Miniature linear motion components maximize space efficiency

Laboratory instruments are getting smaller. Analytical instruments that required their own room now sit on the benchtop. The trend toward miniaturization is welcome among laboratory managers and diagnosticians seeking to make the most cost-efficient use of floor and benchtop space. It also fast-tracks testing by eliminating the need to send samples out to a lab and wait for results.

Complementing the miniaturization trend are cartridges that enable multiple reagent tests at a single point and well plates that can handle multiple assays and specialized instruments dedicated to small batch assays.

The move toward miniaturization and process efficiency involves automation, challenging motion control system designers to scale down systems while achieving the same or better performance. Designers developing motion control systems to fit into smaller spaces have three primary options: using smaller components, eliminating external support, or working with manufacturers to develop custom solutions.

Designing with smaller components

Once designers know how much space they have, they’re better equipped to meet customer requirements with standard components. Increased demand in miniaturization of laboratory systems has resulted in wider market availability of smaller components, including size 8 stepper motors and 3mm ball bushing bearings.

Blood diagnostic and treatment systems are getting smaller. A large, standalone blood-cleansing device needed to be redesigned to fit on a desktop. The system used UV light to kill pathogens and motion control to agitate the sample constantly for maximum UV exposure. Reducing the unit’s width was accomplished with miniature profile rail assemblies, which also reduced the height. The designer also specified motorized lead screws, which could be tucked behind other components rather than extending outward in any direction, producing a more compact design.

Miniaturized innovations are also being applied to point-of-care diagnostics, which would bring blood test results right to the doctor’s office or portable devices that could be used in the home. With smaller-scale testing instruments, lab diagnostics could be available in minutes instead of days, potentially saving countless lives.

Eliminating external linear support

For space-constrained, force-sensitive applications requiring shorter strokes that must be repeated with high precision – such as vertically positioning a pipette over a test tube array – designers can economize space using a motorized lead screw actuator (MLA). Using a conventional basic stepper motor and lead screw assemblies requires designing external linear guidance for anti-rotation of the nut and system guidance. The hybrid approach eliminates external linear guidance by surrounding the shaft with an aluminum cover tube with molded internal splines that lock onto the nut to keep it from turning. This provides linear guidance, giving the designer more flexibility to reduce the size of the axis and footprint of the instrument.

Customization

If designers can’t get the required motion with standard components, they must work with manufacturers to create custom solutions. Customization usually doesn’t start from scratch but modifies existing standard components to overcome limitations. Ball nuts are designed for screws of different diameters, reducing the cost but requiring a larger nut. To save space using a smaller diameter screw, a smaller nut could be developed.

Modifying the mounting also is an option. Working on a new spectrophotometer to analyze color samples on the desktop, a designer needed compact linear motion components, and selected a single miniature profile rail assembly to guide the spectrophotometer lenses into position. The miniature rail enabled a compact profile, high load capacity, and quiet movement. High rigidity was critical in this application, achieved by attaching the miniature profile rail to another component within the machine instead of a separate mounting surface. This required a customized counterbore of the standard mounting holes of the profile rail assembly.

Manufacturers depend on external part sources in the supply chain for sub-components, plating, materials, engineering services, or other contributors, which must be evaluated to determine if standard products are suitable for smaller-scale designs.

Smaller technology, bigger difference

Market demand for immediacy, space constraints, and pandemic-induced health concerns will continue to drive the need for smaller medical equipment. Motion control components can be a substantial portion of medical machinery footprint, and manufacturers are innovating to deliver full functionality in smaller spaces, resulting in lower healthcare costs and better outcomes for patients.

Thomson Industries Inc: https://www.thomsonlinear.com