Image Processing Inspecting Very Small Precision Mechanical Parts With Great Accuracy

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A Swiss specialist in high-precision technology has developed sophisticated applications that allow micromechanical components to be cleaned and precisely measured during the manufacturing process. The suitable machine vision algorithms for this are included in MVTec Halcon.

Precise, repeated measuring and testing of small parts at high speeds are important requirements for the watch industry and all sectors working with micro-components. This helps avoid production waste and ensures the manufacturing of precise parts.

Petitpierre SA, headquartered in Cortaillod, Switzerland, is dedicated to realizing this ideal as a specialist in sophisticated microtechnology—with the help of machine vision. The service portfolio of this family-owned company, founded in 1973, includes complex measurement systems for the watch and jewelry industry, as well as for medical technology and aerospace. Additionally, the company develops and produces high-precision systems for the automated assembly of microtechnical high-end components and sophisticated watchmaking tools.

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Contactless Inspection And Cleaning System

One of Petitpierre's clients is KIF Parechoc, a flagship company of the Swiss watch industry based in Vallée-de-Joux. To comprehensively optimize and automate its processes, Petitpierre developed a contactless inspection and cleaning system. This is suitable for a variety of components for mechanical movements, such as shock absorbers, index assemblies, wheels, screws, trains, and complete barrel housings. To elevate process quality to a new level, the measurement of these finely mechanical parts had to be optimized. "Our goal was to perform the entire measurement process with just one click. Additionally, we wanted a variety of different finely mechanical parts to be automatically recognized and the data directly transferred to our quality assurance software," explains Yoann Canon, COO at KIF Parechoc.

The biggest challenge in implementing the project was to carry out a highly precise and very fast series of measurements under harsh production conditions. We were only able to overcome this challenge by using the machine vision software MVTec Halcon.

Yoann Canon, COO bei KIF Parechoc

Process Relocation from the Clean Room to the Production Facility

Until now, the process was conducted with multiple systems including contact measurement in a clean room. "We wanted to shift the measurements directly to the production facility to reduce effort and thus ensure continuous process chains. Additionally, it was our goal to significantly reduce control time compared to conventional methods and thereby also increase productivity. Lastly, the required measurement accuracy should also be transferred to a rough mechanical production environment. It was important to minimize employee intervention in the process," adds Yoann Canon.

To meet the diverse requirements, advanced measurement technology was needed. "It quickly became clear to us that we couldn't bypass industrial image processing in this application case. With the technology, it is possible to continuously automate the entire process with minimal effort. Additionally, in measurement, we benefit from a speed and precision that hardly any other technology can offer, thanks to machine vision," explains Thomas Majoulet, Head of Metrology at Petitpierre.

Efficient Combination of Cleaning And Measurement

The solution implemented by Petitpierre is a dual system that combines the products drop and lumen and is enhanced with machine vision software. Drop is a device for the automatic cleaning and drying of fine components, ensuring optimal repeatability of cleaning quality. Lumen is a telecentric optical device for the intelligent, automatic, and highly accurate measurement of finely mechanical microcomponents. The system was specifically developed for use in demanding production environments. It is compact, lightweight, and easy to handle.

The application, in which the micromechanical components are cleaned and measured individually, works as follows: the operator initially places the components in a container of the drop system and starts the cleaning process. The first part is cleaned. Once it is clean and dry, it is transferred into the lumen system using a vacuum gripper that has also been cleaned and dried. The cleaning and drying cycles are freely configurable: the amount of solvent, cleaning and drying time, as well as the number of cycles, can be set by the operator.

Once the part has been transferred to the lumen system, the integrated machine vision software automatically recognizes it and starts the actual measurement process. A "start" click by the operator is enough to conduct the measurement without manual adjustments. The measurement processes are then repeated for additional components. Once all parts have been inspected, the measurement results are seamlessly exported to KIF Parechoc's quality assurance software and are available for the further process chain. The process can now be repeated with the other components.

The optical measurement line in the lumen system consists of a telecentric lens, including lighting, a V-shaped fixture for the correct placement of the parts, and two prisms that reflect the image onto a telecentric optical sensor. The setup also includes a motorized shutter to protect the measurement area from dust and oil, as well as an LED to indicate proper system functionality. All components are controlled by an electronic circuit board.

Highly Accurate Measurement Thanks to Matching Technologies

The image processing software used is MVTec Halcon. "We chose Halcon because it offers all the functions we need for our application. In addition, the features are highly robust and technologically ahead of many other providers in many cases," comments Thomas Majoulet. This allows 2D shape matching technologies to precisely identify and locate the tiny parts, so they can be accurately picked up with the vacuum gripper and measured with sub-micrometer precision. The software reliably detects even the smallest contours and checks them accurately. In detail, diameters, lengths, run-outs, radii, and angles are measured and checked with subpixel accuracy using the "subpixel threshold" technology. Additionally, MVTec Halcon simplifies the precise camera calibration of the lumen system.

Precisely Map Telecentric Optics With Halcon

Another advantage is that MVTec Halcon is capable of precisely addressing the specific requirements of telecentric optics, as used in Petitpierre’s lumen system, right out of the box. Thanks to a 360-degree measurement of the object, no perspective distortion occurs that would require laborious correction afterward. This paves the way for exceptionally high measurement accuracy.

Fully Automatic, Much Faster And More Accurate: All Goals Achieved

"MVTec Halcon is the ideal image processing software to tackle our challenges. It not only offers the necessary accuracy and detection speed but also enables a completely contactless inspection process. This provides additional protection for the delicate and easily breakable watch components and prevents micro-contaminations. We can now fully automate the entire measurement process, including cleaning, drying, and transferring the parts to the lumen system. This ensures reproducible processes and minimizes manual intervention by staff. Since we can now start the entire inspection process with a single click, we have achieved our goal of significantly accelerating it. As a result, KIF Parechoc can reduce costs and elevate productivity to a new level," concludes Thomas Majoulet.

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