How do you get an electric motor to do this?

[Watco]

Hello, we are assembling 1.5" OD brass tubing, one end is threaded, into a female threaded brass fitting. (Plumbing application). We want to automate it, by holding the tubing with an air actuated collet check, then spining the collet chuck until the fitting is tightened onto the tubing. We want to use an electric motor that will stop the tightening when it reaches 30 ftlbs of torque. Where would we find such a motor or motor controller combination?

 

[Heckler]

That would depend if your company has the knowledge base in house to automate assembly processes. We have automated a lot of our assembly processes. I would suggest calling a local motion control specialist. We use air activated torque controllers on our assembly fixtures.

Best Regards,

Heckler
Sr. Mechanical Engineer
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Never argue with an idiot. They'll bring you down to their level and beat you with experience every time.

 

[CoryPad]

The power tool segment of the fastening industry provides turnkey systems to do this:

http://www.boschrexroth.com/business_units/brc/subwebsites/product_catalogue/en/tps_en_neu/index.jsp

http://www.aimco-global.com/

http://www.atlascopco.com

Regards,

Cory

Please see FAQ731-376 for tips on how to make the best use of Eng-Tips Fora.

 

[zekeman]

A permanent magnet DC motor would be a simple and very good solution for this application, since the stall torque is directly proportional to the current and terminal voltage so all you have to do is get an oversized DC motor and first apply a nominally small DC voltage to get a stall torque. The torque you need would be in direct proportion to the voltage.
For example, say you 10 lb ft of torque and the motor you choose develops a stall torque 4 lb ft at 20 volts DC, then the voltage you would need would be
10/4*20=50 volts.
In the application the voltage could be ramped up to the final value at a rate depending on the rotational speed you need. Some of the background for this follows:
If you write the equations of a DC motor, viz
V=IR+K1S
T=K2I
where
R= armature resistance
S=speed
T=torque
V =terminal voltage
K1= constant
K2 = torque constant
From these equations, tyhe stall torque (S+0) is
Tstall=K2V/R which demonstrates the proportionality of T vs V.

 

[KiwiMace]

Or a slip clutch like a power drill.