PM-728VT CNC Conversion Instructions

@JimDawson I'm definitely leaning towards the Centroid Acorn and software. I thought I remember reading something to the effect that their G code may be a little different. I can't remember where I read it though. Anyway... In my previous post, I meant proximity switches (limit switches) for the X, Y, and Z axis' so an accidental programming error doesn't cause the motors to crash the table. That would be nasty and likely expensive. Now I just have to narrow down which motors.
 
chipinator said:
@JimDawson I'm definitely leaning towards the Centroid Acorn and software. I thought I remember reading something to the effect that their G code may be a little different. I can't remember where I read it though.
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Fusion 360 has a Centroid post built in. There are no two software brands that use exactly the same G code. The basics are the same across the board, but some of the canned cycles can be different. For the most part, the primary codes that are used are G0, G1, G2, G3, and G81. You can make any part that your machine could possibly cut with only those codes, in fact, you really could cut any part only using G1, which is just a straight line cutting move.

chipinator said:
Anyway... In my previous post, I meant proximity switches (limit switches) for the X, Y, and Z axis' so an accidental programming error doesn't cause the motors to crash the table. That would be nasty and likely expensive. Now I just have to narrow down which motors.
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I figured that's what you meant. :) A lot of machines do use prox sensors, but it's my preference to use normal limit switches for this purpose. From a controls perspective, it really doesn't matter what type of switch you use as long as they work. Crashing a machine can really ruin your day. :eek:
 
@JimDawson In a perfect world, and you had precision ground double-nut ball screws, which motors would you use/prefer if you had my mill?
 
chipinator said:
@JimDawson In a perfect world, and you had precision ground double-nut ball screws, which motors would you use/prefer if you had my mill?
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I think I would go with the Automation Direct LS servo motors. 400W for the X & Y and 750W for the Z. These are the same motors I would use on my machine. I'm a little undecided on the need for the Z brake, I'm thinking a counter balance would be the better option.
 
@JimDawson I looked on the Automation Direct website and found the following servo motors -

APMC-FBL04AYK-AD [400W]
APMC-FCL08AYK2-AD [750W w/integrated brake]

I couldn't find a NEMA number on either of the motors. If the 400W motors are NEMA23 and the 750W is NEMA34, I'm good.

I know you aren't interested in an integrated brake, however, I had seen a couple of Tube videos with counterbalances and one with the integrated brake. I think I will try the integrated brake first and see how that performs. I do understand the counterbalances though.

Do you think the servos I listed above are ones that you would use or would you have different motors in mind?
 
chipinator said:
@JimDawson I looked on the Automation Direct website and found the following servo motors -

APMC-FBL04AYK-AD [400W]
APMC-FCL08AYK2-AD [750W w/integrated brake]

I couldn't find a NEMA number on either of the motors. If the 400W motors are NEMA23 and the 750W is NEMA34, I'm good.

I know you aren't interested in an integrated brake, however, I had seen a couple of Tube videos with counterbalances and one with the integrated brake. I think I will try the integrated brake first and see how that performs. I do understand the counterbalances though.

Do you think the servos I listed above are ones that you would use or would you have different motors in mind?
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Yes, that would be the correct motors.

They are not exact NEMA frame size equivalent. You would not know it unless you had them sitting side by side with a NEMA frame motor.
The 750W motor (80mm frame) has a slightly smaller face than the NEMA 34 frame, and has a 19mm shaft vs. the 1/2'' shaft of the NEMA 34.
The 400W motor (60mm frame) I'm not sure about yet. It does have a 14mm shaft vs. the 1/4'' shaft of the NEMA 23 motor.

I'm trying to get accurate dimensions but Fusion 360 is not cooperating tonight, having some file upload problems. It would be a simple project to make adaptor plates to fit the NEMA mounting brackets.

EDIT: The 400W motor face is just slightly larger than the NEMA 23 face.
 
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@JimDawson Thanks for that Jim. I appreciate your insight. This is very helpful.

