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Author Topic: Backlash and taper turning  (Read 2632 times)

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Backlash and taper turning
« on: May 09, 2012, 12:19:39 PM »
This is probably a silly question but I'll ask it anyway...

I have now got both my lathe (Super 7) and mill (Denford Novamill) working under Mach3, generally pretty successfully.  The lathe uses the standard Z leadscrew though I made a new screw and nut for the X-slide because I didn't want to start modifying Myford's components.  Because I'm not using ballscrews of course I have some backlash in both axes.  From a static point of view I could compensate this by switching on backlash comp.

The normal taper turning wizard cuts towards the headstock with increasing diameter.  This means that the X-slide is at the "wrong end" of its play, and is only constrained to the taper path by cutting forces.  In particular as you reach the end of the cut and the tool runs out of the work, there is a danger that the diameter will increase by more than it should given the taper - in fact I think I have seen this behaviour.  The alternative would be to cut away from the headstock, but then you could have the same problem with the other axis.

Ideally one would start by grooving the work near the headstock and cutting the taper inwards towards the headstock so that both axes are being driven against their play, so to speak.

Am I right in my thinking here, and are any wizards available that work in this way please?  (Or should I write my own gcode?)

John.

Offline Hood

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Re: Backlash and taper turning
« Reply #1 on: May 09, 2012, 04:01:49 PM »
Do a search for Turn Extras.
Hood
Re: Backlash and taper turning
« Reply #2 on: May 10, 2012, 07:31:18 AM »
Thanks Hood - er, where should I search?  I can't find anything on this forum or google.  Please could you give me a hint?

John.

Offline Hood

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Re: Backlash and taper turning
« Reply #3 on: May 10, 2012, 10:28:40 AM »
I was thinking a search for Turn Extra would possibly bring them up, if not I should have them at home and can attach later.
Hood
Re: Backlash and taper turning
« Reply #4 on: May 10, 2012, 10:36:12 AM »
Ah, would that be "extra turn wizards" by zarzul?  I just found those attached to a post and downloaded them.

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Re: Backlash and taper turning
« Reply #5 on: May 10, 2012, 11:53:07 AM »
sounds like it may be :)
Hood
Re: Backlash and taper turning
« Reply #6 on: May 11, 2012, 11:38:59 AM »
OK, that's the one!  It has a wizard to turn tapers to faces, either way round.  Looks just the ticket, thanks for your help Hood.

John.

Offline Hood

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Re: Backlash and taper turning
« Reply #7 on: May 11, 2012, 01:10:36 PM »
Hopefully it will help you out a bit but nothing is better than having zero (or as close to) backlash.
Hood