Re: [CAD_CAM_EDM_DRO] Motor Question(cross posted)

metlmunchr wrote:

>I've got a flame cutting machine with an optical tracer which I'd like
>to convert to CNC control. It has small DC gearmotors which drive
>both axes now via the output from the optical tracer. Here's the
>complete data from the motor nameplate. The machine was built in 1983.
>
>Pittman
>MT9414C369
>3501D74H01 Rev A
>19.1 VDC
>
>Pittman's website shows a GM9414 gearmotor which has roughly the same
>physical dimensions. Here's where I'm stumped though:
>
>There are 4 wires to each motor, all running in a common vinyl
>jacketed cable. Two wires go into the motor at the shaft end, and the
>other 2 go into some smaller "device" which is attached to the
>opposite end. I'm assuming these devices aren't encoders, since all 4
>wires are running together? Pittman's site mentions the availability
>of pulse generators outputting something like 120 counts per rev, but
>there's no picture I can use to see if this is what they may be. A
>burning machine is a slow and relatively low accuracy machine, so I'm
>sure these aren't rocket science caliber drives, but I'd like to know
>whether anyone has any idea whether I can use them for a conversion or
>if I need to just forget them and adapt something else. I haven't
>actually checked to see if the device attached to the motor is
>removable or not. Guess I should do that to determine if proper
>encoders might be mounted in their place? Any ideas?
>
>

My guess is these are DC tachometers, to help stabilize the control
loop for the tracer. Some analog servo amplifiers need analog velocity
feedback, too. For CNC control, you will have to add encoders to the
system. That may not be hard at all. Probably the other end of the
leadscrew,
if so equipped, or the shaft that drives the belt or chain, would be the
easiest
place to attach an encoder. You could use Gecko 320 drives to run this
from a PC's parallel port. There is a wide choice of software for this.

Jon