Servo and Selection of mechanical components

Servo and Selection of mechanical components

The engineer must decide which mechanical components are required for the application. For instance, a linear application may require a leadscrew or a conveyor. For speed transmission a gear or a belt drive may be used.

1. Direct Drive ?
2. Special application or standard mechanical devices ?
3. If linear application: Use of linear motor or leadscrew, conveyor, etc. ?
4. Reducer required – Gearbox, belt drive, etc. ?
5. Check shaft dimensions – select couplings
6. Check mechanical components for speed and acceleration limitations

The most common mechanical components for a motion application are:

For speed transmissions:

1. Gear
2. Belt Drive
3. Chain Drive (Chain-Sprocket)

For linear movements:

1. Conveyor
2. Leadscrew
3. Linear Actuator
4. Rack-Pinion

For other purposes:

1. Coupling
2. Brake
3. Encoder

Other applications:

1. Rotary Table
2. Nip Roll
3. Winders
4. Hoist

While a detailed functional description of these components is not in the scope of this book, it is nevertheless mandatory for motor sizing and selection to document the corresponding inertia and torque calculations. For detailed information on these calculations refer to Chapter 4 – Load Inertia and Torque Calculations. The knowledge of how to calculate inertia and torque of these components will also help in the calculation of more complex mechanical units.

In the following we will examine a very simple mechanical application, i.e. a motor and a disk as shown in the picture below.

Picture : Disk Application

A disk actually represents the majority of motor load components, i.e. when

you can calculate the inertia of a disk you can do the same for a leadscrew,

conveyor, belt pulley, and many other loads. Screws, pulleys, gears, etc. can

be seen as disks and hence use the same inertia equations.

Sample Application: Disk Application

The motion objective of this sample application shall be to accomplish a trapezoidal some time and then decelerate to zero speed again.

The disk shall be 2” in diameter, 1.2” in thickness. The material shall be steel,

which has a material density of 0.28 lbs/in3.