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Servo motor application question

Servo motor application question

Servo motor application question

(OP)
Hi, I am new to this forum and also very new to automation. I am a mechanical engineer but the plant I work at is small and we don't have any electrical engineers. Anyway, long story short, I am looking to replace an existing air-actuated rotary gate with a servo motor setup. The problem is that I don't know a whole heck of a lot about servo motors, controllers, etc.

The gate is basically a cylinder with 4 sets of cups located   90° apart around the circumference that take dough balls from a belt and load them onto an overhead proofer. The gate receives the balls, gets a signal from a proximity switch, rotates 90° and drops the balls into the proofer trays. Acceleration is moderate, torque requirements are very small, but the accuracy is important.

I guess what I am wondering is will a servo motor and controller be a decent solution for this application and if so, is the motor and controller basically all I need or are there other components that I am overlooking? In other words, can a servo motor with a controller be used as a stand-alone device or does it require other control/power components? (we have 3-phase, 480v at the plant)

The reason we want to change the setup for this operation is that the air actuator we are using right now has been failing on a monthly basis at $2500 a unit - primarily due to poor maintenance. We are hoping a servo motor setup would provide us with much better control and negligible maintenance. Any input is appreciated - thanks:)

RE: Servo motor application question

If the power requirements are small and accuracy is important, then you may be better to consider a stepper motor.

Best regards,

Mark Empson
http://www.lmphotonics.com

RE: Servo motor application question

You may review servo controller with build-in amp and direct AC supply from Elmo (www.elmomc.com) also. But at first you must define main motor requirements - cont/peak torque, max speed, gear ratio, resolution...

RE: Servo motor application question

For the moderate performance you are looking for a stepper system is probably the correct choice.  Mitsubishi makes some nice ones.  The system is turn-key with a controller/amplifier and a motor.  There is encoder feedback to avoid mis-positioning.
 
You program canned moves and the moves are executed when a signal is asserted (usually from a PLC). For your application an inline gearbox should be used to decouple the motor from the load.

The Mitsubishi reps can basically recomend-design the system for you.

RE: Servo motor application question

I agree that if the air cylindar was accurate enough, the stepper will be much more accurate and less expensive than a servo. However, there are several integrated servo motor / controller units on the market that make it very easy to implement them if you don't have another control system like a PLC in place already. If you did use a PLC for the air cylindar control, then stick with the stepper.

Here is a decent overview on stepper motor basics.
http://www.ams2000.com/pdf/step101.pdf

This company makes a decent all-in-one servo motor/controller, and in looking at their site again, it appears they may have a new version that is a stepper as well.
http://www.animatics.com/index.html

"Venditori de oleum-vipera non vigere excordis populi"


RE: Servo motor application question

(OP)
Hey, I really appreciate all the replies. I hadn't even thought about a stepper motor as the only ones I have ever worked with in my short career have been on some steam boilers for the purge air system. I will definately look into this closer. I just have some rough ideas on this project so I will look into the existing control system a little more and I may have a few more questions for you all. I am not positive, but I believe it is controlled by a remote PLC unit. I will certainly look over the articles/links that have been posted. Thanks Again

T. Dent

RE: Servo motor application question

Is your compressed air wet and dirty, particularly on humid or rainy days? If so, you need to spend something on fixing that problem.

If the air going into a rotary screw air compressor is more than 33% relative humidity, you are going to have problems with water emulsifying with the oil. Hooking up a set of household dehumidifiers to the pump intake filter comes to mind as a cheap solution.

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