Softstop

Softstop is a term used to describe a mechanism or technique that prevents abrupt cessation of motion by introducing a controlled deceleration or a cushioning element before a moving part reaches a physical limit. It can be realized as a mechanical cushion at the end of travel or through drive-level control that slows the axis before contact with an end stop.

Mechanical implementations include elastomer or polymer cushions, springs, dampers, or compliant mounts that absorb energy and reduce impact. In some cases, hydraulic or pneumatic dampers are used to further smooth the stop. Electronic soft stopping employs programmed motion profiles, such as S-curve or trapezoidal deceleration, to bring the system to rest within the available travel without triggering a hard contact.

Applications are common in CNC machines, robotics, and other precision equipment where end-of-travel contact can induce vibration, misalignment, or excessive wear. Soft stopping is often used in conjunction with soft limits, which prevent motion from exceeding defined software-defined boundaries.

Advantages of soft stops include reduced peak forces, lower vibration and noise, diminished wear on guides and gears, and improved near-limit accuracy. Potential drawbacks are added cost and complexity, plus the need for proper tuning of the deceleration profile to balance cycle time and safety.

See also: soft limits, hard stop, velocity profiles, end-of-travel cushioning.