Small lathe conversion

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09 Apr 2017 15:32 #91087 by Biersmythe
Hello all this is my first post, I hope i put this in the right place. I am converting a G0602 lathe to cnc and I have a few questions. I have read a lot of posts on this forum, cnczone and everywhere I can find to get an idea of what i need. I still have many questions. I know I will be using linuxcnc for the the control. I have been using linux as my only computer software for years so its a no brainer. I wanted a touch screen as well and have bought an Asus VT207 after seeing most people on this forum recomended it. What I want out of my project is a full functioning albeit small cnc lathe. I was a machinist for about 12 years so I have run many machines and i understand this small machin will have its limitations. Now this is where I need some advice. I am thinking I want a motion control card but not sure which one,
because I would like to use a small form factor pc like the ZOTAC ZBOX C Series that has been recomended by a few. I see there is a lot of back and forth about steppers and servos and about what to use for the spindle motor. I would like CSS, quality surface finish, good quality threading is a must and would like to have enough IO left over for coolent pump and a few accessories. I wont say money is no object, but im not afraid of buying quality if it keeps me from having to do it over again. Thank you all for the information you have already posted in this forum it has been very educational so far. Looking forward to the replys.

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09 Apr 2017 20:36 - 09 Apr 2017 20:37 #91098 by rodw
Replied by rodw on topic Small lathe conversion
If you want to use a small form factor PC, then your decision partly made for you as you will need to use a Mesa ethernet based cards. If you are using steppers, then the 7i76e would be the easy choice and give you way more features than you need for a lathe.
Last edit: 09 Apr 2017 20:37 by rodw.

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10 Apr 2017 01:43 #91105 by Biersmythe
Replied by Biersmythe on topic Small lathe conversion
Thank you Rod for the reply. I was thinking Mesa was probably what i was going to run by the amount of people running the cards. I am interested in what people say about servo vs stepper and what 3 phase/vfd combo people think will be best for CSS and the finish they are getting. I have read a lot of people run the Leeson/teco combo and are happy and a plus it works well with Linuxcnc. I would like to hear from some peeps that might have run that combo and how they are fairing before I make anothre hadeware puchase . Thank You again all.

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12 Apr 2017 10:53 #91237 by andypugh
Replied by andypugh on topic Small lathe conversion

I would like CSS, quality surface finish, good quality threading is a must and would like to have enough IO left over for coolent pump and a few accessories.


You can actually achieve all that with steppers and a parallel port. More critical than electronics will be the machine hardware: acme scres of ballscrews? Spindle encoder?
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13 Apr 2017 00:20 - 13 Apr 2017 01:22 #91278 by Biersmythe
Replied by Biersmythe on topic Small lathe conversion
Thank you for your reply Andy. There is a kit on ebay that has ball screws and mounts available for the small lathe I am converting. I could make all the mounts and source the ball screws but this kit has it all for a resonable price, plus currently I do not have access to a mill. As far as the spindle encoder I am looking at posts for what people have done and what I need to do. After more reading, I think with the use of the small form factor pc I want to use, a motion controller like 7i76E and some steppers might be the ticket. Any insite on stepper choices would be appreciated. I would want the largest steppers that would be in the nema 23 range. Thank you

Edit: changed wording.
Last edit: 13 Apr 2017 01:22 by Biersmythe.

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13 Apr 2017 11:53 #91296 by andypugh
Replied by andypugh on topic Small lathe conversion

Any insite on stepper choices would be appreciated. I would want the largest steppers that would be in the nema 23 range. Thank you


I wasn't specifically recommending steppers over servos, I was just saying that you can have all the features you mentioned irrespective of the motor type or interface chosen.

If I was looking at a conversion such as you are proposing then I would give serious consideration to the new closed-loop stepper systems that have started to appear.
One example (not a recommendation) is www.ebay.co.uk/itm/112141643273
I would spend some time working out whether 3-phase steppers are worth the extra cost (to you) and perhaps try to find a set where the drive can be connected directly to the AC mains.
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13 Apr 2017 12:53 #91300 by emcPT
Replied by emcPT on topic Small lathe conversion
Steppers if well sized will do the job and the overall wiring and complexity of the work will be much less. Expense will also be less, BUT if someday will will run out of position or the parts do not comply for what you are expecting, you will get your head bouncing thinking: what is wrong? The stepper, the coupler, the screw, the nut, the calibration, did I saved the tool table ????

You can also place encoders on the stepper, but if you reach that point then your should started with the servo.

In resume, and in my opinion, if you plan to learn and play with your machine go to steppers, if you plan to do actual work on it go for servos.
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13 Apr 2017 14:47 #91317 by andypugh
Replied by andypugh on topic Small lathe conversion
The closed-lop stepper systems seem to give very similar performance to a servo, at a very much lower cost.
Not that I have ever used one, my last lathe conversion uses 1kW servos. :-)

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13 Apr 2017 22:09 #91328 by rodw
Replied by rodw on topic Small lathe conversion
There are many small CNC systems on small machines as you propose running open loop service and I have a friend who has a slightly larger lathe (38mm spindle bore) that has worked that way for years. He's using a small NEMA 34 on the long feed and a NEMA 23 on cross feed. I think your sized machine is well inside stepper territory.

I think if I started again, I would look at closed loop steppers and matching controllers. You have so much to learn, steppers will simplify the journey on your first build.

Or as said, I would look at servos to increase my understanding of CNC machines.
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13 Apr 2017 22:46 - 13 Apr 2017 23:10 #91332 by tommylight
Replied by tommylight on topic Small lathe conversion
Not to hijack the thread, but today i did a quick and dirty retrofit of a smal lathe ( 20 mm bore, Rod :) ).

Will attach some bad pictures in a while, i need food.

Pictures attached.
Attachments:
Last edit: 13 Apr 2017 23:10 by tommylight.

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