[dtw]

I have a Vectrax MSC Centroid M-15 knee mill that I would like to modify the quill to function as the X & Y axis in "free" mode. I realize the only way to make that hapen is to replace the rotary encoder with a 6" glass scale. Tha z axis kit is an early Elrod design, and by drilling a 1/4" access hole that lines up with the ball nut housing clamp screw when at the bottom of travel, I can free the nut from the clamp housing and have a freed quill. With the glass scale reader head attached to the clamp housing I should "theoretically" have a manual Z dro like the X & Y if there is a way to go into setup and activate a Z axis free command. Is this possible?

Thanks for any help,

Woody

[cncsnw]

Yes, that is possible. It is routinely done with the newer Elrod kits, with his "Smart Z" feature (essentially the modifications you are describing).

Look up Machine Parameter #130 in the Operator's Manual. The level of support for various features depends upon your CNC7 (or CNC10) software version.

[dtw]

Thanks, cncsnw, I sent an email to Centroid and they confirm it should be possible. They said they need to check the version I have to be sure, so I'll get that done. The only other thing I will need is a compatible scale for that vintage control. The encoder connector looks like a VGA connector with 9 pins, 4 over 5. An eBay search located only modern scales with many more pins.

dtw

[cncsnw]

"Vintage" is not relevant. Each control system and DRO manufacturer is going to have their own convention for connector style and pin-out. You always have to adapt the scale you buy to the control you have.

Centroid's convention, on all DC-servo controls they have built in the last 24 years, is to use a male DE9 (commonly called a DB9) on the encoder or scale, plugging into a female DE9 receptacle on the control. The pin-out is:
pin 1: n/c
pin 2: COM (0VDC)
pin 3: channel /Z
pin 4: channel /A
pin 5: channel /B
pin 6: channel Z
pin 7: channel A
pin 8: channel B
pin 9: Vcc (+5VDC)

As implied by the Vcc level and the complementary channels in the above list, you need to use an encoder or scale which operates on 5VDC and which provides a differential (line driver) output.
For a quill scale, an index pulse (Z and /Z channels) is not required.

[Jim Dawson]

Rather than glass scales, you might look at magnetic scales. I have them on all of my machines. Much more compact, especially nice on the quill. Functionally just like glass scales. About $120/axis