CNC Motion Control

CNC technology developments help engineers cut corners in all the right ways

Cover Story: Automation technologies continue convergence across platforms and computer numerical control (CNC) technology advances, along with faster control hardware and software, allow engineers to complete more accurate cuts in less time.
By Matt Prellwitz June 11, 2019
System-integrated motion design software promotes proactive machine design by making it easier to match motor and drive equipment to all mechanical machine components. Courtesy: Beckhoff Automation

The roots of computer numerical control (CNC) technology stretch back to the 1950s, but the technology remains relevant for machinery to this day. The options for modern CNCs continue to increase, providing a wider toolset for all industries that need this level of control. Advances in different cutting head types, along with faster control hardware and software, allow engineers to complete more accurate cuts in less time. CNC benefits include greater throughput and precision, fewer rejects and less finishing.

As higher performance options for cutting heads and multi-axis servo systems emerged, CNC applications forced software platforms to improve. More complex application demands placed on plasma, waterjet and laser cutters, plus routers and blades, pushed conventional CNC software to its limits, leaving controls engineers seeking more flexible options. PC-based control platforms integrated CNCs, motion control and programmable logic controllers (PLCs) on the same platform. This was due, in large part, to the higher processing capabilities of multipurpose industrial PCs (IPCs), which helped increase CNC performance and precision by eliminating previously separate hardware devices. Removing multiple devices that used to communicate with each other improved cycle times.

Cloud communication for computer numerical control (CNC) is implemented directly on IPCs via accepted standards such as message queuing telemetry transport (MQTT), advanced messaging queuing protocol (AMQP) and open platform communication unified architecture (OPC UA). Courtesy: Beckhoff Automation

Cloud communication for computer numerical control (CNC) is implemented directly on IPCs via accepted standards such as message queuing telemetry transport (MQTT), advanced messaging queuing protocol (AMQP) and open platform communication unified architecture (OPC UA). Courtesy: Beckhoff Automation

Today’s PC-based control platforms also offer easy integration of simulation and computer-aided design (CAD) software in the same engineering environment. For example, simulation software programs can link directly with PC control software to incorporate existing CAD and CNC models for faster machine design. It also can help speed the development of prototype parts in cost-effective ways. The overall machine design also can be adapted to suit changes in part prototyping, which was not possible before.

System-integrated motion design software can push this proactive machine design even further by expanding the range of tools for easier specification of required motor and drive equipment, precisely matching them to all mechanical components in the machine.

Cheat the axis, eliminate deflection

Even the best-designed machine must be refined and optimized based on real-world conditions observed after commissioning. These conditions, especially for CNC applications, can vary depending on the industry, application and material type. In cutting applications, users can see blade deflections that may require system adjustments for different speeds and different materials. This requires real-time software that can read data from advanced sensors.

This process is described as “cheating” an axis by looking ahead and monitoring real-time sensors. It allows engineers to work around or work with blade deflection to increase cut performance. Creating an effective algorithm to cheat the axis in CNC applications can eliminate the deflection, which can increase throughput without sacrificing accuracy. This improves overall efficiency by minimizing raw material waste and scrap.

PC-based control platforms can integrate CNC, motion control and programmable logic controller (PLC) on the same platform. Courtesy: Beckhoff Automation

PC-based control platforms can integrate CNC, motion control and programmable logic controller (PLC) on the same platform. Courtesy: Beckhoff Automation

Regardless of the application type, advanced CNCs can leverage 3-D CAD models and visualize cutting imperfections so engineers can correct them in software. PC-based control software with a CNC library can run an interpolation to compare axes and calculate the best vectors based on spline control and the exact dimensions of a finished part. With this information, simulation software can determine the optimal part cutting paths using data insights from the observed trajectory of the axis and its defined velocities. Using simulation for CNC design can enhance existing operations with familiar workpiece materials. It also can provide invaluable benefits when working with new and prototype materials. This ensures greater success when deploying and commissioning machines.

CNC meets IoT

This level of CNC refinement, however, generates significant amounts of data that must be managed. Fortunately, PC-based control architectures offer advantages here too through hardware, software and networking standards ready for implementing higher-level databases, structured query language (SQL) servers, Internet of Things (IoT) concepts and cloud services. Whether managing data onsite or off, this does not require the addition of another layer of controls technology as the new functionality is added in the standard software. One IPC can multitask CNC and IoT duties on one CPU without adding a special gateway or managed switch.

Cloud communication is implemented directly on IPCs via standards such as message queuing telemetry transport (MQTT), advanced messaging queuing protocol (AMQP) and open platform communication unified architecture (OPC UA). In the context of PC-based control, the IoT programming is handled in the same engineering environment used to program the CNC, PLC, robotics, machine safety and more. Multipurpose PC control ecosystems also help engineers develop their skills and blur the line between who’s a CNC programmer, versus a PLC programmer or an IoT programmer.

The good news is users don’t need to crunch code to push data to the cloud. Simple IoT bus couplers establish cloud communication via a configuration page instead of programming. This approach to IoT and cloud is good for retrofit applications because it is possible to harness machine data from older CNC machines that may have a legacy fieldbus such as DeviceNet (ODVA) or Profibus (PI North America). This provides analytics and dashboards with actionable information that can be viewed on premises or globally by manufacturers or the CNC machine builders.

CNCs learn new tricks

Although CNCs were introduced over a half-century ago, many modern systems have kept pace with major automation technology developments. The advent of PC-based control technology for CNC applications has accelerated these developments. The convergence of previously separate hardware and software platforms multiplies efficiencies that can be measured from design and programming to commissioning and runtime.

System-integrated motion design software promotes proactive machine design by making it easier to match motor and drive equipment to all mechanical machine components. Courtesy: Beckhoff Automation

System-integrated motion design software promotes proactive machine design by making it easier to match motor and drive equipment to all mechanical machine components. Courtesy: Beckhoff Automation

In the beginning stages of CNC machine design, simulation in a PC-based engineering environment provided the fastest possible development times with the fewest possible errors and redesigns. Simulation also sped up time to market and installation by weeding out the most time-consuming surprises previously discovered during the commissioning stage.

PC-based control platforms that consolidate machine control functions boost performance and accuracy while adding the latest features such as cloud connectivity throughout the entire lifecycle of a CNC. Enabled by IPC hardware and software, CNCs will remain open for future automation and motion control advancements.

Matt Prellwitz, drive technology application specialist, Beckhoff Automation. Edited by Chris Vavra, production editor, Control Engineering, CFE Media, cvavra@cfemedia.com.

MORE ANSWERS

Keywords: CNC, computer numerical control, industrial PCs

The options for modern computer numerical controls (CNCs) continue to increase, providing a wider toolset for industries desiring a greater level of control.

CNC advances produce a lot of data, which can be controlled and harnessed and focused with the cloud and the Internet of Things (IoT).

The advent of PC-based technology has accelerated CNC automation technology developments.

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What CNC advances would you like to see next and why?

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Matt Prellwitz
Author Bio: Drive technology application specialist, Beckhoff Automation.