Backlash, friction and temperature changes in these drive components skew the relationship between counts and the actual tool position, creating significant linear positioning errors. Alson s engineers use a variety of techniques to compensate for sources of linear position error. Machines are regularly calibrated with a laser interferometer to help ensure accuracy. To compensate for thermal expansion and contraction in the parts, which, for aluminum can produce linear errors 10 times greater than those of the machine, Alson monitors ambient temperatures and adjusts the time of day when it does a manufacturing operation. The bottom line for Alson is meeting customer specifications.
Customers expect much more today.
The game has changed. Putting new cards on the table Alson anticipated the changes in tolerance requirements and installed laser scales and temperature compensation systems on its large machines in the mid-1990s. The scale uses the same technology, laser interferometry, that machine calibration specialists use for linear error compensation, except that it is designed to be a permanent scale on the machine, replacing resolvers and encoders. The splitter and reflector splits the beam in two and reflects one beam, called a reference beam, back to a set of detectors mounted on the source. The second beam strikes another reflector, mounted on the moving part of the machine, that reflects it back to recombine with the reference beam on its way back to the detectors.