Electromechanical

When to Use Gearing in Motion-Control Designs Part 1 of 2

Electromechanical gearheads gearmotors - Plastic bottle extrusion equipmentEstimates say that only about one-third of the motion control systems in service use gearing, although there are good reasons for doing so. For example, when your motion control system must run at 1,000 rpm or less, the use of a gearhead is advantageous. It’s also wise to use gearing when designing systems that have size constraints. Pairing a gearhead with your servo motor or using an integrated gearmotor can let you employ a smaller motor, thereby reducing the system size.

Advantages of using a gearhead

Advantages of using a gearhead with your servo in a motion control system include:

  • Torque multiplication. Gearheads can provide a mechanical advantage when mounted to the motor output shaft. That’s because the number of gears and teeth on each gear provide a mechanical advantage defined by a ratio. Say a motor can generate 100 in.-lbs of torque, and a 5:1 ratio gearhead is attached. Depending on the gearhead’s efficiency, the resulting torque will be close to 500 in-lbs. The use of a gearhead generates a higher torque output in a smaller envelope.

 

  • RPM reduction. Gearheads are often referred to as gear reducers because they increase torque output while decreasing motor rpm. For example, when a motor is running at 1,000 rpm and a 5:1 ratio gearhead is attached, the speed at the output is 200 rpm. Such speed reduction can improve overall system efficiency. In a recent example, a stone-grinding mechanism required the motor to run at 15 rpm. The slow speed made turning of the grinding wheel difficult because the motor tended to cog. Here, using a 100:1 gearhead caused the motor to run at 1,500 rpm, providing a smooth, continuous rotation.

 

  • Inertia matching. The past fifteen years or so have seen servo motor manufacturers introducing lightweight materials, dense copper windings, and high-energy magnets. Servo motors are therefore generating more torque relative to frame size than in the past, resulting in greater inertial mismatches between servo motors and the loads they control.

 

The use of a gearhead such as this in a motion control application can make it run at lower rpms and provide more torque.

Fig 1. The use of a gearhead such as this in a motion control

application can make it run at lower rpms and provide more torque.

Recall that inertia is a measure of an object’s resistance to any change in its motion and is a function of the object’s shape and mass. The greater an object’s inertia, the greater the amount of torque needed to accelerate or decelerate the object. 

When the load inertia is much larger than the motor inertia, it can cause excessive overshoot or increase settling times. Both conditions decrease production line throughput.

On the other hand, when the motor inertia is larger than the load inertia, the motor will need more power than necessary for the particular application. This increases costs because you’re paying more for a motor that’s larger than necessary and the increased power consumption means higher operating costs. The solution is to use a gearhead to match the inertia of the motor to the inertia of the load. Choosing the appropriate gearhead lets you use a smaller motor as well as develop a more responsive system.     

Help cut system cost

The upshot is that torque multiplication, rpm reduction, and inertia matching help cut system cost because the use of a gearhead allows the uses of a smaller size motor and drive.

For example, say an application requires 200 in-lbs of torque at a speed of 300 rpm. To drive the load with a servo motor alone (at standard performance attributes found in the industry), a servo motor with a 142 mm frame size and a drive that can supply 30 A continuous is necessary. The system costs about $6,000. But using a gearhead for the application lets you use a 90 mm servo motor and a correspondingly smaller drive. This system costs about $3,300.

 

For more information, on the range of gearheads and gearmotors for use in your design see Parker's Electronmechnical Division page

This is Part 1 of a 2 Part series

shared by Jeff Nazzaro, Gearhead and Motor Product Manager, Parker Hannifin - Electromechanical North America DivisionArticle contributed by shared by Jeff Nazzaro, Gearhead and Motor Product Manager, Parker Hannifin - Electromechanical North America Division

See Part 2 - When to Use Gearing in Motion-Control Designs Part 2 of 2

What You Should Know About Gearhead Sealing

How Gearheads Reduce Inertial Mismatches Solving Design Challenges

What’s Trending in Industrial Automation?

 

Categories
Recent Posts by Author

Key Technology Considerations for Dynamic Metrology Applications

Throughout the world, various types of metrology applications share a common need for increased precision. Metrology is the scientific study of measurement. Metrology applications take some type...

Gearbox Test Rigs Need Reliable, High-Precision Parts

When it comes to gearbox test rigs deployed in the automotive and aerospace industries, one thing is certain - there is no margin for failure. A test rig or system that is unreliable or...

Synchronous Motors put Swiss-type Machine Builder Ahead in Space Race

Modern Swiss-type lathes have evolved from simple screw machines to high-precision, high-production machines and are now widely used across many industries to completely machine small parts, even...
Comments

Have a question about Parker products or services? We can help: Contact Us!

Comments for When to Use Gearing in Motion-Control Designs Part 1 of 2


Please note that, in an effort to combat spam, comments with hyperlinks will not be published.

Leave a comment





Captcha