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Author Topic: Recommendations needed for motion controller to use on CNC lathe project.  (Read 3828 times)

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Hi Folks,

I am still debating converting an old (but little used)small  manual lathe to CNC, using stepper motors & ball screws.

I have  worked out ( and had recommendations) on what direction to go mechanically.
I am however stuck on one point. I wish to do screw cutting on this lathe.
I have been informed that Mach3 can only handle 1 pulse per main spindle rotation. I understand that this may cause issues with screw cutting and make's multi start threads a no go area.

I have also been informed that the only solution to this, is to use a motion controller. I know the CSMIO plus the additional threading module will work. I realise that these are designed for industrial applications, but that is  a bit out of my budget.

Are there alternatives, know to produce good results at a more affordable price?

Thanks

Offline Hood

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The CSMIO is an excellent controller and definitely it conforms to Industrial practices such as 24vI/O etc but that is not to say it should not be used on a machine that is deemed not to be industrial.
As you say however the cost is more and if that is a problem then I do know the Smoothstepper threads very well, but it does just use a single pulse so your spindle motor would have to be fairly good at maintaining rpm.
Sadly the CSMIO/IP-M doesnt support threading at this time as if it did it would be a very economical controller for the smaller lathes as there is no need for breakout boards, spindle controllers etc that the other offerings really require.

The other option is to try the parallel port, lots of people have used it very successfully in the past for threading, me included. I have moved on from the PP now as my machines are mostly servo driven and the PP just could not give me the resolution and velocity that I required but for a stepper driven machine it is fine.

Hood
I have been threading quite well with the standard PP set-up.
Like Hood says, I think the main issue is to have ample power at the spindle.
Maybe just over-sizing your spindle motor would be your most economical approach. ? ?

And, here is a cool post on multi-start threading.
http://www.machsupport.com/forum/index.php/topic,10385.msg64665.html#msg64665
Don't recall seeing anyone post any actual progress with footage.
Would be neat to see though.

Russ

Offline Hood

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Russ, I tested out the multi start a long time ago but cant remember if I tried the method outlined in your link or not. Think I did and it didnt work but could be wrong.
  I am sure the method I used was just to alter the start distance by the pitch amount. Now if I recall, say you were wanting a 2mm pitch 3 start you would code to have the pitch of 6mm and start maybe at Z10 then next pass would start at Z8 then final Z6.
Will have to test it out again to see if my memory is correct.
Hood

Offline Hood

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Thanks Hood, I wanted to try the #99066 method back when it was posted, but never got around to it.

Altering the start distance , , , just as simple, I guess.
But, you have to alter the STOP distances as well, right ?

#99066, Copy/Paste a few times ...... only need to change the angles. Might be easiest ... IF it works.

Might try it someday.
Thanks again,
Russ
Good link ! ! !
Answers MY question.
Thanks

Offline Hood

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Russ, end would just be the same, if that is what you are meaning by "STOP distance" Its the same Z position just 120 degrees further round on the material (assuming 3 start)

Hood
Good link ! ! !
Answers MY question.
Thanks

Thanks Hood,
Russ
Russ, end would just be the same, if that is what you are meaning by "STOP distance" Its the same Z position just 120 degrees further round on the material (assuming 3 start)

Hood

Guess I was loosely envisioning a shift, like a G52.
I hope to NEED this someday.  :)

Russ