Re: [CAD_CAM_EDM_DRO] Re: Timing Pulleys - Chain & sprockets?

In a message dated 11/2/2003 12:52:02 AM Central Standard Time,
rawen2@... writes:
Would appreciate hearing from anyone who's used a setup like this.
Well, not EXACTLY like that, but I did a rather large X-Y Router nearly
twenty years back with a gantry that was over 5' wide (across a 12' table!), and I
was fearful of "play" due to flex in the frame, etc., so I put a ball-screw
down BOTH long-sides ("X axis") of the table, with ONE huge stepper ($$!!)
connected to both screws with #35 sprocket-chain. I figured for the woodworking
application, any unknown manufacturing-tolerances would be unnoticed. Yep. But
this rig got SO much use six days a week that the chain gave out every
several weeks, and I am told, after TWO chain-replacements, the bearings on the
idler-sprockets got so sloppy, that... Well, YOU get the picture! So, the clever
owners of the machine removed the one stepper and one of the two screws, and
put that stepper on the END of the one remaining screw, using an appropriate
"spider coupler" or whatever, and a new welded-up motor-mount, and the flex in
the iron then proved tolerable, and that is still going 45 hours a week to
this day! GOOD ol' American iron, that!

Were I (much!) younger, and asked to design/build another huge X-Y, I'd go
with SINGLE screws per axis, and rigid gantry-framework. OH, and EXCELLENT
linear ball-bearings.

Jan Rowland
Geriatric with Attitude


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