Laser sensor's intelligence controls inspection process

Cerulean designs and manufactures a range of quality assurance systems and instrumentation for applications in analytical laboratories and manufacturing processes, mainly in the tobacco industry. The company's CD Express is a benchtop instrument that measures and displays the circumference, diameter and ovality of cylindrically shaped objects - such as cigarettes, cigars and filters. At the heart of the CD Express is a non-contact laser micrometer from Micro-Epsilon UK.

Micro-Epsilon's optoCONTROL ODC 2500-35 sensor is a non-contact, laser-based measurement system with an integral, high-resolution CCD camera. It offers high sampling rates, outstanding accuracy and excellent resolution. Steve Frankham, sales and marketing director at Cerulean, states: "We selected the Micro-Epsilon sensor for its robustness and ease of use; particularly the fact that it could be easily configured to fit the required application."

With the CD Express, the sample under test is simply dropped into the machine and held in the path of the laser beam using a custom vacuum-operated rotary chuck. 100 individual measurements are taken during one complete 360-degree rotation. From the results, the minimum, maximum and average diameter or circumference is calculated and displayed, together with the ovality. Batch statistics are also available and the individual results can be exported via an RS232 interface. The sample is then ejected automatically.

Customised software

Cerulean's CD Express system uses a special version of Micro-Epsilon's ODC 2500-35 laser micrometer, with modified software inside the controller module to suit the customer's application. Chris Jones, managing director of Micro-Epsilon UK, comments: "The unique aspect about this application is that our ODC 2500-35 sensor controls the complete CD Express system via its modified software, which enables it to send and receive signals to start and stop the mechanical components and record the measurements. This means that no additional control hardware was needed to make the system function correctly."

The CD Express was originally designed to inspect cigarettes, filters and small cigars. It was designed to provide the tobacco industry with a simple, fast and easy-to-use, manually fed, non-contact measurement instrument compliant with ISO standards. According to Frankham, the machine has been readily accepted, both as a primary measurement device for small and independent producers, as well as by larger producers who have been looking for a manual instrument to provide a rapid check of product circumference when high-speed processing machinery starts up.

However, Cerulean has realised that instruments such as the CD Express have applications in other industries besides tobacco. The first such application related to measuring the ovality of shoulders for extruded laminate tubes (for toothpaste). Frankham says: "With only minor modifications, the CD Express quickly demonstrated that it was capable of meeting these requirements."

Cerulean is now working closely with Micro-Epsilon to identify and exploit new applications for the instrument. Frankham continues: "We are currently investigating a wide range of potential applications for the instrument, including how it can be used to measure the dimensions of wires, rods, plug gauges and tubes."

How the sensor works

Micro-Epsilon's optoCONTROL sensors measure the dimensions of a target or the position of an edge by using the shadow principle. Each optoCONTROL system consists of a sensor unit and a controller. A parallel light curtain is generated by using a laser light source. The CCD camera in the receiver section measures the target contour formed by the shadow with high accuracy. The sensor unit is controlled and evaluated by an intelligent controller; an integral screen displays measurements and acts as the user-interface during operation.

For more information on Micro-Epsilon's optoCONTROL 2500 range of laser micrometer sensors, please call +44 (0)151 355 6070 or email [email protected].

For further details on the CD Express, contact David Walker on +44 (0)7739 541951 or email [email protected].