Z Axis Power Feed for Precision Matthews PM-728VT Mill

[chipinator]

Hello all. I hope everyone is staying well. Looking around my Precision Matthews PM-728VT mill, I began wondering if there is a way to mount a power feed such as an Align power feed to the Z axis and still be able to use the hand crank/wheel for finer adjustments. I realize I can purchase a 3rd party Z axis power feed but I thought it might be a fun challenge to fabricate one. Before starting, I was wondering if anyone else has attempted a project like this? Anyone have any ideas? Any suggestions would be helpful.

 

[GunsOfNavarone]

I know there are a few threads here on the subject....some toying with the idea, some completed. The ideal way is a motor connected to end of ball screw at top, short cut/easier is connecting to the spline under the crank handle. I have eyeballed my PM727m's for a while, I hate cranking that thing BUT...if it wasn't for cranking it, I'd forget to lock down the gibs and our machines have BUTTLOADS of movement in the Z axis if not locked down.

 

[chipinator]

Hey GunsOfNavarone. Thanks for your insight. There is a 3rd party motor that connects as you descibe at the top end of the ball screw but I think that's going to be my last option. This is my first mill and wanting to be self sufficient, and maybe to learn a thing or two, I wanted to give it a try first or at least think through the process to see if it was even worth attempting. Would you happen to have an idea on what type of motor I could use to connect to the spline under the crank handle or how I could even do this? I'm trying to get some ideas at the moment.

 

[GunsOfNavarone]

There is a few threads here on the subject, here is that went to completion.
Z axis
I know there are simpler versions, though simpler may not be as ideal, but get you moving in the right direction.

 

[GunsOfNavarone]

Reviving an old thread, but have you solved this yet? If not, this looks like a great/easy fix. I'm wondering if the 728vt is close enough to my 727 to work as well...
Power lift

 

[addertooth]

According to some sources, the Priest kit has a motor which is slightly under-powered. This resulted in the users either having to loosen their Z-Axis Gibs, or add a gas-spring to help lift the head. Other than that limitation (which is serious) I like the way they tie into the existing mechanism to drive the existing gear train. A beefier motor (or geared down more) would resolve the challenges the Priest modification suffers from.

I have a PM728vt, and will admit my right shoulder is not fond of cranking the head up and down.

 

[GunsOfNavarone]

Hmmm…the gear reducing motor is probably cheap/easy to source, I wonder if that’s an easy swap?

 

[fursphere]

Blondihacks just did a video on installing one of Priest Tools on a PM25. Similar in nature.

 

[chipinator]

@GunsOfNavarone & @addertooth
I considered purchasing a Priest Z axis power feed and spoke directly with Mr. Priest concerning the undersized motor issue. At the time I spoke with him, it's been several months ago now, he didn't seem to think there was an issue. Maybe he's changed his mind. I haven't spoken to him since though. If he sourced a bigger/better motor, I would be interested in making the purchase, but until then, I won't buy it.

 

[fursphere]

Why not just get a stepper motor, stepper driver and power supply then add a rotary manual pulse generator?

At first it probably sounds expensive, but a power feed from PM is around $300, and the Priest Z Power Feed is $300 (with a questionable motor - I had the same thought when I saw the thing)

https://www.automationtechnologiesinc.com/products-page/mpgs/rotary-maunal-pulse-generator - $30 (this won't work without some additional equipment
Pulse generator on amazon - $15
Nema 23 is $20 - $50 depending on rating / Nema 34 is $30 - $80 depending on rating (amazon)
Stepper Driver - $40 (+/- (amazon)
Power Supply - Meanwell is around $40 for a 48v PSU (amazon)

$150 + some odds and ends like bolts and coupler and stock to machine a mounting plate? I dunno, something to think about. And you'd get a power down feed out of it too. If you don't might waiting a month or two, you can get it all cheaper from AliExpress.