Centroid Community CNC Support Forum

I recently purchased this 1996 Chevalier CNC bed mill, NMTB 40# taper spindle. 6,600 lbs. Since I'm making real progress on refurbishing the mechanical I ordered up the first batch of electrical and CNC retrofit gear today. This will be my first Centroid Acorn retrofit. This is replacing the 1996 Dynapath CNC controller, drives, software.

Inbound

1. Acorn CNC Controller Kit (cnckeith added: https://shopcentroidcnc.com/acorn-cnc-controller/)
2. WMPG-6 Control Pendant
3. Centroid CNC12 Mill Pro
4. Clearpath 2.52hp AC brushless servos (3)
5. Eaton miniature circuit breakers (3) recommended by Clearpath
6. 20x28x8 electrical enclosure
7. Yaskawa VFD
8. Marathon Motors 5hp Black Max
9. Viewsonic single point resistive touch screen monitor. (cnckeith added: https://amzn.to/3AoIQHE )

The forum has been quite informative. Searching I found answers to all my questions thus far. Centroid was also exceptionally helpful when I spoke with them via phone. It's been 18 years since I last did a CNC mill build so I have some catching up to do.

right on, thanks for creating a build thread! photos looks fantastic, and looks like you are off to a great start.

Ugh the Marathon Motors 5hp Black Max arrived today, mangled beyond repair. Way to go Fedex. Naturally they dropped it on my porch and ran.

I completed the first ball nut rebuild, for Z. These are 32mm double ball nuts, with 8 separate recirculating ball tracks, 232 ball bearings total. With the proper size plastic tube it was actually pretty easy to load.

Nobody sells the ball screw wipers, you have to buy a whole new nut so I fired up the 3D printer and printed new wipers in nylon.



Installed and cross drilled for the set screws.

That looks like a really nice machine. It's a great help that you are starting with a "proper" CNC machine with good quality, zero backlash ballscrews etc. I assume the thrust bearings, spindle bearings etc are also top notch. This thing should fly along when it's up and running! Looking forward to following your build log.

Muzzer wrote: ↑Sat Jan 25, 2025 7:47 am That looks like a really nice machine. It's a great help that you are starting with a "proper" CNC machine with good quality, zero backlash ballscrews etc. I assume the thrust bearings, spindle bearings etc are also top notch. This thing should fly along when it's up and running! Looking forward to following your build log.

Thanks!

I purchased new bearings for the entire machine (29). Chevalier used NSK Japan bearings when it was built, the spindle bearings are P4. I purchased the same NSK Japan bearings in the same class they used. I think the only bearing not NSK Japan are the 4 needle bearings for the counterweight chain sprockets, they are IKO.

I was hovering over buying a hobby mill and converting it to CNC when this beast popped up for sale only an hour from my house. I got it for half what the hobby mill cost, and they guys delivered it into my garage for that price.

Some details on the machine - Box ways on Z and Y. All three axis have Turcite. Z has a huge cast iron counterweight in the column so you can move the Z screw by hand with little effort. Large X40 x Y20 x Z24 inch work cube. The table measures 17 x 59 inches. The Y saddle is 49 inches long and 13.3 inches deep. In places it's 9 inches thick, with ribbing and cavities of course.

I went with larger 1,147 oz-in AC servos vs the original SEM DC servos 640 oz-in. The factory capped rapids at 300ipm for X and Y and 200 ipm for Z. The new servos will move 540ipm for X and Y and 240ipm for Z (Z servo has a 2 to 1 reduction pulley). Which I could change, but 4.5 inches per second is fast enough to crash into something.

Interesting...I have found chips in every nook and cranny of the machine but have yet to find a single steel chip they are all aluminum!

I had to replace all the bearings in mine due to moisture damage after being in storage for 15 years. Mostly HSK but at least they were std sizes.

Once you have that machine set up and optimised, it will run modern tool paths is a way the original manufacturer would never have dreamed.

My Shizuoka AN-SB has a table that would be big enough to lay someone out on. The real benefit of that is that I can leave the 4th axis, machine vise and tool setter in place without needing to disturb them for anything but the biggest jobs. The downside is that an enclosure would occupy much of the workshop. My solution would be curtains at each end but impetus was lost before that happened - the result is chips and coolant all over the shop which can be helped to some degree by the use of shields. I expect you may have the same issue.