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Metalworking (rec.crafts.metalworking) Discuss various aspects of working with metal, such as machining, welding, metal joining, screwing, casting, hardening/tempering, blacksmithing/forging, spinning and hammer work, sheet metal work. |
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Lathe conversion, mostly Iggy, but all
Ig, I'm having a thought that I can do a really bang-up job on the
precision of my lathe conversion with the most crappy ball screws on the planet. I have found some very affordable magnetic DRO scales and readers that provide simple quadrature output (and a zero index) at TTL levels, and can be had in both 2 micro-inch and 1 micro-inch resolution for very little difference in price. So, I'm thinking that instead of using the motor shaft encoders (which are already there), I could use these scales to provide absolute positioning accuracy down to .0002" in Z and .0001" in X, without much if any changes in EMC's manner of looking at the data. It seems to me that the "counts per revolution" datum could be used the same with a linear scale as with a shaft encoder. Any errors in the screws are simply going to be interpreted as speeding or slowing of the CPR figure, rather than skewing the end position, so long as the motor doesn't know or report what its rotational position is. I think it might take a little code to get the motor to continue (or stop) moving, unless I only use speed input on the drives, and not positioning input. What do you think of the idea of having absolute positioning information in EMC, rather than the "dead reckoning" positioning provided by screws of unknown accuracy? Do you know if anyone else has approached it this way? (i.e. - taken a DRO, and used it for the positioning info?) (Not just Ig... any other comments are welcome) LLoyd |
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