For more than 30 years, Laser Cheval has been a pioneer in the design and production of laser micromachining equipment. Laser Cheval produces machines for laser marking, welding, cutting and drilling, as well as custom devices.
One of the latest designs from Laser Cheval laser engraves logos on watch components with extremely small dimensions (e.g., watch crowns measuring 5 to 8 millimeters in diameter), while maintaining positioning tolerances of less than 50 microns. The machine processes up to 1,200 workpieces per batch over a 20-hour period.
Engraving process automation demands
Formerly, each workpiece was manually and precisely positioned under the laser head, one by one. The logos were then engraved on the workpieces. Finally, each piece was visually inspected for engraving quality by an operator who had to be present constantly to carry out these tasks.
Building on their successful integration of Cognex vision systems for several existing products, Laser Cheval decided to automate the engraving process on this new machine. There were numerous constraints that had to be met:
- The automatic vision-based positioning system had to match the positioning tolerances obtained with the old manual system (under 50 microns)
- Workpiece positioning had to be easy, with no pre-positioning required
- The system had to be able to run without operator intervention for at least 20 hours (the time required to process its capacity of 1,200 workpieces)
- The need for additional quality checks had to be kept to a strict minimum
- The vision-based system must have the same cycle time as the old system (processing a workpiece every 60 seconds)
- Laser Cheval wanted the machine's users to be able to easily and single-handedly modify the job configuration (as a function of the workpiece type).
All these requirements made it imperative to select a high-performance vision system.
Conclusive feasibility tests
After research and consultation with various suppliers, Laser Cheval turned once again to Cognex. Given the combined constraints of the application, Laser Cheval rapidly adopted a solution based on a VisionPro-equipped PC.
"VisionPro vision software tools provide the richness, diversity and power that our application needs," explained Michel Bertin, IT development director at Laser Cheval. "The Cognex PatMax® part and feature location technology, geometry tools and calibration functions, among others, bring us significant advantages." These calibration issues, in particular, led Laser Cheval to choose a PC-based solution, the only one powerful enough to handle the algorithms they wanted to implement.
"VisionPro proved to be the best choice in terms of vision tool performance; flexibility, with programs based on a rich, comprehensive object library; integration with our development tools; and quality and range of integrated graphics components. None of the competitors could beat this combination of advantages," said Bertin.
Laser Cheval created a prototype using VisionPro and conducted full-scale tests at the customer site. The feasibility tests surpassed the tolerance specifications, the primary criterion for selecting an automated solution. Finished workpiece engraving quality was measured statistically. The result: positioning with a standard deviation of barely 20 microns, for an angular tolerance of under 0.5°.
Laser Cheval was able to solve this application by drawing upon nearly a decade of experience and expertise in machine vision, as well as their proven ability to integrate this technology into the machines they build. In view of the positive test results, the customer approved the automated engraver and its machine vision component, a key element of the automation.
Automatic workpiece location, micron-accuracy positioning, simple, flexible and secure operation and more
Laser Cheval's logo engraver is equipped with motor-driven axes. Controlled by a Cognex vision system, these axes precisely position each one of the 1,200 workpieces, loading up to 12 at a time in any sequence.
VisionPro automatically locates each workpiece, regardless of its position on the work table. It then communicates the precise coordinates of the workpiece (x, y and θ in the laser's coordinates) to the axis control system, which moves the workpiece under the laser engraving head with a positioning precision far superior to tolerances obtained manually.
On this project, Laser Cheval took charge of programming the automated control of the machine's components (axes, laser, vision system); developed a user-friendly interface for implementation and modification of vision programs; ensured secure user access to modifications; integrated full user configuration of the machine (product codes, packaging, parts programs, vision system calibration, etc.); and designed an extremely simple operator interface.
Easy setup; functionality and performance that exceed requirements
The laser engraver equipped with Cognex vision exceeds customer requirements for both functionality and performance.
It can process a complete batch of parts without stopping, from the first one through to the last in every batch. Operators are impressed by the machine's easy setup and user friendliness. The customer also particularly appreciates its ability to adapt to new sets of workpieces. The rich VisionPro graphics library furnished by Laser Cheval lets the customer take full control over maintaining jobs and creating new patterns.
With the automated system, the customer only carries out a few quality checks on the logos, using sampling techniques. One workpiece is checked at the start of a batch and another at the end; sometimes this is supplemented with random sampling. The customer points out another advantage: "We can even run the machine over the weekend."
The customer now plans to deploy additional machines incorporating machine vision to automate all of its engraving work.
And at Laser Cheval, engineers are already planning how else they can use Cognex vision tools: controlling other automatic engraving applications, 3D applications, and more!