News Release from: Envisage Systems
Edited by the Electronicstalk Editorial Team on 27 June 2006

Visual inspection system ROI under two years

To improve its quality control, BI called in Envisage Systems, a company specialising in automated visual inspection systems for the electronic components industry.

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BI Technologies is a wholly owned subsidiary of TT electronics and has been an innovator and leader in electronic components for 50 years. The product line encompasses trimming potentiometers, precision potentiometers, position sensors, turns counting dials, resistor and resistor networks, integrated passive networks, transformers and inductors, hybrid and power hybrid microcircuits, and custom integration of these technologies. The company manufactures products on three continents and service customers globally from nine direct sales offices and over 200 representative and distributor offices, all over the world.

Among BI Technologies' products are a number of surface mount components, which are produced on a reel containing up to 4000 components.

Many of these components are glass covered, which presents particular problems in quality control testing.

According to Stewart Beveridge, Senior Manufacturing Engineer at BI, 'We had four highly trained and experienced people checking the components through microscopes'.

'It took up to an hour to check each reel and, although the components are sitting in a clear pocket with clear tape over it, the result was not easy to view and made the inspectors very tired'.

'Even the most experienced operators could only work for 2-3 hours before needing a break and working for another 2-3 hours'.

'When people get tired faults can be missed.' 'When an operator found a faulty component it had to be cut from the reel and if more than seven components were found on a reel, the entire reel had to be scrapped and reprocessed'.

'It takes an hour to reprocess and another hour to inspect'.

'However, we found that many components that were being rejected for cosmetic reasons rather than malfunctions and this was having a detrimental effect on production costs'.

'We clearly needed to find a better, more automated way to inspect these components.' BI decided to call in Envisage Systems, a company specialising in automated visual inspection systems for the electronic components industry.

According to Mike Phillips, Managing Director of Envisage Systems: 'We have produced many bespoke visual inspection systems for electronic components manufacturers but the glass covered components at BI presented particular problems with reflection'.

'These problems were the same for us as they were for the manual inspectors.' 'We consulted Multipix Imaging, the suppliers of the cameras, frame grabbers, lenses and image processing software that we use in our visual inspection systems,' continued Mike Phillips, 'and they were able to help us understand the problems and convince ourselves that we could solve these problems'.

'With Multipix' help, we were able to put together a viable system, integrating the various hardware and software components.' Stewart Beveridge continued,' Envisage Systems did a lot of work on the lighting side as this was critical in removing the glare from the light source'.

'They were also greatly involved in the installation of the new system, which is now working very successfully'.

'The parts per million failure rate on these components has dropped dramatically as have inspection times, we have halved the number of full time inspection operators and our rework costs are nil, with 100% of production going through'.

'The system does exactly what we want it to do'.

'It misses some non-critical, cosmetic failures but has, so far, missed no critical failures'.

'We expect new systems to pay for themselves in two years but this Envisage system looks like paying for itself much sooner than that.' The system used at BI was based on a flexible mechanical design known as CAPVIS.

This machine was originally built as a capacitor inspection system but quickly evolved into a general purpose small part handling unit.

Capable of accepting all formats of cameras (including linescan), the system has been designed around the concept of keeping the mechanical elements as simple as possible and doing the more advanced features in the system control/image processing software.

This approach has been justified many times in practice where a machine has been delivered to site and introduced to engineering staff who have all the knowledge necessary to maintain the machine within the first half hour of training.

In this case the components are loaded into a vibratory bowl feeder (supplemented with a bulk storage hopper where necessary).

The singulated components are then passed into a linear feeder, the speed of which determines the ultimate feed rate of the whole system.

At the end of the linear track the components are allowed to flow onto a belt transport mechanism, which moves the units into the inspection stations.

Image capture is initiated by passing through some form of trigger device (through beam, retro-reflective or laser unit depending on component).

If a delay is required between the trigger and the image capture position, the trigger signal can be diverted to a system PLC, which will run the required timers before outputting single or multiple trigger signals of its own.

Once a valid trigger signal is received, an image is captured (the speed of which is determined by multiple factors such as component velocity and the amount of light available within the system).

The resultant images are processed by the image processing algorithms and a result determined.

In this system the defective components are removed from the line immediately but other systems can encompass shift registers to enable all reject components to be removed at a single point later on in the inspection process.

In order to gain access to the other surfaces of the unit (the one lying on the belt etc) the components are turned over in a simple two-belt grip system.

Once again, the simplicity of this mechanism means a potentially difficult task is incredibly simple and completely trouble free.

One of the other advantages of this approach is the lack of jam points.

Due to the fact that these systems generally handle small parts, the potential for machine jam-ups is fairly high.

In the past many systems using more complex mechanical design principals have not taken this into consideration, and have therefore failed (or not met with full approval).

The modular design of the system also enables different camera configurations to be used.

Originally the system was set up to house four cameras at two inspection stations, these providing a top and side view of each component.

The system has evolved with differing customer requirements to now hold as many as twelve cameras (although in this case the machine had to be slightly extended).

These different camera configurations are often brought about by the differing illumination requirements for inspected parts.

It will often be the case that certain defects will not be visible under the same lighting conditions as others.

This was particularly pertinent in the BI case.

Whereas the two standard (two camera) stations were fine for the bulk of the inspection task, the customer had a special requirement to inspect a unique edge aspect of these devices.

This particular problem was exacerbated by the fact that the unit surfaces were extremely reflective and standard lighting techniques caused significant glare rendering the inspection task useless.

It was therefore necessary to introduce two further single camera inspection stations to the machine.

These stations were fitted with illumination systems designed specifically for the one inspection task relevant to those stations.

There are a huge number of standard lights available on the market today.

Unfortunately, due the nature of the small size of the units inspected by the CAPVIS system, (typically ranging between 0.8 x 0.6 to 6 x 3mm), the illuminated area provided by these sources is often far too large to be of real use.

A special lighting solution had therefore to be developed.

This involved an array of carefully angled and extended ultrabrite LEDs being positioned at a specific height in relation to the unit.

The software written for any inspection system is obviously of prime importance to the success or failure of the project.

Where possible, it should be the case that this software is written in truly modular fashion in order to enable enhancements to be made to the system at future dates.

One very common phenomenon is that a customer will provide a specification, either written or in the form of reject samples.

By the nature of this process, concentration will be on known and major defect types.

Once the system is installed and commissioned and seen to be doing its job (and therefore pulling out all critical defects) concentration will shift to minor defect types which may not have been considered as important up until now but would nevertheless be desirable to remove.

It is entirely possible that a method for identifying these particular defect types was not considered in the original software version so a software architecture, which enables the addition of extra image processing modules is an ideal solution.

The operator interface is one of the single most important features of a vision system.

This is because it is the main point of contact with the system.

It must therefore be designed in such a way as to be understandable by all levels of employee likely to be interfacing with it.

One major consideration is that it should also include all of the tools necessary to help diagnose problems.

Typical features, which should be included, would be a means of capturing sequences of good and bad images as well as current tolerance file settings.

These files once sent over the Internet, will enable the system designer to diagnose problems far more easily, which can therefore be rectified in a very short time scale.

Although the intelligent camera approach to inspection tends to do away with this aspect of the job, (cameras once set up, simply output reject signals where necessary), a complicated system involving numerous checks should give real time feed back as to the current success of these checks.

In this way it is possible for a line operator to instantly warn the production department that a particular problem is occurring at some point in the production process.

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