Precision Matthews PM-728VT CNC conversion

[koenbro]

Good morning All!
I trust this finds you all safe and keeping well?

Thank you for this wonderful build post and all the insightful advice as I too just received my PM-728V-T this past weekend and would like to convert it eventually to CNC. I also received the PM-1130 lathe which I will convert to CNC at a later time as well. If I may trouble those of you who have built enclosures for your PM-728's; what are the dimensions of your enclosures and the clearances you have allowed for on each side, front and back from the machine?

I'd like to construct the base(pan) first and then mount the machine on it.

Mine is 48” wide x 31” deep x 27” high. There are photos of it earlier in this thread.


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[koenbro]

Have installed yesterday the rapid tool changer from Priest. Works well, ave to figure out how to stop air leaks.


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[koenbro]

Also have broken down and bought the Teknic x-axis brake. After some fumbling because noob, it was easy to wire into Acorn and works very well. My concerns about weights with a pulley or the air cylinder is that they will not precisely keep the z position. With the brake if I press cancel or e-stop the system keeps z.

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[adamyq]

I have been following this for a while and bugging koenbro via PMs, he suggested we move it to the main board.

I have duplicated the teknic order to include the brake (and forgotten AC powder cord). Doesn’t appear prices have moved at all. I share koenbro’s philosphy of buy once cry once, so I went with all the upgraded motors and e-brake.

 

[adamyq]

I just got my PM728 into the shop and started teardown for the ball screw install (I assume you swap them in order of Z-Y-X). My current questions:

1. Does the e-brake require an additional coupler? I haven’t ordered the McMaster items previously linked yet.

2. I know the 728 has 12mm slots, and I have a Kurt DX6 vise. I need to snag some keys, but they only list 1/2” standard keys. I assume they’ll fit/work, but figured I would ask.


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[koenbro]

1. Does the e-brake require an additional coupler? I haven’t ordered the McMaster items previously linked yet.

2. I know the 728 has 12mm slots, and I have a Kurt DX6 vise. I need to snag some keys, but they only list 1/2” standard keys. I assume they’ll fit/work, but figured I would ask.

Thank you @adamyq for your messages and agreeing to transfer here.

You do NOT need an extra coupler for the Teknic brake. To clarify, you already need one coupler to connect the servo motor and the ball screw, so you do not need a second coupler. The brake has a both a female end into which connects the z servo motor, and a male end that mates with the Z-axis screw via the one coupler you need. The female end of the brake has a built in coupler-like tightening mechanism to attach the 1/2" motor shaft. The brake's housing has a hole/tunnel and you rotate the brake shaft until you can reach the built-in coupler's screw with an allen wrench.
As I posted earlier in this thread, the coupler provided by PM is metric so it attaches to the ballscrew, but then you have to provide your own replacement end to attach the inch motor shafts (3/8" x2 and 1/2"). I got them from McMaster Carr ( 2401K14 and 2401K15 ) and were pricey ($130 for the three). You reuse the spider from PM.

As for the 1/2" keys for the vise, I do NOT think they will work in the 12mm slots. If someone knows otherwise please chime in because I am also interested in mounting keys for my DX4 vise.

 

[koenbro]

@adamyq , you mentioned that you will use a Masso controller. I am not familiar so looked it up; this looks fantastic!!

I might have gone with this solution had I known about it at the time. It is so nice to know that amateurs like us have access to high-performing controllers.


Will follow with great interest your build to see how you integrate probes, limit sensors and touch off devices. I found them to be invaluable and love the KP-3 probe, MPG and limits.

 

[adamyq]

[mention]koenbro [/mention] I think I am actually going to chicken out of the mass for the time being and mimic your acorn setup, main reason being I like the wireless pendant option better. I’m simultaneously building an airplane and often need to manually mill some brackets or special tooling. Also very interested if you can essentially control the system like a power feed for refacing surfaces.

Full disclosure, I started going down all sorts of rabbitholes because of this thread (4th axis, pneumatic tool changer, touch probes, etc), but I’ve forced myself to dial back and really focus on getting it back to being a functional semi-manual (mpg) mill.

Maybe someday I’ll get me up going the Masso route…the benefit of the acorn is that it’s very inexpensive and there is a cult following that May be interested in resale of components.


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[adamyq]

As for the 1/2" keys for the vise, I do NOT think they will work in the 12mm slots. If someone knows otherwise please chime in because I am also interested in mounting keys for my DX4 vise.

I know the PM clamp kit acknowledges that it’s a 1/2” kit but says it will work on the 12mm slots. I may just order the 1/2” and, you know, mill them down to 12mm.


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[adamyq]

Ok, just spent 2 hours disassembling and reassembling with the ultra precision cnc screw kit. As koenbro said, the drawing is fairly sufficient, though I had to stare at the y axis screw covers for a minute because I didn’t pay attention to their orientation when I pulled the Y off.

I was pretty proud of myself….until cleaning up I discovered the dreaded bag of extra parts. Looks like 3 grease fittings, and I’m betting they go on the double bearings somewhere.

Hard to tell if I got the gibs reinstalled correctly (again they fell out before I could note orientation). I put the smoother sides against the dovetails, which would make sense.

Other thing worth noting was the same comment made early about the bearing nuts. Having read that, I played around a bit and see how one could easily end up with backlash. I’ll have to make a spanner to properly tighten them, but good enough for now.

Thanks to everything who provided comments and feedback, it made this step of the conversion much easier.


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