Imagine a machine that can create living tissue using the principles of computer-aided design and manufacturing, and the latest digital printing techniques. In a collaboration of scientific disciplines, Sciperio Inc. (Stillwater, OK), Spectra Technologies Inc. (Euless, TX), and BioAssembly Inc. (Stillwater, OK) developed a digital printing machine that can create living tissue by design in a layer-by-layer fashion.

The BioAssembly Tool (BAT) directly deposits cells, bioactive factors and supportive scaffolding to enable the next wave of discoveries in regenerative medicine, advanced diagnostic therapies and preventative immunotherapy.

A key component of the BAT dispenser is a motion system that requires precision (to a tolerance of 2 microns), high-speed operation (moving the dispenser head at speeds up to 300 millimeters per second) and high-duty cycles (able to run continuously in production environments).

Spectra Technologies developed the three-axis motion system to position the substrate under the dispensing head. An additional X axis positions one of a group of alternative dispensing heads at the dispensing position. Working with Sciperio's functional specifications, Spectra engineers developed a list of detailed requirements for the motion system component vendors.

In developing requirements for the motion stages, Spectra's engineers paid attention to more than speed and precision specifications. Environmental issues can have dramatic impact on any high-speed, high-precision application. For example, temperature changes can dramatically affect the precision and repeatability of motion. For the BAT, the designers decided to use a ballscrew driven by a conventional motor, rather than a linear motor that can generate more heat than ballscrew-based motion stages.

Primatics Inc. (Corvallis, OR) was selected to supply a stage that satisfied the precision, speed and form factor requirements. To ensure precise relative positioning of the machine's axes and to eliminate the inertial effects of high-speed motion, the stages needed to be mounted to the structure of the machine. Spectra worked closely with Primatics to find a cost-effective solution. The solution was to affix all four axes to a granite platform.

Primatics provided a frameless motor that is coupled with the ballscrew. This increases the effective stiffness and smoothness of the system, and reduces cost and overall size. Primatics engineers performed calculations using motor efficiency and predicted axes usage data to incorporate the stage's integral frameless motor. Adept Technology (Livermore, CA) rounded out the collaboration with a high-performance, distributed control amplifier package to control the motor.

Adept's system controls the motion, as well as servo valves in the dispensing heads, and also interfaces with the vision system that monitors the dispensing process. The system controls up to 12 axes of motion with extremely tight coordination between the axes. Adept's team worked with Spectra to tailor its standard software and hardware product offering to meet the unique requirements of the application. The Adept controller handles the complex path generation, motion kinematics and vision guidance calculations dictated by the application, while the servo control of the axis motors is accomplished at the amplifier level. Systems configured for vision guidance and inspection use a separate processor for vision processing to reduce the load on the main motion controller.

Sciperio developed a complex software application to translate computer-aided design data into desired position, velocity and acceleration for each motion axis based on fluid properties, pump parameters and substrate properties. Spectra and Sciperio combined this theoretical data with Adept's vision-generated data to provide the precision multi-axis path data used by the system when dispensing.

For more information on motion control systems, call 800-779-5678 or visit www.spectratechnologies.com.

For more information on motion control stages, call 541-757-9678 or visit www.primatics.com.

For more information on motion control systems, call 800-292-3378 or visit www.adept.com.