Special purpose machine tools with integrated machine vision spur on automotive manufacturing quality drive

Citation

(2000), "Special purpose machine tools with integrated machine vision spur on automotive manufacturing quality drive", Assembly Automation, Vol. 20 No. 3. https://doi.org/10.1108/aa.2000.03320caf.011

Special purpose machine tools with integrated machine vision spur on automotive manufacturing quality drive

Special purpose machine tools with integrated machine vision spur on automotive manufacturing quality drive

Keywords: Machine tools, Assembly

Special purpose machine tools and assembly systems, with Cognex machine vision systems as an integral part of the design, are being supplied to the automotive industry by Douglas Curtis Machine Tools (DCMT) (see Plate 10 ). A Cognex Systems Integrator, the company is also able to retro-fit the vision systems to existing machines, in the same way as CNC capability might be fitted to machine tools.

Though most of the company's interest in machine vision is directed towards the automotive industry, and in particular at automated high-pressure hydraulic test machines for testing two-stage opening hydraulic valves, the technology could equally well be applied to a wider range of repetitive processes where the drive towards higher quality and the need for component traceability makes automation an attractive option.

Plate 10Douglas Curtis Machine Tools (DCMT) supplying the automotive industry

Companies in the automotive supply chain have to be able to deliver components to the highest automotive quality standards. At the same time, component manufacturers and end users alike need to know the exact build history of a component. To be able to verify that the correct component has been used means being able to find out performance and date of manufacture information for components within a complex engineering product.

Parts arrive at final assembly, in sealed boxes, with a barcoded label printed when each container has been filled. Both supplier and user need to be confident that boxes contain the correct number of units of the correct specification. The only practical way to achieve this is with automation, using camera systems that read identification markings on individual components. In this way, there is complete traceability as the progress of a component through manufacture, testing and assembly is tracked.

The first application of machine vision, which DCMT addressed for the automotive industry, was loading verification. Was the correct part about to be machined?

Rick Baker, Managing Director of Douglas Curtis Machine Tools, says:

We needed to find a system to integrate to our machine tools to check that the right component was being inserted. The components are laser etched with a 2D data matrix code, so we needed a system capable of reading these chequer-board patterns of tiny squares, and appearing grey on a black background. Once it has been read, the information may be transmitted via a network to a database, so the complete component history can be logged against the data matrix code.

But this one vision system, added at a customer's request to help traceability, was just a start. Soon Douglas Curtis was installing vision systems on to other manufacturing equipment. Engineers saw the early systems and realised there were several more opportunities and started retro-fitting them to existing equipment and new applications.

Baker continues:

We didn't initially use Cognex, but when we saw their product we were impressed with how advanced it was and persuaded an existing customer to convert. This was difficult as it is not best practice to have machines in use with different vision systems, because of operator training; the technologies are different and support comes from different sources. We persuaded our customer that it was a good move, especially from the international support side, and since then we've retro-fitted Cognex systems to other machines as well as new projects.

Douglas Curtis's use of Cognex machine vision systems has progressively become much more sophisticated. For example, component orientation may be checked with a vision system, something that is critical when there is a key feature to be picked up on for a machining operation or a test. The data matrix code can also be used at the end of a line to detect that the machinery has processed the right part before it is packed, to ensure that there has been no human intervention substituting one part for another.

Baker says:

Since we integrated that first system on a machine as a simple means of identifying whether we have the right component, rejecting it if incorrect, we've come a long way. Now we make special purpose test machines for the automotive industry which perform high pressure hydraulic testing up to 2000 bar. The vision system has been installed at the customer's request to help with traceability.

Applications have become more advanced, as we have more than one camera system on a machine, so we can identify the part being loaded. After it has passed through component testing, we re-identify it to make sure it's correct as it goes into final packing and to verify that an operator hasn't intervened in the meantime. There shouldn't be anything wrong, but a part might have been removed for an SPC analysis or something similar and incorrectly readmitted. It could even be wrong for the date it was manufactured or that particular batch number. Re-identifying components before they are placed into the final packing box ensures that the end user gets the correct amount of absolutely what is required.

For further information, please contact: Colin Graves, Cognex UK, Chancery House, 199 Silbury Boulevard, Milton Keynes MK9 1JL, UK. Tel: +44 (0) 1908 206000; Fax: +44 (0) 1908 392463; E-mail: cgraves@cognex.com