Vision system provides 100% bottle inspection

A Panasonic Electric Works UK product story

Edited by the Engineeringtalk editorial team Sep 17, 2004

With the increasing financial penalties and cost of returns from the customers of bottling and filling companies there is a need to perform 100% inspection of the finished product.

With the increasing financial penalties and cost of returns from the customers of bottling and filling companies there is a need to perform 100% inspection of the finished product.

This requirement led one bottling company to turn towards vision system technology for a solution.

The brief was to provide a system to inspect milk containers for presence and legibility of the printed date code.

In addition, the label position and cap presence and position was also required to ensure that the container looked good on the shelf and that there was little possibility of the cap leaking.

It is the manufacturer's responsibility to ensure the best before date can be read clearly from a health and safety requirement, and for aesthetic reasons the labels on the front and rear of the containers needed to be positioned within a 5mm tolerance window.

The typical production line speed for inspecting the containers was 400 parts per minute.

With the release of the new A230 OCR/OCV device from Matsushita, a variation of the successful A-series of machine vision products, the company had found a candidate.

The A230 has optical character recognition and verification, a system for reading and verifying print quality, along with tools capable of checking for the other requirements.

A decision was made to take advantage of Matsushita's evaluation offer of proving the system both offline and online before purchase.

A collection of sample containers comprising pass, fail and borderline product was taken to carry out the offline evaluation.

The tests were designed to simulate the system as it would be on the production line with the same background and lighting that was proposed for the installation.

The A230 vision system has a large variation of pre-programmed tools on board that the user configures via a keypad and in this case optical character verification, measurement and presence checkers were used.

OCV employs a window around the print that sets variables to teach the system pass and fail conditions of the inspected print.

Measurement and presence checks are performed on the containers' caps to ensure the system is able to pick out the product that was to be rejected.

After many tests the customer was confident that there would not be any performance issues so camera and lighting mounting fixtures were installed on the production line.

An LCD monitor was mounted in the control cabinet to show images from the cameras with an option to have another local to the cameras to assist during commissioning.

The vision system CPU was installed in an enclosure next to the control system for the reject mechanism to simplify connection of a signal to the machine to divert product that failed the inspection.

At this stage an operator terminal was connected via one of the two serial ports on the vision system.

This allowed the machine operator to view statistical data on production as well as pass and fail counts and general status of the line.

Running online the vision system met its target of 400 parts per minute with room to spare for a further increase in production capacity but the test was to come in changing over from one product batch to another.

Although the containers would be the same and labels would be similar the date to be inspected was different.

The A230's Easy Teach facility made this a simple exercise by allowing the operator to approximately position the new container in front of the cameras and with just two key presses on the touch screen operator terminal the new variables were set with confirmation of the change displayed on screen.

After a period of time the vision system even highlighted areas of the process that could use some attention, this was indicated by the recording of images of failed containers thereby giving the process engineers actual evidence of the problem.

Modifications were made to the process and again over a short period of time the results of these changes were seen in the production of better quality product and lower customer returns and complaints.

Due to the benefits of installing this system further systems are to be installed, not just for this application but also on other production lines.

This is due to the flexibility, ease of installation and short pay back time the company is experiencing with Matsushita vision systems.