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PM 940-m to cnc

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Davd Flowers

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#1
Its been about 2 years since I converted my g0704 to cnc and its been a good little mill to learn the basics of cnc but its smallish size has kept me looking for a larger cnc mill. I had been looking the the tormach 1100, and the charter oaks mill when I ran across the PM 940.
Looking at the PDF the mill seemed quite stout and very reasonable on price so I went ahead and pushed the button. The mill arrived yesterday and three of us wrestled it into the garage and up onto its stand. There is no picture or video on the net that can accurately portray just how large this mill is. you just have to see it in person. I'm waiting on a few more pieces but have nema 34 1200 oz stepper for all 3 axis, 70v 20 amp power supply, break out board, and the bearings. Just waiting on the 2005 double nut ball screws to come in.
The build will be done in stages. First I will get the axis up and running so I can put the mill to work, then later on in the year switch over to belt drive with a vfd to get things sped up. Further down the road i may build a tool changer, but i need to research that one some more.
If you are looking to convert a large mill take a good look at the pm 940, I am very happy with what I see so far. One thing i would suggest though is to order the deluxe model with hardened ways. If you order the stripped down version (like I did) it will not come with the electrical box on the back, control box with e stop button, or any limit switches and by the time you tally them into your build you will not save any money by omitting them.
Well thats it for now. I have to do some rearranging in the garage, get the goo off the mill, and then im going to start tearing it down. More to come, although it may be quite slow.

Hmmm, cant get pics to upload???
 

jbolt

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#3
Try converting .jpg files to .png. The site software has issues with some formats of .jpg's.
 

TomS

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#8
For info on my PM-932 conversion I used a 4200 oz. in. stepper on the Z axis and 1600 oz. in. steppers on the X and Y. All are direct drive. I have my Z axis gib tightened fairly snug to minimize nod and the 4200 stepper moves the gear head like it's not there. I don't know how much bigger the 940 head is so I can't comment on whether a 1200 stepper will work. All this being said I'm anxious to see more as you move through your conversion.

BTW - my stepper setup is the same as jbolt's and jumps4.

Tom S.
 

Davd Flowers

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#9
On the PM 940 CNC (factory conversion), they used 640 oz X and Y and 1200 on the Z. So Im hoping that since it works for them it will work for me. But I have to admit I do have some concerns on the Z.
If it does not work out the way I would like its no big deal. I ordered this set up as a kit with 3 steppers, drivers and single 70v 20A power supply and would just pick up one more stepper with an A/C drive for the z and use the extra drive for the A axis.
4200 oz sounds like a hell of alot of stepper!! If there isnt much of a price difference between them I may go that route as well....
 

phazertwo

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#11
I should be getting my PM-940 CNC tomorrow, and I also have some concerns about the 1200oz-in driving the Z. I am wondering if a 2-1 belt reduction will work for the z, essentially giving you 2400oz-in... There are also a bunch of guys running gas shock helpers on the Z, so you may have some options vs buying a N42 motor and making new mounts.

PZ
 

Davd Flowers

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#12
I should be getting my PM-940 CNC tomorrow, and I also have some concerns about the 1200oz-in driving the Z. I am wondering if a 2-1 belt reduction will work for the z, essentially giving you 2400oz-in... There are also a bunch of guys running gas shock helpers on the Z, so you may have some options vs buying a N42 motor and making new mounts.

PZ
Not what I call blazing fast, but it moves it and its only a 900 oz on a machine with about the same weight head...
 
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