Precision Stop req - Motor & necessary info required. Pls HELP.

[applyingthought]

Hi

I am working on a "Automatic Lathe" machine, Now we have come across a challenge where in the spindle motor needs to stop for few seconds for the job to get loaded into the chuck and start immediate after loading.

The main difficulty we are coming across is that the spindle motors needs to be stopped at a fixed point every time (i.e. Below mentioned are the frequency of stop & cycle time. We are currently using 3 PH, 1.6 KW conventional motor which powers the spindle to go to 2000 rpm.

Cycle time for the component to get manufactured : 30 seconds

Component loading time: 1 Sec

Spindle accurate positional stop required for : 2 seconds.

We need the spindle motor to stop accurately in same position every time because the component which is getting loaded and machine is an eccentric in nature.

Options being considered: Servo Motor, Stepper motor etc. Please suggest the best option available and low cost aswell, without compromising on accurate positioning requirement.

THANKS IN ADVANCE, REQUIRE GUIDANCE/suggestions at he earliest.

 

[Skogsgurra]

The term used in CNC machine tools is "Oriented Stop" and it is usually a very accurate and rather expensive technique. It is available from many sources and one of the more capable ones is Beckhoff:

http://infosys.beckhoff.com/italian...bPackAL/HTML/TcPackAL_PS_OrientedStop.htm&id=

For less demanding oriented stops, I would use a good vector controlled induction motor plus an encoder or resolver. That would allow moderate accuracy - say within a few degrees - and if you do not need to change the stop position frequently, I would use a photocell for deceleration and ramp down to crawl speed just before the final position where a good hall element says when to stop.

A DC motor used to be a better choice. But probably not today. A stepper *can* work, but I wouldn't use it. The VFD needn't be a 4Q one. But you will need a braking resistor.

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[itsmoked]

I agree pretty much with everything skoggs suggests.

Any servo motor with a mating servo drive can do this without issue.

Typical example:
[URL unfurl="true"]http://www.airdryers.com/air-dryers/vsa.html[/url]

You'd want the 3kW drive and 2kW motor for your 1.6kW application. Not sure you need the brake option which is usually used to hold a machine stopped with a gravity load. You seem to just need a chuck held while a tool changer chucks an spits which the servo drive can usually manage. If there is actual wrenching torque going to be applied to the stopped spindle then you would want a brake.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[zappedagain]

"stop accurately in same position every time" - How accurately do you want to stop at the same position? i initially read your 2 second 'stop duration' as '2 arc-second' of rotation. The latter is tricky (1/648000 revolution)!

Z