Multipoint Measuring Machines
Multi-point measuring systems are special measuring machines or devices for fast synchronous acquisition of a large number of measured values with a large number of contacting or non-contacting transducers. The multi-point measuring technology is basically workpiece-specific or task-specific in design. It is used for static and dynamic measuring tasks for the geometry inspection of workpieces in series production as well as for statistical process control, with which the condition of the processing machines or of processes is monitored.
A measuring device always comprises a workpiece holder with corresponding handling, measuring slides and measuring probes of various designs with electrical or pneumatic infeed as well as a measuring computer for measured value acquisition, evaluation, visualization and data storage. The assembly is often carried out with standardized components in a modular system.
The workpiece is fixed in a workpiece holder. The workpiece-specific measuring probes are typically arranged on a measuring slide, which is fed manually or automatically. The probes are movably mounted in the measuring head and are pressed against the workpiece, e.g. pneumatically or by spring force, and permanently probe the workpiece surface. Non-contact sensors can also be used, and combinations of contact and non-contact displacement transducers are also possible.
Rotationally symmetrical or shaft-shaped workpieces are clamped either upright or lying down and rotated in the circumferential direction during measurement. They can rotate during the measurement or they are stopped and measured in pre-programmed positions. The measured values are recorded, evaluated and visualized by a measuring computer, and a test decision is made as to whether the workpiece meets the pre-programmed target values.
When used as a post-process measuring device, the measuring station is either integrated directly into the processing station or is a separate measuring station downstream of a process and processing station. At each manufacturing step, product quality can be affected by systematic or random errors that cause deviations in part geometry at various points. Random errors, such as machine vibrations, occur due to manufacturing processes and are hardly correctable. In contrast, systematic deviations, e.g. due to tool or machine wear, temperature changes or clamping errors of the processing machine, can be detected with the aid of regular multi-point measurement. By evaluating and storing a large number of data, such systematic deviations can be localized and reduced or completely eliminated by suitable corrective measures.