Trying to find out how much I don't know
Michael Gilligan | 07/06/2017 12:42:46 |
![]() 23121 forum posts 1360 photos | Richard, I must confess that I had not considered that 550W might be needed for a pen-turning lathe. ... I was thinking of something scaled-up a little from the Sherline version: http://sherline.com/product/6500-stepper-motor-mounting-kit/
[quote] NOTE: Stepper Motor RPM Range We have had customers who want to use the stepper motor (on the headstock) as a dual purpose motor. They want to use it to index the headstock to do machine work (mill flats, or cut out inlay areas on a pool cue). They also want to use it as a drive motor to turn stock (to replace the DC motor). So, they keep asking what the maximum RPM of the spindle is with the stepper motor and cog pulley mounted to it. [/quote]
MichaelG. Edited By Michael Gilligan on 07/06/2017 12:48:21 |
Andrew Johnston | 07/06/2017 13:24:44 |
![]() 7061 forum posts 719 photos | While not an absolute distinction there is generally a fundamental difference between the two drive options: A servo system uses sensor feedback to move the driver to the required position, and is thus a closed loop system, by definition A stepper motor system does not usually use feedback and is therefore an open loop system For the relatively slow helical patterns shown I would think that a stepper motor spindle drive is more useful, and simpler. Basically a 4-axis mill albeit it with limited rectilinear movement options. Andrew
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richardandtracy | 07/06/2017 15:06:28 |
![]() 943 forum posts 10 photos | OK. I think I have gathered the following:
While this is not entirely welcome, it's not unexpected. So, thank you all for your help. I think the solution will be to have a spindle encoder permanently fitted. I shall use the standard Clarke 550W motor to power the spindle when it working as a lathe. Then take the drive belt off and engage a stepper motor through a big reduction to turn the spindle when engraving. Whether the reduction will be through a worm or belt drive, I shall have to investigate. Zero backlash worm drives seem to be quite unusual. Having established this, the controller needs to be identified, but that is a problem for another time. Your help has been greatly appreciated & has clarified the scope of the problem I face. Regards, Richard.
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Muzzer | 07/06/2017 16:28:38 |
![]() 2904 forum posts 448 photos | You shouldn't need a "big reduction" between the stepper and spindle - you could drive the spindle directly in many cases, depending how good your driver is. You are talking about machining a pen barrel here. However, you need to ensure that you have enough (micro)steps per revolution to give a smooth, almost stepless movement. BTW, you can get "closed loop stepper" systems, where the stepper has an integrated encoder. When operated with a high microstep setting, this can provide very accurate positioning. And being closed loop, you generally don't need such a powerful motor. The Leadshine ones even have the driver built in to the motor so you only need to provide the step/dir signal and the DC power (24 or 36V). Murray |
Mike Poole | 07/06/2017 17:04:27 |
![]() 3676 forum posts 82 photos | The two motor option is common practice on industrial machine tools, an AC motor for rapid traverse and a DC motor for feed speeds. The changeover is usually automatic though. Mike |
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