Apparent mass of moving machine elements

The moving elements of a machine tool have mass. Forces from the actuators cause the masses to move and accelerate. As the speed of the machine tool motion increases, the ability of the actuators to cause acceleration becomes more important.

Rather than the physical masses of the moving elements, the actuators see the “apparent masses” of moving elements, which are often significantly less.

Figure 1. An actuator sees the apparent mass of moving elements instead of the physical mass. All images courtesy S. Smith.

Figure 2. Summing the moments around the pin determines the applied force.

A force (F) applied to a mass (m) causes an acceleration (A), according to the formula F = mA. One way to measure mass is by measuring the force required to cause acceleration. The ratio between the acceleration and the applied force is the mass (F/A = m).