Advertisements

Archive for July 19th, 2012

Sherline CNC Mill Y Axis Home Switch: To The Front!

Reassembling the mill provided an opportunity to move the Y axis Home switch from the rear of the axis to the front. The key discovery happened during the teardown: I can get the saddle off the Y axis dovetail by removing the gib, without sliding it off the front, which means a front switch can remain firmly glued in place.

A few random hunks of steel and a wire nut held the switch in position while the epoxy cured:

Mounting Y axis home switch

Mounting Y axis home switch

The switch actuator bottoms out with the saddle just touching the preload nut, so the saddle can’t dislodge the switch: the switch trips just before the saddle hits the nut, at which point all motion stops and the motor stalls.

Moving the switch means I can remove all the gimcrackery that poked the rear switch with the tooling plate in place; I was never happy with that setup. I also removed the small block that trapped the rear end of the Y leadscrew, under the assumption that, as I haven’t yet dropped anything on the leadscrew, I probably won’t. That adds about 1/4 inch to the maximum travel and allows the tooling plate to whack into the column.

The switch wire runs along the stepper cable, a tidy technique that hasn’t introduced any glitches into the shared Home signal from the X axis drivers:

Sherline mill - X and Y axis home switches

Sherline mill – X and Y axis home switches

The Y axis now seeks the Home switch in the positive Y direction, so that stanza in Sherline.ini looks like this:

[AXIS_1]
TYPE = LINEAR
MAX_VELOCITY = 0.400
MAX_ACCELERATION = 5.0
STEPGEN_MAXACCEL = 10.0
SCALE = 16000.0
FERROR = 0.05
MIN_FERROR = 0.01
MIN_LIMIT = -0.5
MAX_LIMIT = 4.90
BACKLASH = 0.003
HOME_IS_SHARED = 1
HOME_SEQUENCE = 2
HOME_SEARCH_VEL = 0.3
HOME_LATCH_VEL = 0.016
HOME_FINAL_VEL = -0.4
HOME_OFFSET = 5.125
HOME = 5.0
Advertisements

, ,

Leave a comment