Timex is America´s leading watchmaker and is present in more than 80 countries. Fralsen, its French entity, makes watch movements using three technologies — plastic injection molding of small parts with very fine details; turning and cutting of parts such as wheels, pinions, arbors and rivets; and cutting and coiling of complex springs. These precision parts must be inspected with contact sensors (comparators, Cary equipment, feeler-spindles) and optical systems.
“We wanted more modern and more efficient optical inspection equipment. In other words, we wanted to be able to inspect more parts in less time,” says Sylvain Scotto of Fralsen´s quality control department. “We also wanted a machine that could be operated by non-specialists and be able to log measurements.”
The tolerances and accuracies are 15 µm for concentricity and ± 10 µm for center-to-center spacings and distances, says Scotto, and there are at least five critical points per part.
“With conventional inspection equipment, measurements took too long. As a result, we couldn´t measure many parts and there was a risk of overlooking significant variations within batches,” says Scotto.
The Timex/Fralsen QC department had been using a variety of equipment: “Our optical measuring device, although very accurate, is not very practical for quick measurements on a daily basis. Furthermore, it requires a high level of skill to operate,” says Scotto. “The shop microscopes provide accurate measurements, but are tricky to operate and severely limit the number of measurements and parts. In addition, a reference point for truing-up had to be created. Lastly, due to the sometimes long inspection times, our templates and projectors allow only a limited number parts to be measured, and there is a risk of misinterpretation.”
Fralsen chose an image dimension measurement system from Keyence called the IM-6500 Series to improve its quality inspection process. The IM Series eliminates the need for X-Y stages and instead measures the dimension of an entire target simultaneously, greatly speeding up the time required. It also eliminates variations of interpretation of measurements: Results are displayed green (for good) or red (for bad).
The Keyence solution also allows several parts to be measured simultaneously. The size of the parts and the number of elements making up the program are the only limits. And there is no need for manual truing-up, because the system recognizes each part´s geometry. Part profiles can be compared against master profiles imported from computer-aided design (CAD) files, and all results can be saved and statistics tracked.
With the IM-6500 Series system, “We no longer need to position templates on parts and measure differences in shape by eye,” says Scotto. “The machine does so automatically and extracts an image of the contour showing the difference with the tolerance. All in all, measurements are fast and do not require special skills.”
To measure features, users place a target on the stage and press the button. Up to 99 points are measured in a matter of seconds with a repeatability of ± 1 micron. Targets are found and measured regardless of their position or orientation because the system’s iPASS shape-detection software determines the position and angle of targets.
“Getting to grips with the system was easy because all you have to do is adjust the focus and load the program for the part being inspected,” says Scotto. “All the QC technicians use the machine for final inspection of parts before their placement in stock. The operators in the cutting shop also use it to measure certain parts during production.”
Scotto says the faster inspection times enable Fralsen to track dimensions better and thus improve the quality of a large number of parts. For example, to inspect a stator, the contour of the stator is superimposed on the CAD file. “With the old method (template and projector), this process was long. Now, three parts can be inspected in less than one minute, instead of five in five minutes,” says Scotto. “The profile also allows the Mechanical Engineering department to see where parts need reworking.” In the photo, the red contour shows that the stator is at the tolerance limit in places (blue zone).
In another example, QC technicians use the system to inspect the concentricity of every single cut wheel and automatically record the measurements. The system inspects the concentricity of the toothing with the inner bore. “With a profile projector and a template, three parts were inspected in three minutes; with the IM Series, Fralsen can inspect (and record) more than 10 parts simultaneously in the same amount of time.
Edited by Renee R. Bassett, [email protected]
