As Easy as CNC

By John Mitchell, Global Sales & Marketing Director, CP Automation

Modern computer numerical control (CNC) machines are often marketed as requiring much less maintenance than their predecessors. While there’s less need to replace cutting tools in these machines, there’s more complexity to their upkeep. This article explains how poor power quality can cause recurrent issues for CNC machines.

CNC machines have brought many advantages since their inception in 1989. Improved accuracy, productivity, efficiency and safety in newer models replaced the older, manual machines, changing the way metalworking and fabrication was performed forever. With further development from three axis to five axis models, the increased complexity of processes has not been without its pains.

To operate effectively, it is imperative that CNC machines are equipped with the right tools, settings and programming. The wrong choices can spell disaster for both the product and the CNC machine. One of the most important considerations relate to ensuring good power quality.

Poor power signal can cause issues with random lockups, loss of synchronization and other ‘no trouble found’ service calls. Partially, this is due to the computer processors of CNC machining centres becoming more complex.  But, what can be done to resolve this issue?

A Sine of the Times

The sine wave, the ideal waveform for the transfer of AC power, has remained the same since the late 1800s. However, the sensitivity of the equipment that is connected to the grid is now much more sensitive, including CNC processors. This computer is very sensitive to power quality, explaining why inexplicable issues can plague these machines if power quality isn’t adequate.

Some of these power quality issues are caused by transient surges in power. Transient surges are a change in fundamental frequency that occur thousands of times a day. Built in CNC surge protection is voltage triggered, and therefore does not account for these transient surges.

Transient surges can lead to false zero crossings of the sine wave — the instantaneous point at which there is no voltage present. In a sine wave, this normally occurs twice during each cycle. Devices can be falsely triggered because of fast changing signals caused by transients, as they believe the zero point has been crossed, even when it hasn’t. Typical surge protection devices are unable to prevent this confusion.

These events can lead to loss of synchronisation and unexplained reboots or resets in CNC machines — a huge headache for factory managers.

Bringing Surge Protection Up to Speed

Built in surge protection devices are not doing enough to protect valuable CNC systems and prevent false zero crossings caused by transients. One alternative that has been created for this purpose is atheSineTamer cascade system.

This is not a common surge protection device. Instead, it is an engineered transient disturbance filter that is designed to monitor all 360 degrees of the sine wave. Using 360 degree monitoring, the SineTamer is capable of preventing issues caused by false zero crossings of the sine wave.

Results From the Field

SineTamer is currently being used globally by end users of Mazak, HAAS and ROMI machines.

One CNC dealer in Africa experimented by installing SineTamer® on 70 machines. Following the installation, the company reported that over half its usual maintenance related phone calls and call outs had been eliminated.

In Brazil, a ROMI machine operator experience a 95 per cent reduction in downtime due to limitation of drive failures and various resets. Similarly, a Mazak operator in Ecuador reported losing $25,000 a month due to programming loss and confusion related events. Following implementation of the SineTamer cascade system, and the engineering team reported a successful return on investment, in one day.

While CNC machines are marketed as low maintenance, it would be unfair to provide such machines with poor power quality and expect the same output. Ultimately, you get out what you put in.

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