October 2020

38 n PRECISION ENGINEERING AND MOTION CONTROL October 2020 www.drivesncontrols.com Three-axis micropositioner helps to test sensors E xpoPharma, based near Heathrow Airport, is the pharmaceutical manufacturing division of Expo Technologies, which specialises in engineered systems for electrical protection by purge and pressurisation. One of its recent developments is a PAT (process analytical technology) powder-stream conditioning chute used to characterise analytical sensors for use in continuous pharmaceutical and similar manufacturing processes. The Spectrummulti-probe chute allows multiple PAT technologies to be evaluated simultaneously, thus reducing API software- related use and accelerating production development by providing optimised interfaces for several types of sensor that gather data in sequence during the same process stream. The various sensors gather precise data from the powder stream, including information on chemical structure, identity, particle size and contamination. The machine incorporates an Ethernet- based three-axis micropositioning sub- system. The three positioning axes are based on all-in-one motion control devices that combine a motor, drive, controller and comms in one package. These are fitted with 10:1 ratio planetary gearboxes to provide high-resolution angular positioning. Each drive micropositions special flipper-shaped end-effectors that are designed to collect sample material from the powder stream and present it through a probe window to the sensor being assessed. The sensors are typically particle image analysers, Raman spectroscopy probes and a near-infrared spectrometers. The characterisation process requires a different- shaped end-effector to manage the sample collection for each sensor (as well as a PAT probe cleaning regime for some). Different positioning sequences are needed for each sensor in terms of angular travel, speed, acceleration and deceleration. At the early stages of developing the new product, ExpoPharma turned to the motion control specialist Mclennan for assistance. It recommended using“distributed”integrated stepper motors that would provide cost and functional advantages, and help achieve the portability required for the multi-probe chute. The compact, all-in-one drives simplified the product development process and, because of their reduced need for cabling, required much less installation and commissioning effort. The integrated motor technology is also well protected against electrical noise, which can be a significant problem for traditional panel-mounted motion control systems, where power, signal and communications cabling is typically longer and can suffer from interference. This was a particularly important requirement for the sensitive sensor equipment being evaluated on the platform. Absolute encoders Electrical installation of the JVL MIS232 microstepping motors was achieved using on-board M12 connectors for power, as well as daisy-chained Ethernet connections to a Kinco MT400 HMI. To improve the positional accuracy and to ensure that the axis positions are always known on power-up (thus avoiding the need for a homing procedure), optional absolute encoders were wired to the HMI from another M12 connector on the integrated motor. Each end-effector includes a heater and temperature sensor to reduce the possibility of powder material sticking, and to help clean the PAT probe windows. An Emko PIDQuadro temperature controller was used for this purpose. Mclennan programmed and commissioned the motion sub- system for the chute, with the three motor axes forming part of a Modbus TCP network segment, which also included the HMI and temperature controller. The three axes, pre- programmed for comms interfacing and configuration, are slaved to the HMI which is assigned as the sub- network master. A series of graphical screens were configured using Kinco’s HMIware software to display or assign values for the positioning axes. Each axis can also be positioned manually using jogging and other functions to develop specific motion sequences used for evaluating the sensors. Also slaved to the HMI via the Modbus TCP network are the temperature controller’s display, level setting and alarm functions for each of the three end-effector mechanisms. Thus, each axis with its individual position and dynamic motion requirements, and corresponding end-effector temperature settings, can be selected, interrogated or diagnosed via the HMI. The evaluation of the various analytical sensor probes is managed using another Ethernet segment. n A UK company that specialises in analytical equipment for the pharmaceutical industry has developed a machine that characterises the performance of several different sensors simultaneously. A key element of the machine is an Ethernet-based three-axis micropositioning system that uses integrated stepper motors and includes planetary gears, an HMI and a temperature controller. ExpoPharma’s Spectrum Multi- Probe Chute (shown with its covers removed) is used to characterise several analytical sensors simultaneously