When I first looked at the DMM AC servo motors, I noticed that their NEMA23 motors didn't have straight through mounting holes. The company kind of oblonged the holes I guess in an effort to allow them to mount easier. DMM emailed me that they have an 8mm adapter plate for those as well. When those motors were mounted, standing in front of the mill, instead of looking like a square with the flat sides at the cardinal points, the 90 degree edges of the motors were at the cardinal points, kind of in a star mounting position. Not a big deal I guess.

For the PM's ultra precision ballscrew kit, https://www.precisionmatthews.com/shop/cncballscrewkit-pm-728vt-up/, it looks like the provided couplers wouldn't work for the Automation Direct motors. I don't know if there are couplers that are made that would fit the Automation Direct motor shafts to the ballscrews given their size. I wish this were easier! I know, nothing in life worth having is easy.
 
chipinator said:
@JimDawson Thanks for that Jim. I appreciate your insight. This is very helpful.
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Thank you

chipinator said:
When I first looked at the DMM AC servo motors, I noticed that their NEMA23 motors didn't have straight through mounting holes. The company kind of oblonged the holes I guess in an effort to allow them to mount easier. DMM emailed me that they have an 8mm adapter plate for those as well. When those motors were mounted, standing in front of the mill, instead of looking like a square with the flat sides at the cardinal points, the 90 degree edges of the motors were at the cardinal points, kind of in a star mounting position. Not a big deal I guess.
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It's pretty common to make motor adapter plates, and the normal way of doing it is to rotate the motor to get hole clearance.

chipinator said:
For the PM's ultra precision ballscrew kit, https://www.precisionmatthews.com/shop/cncballscrewkit-pm-728vt-up/, it looks like the provided couplers wouldn't work for the Automation Direct motors. I don't know if there are couplers that are made that would fit the Automation Direct motor shafts to the ballscrews given their size. I wish this were easier! I know, nothing in life worth having is easy.
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You buy the coupler pieces separately. Yes, there are couplers that will fit.

EDIT:
X & Y axis
10mm

14mm

Spider for above

Z axis
10mm

19mm

Spider for above
 
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@JimDawson Jim...Thank you so much for your kindness in helping me. It truly doesn't go unnoticed.

I'm typically a person that tries to look far enough down the road to take into consideration issues that may arise. For instance, if a motor for some reason stops functioning and your CNC is now down. Have you ever seen a shaft coming out the back of these types of motors so that mill crank handles could attach? At leaset you would have manual control at that point. What do you think?
 
chipinator said:
@JimDawson Jim...Thank you so much for your kindness in helping me. It truly doesn't go unnoticed.
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My pleasure to help out where I can.

chipinator said:
I'm typically a person that tries to look far enough down the road to take into consideration issues that may arise. For instance, if a motor for some reason stops functioning and your CNC is now down. Have you ever seen a shaft coming out the back of these types of motors so that mill crank handles could attach? At leaset you would have manual control at that point. What do you think?
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A subject that is near and dear to my heart :) I have hand cranks on my machine and can operate full manual, 2 axis CNC with manual quill, 3 axis CNC with manual 4th axis, or full 4 axis CNC. All with change over in seconds. (Ok, it takes more than a few seconds to set up the 4th axis :grin: ) If I could only have one CNC machine in my shop, this would be the prefered system.

I have never seen a dual shaft servo motor. There are dual shaft stepper motors available, and I have seen handwheels attached to those. Not the best IMHO. The better way to do this is to offset the motor from the ball screw and drive the ball screw with timing pulleys. Then attach the handwheels directly to the ball screws. There are hundreds of machines out there configured like this.

Here is a picture of my machine showing the X and Y drives with the offset motors. The exact motor placement would be a bit different on your machine due to the different frame design. But maybe easier because your motors would be much smaller, my motors are about 12'' long and about 4'' diameter, old school brushed DC motors. Where your motors would be about 2.5'' square and 4'' long
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The down side of this is that the standard CNC kit would need to be modified a bit to accommodate the changes. Not really a big deal but would require a bit of engineering and fabrication. The extra parts and modifications could easily be done on the machine, before starting the installation of the new CNC conversion hardware.
 
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