PM-728VT CNC Conversion Instructions

@JimDawson If you were to have to use stepper motors for a machine like mine, which brand and model would you use that's able to accommodate mill crank handles? I'm interested mostly out of curiosity. Thanks.
 
chipinator said:
@JimDawson If you were to have to use stepper motors for a machine like mine, which brand and model would you use that's able to accommodate mill crank handles? I'm interested mostly out of curiosity. Thanks.
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I would probably go with Automation Technologies products, they have several dual shaft NEMA 23, and NEMA 34 motors available.

NEMA 23 Stepper Motor |

www.automationtechnologiesinc.com www.automationtechnologiesinc.com

Not better products than eBay or Amazon, at least they are a stocking USA distributor. And the one time I did have a problem with one of their products they were very responsive and sent a replacement with no hassle.
 
@chipinator I would consider servo motors if you want to maintain manual functionality. Stepper motors have a certain degree of "cogging" to them when rotated by hand. This is inherent in all stepper motors, but it does vary with the size of the stepper, and I also believe the manufacturer, although I do not have first-hand knowledge on that aspect, but rather, only from what I have read.
My mill and Jim's mill both have servo motors that are connected to the ball screw via timing belts. This system works very well and allows for easy manual control. One safety item I should mention is to purchase cranks that have the handle stow away. I feel that this is very important for a machine that has both manual and CNC capabilities. You don't want that handle sticking out when the axis activates.
Also, counterbalancing the Z-axis, in my opinion, would be important because when power is taken away from the servo motors, they are free to move, so your Z-axis will self-lower until it gets to the table.
The picture I have included shows the servo motor at the left end of the x-axis and the y-axis at the front,
IMG_20220526_204554475.jpg
but it is mounted low nearer the base. The handles are stow-away type. (This is a picture from the day when I brought it home)
 
I followed koenbro's thread when I converted mine. Bought the same acorn and clearpath servos. It's pretty decent. The clearpath stuff is fast and accurate, the PM precision ballscrew kit mounted with little trouble, and the acorn stuff has been great. After backlash adjustments I'm within .001.

schu
 
@7milesup Thanks for the picture; very nice acquisition. I have a cousin who's been a machinist/tool and die maker for a lot of years and he mentioned the same about timing belts. He told me that direct connects do not have the fidelity that timing belts do. In my case, without doing a lot of designing and fabricating, it looks like at least for now I'll have to stick with direct connect.

In the beginning, which is where I'm at, I just want to make sure I'm making all of the correct decisions up front. I'm not one that typically steps out immediately on a high dollar purchase - I mull it over for a couple of months going back to what I've decided on again and again until I feel I've made all of the best informed decisions.
 
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