We recently designed and supplied a semi-automatic parts handling and vision inspection system to Oxford MEStar, the Oxford University – Institute of Biomedical Engineering spin-out Company.
Used for quality checking and product sorting of specially packaged ‘corneal scaffolds’ that are produced in the emerging technology of regenerative bioengineering, the system was urgently required and delivered quickly thanks to our design & production and motion control system integration service.
The cornea and its integral support scaffold, measuring about 35 mm diameter, is packaged in a sealed clear plastic blister pack measuring 80 x 100 mm.
The near translucent items are suspended in a transparent gel similar to a ‘petri dish’ solution, making it difficult to determine their exact position with relation to the packaging. To resolve this initial challenge, we worked with imaging specialist Scorpion Vision to develop a suitable camera vision system to evaluate the appearance and location of the corneal scaffold.
Operation
The basic machine requirement called for the vision system to be integrated with a two-axis (X,Z) linear positioning system and PC motion control software that included HMI screen prompts and status information.
A technician operator manually feeds the packages into the machine and the semi-automatic operation presents them to the vision system which then locates the scaffold position within 0.1mm.
The data from the vision system is used to reposition the scaffold to an optimal location within the full view of a customer supplied laser analysis system used to determine the condition of the cornea from its optical properties.
Finally, the package is accepted or rejected and transferred into pass or fail chutes for further processing.
Fast Solution Delivery
No stranger to special requests, fast deliveries and machine development flexibility, we were able to harness our experience to integrate multiple technologies in to a single, easy to use system, rather than specifically agreeing a rigid specification before commencing work – which would have extended the potential delivery timescale.
The motion mechanics – custom stepper driven ballscrew positioning stages with single linear motion guide bearings – are designed specifically for the application to maximise the space on the work platform.
With a 500 mm travel range for the horizontal axis and 50 mm vertical travel, the stages include manual drive wheels to allow the operator to position the axes under power-off conditions to maintain the machine. The design, production and quality inspection all took place at our Basingstoke plant and the stages were designed, manufactured and built in-house along with the gripper mechanism, brackets and the fixtures for locating the imaging and laser inspection sub-systems.
Front-End Software
The motion control system was developed in parallel with our modular application development front-end software, which works with stepper drives over Ethernet to build user-friendly programs that synchronise motion and machine I/O.
Whilst the front-end software is capable of complex machine control, the relatively straightforward repetitive processes which this machine required were easily taken care of.
Safety Integration
The machine includes a host of safety and machine I/O with emergency stop, over-travel limits, home switches and other sensor interfacing. The HMI touch-screen displays the machine phases – loading the package, automatically locating the cornea and its scaffold, the laser inspection phase and pass or fail for acceptance or rejection – then prompts the technician to load another package.
Move parameters, speeds, time delays and other adjustment features are included along with display of status information such as system state, axis position, I/O condition, axis and drive faults etc.
The machine is now in operation with Oxford MEStar’s production and research facility in China, where it is helping to develop and improve the quality of the cornea inspection process.
