Vision Systems for Robot Guidance

Machine vision is the ideal tool for robot guidance, allowing visual inspection of the robot working area as well as guidance based on the detected position of a product or component. Vision systems can be used to identify the product in pick and place operations, for example using OCR, barcode reading or other visual cues.

As end-of-line packing is increasingly automated, many factories have discovered that end-of-line packers often provided a final quality inspection of which managers were not aware. Vision systems can carry out this function in addition to robot guidance. In addition, vision systems never tire, never slow down and are consistent between shifts.

MVT is working with a logistics company to provide robot guidance for a supermarket distribution centre. The requirements include identifying the type of crate, the number of crates in the stack and position of the top crate

A further requirement is to read barcodes on the crates to identify the contents. One of the advantages of modern vision systems is that their large number of tools allows ‘multi-tasking’: the ability to carry out several tasks rather than just one. Increasing processor speeds mean that this can be carried out within the cycle time of the rest of the line.

Vision systems in the Printing Industry

The printing industry is a natural home for vision systems; high speed lines can take advantage of ever-faster processing speeds allowing on-line inspection. MVT has been involved in the use of vision systems for print verification and optical character recognition (OCR) in numerous industries.

Vision systems are able to perform print verification, which may incorporate optical character verification (OCV), and is usually a high speed process with applications to inkjet, laser, pad and screen printing processes. Typical installations are checking print quality, sometimes in conjunction with a changeable target, for example serial numbers. Installation usually requires a ‘linescan’ camera. This has a single row of pixels and takes advantage of the movement of the line to build up an image. In this way, camera installations take up minimal space on the line.

Print verification techniques can be applied to other fields such as printed circuit boards and automated assembly processes.

MVT are happy to provide trials and to discuss customer requirements to ensure that the final system meets all of the job specification.

Production Engineering Vision Systems

Production engineering is well-placed to take advantage of a large number of vision system tools developed for other industries. As well as tolerance-checking on machined parts it is also possible to check for defects in parts such as scratches, cracks and missing/extra components.

There are also opportunities to use OCR (optical character recognition), data matrix (2-D barcodes) and 1-D barcodes to allow part tracibility throughout the production process and into customer usage. This allows faulty batches to be traced even after they have been delivered to customers and has become widely-used in the aerospace and automotive industries, where safety-critical components must be tracable.

Electronic Vision Systems

The machine vision industry has produced a number of vision systems tools for the electronics and semi-conductor industries in recent years. As such, the vision systems applications for these industries are numerous and well-proven. However, as the computing power available in PCs and smart cameras increases, what was once a specialist branch is becoming more mainstream with the attendant cost reductions.

The electronics industry can benefit from machine vision in a similar way to both the pharmaceutical and print industries. High speed production lines and microscopic details can be verified by vision systems on-line. On a macroscopic level, a vision system can check batch numbers on chips, read datamatrix codes (2D barcodes), ensure that all components are correctly positioned and no foreign bodies are present. Other applications include printed circuit board verification, flaw detection (such as scratches and foreign body detection) and LCD screen fault detection.

Automotive Vision Systems

MVT has a great deal of experience with automotive vision systems, having worked with major automotive OEM component suppliers. Typical vision systems applications include checking that manually-assembled automotive components are complete and correct and measuring machined parts to check that they are within tolerance (non-contact gauging). It is not unusual for automotive dimensional gauging to be carried out using moving cameras (for example on a robot arm).

Our experience

Automotive companies increasingly demand 100% quality checks from suppliers: vision systems have an important role to play.

It is possible to check for colour matching, character recognition for batch or product codes and barcode or datamatrix (2D barcode) decoding. The use of datamatrix marking in the automotive sector is becoming increasingly prevalent as manufacturers and suppliers fight counterfeit products and require traceability of defective batches. Datamatrix marks are able to hold far more data than is possible with barcodes and in a much smaller, permanently-marked area. They also incorporate a degree of redundancy to account for any damage that may be incurred during the lifetime of the part.

Automotive components being checked include suspension units, air springs, automotive interior fittings and even tyres. In addition to quality and dimensional checks, vision systems can be used in robot guidance and product identification for a ‘pick and place’ operation. The identification may be in the form of product features, e.g. shape, or from labels using datamatrix, barcode or text. Some of our customers like to use this functionality as an extra check when various products or variants may pass down the same production line.

Food and Packing Vision Systems

Vision systems are becoming increasingly important in the food industry as end-of-line packing is being automated. Food suppliers have found that packers used to check the quality of goods before they were packed; automation has brought about a requirement for vision systems to take over this function. We are now in the position of being able to apply vision system techniques, label inspection and character recognition to the food industry. This has allowed customers to improve their quality and reduce wastage.

Our experience

MVT has built a relationship with two companies in the food industry. Western Mechanical Handling are specialist manufacturers of food handling systems.

In a recent application we provided the vision for a ‘pick and place’ unit for loose pork pies. Due to the irregular nature of the pies it was found that they were sometimes damaged by the picking mechanism. By incorporating vision, the precise location of 48 pork pies on a tray was verified and measures could be taken to reduce wastage. This is one of the applications that vision systems have been used for extensively in other industries.

Other potential applications include checking the presence or absence of labels, character recognition (for example date code recognition, product type), print verification and the identification of errors in packaging. This can include identifying food trapped in seal areas and seal integrity on boxes. Quality checking of food items is also possible, this may involve a presence/absence check of a number of items or checks on the colour, size or shape of items. With respect to cooked items, colour may indicate burnt or uncooked areas; size and shape measures can indicate mis-handling. All of these checks can help to improve quality and reduce wastage.

Pharmaceutical – 21 CFR part 11

The pharmaceutical and medical device industries have been served by us since the company was founded. We can provide 21 CFR Part 11 ready solutions. The pharmaceutical and medical device industries offer an ideal application to vision systems.

Vision systems can check 100% of products, even on high speed lines, allowing statistical process control (SPC) to be used to monitor any variations in quality. Applications include print recognition and verification (OCR/V), including verification of date/lot codes, checking the presence of all components and colour checks in pharmaceutical devices.

In addition to standard vision systems, MVT is able to supply customised solutions and specialist vial readers for the pharmaceutical and medical industries . These are able to read datamatrix marks (2-d barcodes) from a complete tray of 96 vials. The advantage of this type of automated reading is that vials can be marked for their entire life. Vials are usually given a serial number that, when correlated with a database, allows the full history of the vial to be viewed.

Trials have been carried out using vision systems on tablet inspection to find damage to the outer coating, perform colour measurements and check size and shape.

OCR (optical character recognition) and OCV (optical character verification) has been carried out on pharmaceutical devices to ensure that laser printing was correctly set and completed for 18 different languages. These checks were carried out on-line and did not restrict the production line speed.