It is common for precision laser cutting and drilling applications to require probing of one or more reference surfaces of a part once fixtured in the machine but before processing. Probing determines the actual shape of real-world parts. It also determines their actual location and orientation as they sit in the machine.
While the part program assumes an ideal part in its ideal location, information from the probing routine creates offsets used by the part program to achieve the required precision, such as hole location.
We have tested the possibility of using SmartSense™ and OFC2 ABSOLUTE™, instead of a mechanical touch probe for probing metal surfaces.
This article highlights results from tests to quantify the accuracy of OFC2 ABSOLUTE to measure the position of surfaces of cold rolled and cast materials. A separate article will present results for detecting the edge of a part, another common function of a mechanical probe.
SmartSense™ is one of the latest LASERDYNE SmartTechniques™. Based on OFC2 ABSOLUTE™, SmartSense is currently used in production for measuring the location and orientation of ‘real-world’ parts for aerospace and automotive applications.
OFC2 ABSOLUTE uses a non-contact, laser-based sensor that is able to measure metallic and nonmetallic surfaces at distances up to 100 mm from the focal point of the processing laser at angles as steep as 10 degrees off the surface.
Collecting the data
Tests were designed to determine the accuracy and repeatability of measurements of surfaces of Inconel 625 with two different surface conditions and at various angles to the workpiece (90, 60, 45, and 30 degrees).
The two surface conditions evaluated were: (1) as-received wrought (cold rolled) and (2) grit blasted. The latter surface condition simulated the roughness of a typical cast component, such as turbine blade or vane.
Accuracy and repeatability of measurements using OFC2 ABSOLUTE and the SmartSense probing algorithm were determined using the following process repeated multiple times for each material surface condition and angle:
- Move the machine 10 mm away from the part in the R-axis (pseudo-axis of the laser beam).
- Measure the distance to the surface using OFC2 ABSOLUTE.
- Move the machine toward the part in the R-axis the distance measured using OFC2 ABSOLUTE in the previous step.
- Record the position of the linear axes from the motor encoders.
A minimum of 1,000 measurements were taken for each combination of angle and material surface condition. With the data in Excel, the standard deviation for each set of measurements was calculated.
Figure 2 summarizes the results of the measurements. These show that SmartSense is repeatable at angles ranging from 30 degrees up to 90 degrees to the surface. The maximum standard deviation of 2.5 µm (0.0001 inch) is, in our experience, as good as or even better than the repeatability expected from a mechanical touch probe.
SmartSense™ with OFC2 ABSOLUTE has proven to be a viable alternative to a mechanical touch probe in terms of accuracy, repeatability, and flexibility.
OFC2 ABSOLUTE is fully integrated into the laser machine. Measurement is coaxial with the laser-processing beam. Switching between processing and measurement is instantaneous and the measurement occurs at the location of laser processing.
We expect SmartSense to be effective in probing machined surfaces as well based on results with the wrought (cold-rolled) material.
Have questions or comments?
Contact your local Prima Power sales person or write to us at firstname.lastname@example.org to learn how you can make use of SmartSense in your laser processing application.
If this article was of interest…
If you found this article interesting, you may also want to read the following articles from previous issues of this newsletter: