[Big Caveat: I’m going to take a stab at answering these questions, but I’ll make sure I eventually find someone with more electrical and controls talents to contribute to this section. -tjw]

What is a drive?

Definition: A drive is an electronic device to provide power to a motor or servo.

You can divide the world of electronic motor drives into two categories: AC and DC. A motor drive controls the speed, torque, direction and resulting horsepower of a motor. A DC drive typically controls a shunt wound DC motor, which has separate armature and field circuits. AC drives control AC induction motors, and—like their DC counterparts—control speed, torque, and horsepower.

(From “What is a drive?” web page of IEEE Kansas City chapter.)

What is a drive point?
What is a master drive point?
What is a tensioning drive point?

A drive point is any non-idling component intended to maintain or change web speed or tension in the machine direction (MD), typically rollers connected to a brake, clutch, or motor. (Note: Clutches are usually have a driven input shaft connected to a motor, but can be used as a brake without a motor.)

The master drive point is the single drive point intended to control the overall speed of a web line. The master drive point (also called the pacer or line speed reference) leads the entire line through acceleration, steady speeds, and deceleration. If the master drive point slips, the web speed and tension will be uncontrolled.

A tensioning drive point is any additional drive point that is not the master. Each additional tensioning drive points (also known as followers) creates an additional tension zone. Tensioning drive points will run near the master speed, but trim their speed or torque, as needed, to increase or decrease tension.

Can a non-roller be a drive point?

Yes, a non-roller can be a drive point. Anything that has sufficient traction with the web and can exert significant driving or braking force on the web or control web speed can be a drive point.

Example 1: Tenters or stenters – These devices are used for maintaining or controlling web width by grabbing the web edges with closely spaced pinching jaws or pentrating pins. Tenters are used in biaxial orientations of polyester and polypropylene films. Due to their high mass and inertia, tenters are commonly the master drive point of the film line.

Example 2: Drive belts – Bels are commonly used to transport web that may note have the elasticity to support tension. Web-to-belt traction may be created by web weight, force air, electrostatics, or vacuum.

When would a roller not be a good drive point?

Any roller that lacks sufficient traction with the web to exert significant driving or braking force on the web would be a poor choice for a drive point. Traction is created by tension over radius, by web weight, by nipping, and occasionally by vacuum. These factors create the normal load that then develops friction. If these forces are low or the system coefficient of friction is low, then traction is insufficient to be a reliable drive point.

Some rollers at first appear to be drive point candidates, but if they are highly susceptible to air lubrication, they will be poor drive point candidates. Air lubrication becomes significant when it is greater than the combined surface roughness of the web and roller. Therefore, smoother rollers are often poor drive points without nipping to prevent lubrication. Lubricating air layers thickness increases with roller diameter and speed-to-tension ratio. Therefore, large diameter rollers are more prone to trouble. Also, high speed and low tension processes need special attention to avoid lubrication. An example of a poor drive point is a larger diameter, chrome (smooth surface) roller in a high speed, thin-film (smooth and low tension) process.