Surface inspection machine uses laser triangulation sensors

Photocopier rolls are produced in high volume and to extremely fine tolerances, yet the complete surface of each roll has to be free from defects that would otherwise impair the quality of the resulting copy. Trac Measurement Systems, which is part of the Trac Group, was recently tasked with designing and supplying a complete automated inspection machine with the following key criteria:

• The machine must be integrated into a robot-loaded cell
• Rolls up to 3kg in weight and up to 450mm long must be accommodated
• No mechanical changeover between parts permitted
• Inspection must be non-contact to avoid surface damage
• The complete length and circumference of each roll must be checked
• Surface defects down to 0.010mm in depth must be detected
• Surface area detection down to 0.200mm2 must be achieved
• Inspection rate must exceed 150 parts per hour - equivalent to a cycle time of approximately 25s per part

Trac has extensive experience in the design, build and project management of both standard and bespoke inspection systems for a wide range of industrial applications. In this instance Trac chose the Micro-Epsilon ILD2200 non-contact laser triangulation sensor and the two companies worked closely together to complete a detailed initial feasibility study and, ultimately, the final inspection system.

The ILD Laser range offers high accuracy coupled with a small spot area and fast data collection speed - and was highly suitable for this application. To ensure that the complete surface area of each roll could be checked within the allocated time, a total of six sensors were arranged in a bank on an axial motorised slide to scans the length of each roll as it rotates at high speed. Each sensor collects data at a rate of approximately 1000 points per revolution and the machine automatically rotates the roll at approximately 600-800rpm.

Using a high-specification 3GHz processor the machine collects tens of thousands of data points that are then processed into practical measurement data. Each roll is classified as having minor, moderate or major defects and is automatically sorted after inspection.

The inspection machine is fully integrated into the production cell and interfaces with the robot loader and other equipment in the cell to provide a complete turnkey on-line surface defect analysis system to ensure the quality of every roll delivered.