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Author Topic: Lathe controls  (Read 11372 times)

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Offline TT350

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Re: Lathe controls
« Reply #20 on: October 27, 2007, 09:03:25 PM »
My plane is to go direct drive, 100 IPM is plenty fast enough.

Offline Hood

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Re: Lathe controls
« Reply #21 on: October 28, 2007, 04:17:19 AM »
Well I would say that the 916oz/in I have would be more than adequate for your needs on the Z and probaly smaller needed for the X. If however you did run into problems then you always have the option of gearing as Direct drive would put your rapids in the range of 200IPM and you are saying 100IPM is more than enough.
  The only experience I have of Lathes is the one I am doing at the moment but its a different beast altogether as it uses AC Servos and I have my doubts whether the Torque figures of Steppers and AC Servos can be compared for like for like. I have 10NM motors on the Z Axis which is about 1400oz/in  this however is a big lathe that I have taken 20mm off the diameter of 75mm stock in one pass with no problem, but as I said whether the torque of AC Servos and Steppers can be compared I doubt.

Hood

Offline Hood

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Re: Lathe controls
« Reply #22 on: October 28, 2007, 04:18:04 AM »
Well I would say that the 916oz/in I have would be more than adequate for your needs on the Z and probaly smaller needed for the X. If however you did run into problems then you always have the option of gearing as Direct drive would put your rapids in the range of 200IPM and you are saying 100IPM is more than enough.
  The only experience I have of Lathes is the one I am doing at the moment but its a different beast altogether as it uses AC Servos and I have my doubts whether the Torque figures of Steppers and AC Servos can be compared for like for like. I have 10NM motors on the Z Axis which is about 1400oz/in  this however is a big lathe that I have taken 20mm off the diameter of 75mm stock in one pass with no problem, but as I said whether the torque of AC Servos and Steppers can be compared I doubt.

Hood

Offline TT350

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Re: Lathe controls
« Reply #23 on: October 28, 2007, 11:31:40 PM »
Who makes the most accurate limit switches,
Optical or mechanical? I would like to put 2 of the 4
I will need for accurate homing.     

Offline DAlgie

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Re: Lathe controls
« Reply #24 on: October 28, 2007, 11:45:17 PM »
Optical switches are the most accurate, all other things considered. However, you really don't need great accuracy on the Z axis, a mechanical switch there is just fine. A lathe needs high homing accuracy on the X axis because you keep all the tools set, or at least the main ones anyway, roughing, finishing, parting off. So, you need to have good accuracy on the X axis so that these tools will always be set to maintain your diameters, different stock materials will slightly alter your finish diameters though. The Z axis, on the other hand, you usually set the Z zero point off the end of the stock with each new job, so the Z axis does not need to be as accurate.
                   DaveA.

Offline TT350

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Re: Lathe controls
« Reply #25 on: October 29, 2007, 08:22:31 AM »
Thanks Mr airplane :) Where do I buy the best ones?

Offline Hood

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Re: Lathe controls
« Reply #26 on: October 29, 2007, 04:20:49 PM »
You can easily make up optical switches especially if you will not be using coolant. For that all you need is something like this OPB916B (go to rswww.com and type it into the search) and a 220ohm resistor.
 If you need coolant proof then you will have to make up some form of box and plunger arrangement.
Industrial Hobbies used to make nice ones complete but dont think they do them anymore but you may still find pics/info on their site about them.

Hood

Offline TT350

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Re: Lathe controls
« Reply #27 on: October 29, 2007, 08:28:29 PM »
The more I dig the more I find, this DIY cnc thing has a LOT to choose from.
I've made my mind up that Gecko is the most popular drive out there so I'll
be useing those.

Has any one used any CNC4PC.com stuff?

Offline drew

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Re: Lathe controls
« Reply #28 on: October 30, 2007, 12:56:02 AM »
I am using a cnc4pc parallel port opto card that is a few years old. It doesn't have any bell or whistles like leds for I/O state. The motor steps and direction plus PWM for spindle speed all come from outputs from this card via LPT1. I had planed on using the inputs for an encoder/MPG and did test it but with a shuttle pro for jogging I just don't see a need for it but I do send the Index mark through this card.
The LPT2 is heavy on inputs so I used a opto22 G4PB16 with it. You can get a good deal on them off eBay. Also I don't think the opto22 stuff is fast enough for motor steps or direction with regards to timming sync. Pics of my lathe can be found here http://www.machsupport.com/forum/index.php/topic,4618.0.html
Drew 
If I had something important to say it would be here.