Positioning & control for process technology research

The aim of the project is to demonstrate the potential benefits of this approach over existing manufacturing routes. For the application LG Motion was asked to provide a cost-competitive mechanical positioning and motion control system that would enable a scanned area of 300 x 300mm in the horizontal plane with a  vertical axis to position the spray head over 200mm.

The gantry system specification called for relatively low speeds, low duty cycle and medium precision to perform the required scanning with a load of up to 3 kg. To keep costs to a reasonable level an open loop stepper motor based positioning system, centred on LG Motion’s XSlide range of leadscrew driven linear positioning stages with NEMA size 17 high torque motors was used. This compact and low-cost positioning system is well proven in medium precision applications across manufacturing production, test and research, and is easily adapted for travel length and configuration in custom engineered multi-axis set-ups.

The gantry, mounted on a machine frame fashioned from MiniTec’s Profile System, consists of a single XSlide stage to one side with its moving carriage coupled to linear bearing guide and carriage on the other side of the gantry. These carriages together support the Y-axis XSlide with the Z-axis vertical stage simply mounted via an angle bracket. Throughout the mechanical set-up, standard bracketry and modular mounting make assembly easy and adaptable.  The stepper motors are fitted with hand wheels to aid manual positioning and over-travel limit and datum switches ensure safe operation under full control. The mechanical system also includes a cable management system which is easily supported within the design using the MiniTec machine frame.

Adaptability was also a key factor for the motion control system and LG Motion specified its Arcus Technology range of cost competitive stepper motor controls for the job. The PMX-4ET-SA is an advanced 4-axis motion controller and stepper drive with 10Mbps Ethernet communication that provides advanced features only found on more expensive motion controls. With linear and circular axis interpolation and with fast synchronising inputs and outputs, the controller provides up to a 6 MHz step and direction pulse rate which suits smooth and fine resolution microstepping combined with the coordination of motion and external events required for the application.

The Arcus PMX series allows the easy and straightforward programming of a scan area with predetermined firing of outputs to synchronise the spray deposition process. This can be achieved via Ethernet using simple BASIC like programming commands and a terminal facility supplied with the controller. LG Motion also provided a simple GUI front-end program to handle this requirement and alternatively the controller is able to process motion and I/O commands from a PC using free of charge source code for Windows programming languages such as Visual C++ and Visual Basic, .NET as well as LabVIEW. This programming flexibility will allow Oxford Materials to adapt the system as the research project progresses. The PMX also has the ability to include encoder feedback with a novel closed loop algorithm that allows position verification should they wish to increase the system repeatability in the future.