High dutycycle motor app.

[itsmoked]

I have to run a chain conveyor [green]1 second ON[/green][red] 2 seconds OFF[/red] for a bazillion hours. It has to be very reliable.

The load is not very large. It's a two chain conveyor that moves about a foot per cycle. The chains probably weigh less than two pounds total and one end would be common shaft driven (4" sprocket). The other ends have idler sprockets.

A 1/4hp 3ph gear motor was selected driving a gear box using a VFD. I saw this and think THAT would be a big problem. We are now casting about for an alternative.

Possibilities:
1) Perhaps I'm wrong? The 1/4hp 3ph would actually be fine?

2) Using an air cylinder to 'shuffle board' the process instead. (This has be shelved due to process interferences.)

3) Using an air motor run thru a gear box. (Compressed air volume would go way up and exhaust noise would need to be mitigated.)

4) A smaller servo drive has been investigated but the price is abhorrent. ($3K+) Whereas the VFD 'solution was about $1.3K.

5) ?

Anybody got any suggestions?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[waross]

I like the VFD option Keith. I'd buy a larger VFD to cover my assets in the event that the motor has to be up-sized.
You may consider a cooling fan as the one minute on and two minutes off is not conducive to good cooling.
The biggest load will probably be break-away torque. If you need a little more, you may be able to gear down and run over speed by the inverse ratio of the gearing change.

Bill
--------------------
"Why not the best?"
Jimmy Carter

 

[MikeHalloran]

Hydraulic motors thrive in applications like that.
Bring your wallet.

Or, keep the chains, and 'shuffleboard' them with a big ol' ratchet mechanism driven by an air cylinder or a hydraulic cylinder. Beware: ratchet mechanisms are deceptively hard to get right, and can suck up development resources like crazy.

Or, leave the motor running all the time, and start/stop the chain with air operated clutches. Industrial rated clutches can be engineered for high duty cycles like you want.



Mike Halloran
Pembroke Pines, FL, USA

 

[jraef]

keith,
Is this just a back and forth operation? Did you consider a Linear Actuator? 1/4HP is small enough to make that viable I would think.

"Dear future generations: Please accept our apologies. We were rolling drunk on petroleum."
— Kilgore Trout (via Kurt Vonnegut)
For the best use of Eng-Tips, please click here -> faq731-376

 

[itsmoked]

Thanks folks for the thoughts.

Bill; I didn't think of using a fan on continuously. DOH!


Mike: This is a machine that is being completely revamped because of clutches and ratchets failing continuously. You're right too, hydraulics are an added headache allowing even less control.


Jeff; Unidirectional. Accel up to halfway, decel down to stopped. 1/4HP is probably 3X what is needed. I just haven't seen many(any) 1/8 or 1/10 hp 3ph motors.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[electricpete]

That sounds like an interesting project. I've never worked on control applications and have absolutely nothing practical to contribute. Just a whimsical idea. Take a look at this:

http://www.youtube.com/watch?v=TvSp_5TUiAM

Imagine the motor was operating the hand crank at high speed and the slow large gear in the center drives the belt. Then the motor doesn't have to continually accelerate/decelerate. I realize acceleration/deceleration isn't nearly as bad with vfd, but I tend to think it's better to avoid it if you can.

Then again, complicated special-designed mechanical stuff is not known for being reliable.

Maybe instead of using an electric motor, you could hire that Santa-looking guy and just feed him a regular supply of milk and cookies!

=====================================
(2B)+(2B)' ?

 

[Skogsgurra]

Keith
I fail to see any problem. You don't have any difficult starts. Your inertia is low (divide actual inertia by gear ratio squared). Dave (zdas) has a similar project - only a few times tougher - and his thing works.
No probs.

Gunnar Englund

http://www.gke.org

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

 

[MikeHalloran]

Pete, thanks for that. I love the wooden roller chain; he probably wore it out just filming the demo.

It sounds like it's maybe at the high end of what you can do with a stepper, but these days, the VFD will be cheaper and simpler anyway.

A full time fan for the gearbox might be as appropriate as it is for the VFD.


Mike Halloran
Pembroke Pines, FL, USA

 

[itsmoked]

Oh? What did zdas run?

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Have a look at thread237-316104

Gunnar Englund

http://www.gke.org

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

 

[itsmoked]

Thanks everyone.

Get this.. After reviewing the situation they've decided to run a SPhase gear motor continuously and to have me control an electric clutch...

Sometimes it's like bailing a boat over the stern while a committee is bring in buckets over the bow.

Thanks for the link Skogs.

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Talk them out of it, Keith. Bad decision.

Gunnar Englund

http://www.gke.org

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

 

[itsmoked]

New plan Gunnar. I will make sure we can control a motor later - when they realize the error of their ways..

Keith Cress
kcress -

http://www.flaminsystems.com

 

[Skogsgurra]

Good plan, Keith! If you cannot convince them, let them convince themselves by doing the mistakes.
I feel like setting something like that application up and do some measurements.

Gunnar Englund

http://www.gke.org

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

 

[cswilson]

Possibly an off-the-wall idea, but would there be any way of employing a "geneva wheel" in this application? Their whole point is to turn the continuous rotation of the motor into intermittent motion. Their most common use is the advance of film through a motion picture projector.

 

[itsmoked]

Nice idea cswilson.

Wait. An issue for that is that this machine has all this coordinated movement. Using a geneva wheel doesn't offer much in the way of having this separate function staying synchronous with the rest of the machine. Oh... . Yeah this whole machine's speed is controlled by the following machine's speed which is changed regularly. So that would put us back to needing a VFD and a 3ph motor to work with the geneva solution . Once there, I'd just try a motor/gearbox as Gunnar is voting for.

The load is really just the motor's rotor and whatever the gearbox dishes out. The actual function is piddly. Like a fart in a hurricane.

Keith Cress
kcress -

http://www.flaminsystems.com