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| CNC mad |
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| mattinker:
Hi, The Electronic Lead Screw group on yahoo is a group project which was lead by John Dammeyer, with the goal of producing a low cost alternative self contained threading and taper cutting unit. This replaces the frequently missing change gears. It uses a single pulse encoder and a circuit designed and built by John. It is designed so that if you add a a 100 step encoder and instal the second optional stepper motor, it will plug straight into a PC to run it on EMC2 or Mach. https://groups.yahoo.com/neo/groups/e-leadscrew/info I have as yet to finish mine, it's taken me far too long! I've made all the parts, including the electronics, just needs wiring! Regards, Matthew |
| bertie_bassett:
--- Quote from: vtsteam on January 16, 2015, 07:24:00 PM ---Bertie, even with a single pulse encoder on the spindle shaft, the gear train ratio will, as a guess, ensure enough pulses per leadscrew revolution for the stepper driver to sense and compensate during a change in motor speed. --- End quote --- gear train?? if its an electronic lead screw there isn't a gear train. the encoder is directly on the spindle and the computer does the work of the gear train. unless im misunderstanding?? I know from my lathe that a deep cut at slow speeds can easily bog down the spindle speed and I wouldn't trust a single pulse to be able to give the accuracy needed for screw cutting. in a worst case scenario if the spindle was to stall at say 60 rpm, youd have at least a second befor the computer realised something was wrong. that's at least a second with the leadscrew dragging the tool through the non spinning work piece. :bugeye: ' in reality things are probably a lot better then that and it probably works just fine. just my head doesn't trust it note* my lathe isn't a very good example of a standard lathe as its not in the best condition and its single phase motor isn't great. |
| John Stevenson:
Hard fact, a single pulse encoder isn't good enough for consistent accurate threads. It's needs a multi line encoder to be consistent and unfortunately Mach 3 cannot handle this. I can't comment on the ELS but when Tony Jeffree built one and wrote about it in MEW the ELS 'at that time' could not use a multi line encoder. EMC can |
| mattinker:
--- Quote from: John Stevenson on January 17, 2015, 07:34:06 PM ---Hard fact, a single pulse encoder isn't good enough for consistent accurate threads. It's needs a multi line encoder to be consistent and unfortunately Mach 3 cannot handle this. I can't comment on the ELS but when Tony Jeffree built one and wrote about it in MEW the ELS 'at that time' could not use a multi line encoder. EMC can --- End quote --- The multi line encoder was not used on the ELS for economic reasons, the Pic controller used did not have enough capacity to calculate the pulses. This compromise was the subject of much debate, apparently, the single line functions adequately if one doesn't ask two much of it. This is a hobby solution not an industrial one. I stand corrected about Mach, I've never used it and had forgotten that it couldn't run multi lined encoders. Regards, Matthew |
| vtsteam:
What I said earlier though was dumb. :doh: The spindle doesn't have a gear ratio. It's disconnected -- the stepper drives the leadscrew. I guess I was sort of also thinking of the the drive from motor to spindle being a ratio. But the encoder is on the spindle, not further up the train to the motor, so one rev of the spindle is one rev of the workpiece, and one rev of the encoder. Not a multiple. nevermind.......... |
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