In addition to position, the rate of change of position, or speed, is an important factor in motion systems. The maximum speed specification is provided at the stage's normal load capacity (see below). Higher speeds are possible for lower loads or larger motor drivers. Minimum speeds are highly dependent on a motion system's speed stability. Speed stability is a measure of the ability of a motion system to maintain a constant speed within specified limits. It is usually specified as a percentage of the desired speed. Acceleration is the rate of change of speed, which is often set to achieve the maximum speed in a set amount of time. Friction can play a significant role in the speed, speed stability, and acceleration of a stage. Friction is defined as the resistance to motion between surfaces in contact. Elements contributing to friction may be in the form of drag, sliding friction, depleted lubrication, system wear, or lubricant viscosity. Stiction is the static friction that must be overcome to impart motion to a body at rest. Since static friction is generally greater than moving friction, the force which must be applied to impart motion is greater than the force required to keep the body in motion. As a result, when a force is initially applied, the body will begin to move with a "jump" that results in position and/or speed overshoot.

Load capacity is the maximum allowable force that can be applied to a stage in a specified direction while meeting stage specifications. This maximum force includes static (mass times gravity) and dynamic forces (mass times acceleration). Dynamic forces must include any external forces such as vibrations acting upon the stage. The amount of acceleration a stage can impart to a mass is limited to the accelerating force it can produce without exceeding the load capacity. In particular, the centered normal load capacity is the maximum load (centered on the carriage and in a direction perpendicular to the axis of motion) that can be applied to a linear stage (see Figure 3). For rotary stages, it is the maximum load along the axis of rotation. Transverse load capacity, also called side load capacity, is the maximum load that can be applied perpendicular to the axis of motion and along the carriage surface. This is typically smaller than the normal load capacity. Axial load capacity is the maximum load along the direction of the drive train. For linear stages mounted vertically, the specified vertical load capacity is usually limited by the axial load capacity. The maximum load capacity of a stage is diminished when the load is not centered. Inertia is the measure of load's resistance to change in speed. The larger the inertia, the greater the force required to accelerate or decelerate the load. If there is a constraint on the amount of force available, then the allowable acceleration and deceleration must be adjusted to an acceptable value. Inertia is a product of mass elements and the square of their distance from the axis of rotation. The maximum inertia specified for rotary stage is a value based on available torque.