Need help with stepper motor and gearbox design

[dfowler]

We have a roll forming machine that we are building a safety cage to fit over. The cage is designed as a lid hinged on a solid steel shaft mounted along side of our roll forming machine. The entire cage will rotate and lift up and away off to one side of the roll former. The center of gravity of the cage is centered approximately 6 feet from the shaft when in the horizontal position. This creates a tremendous moment for us to overcome initially – approximately 21,600 in-lbs or 3600 ft-lbs. The rotational speed can be quite slow however, as the cage only needs to be raised in about 10-15 seconds which then equates to an output speed of approximately .7 to 1 rpm.

I initially started investigating stepper motors since they are so easy to setup and control. All of the ones I have seen however have too low of an output torque to work for me. We would like to avoid setting up a hydraulic system if at all possible. Can anyone suggest a source for a stepper motor and gearbox combination that would work for me? Thanks.

Davey

 

[dfowler]

Oops, 21,600 in-lbs of torque = 1800 ft-lbs of torque, not 3600. We need 21,600 in-lbs or 1800 ft-lbs of torque. Thanks.

Davey

 

[jclough]

I'm having a hard time picturing your application but here are a couple of ideas which may help.

Could you attach a counter weight to the cage through a belt or chain or whatever? This could treduce the amount of force needed to move your cage and get things back into the realm of a stepper.

Could you use a linear actuatorin the place of a hydraulic cylinder? as I recall we make one which generates well over a ton of force.

 

[dfowler]

Yes, a linear actuator would work. The way the system is currently setup our maintanence crew, who initially tried to design this, installed an air cylinder to move an arm welded to the shaft. The perpendicular length from the center of the shaft to the line of action of the cylinder is 4.5" The cylinder has a 5" bore and a 10" stroke with 90psi of plant air.
This is way undersized - we would need 3 of these to lift the cage. The max force generated by the air cylinder is 1767 lbs. With the same moment distance and stroke length a linear actuator would need to generate at least 4800lbf or 7200lbf for a safety factor of 1.5.
I did consider the counter weight idea, but it seemed a little hokey and dangerous for our manufacturing environment. Thanks.
Davey

 

[jbartos]

Suggestion: Visit

http://www.thomasregister.com

and type Actuators: Linear under Product or Service, which will return 338 companies to approach to for a right linear actuator that may be the reasonably good solution

 

[ScottyUK]

dfowler,

Have you considered one of the intergrated hydraulic power packs? One manufacturer was Rexa (not Rexroth). We looked at this for an actuator application on a turbine, but it did not have a ATEX certification and was therefore no use. The nice feature was that there is no hydraulic power pack and hoses to worry about. Everything is in one unit, just provide power to it. This company seems to be a distributor - not the one we dealt with, but I can't find their details:

http://www.control-valve.co.uk/acatalog/Actuators.html

Another alternative might be to use a ballscrew actuator. I spotted this company in one of the trade mags which land on my desk now and then:

http://www.powerjacks.com/

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Start each new day with a smile.

Get it over with.

 

[ScottyUK]

Just realised - google was set to UK-Only search.

Here's REXA's website:

http://www.rexa.com/products/products_index.html

-----------------------------------

Start each new day with a smile.

Get it over with.