Re: [CAD_CAM_EDM_DRO] Mill Conversion questions

jchrisj7734 wrote:

>I'm in the process of convertimg my Sherline Mill to CNC. I'm thinking
>(at the moment) about running Sanyo Denki 232-180-DB motors with Gecko
>210 drives.
>
>If I mount the handwheels on the rear motor shafts so I can run the
>mill by hand when I want to, I end up generating voltage when I move
>the handwheels, assuming that the motors act like generators in this
>case.
>
>Are the 210 drivers sensitive to this voltage, particularly when the
>system is otherwise unpowered? Do I need to disconnect the drive motor
>cables, either directly or with a relay, when I use the mill manually?
>If so, do all of the motor leads need to be disconnected? (That's not
>a problem if you just unplug it, but would be a design detail if you
>were going to use a switch or relay)
>
>

This should not be a problem of damage to the gecko drives. But, it may
cause
a very noticable drag on the motors, so you may want to disconnect them.
You need to make sure your disconnect relay does not open up until the
Gecko drives are pretty fully powered down, though. Opening the
motor connection under power is supposed to be a NO-NO, as the energy
stored in the motor's inductance can spark and damage the drive.

>Is there a recommended heatsink for the 210? (I've seen one at the
>Camtronics site that mounts 4 drivers) I was thinking about using a
>variation on a heatsink system I once saw on a high power stereo
>amplifier. The drivers would be mounted vertically on individual
>heatsinks to form a chimney with fans top and bottom. My idea is to
>get really good airflow for efficient cooling, putting the air where
>it it really needed. (In fact, if I used the Camtronics heat sink I
>would be really tempted to box the back side for the same reason.
>
>

This will work, but is not necessary. A modest heatsink with a small fan
is sufficient. The higher the motor current and supply voltage, the hotter
they get. Proper ducting of the airflow is a big help, of course.

Jon