torque, so could be pulley geared to get the speed I want. I think even with using the pulleys my effective torque at the cutting tool would be higher, certainly at the peak power.

The advantages of this are:
-simpler. no VFD, no enclosure needed, could just wire in an additional contactor into my cabinet to control the on/off of my 240v single phase. Can control RPM via PWM. There are tons of cheap converters to go from 0-10v to PWM (
-higher peak HP, by a lot.
-lighter. About 5lbs lighter than the lightest three phase motor I could find
-less potential for EMI? Since the servo is all integrated there may be less interference issues than a VFD. Not sure on this.

Disadvantages:
-more expensive (though only slightly? the motors I have been looing at are in the 280-400 dollar range, plus VFD, plus enclosure)
-adding in conversion steps = not as reliable? (not sure on this, I have had great luck with my Clearpath servos, but this is clearly going a slightly different route)

I would love anyone's thoughts on this!

Thanks!
-jpm
jpmsteadi
Posts: 45
Joined: Fri Feb 19, 2021 5:51 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F1121A-1204204111

Re: Spindle Motor Recommendations

Post by jpmsteadi »

And now for a third post (hopefully this stuff will come in handy for someone else one day!)

It seems Teknic offers an analog to digital converter board as well: https://www.teknic.com/files/downloads/ASU_manual.pdf

About 60 dollars, but interfaces with their motors specifically. I think I would go that route to loose any of the unreliability of using cheaper conversion electronics.
martyscncgarage
Posts: 8462
Joined: Tue Mar 28, 2017 12:01 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Location: Mesa, AZ

Re: Spindle Motor Recommendations

Post by martyscncgarage »

I would recommend a 3 phase motor and a VFD with Sensorless Vector Control.
Automationdirect.com GS3 series or Factorymation.com TD400 series.

Some say they have used AC servos successfully for a spindle motor.

Marty
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
jpmsteadi
Posts: 45
Joined: Fri Feb 19, 2021 5:51 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F1121A-1204204111

Re: Spindle Motor Recommendations

Post by jpmsteadi »

Thanks for the quick reply Marty! I will look at those websites!

What is the thought process for VFD three phase AC vs AC servo? just cost/performance?
martyscncgarage
Posts: 8462
Joined: Tue Mar 28, 2017 12:01 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Location: Mesa, AZ

Re: Spindle Motor Recommendations

Post by martyscncgarage »

jpmsteadi wrote: Sun Mar 28, 2021 11:26 am Thanks for the quick reply Marty! I will look at those websites!

What is the thought process for VFD three phase AC vs AC servo? just cost/performance?
I have tried to use a DMM Dyn4 AC servo for a spindle. Tuning issues for me.
You will need a servo that will take 0-10VDC analog input and has the ability to reverse with an input.

You will have to search Servo Spindle in the search box and research. I won't use the combination.
3 phase motors and SVC VFD's work well for me.

Shame PM just didn't do it this way to begin with, but yes, it would have increased the cost. But its a tried and true combination.
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
jpmsteadi
Posts: 45
Joined: Fri Feb 19, 2021 5:51 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F1121A-1204204111

Re: Spindle Motor Recommendations

Post by jpmsteadi »

Yes, it seems the analog board option (https://www.teknic.com/files/downloads/ASU_manual.pdf) that Teknic offers for the MC line of integrated servos (made for velocity control rather than positional) will take in a 0-10v signal as well as a direction signal (when high CC when pulled low CCW, I imagine doable via a relay as it is done now).

The only issue with the 3 phase motors in this application for me are the weight. To get in the power range I was hoping for they are in the 45 lbs for the motor lines you suggested. I have been looking for an aluminum frame motor and they are out there, just not super common.

It really is a shame PM didn't do it to begin with. If I both knew when I knew now when I was looking for a mill and also knew how much I would enjoy it all I would have gone a slightly different route I think. Though the mill is very well constructed. BLDC motors just aren't really suited for the application.

I am out of town for about two months for work, so I have plenty of time to research and decide what route I want to go!
bleiler60
Posts: 11
Joined: Sat Feb 27, 2021 10:55 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F2C7C9-0211214367

Re: Spindle Motor Recommendations

Post by bleiler60 »

Hi jpmsteadi,
I had a Grizzly G704 that I planned on doing a cnc conversion, which had a 1 hp motor (750 watts). I purchased a 1 1/2 h.p motor from the company that manufactured the motor, which is in China. I noticed that the PMV-30 Mill comes with a 2 h.p motor, this maybe an option for you. I looked into going with a ac motor, but the weight of the motor was an issue. CNC zone has a lot of great info on mill conversions, check it out.
jpmsteadi
Posts: 45
Joined: Fri Feb 19, 2021 5:51 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: No
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: No
CPU10 or CPU7: No
CNC Control System Serial Number: E415F6F1121A-1204204111

Re: Spindle Motor Recommendations

Post by jpmsteadi »

Thanks for the tip! I will look them up!
martyscncgarage
Posts: 8462
Joined: Tue Mar 28, 2017 12:01 pm
Acorn CNC Controller: Yes
Allin1DC CNC Controller: Yes
Oak CNC controller: No
MPU11 & GPIO4D -w/ 3rd Party Drives: No
DC3IOB: No
CNC12: Yes
CNC11: Yes
CPU10 or CPU7: Yes
CNC Control System Serial Number: none
Location: Mesa, AZ

Re: Spindle Motor Recommendations

Post by martyscncgarage »

If you had more head weight you either counter balance it or use a stronger motor on the Z axis.
I would like to hear/see more success stories shared about users replacing their spindle motors successfully with Servos and their experience.
Reminder, for support please follow this post: viewtopic.php?f=20&t=383
We can't "SEE" what you see...
Mesa, AZ
Post Reply