Probe Helps Laser Trackers Measure Hard-to-Access Part Features

A new probe enables laser trackers (portable CMMs) to perform precise, accurate 3D measurements of part features such as small pockets, holes, corners, punch marks, contours, crosshairs, scribed lines, and other large-parts features that are typically difficult to measure with a standard target or probe.

Called the Deep Access RetroProbe400, this device from SMX Corp. (Kennett Square, PA) not only can save time, but also increases the productivity of laser trackers in areas such as scanning, inspection, alignment, building, reverse engineering, and other applications that require complex 3D measurements.

How the Probe Works
Using a stylus that allows measurement of features up to 4 in. deep, the RetroProbe400 has clear sight lines and one-hand operation. The user touches the stylus tip to the recessed surface. It's not necessary to take more than one measurement to determine spheres and center points, which sometimes can be difficult and time-consuming when measuring recessed surfaces with standard probes. This instrument also reduces and can eliminate offset to ensure precise measurements needed for many reverse engineering applications.

The stylus tip on the probe comes with two kinds of interchangeable tips for tight seating against the surface being measured. Point tips end offset when they're used to measure surfaces with scribed lines, crosshairs, and similar features. Ball tips, which come in five sizes from 2–6 mm in diameter, provide a constant offset that equals the ball's radius. The ball tips are suitable for measuring surfaces in pockets, holes, corners, contours, and other recessed areas.

Another feature of the device is its "virtual image" concept. With it, any object viewed in a mirror appears to be located at a point in space behind the surface of that mirror. According to the company, "the virtual distance of the virtual object — as seen "behind" the surface of the mirror — is equal to the real distance of the real object from the "front" surface of the mirror." The probe has a flat mirror on its front, and when the beam from the laser tracker strikes the mirror, it's reflected into the cornercube in the head of the unit. The center of the stylus tip is identical to the virtual image point of the cornercube.

This instrument is used when the probing direction is the same as the direction of the beam from a laser tracker. Another version of this product — the RetroProbe100 — is used when the probing direction is perpendicular to the tracker beam.

SMX Corp. manufactures and supplies laser trackers as well as metrology software, contract inspection services, and training.

For more information, contact SMX Corp., 222 Gale La., Kennett Square, PA 19348. Tel: 610-444-2300, ext. 225; Fax: 610-444-2323.