Video: In-Process Scanning of a Turned Profile—via Robot
A robot reaching into a lathe measures along the entire part length in seconds, determining whether additional machining is needed.
Autonetics of Chapel Hill, North Carolina is a manufacturing automation specialist, but chief technology officer Chris Wezyk says the specialty is more nuanced than that. The company solves automation challenges by combining off-the-shelf devices in unusual ways, he says. This video shows an example—a pair of digital micrometers mated to a robot in order to provide rapid, accurate measurements of the OD features of a turned workpiece. The robot (from Kawasaki) simply sweeps the length of the part in seconds to let the micrometers (from Micro-Epsilon) obtain thousands of data points in seconds—data that can be used to automatically develop a highly precise CAD model. Software written by Autonetics interprets the measurements, allowing the information to be applied to a follow-up machining pass, among other potential uses.
Mr. Wezyk says the accuracy is better than one might imagine. Robot positioning is precise, but a robot typically is not used for the very finest positioning and measurement applications. In this application, though, the digital micrometer provides for the accuracy in the part’s radial axis, while the location of the lathe’s spindle face is a known value along the part’s axial direction. This value gets used as a reference to compensate for the robot’s positioning along the lathe’s Z axis. As a result, a quick sweep through just a small Z-axis range is enough to let the robot pick up any precise Z-axis location where the diameter measurement needs to be known.
The same robot can also be used to inspect internal features, he says. To do this, the robot would release the digital micrometer set and pick up another device—probably an array of capacitive plug gages enabling it to measure a range of inner diameters.
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Virtually every machine tool builder lists, as part of a machine's specification, accuracy and repeatability figures. What's generally not given is the method used to arrive at the figures. Though these methods are defined in linear positioning standards, not all builders use the same standards.