Help with lifting application

I'm looking for ideas on how to control four motors simultaneously in order to move a rectangular platen up and down evenly. Would also need independent control over each motor for leveling purposes.

This is a plastic forming station with tooling on each side of a top and bottom platen. The plastic is heated and then brought into this forming station. The platens then move together with their tooling to form out a part.

Currently our machines use one motor (10-30HP), two hollow gearboxes, and two shafts to drive the platens on four gear racks corner located.

I've looked into electronic gearing with PF750 VFD's and also servo coordinated motion with Studio 5000.

Any help would be appreciated. Thanks!

If your going to mount 4 motors then how about also mounting 4 encoders to them then you will know the actual position of the four corners of the platen

All of the ones I have worked with had hydraulic cylinders controlling them and were self leveling them

Without out exception Yaskawa A1000 or GA800 Vector Drive on each
But because it's a Lifting / Hoist application then it would us Magnetek would be a better choice.
Foe both it would be a Flux Vector Drive the Magnetek is better for lifting they have firmware designed with maximum safety for just this appellation.
with either drive set them up as a master slave / follower. Depending on the exact application you may not even need a PLC

Any quality vector drive with encoder feedback will be able to do "electronic line shaft" control.

Rockwell drives, including Powerflex 527, 755, or Kinetix 5500 and 5700 servos, will be able to do it with the Logix motion instruction set, including using an ordinary MAG motion gearing instruction to make all four axes follow a virtual master axis during the forming cycle.

I worked on a big forming machine last month with a single 30 HP PowerFlex 700 AC drive and a set of eight lineshaft-connected Acme screw actuators. What a racket all that rotating stuff makes ! And the mechanics of the leveling required wrenches that were two-man team tools. I really wish I'd had a cabinet full smaller PowerFlex 755's to do that function, instead of one hefty drive and a machine frame full of gearboxes and shafts and couplings.

On the same project we had some third-party servos that provided a set of AOIs that were designed to work similarly to the Rockwell motion control instruction set. The problem is, some of the AOIs just didn't work correctly. What looked great on paper consumed three days of startup time.

If I'm going to use a ControlLogix and I have a choice between a Rockwell servo and a third party servo that they promise will work just like a Rockwell servo, I'm generally going to choose the one that's been built and tested in Wisconsin.

Thanks for the responses everyone. I'll likely be using the PF755 for this application.

If what you are after is leveling, I would do it as a motion control problem. When I had to do that with Boeing 777 aircraft, we did it based on load sharing between the 4 hooks on the crane carrier, using a weight distribution sensor.

If you are planning to have brakes on the motors, you'll probably find that servo motors will be cheaper than induction motors with encoders and brakes... Also, the peak torque capability would be much higher, and since I assume it's not a continuous motion application, the motors (and drives) could be smaller (most likely).

Please clarify; is the final drive element a screw or rack/pinion arrangement, or is this a hoist with drums/cables that uses gravity only ?

I've done hoists in forming applications using gravity, but only to drop a vacuum bag frame. When the force for forming comes from the motors, the only thing I've ever used is Acme screws.

My experience is in composites, so we tend to shy away from hydraulics in the clean room when we can avoid it.

The encoders better be absolute.

Peter Nachtwey said:

The encoders better be absolute.

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Yes, that was my intention.

Ken Roach said:

Please clarify; is the final drive element a screw or rack/pinion arrangement, or is this a hoist with drums/cables that uses gravity only ?

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Rack/pinion.

Gene Bond said:

If you are planning to have brakes on the motors, you'll probably find that servo motors will be cheaper than induction motors with encoders and brakes... Also, the peak torque capability would be much higher, and since I assume it's not a continuous motion application, the motors (and drives) could be smaller (most likely).

Click to expand...

Yes, every motor will need to have an absolute encoder and brake. I haven't ruled out using servos so you could be spot on with your assessment.