Vision system does not beat about the bush

Citation

(2001), "Vision system does not beat about the bush", Sensor Review, Vol. 21 No. 3. https://doi.org/10.1108/sr.2001.08721caf.003

Vision system does not beat about the bush

Vision system does not beat about the bushKeywords: Machine vision, Automotive industry

Low cost vision system from Cognex inspects bushes for industrial and automotive applications at the rate of up to 80 parts per minute. A stand-alone automated inspection machine operates round the clock at the factory of Dana Glacier Vandervell in Kilmarnock. The system is easily programmed using a hand-held console, enabling engineers on-site to respond rapidly to product changes and refine inspection procedures. The low-cost In-Sight solution opens up the market for automated vision systems in all industries.

Bushes made by Dana Glacier Vandervell Europe in Kilmarnock, Scotland, are being inspected automatically by In-Sight 2000 (see Plate 4), the latest low-cost vision system from Cognex. The £4,000 vision system – one of the first In-Sight 2000 units to be installed in the UK – is easily configured using a hand-held console and needs no specialist programming skills. It inspects up to 80 parts per minute to ensure they meet specified size, shape and feature parameters and is contributing to increased productivity, more consistent quality and lowered unit costs.

Plate 4 Cognex Dana Glacier Vandervell bushes being inspected by a Cognex In-Sight 2000

The Dana Glacier Vandervell site manufactures many different types of bearings and bushes for industrial and automotive markets. The site works a 24/7, four-shift rota making several million parts per week for highly competitive marketplaces which demand constant improvements in productivity and quality. One of only a handful of major bearing/bush manufacturers in the world, DGV knows that a fraction of a penny per part can make the difference between winning and losing next year's order, so the company is always looking for ways to improve efficiency and cut costs. Automated systems play a growing part in this process and a principle objective is to increase throughput while maintaining the highest quality.

The company has been using vision systems for about 15 years and has accumulated a wealth of vision sensing experience. Other on-site systems require substantial programming input and specialist support – clearly not an ideal situation when fast configuration and quick response is needed for production line changes.

Plans by DGV to upgrade a laser height inspection machine at Kilmarnock with an automated vision system provided the opportunity to look at latest solutions. DGV's technical centre at Rugby appraised several systems in Spring 2000 and recommended the new In-Sight 2000 from Cognex, which fills an important market niche between high-end, full-function vision systems and the limited functionality of "smart cameras". Technology advances and a reappraisal of the vision sensing process had enabled Cognex to introduce a solution that was competitively priced but having high-tech features, and these benefits clearly made In-Sight the right system for the vision upgrade at Kilmarnock.

The machine inspects bushes of between 15mm and 50mm diameter and up to 40mm height. A rotary disc feeder delivers parts to a small conveyor driven by a variable speed drive, transporting each bush past two inspection positions under the control of a PLC that relates conveyor speed to the reaction time of the vision system. For correct delivery to the inspection station parts need to be "end-up", but otherwise there is no need to pre-fix their position or orientation since the vision software used by In-Sight 2000 can determine these as part of the inspection process. Although some processing time is involved (approximately 20ms), this valuable function enables the delivery and transport system to be much simpler.

The first inspection station is a laser height-meter that looks for deviations in cylinder height. Non-compliant parts are immediately rejected. Accepted bushes then pass underneath the In-Sight 2000 camera, where their orientation is calculated and each is assessed for roundness and diameter. Physical features such as end slots, oil holes, internal oil grooves and embossing are also checked.

The In-Sight 2000 camera is mounted directly above the conveyor, looking down into each bush as it passes by. A fibre optic light source illuminates the part and the InSight 2000 camera has a wide angle lens which captures a "flattened" image of the inside wall, presenting the processing software with a circular "ring" pattern showing the inside diameter, plus end features and internal features.

DGV Project Engineer Greg Hay had the opportunity during mechanical upgrading work to trial the performance of In-Sight 2000 off-line and begin developing programs;

I used this period to become familiar with the procedures and was able to test out various inspection methods on the bench for the full range of parts. By September, when the machine went on-line, most of the background work had been done. Since then we have introduced refinements to our programs, but by and large the setup and configuration for In-Sight 2000 was simple and trouble-free.

Programming In-Sight involves a unique spreadsheet-based method developed by Cognex with ease-of-use in mind. A hand-held controller is used, similar to that used with a computer games console. Greg is enthusiastic about this:

In-Sight puts power into the hands of the person who really understand the process – me! Commands, computation and parameterisation are simply entered into the rows and cells of the spreadsheet, just like normal, using the hand-held console for cursor control, character entry, feature selection and formula writing. The spreadsheet can be displayed alone or it can be superimposed on a captured image of the part being inspected, allowing distances and features to be identified and parameterised manually for entry into the spreadsheet using a range of software tools provided by In-Sight 2000. Once you're used to it, it is simplicity itself.

Another advantage of In-Sight 2000 is that no program compiling is needed, as it uses the "steps" of the spreadsheet directly. Hay says:

This makes for very fast machine configuration and, better still, means I can refine our inspection procedures almost on the fly. This is extremely useful as the surface lining of our product can vary in tone from one batch to the next. When my production statistics captured from the system indicate a recurring failure mode I can determine whether it is due to either a manufacturing problem or a lighting deficiency. In-Sight 2000 allows these kinds of problems to be rapidly addressed and fixed.

Changing the machine to handle different parts is also easily accomplished. In-Sight can store up to 20 programs, so selecting one is easy, although some manual adjustments may need to be implemented, e.g. to cope with different lighting conditions. More programs can be stored off-line in a laptop and downloaded as required.

The In-Sight inspection system has been operating successfully at DGV Kilmarnock since September 2000.

For more information, contact: Geoff Collins, Cognex UK, Units 7-9, First Quarter, Blenheim Road, Epsom KT19 9QN, UK. Tel: +44 (0)1372 726150; Fax: +44 (0)1372 726276; E-mail: gcollins@ cognex.com