GlossaryKind of term: Manufacturing termOn-machine probing
What is on-machine probing?
On-machine probing uses a touch probe in the machine tool to set the work origin, align the workpiece or check a dimension while the part is still clamped.
In on-machine probing the machine loads a touch probe into the spindle or turret, like a tool. The probe touches the workpiece at a few points and a probing cycle in the control calculates a position, a misalignment or a dimension from them. Common uses are setting the work origin after clamping, aligning a rough block or casting, and checking a bore or face between roughing and finishing so a tool offset can be corrected. Tool measurement with a tool setter or laser is a related but separate function.
How reliable is on-machine probing?
The measurement uses the machine's own axes, control and thermal state. A geometric error or warm-up of the machine therefore sits both in the machined part and in the measurement, and stays largely invisible in the measurement. The result also depends on probe calibration, probing speed, and chips, coolant or burrs on the measured surface. For a reliable measurement the probe is calibrated on a reference and the machine geometry is checked periodically.
How does on-machine probing work in practice?
A probing cycle costs machine time, per setup or per part. On the other hand, it can replace aligning by hand with a dial indicator, avoid a reclamp just to measure and catch a deviation before a batch becomes scrap. In unattended machining, probing is a common way to monitor drift and adjust tool offsets automatically. Whether probing time goes into setup time or cycle time is up to you; either way it belongs in the cost.
What is on-machine probing often confused with?
On-machine probing is not final inspection. Because the machine measures with the axes that made the part, customers usually do not accept it as independent evidence on its own; the final inspection report then comes from a CMM or another gauge. Probing is also different from the work origin: the origin is what you set, probing is one way to establish it.
Frequently asked questions
Can on-machine probing replace the inspection room?
For in-process monitoring often yes; as independent evidence for the customer usually not. A geometric error in the machine sits in the part and in the measurement at once. Some customers accept it with a documented, verified measuring method; that is agreed per customer.
Where does probing time go in the estimate?
Probing the origin and alignment after clamping fits in setup time or as a fixed time per setup. Probing to check a dimension on every part fits in cycle time. Which split you use is a convention; count it once.