Product category:
Vision and Colour Sensors
News Release from: Cognex UK | Subject: Machine vision systems
Edited by the Engineeringtalk Editorial
Team on 20 March 2000
Vision systems retrofitted like CNC
Special purpose machine tools and assembly systems, with Cognex machine vision systems as an integral part, are being supplied to the automotive industry by Douglas Curtis Machine Tools
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) 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
This article was originally published on Engineeringtalk on 20 Mar 2001 at 8.00am (UK)
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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.
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 bar-coded label printed when each container has been filled.
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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? "We needed to find a system to integrate to our machine tools to check that the right component was being inserted," says Rick Baker, Managing Director of Douglas Curtis Machine Tools.
"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 onto 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' 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.
"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," says Baker.
"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." As a Cognex Systems Integrator it has achieved some firsts in its application of machine vision to solve practical manufacturing problems.
One of the firsts is the use of a vision system to detect leaks, which is possible as the Cognex equipment has very fine resolution and it is possible to detect a change in density of a finite number of pixels.
In Douglas Curtis' experience one of the important factors for a machine vision application is the optics - getting the correct lens set up and the right lighting.
With some initial help from the Cognex, Douglas Curtis' in-house electronics and software engineers developed new light systems using white and red LEDs to illuminate the sample in such a way that the camera could capture the detail necessary for analysis.
Now the technology is being taken further, to see whether it is possible to capture the moment that a component operates and the initial spray pattern.
The most difficult challenge yet, it will decide whether it is possible with a machine vision system to examine the performance as if inside a combustion chamber.
Douglas Curtis uses Cognex MVS-8100 vision systems in its applications, and programs them using the comprehensive toolkits that are available to Systems Integrators as part of the product.
The front ends to applications are written in Visual Basic, which uses the Cognex toolkit to process, and analyse images recovered from the cameras.
The Cognex MVS-8100 is a PC-based machine vision hardware and software package that combines the power of Intel's MMX (Multi-Media Extensions) hardware with Cognex's industry leading machine vision software.
The MVS-8100 has a high-performance PCI bus machine vision frame grabber designed to capture bight quality grey-scale images from up to four cameras and transfer them to a host station for display and analysis.
The board supports rapid camera reset for high acquisition rates of rapidly moving parts and also features non- interlaced progressive scan acquisition of arbitrary numbers of video lines.
Images are analysed using Cognex vision technology that has already been successfully deployed in over 100,000 vision systems worldwide.
The software is object-based and the library includes tools for locating objects or patterns, measuring their geometric properties and reading characters or codes with accurate, repeatable results.
Cognex has a tried and proven product, good documentation and excellent international support.
Where machines have to be running 24 hours a day supplying Just-in-Time to major automotive companies, manufacturers don't want to know that they may have to wait several days for a service engineer to be available.
They need reliability, and Cognex deliver this by operating through local Systems Integrators who understand the applications and can look after the software and installation, while Cognex gives hardware support.
At Douglas Curtis, there are two engineers that have been specially trained by Cognex on the intricacies of the system.
About Douglas Curtis: Douglas Curtis Machine Tools (DCMT) is part of the Douglas Curtis Group, based at Ardleigh and Colchester in Essex.
Starting in 1973 by rebuilding and reconditioning machine-tools, the group moved on to retro-fitting CNC to existing machine tools, and three years ago started fitting machine vision systems in the same way.
DCMT mow manufactures special purpose machine tools and assembly systems and is a Cognex Systems Integrator.
It retro-fits Cognex machine vision systems to existing machinery, and builds new automated production equipment that relies on Cognex machine vision systems as an integral part of the design.
The group has a turnover of ?6 million, and employs 80 people. Request a free brochure from Cognex UK ...
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