Challenge

To develop a demonstrator for real-time control and optimisation of CNC operations using 5G technology within the 5G testbed at AMRC North West as part of the Factory of the Future open RAN (FoFoRAN) research programme.

Background

The project, funded by the Department of Science, Innovation and Technology (DSIT) focused on testing the Real-Time Machining (RTM) application software to control the Pocket NC machine.

It forms part of the FoFoRAN research programme, a £4.7 million project developing ways to make 5G Open RAN more accessible and fit-for-purpose for the manufacturing sector.

A demonstration and trials were conducted to validate the system demonstrating the RTM application's ability to control the Pocket NC machine in real time. Machining processes generate chatter, leading to defects in the machined pieces, which directly correlates to potential defects in production scenarios.

Innovation

The AMRC North West team, in collaboration with Productive Machines, devised machine integration and capability to use closed-loop algorithms to control and optimise the machining process in real time.

The team developed the architecture for the demonstrator. The CNC machine (Pocket NC) ran on a custom Linux Image called LinuxCNC, an open-source software that controls and drives the Pocket NC.

A Python script interfaced with a high performance real-time C++ programme controlled the spindle speed and feed rate overrides and read all the necessary machine parameters for optimisations.

These parameters were then sent to the RTM application - an AMRC in-house application suite that visualises, loads software libraries, monitors data pipe flows, etc - over the 5G network at regular intervals.

The RTM application integrates with Productive Machines’ digital twin system by loading its Dynamic-link library file. The digital twin system calculates the optimisations and produces machining parameter overrides which control the forces, chip thickness, torque, power and vibrations in real-time. 

The optimised parameters from the digital twin are synchronised with the Pocket NC machine execution and implemented as overrides. 

The real-time communication was achieved through AMRC North West’s 5G core with Ubiquitous Integration and Time Synchronisation (UbiITS), which is a low-level library that provides low-latency, fast communication.

Data from the auxiliary sensors, such as accelerometers and microphones retrofitted to Pocket NC to monitor vibration data and frequencies, was captured and transferred over the 5G network.

The team used its 5G customer premise equipment boards (called Ventus) with a robust 5G module, and routed the network from the Pocket NC and the sensor to the RTM application. The application was hosted on a Linux-based computer.

The beaglebone board (a controller PCB board) inside the Pocket NC acted as the controller and the AMRC North West application interfaced directly with this control system (for real-time, closed-loop communication) via ethernet and was then routed through the 5G CPE.

A total of three trials were completed:

• Independent testing of the RTM application software
• Air cuts on the Pocket NC machine
• Machine cuts with the Pocket NC machine

The results showed that the RTM application can control the Pocket NC machine in real-time and the machining generated chatter causing defects in the piece after the cut. In real production scenarios this can be correlated to the defects in the products due to chatter.

The RTM application has since been integrated with the Productive Machines digital twin, showcasing optimisations eliminating defects in the parts.

Result

Multiple trials were completed. The RTM application standalone trial to test real-time control over the machine showed the RTM application was able to successfully override the feed rates and the spindle speed of the machine in real time.

Air cuts on the Pocket NC machine to test the G-codes (geometric code) and ensure safe execution of the machine showed that the algorithm is changing the feed rate constantly, and it can be observed through hearing and the web interface. Despite modifying the feed rates along the path, no sudden movements were observed and no crashes occurred on the first air cut trial.

Machining trials with the G-code and the sensor integration showed that although chatter was observed during multiple instances, when later compared with the trial of the integrated system showed the difference in execution with the optimisations. Without further analysis of the source and frequency of these vibrations, it can’t be concluded that the marks were caused by chatter vibration.

A tap test would be required to understand the natural frequencies of the system. The natural frequencies need to be then compared with the frequencies from the process identified via a spectrogram/Fast Fourier Transform to reach a conclusion, although in this instance, it was not possible due to the small scale Pocket NC used.

Impact

The work underlines the potential for 5G technology to transform manufacturing by enabling precision control and real-time optimisation of machining processes, paving the way for improved productivity and quality in advanced manufacturing systems.

The project showed real-time (within milliseconds) closed-loop control of the manufacturing process of a component is possible.

This is beneficial to the industry as it reduces the likelihood of waste components, as the component is manufactured with ’right first time, every time’ accuracy in the manufacturing process

It also contributes to improved sustainability of resources such as the raw materials used to manufacture products as it lessens waste through monitoring the milling process because the intervention is digitally-controlled, avoiding manual intervention, and thus reducing the number of waste components

There is potential to progress this research further with detect defect integration, which would create the ability to avoid defects and/or visualisation to minimise the likelihood of defects.