High-speed laser cutting and milling with a single clamping operation

Chinese machine builder develops advanced eight-axis CNC multi-function machining center

By Gerddy Fu, NUM Numerical Control Technology

CNC specialist NUM has helped the Chinese machine building company Original Point Machine Tools (OPMT) to develop an advanced eight-axis CNC machining center capable of processing many different types of materials, including metal, ceramics, glass and cemented carbide.

The project is a corporation of three parts, which are OPMT, the machine builder; Xi'an Zhongke Microcrystalline Manufacturing, the laser system provider; and Guangdong Industry University, the buyer and investor.

OPMT is a relatively small but fast-growing company that’s acquiring a reputation for complex engineering: after developing a four-axis milling center for an automotive production line, it then created a compact five-axis milling station for the dental industry.

OPMT has built some five-axis milling machines, which are targeted to the dental industry for titanium teeth, so, combined with the laser provider, they established this project.

For its latest project, OPMT was asked by Guangdong University of Technology to develop a machining center that combined high-speed laser cutting and milling capabilities. This provincial university is located in Guangzhou, Guangdong Province, China, and provides a wide range of courses, with a major emphasis on engineering. OPMT chose to partner with NUM for its CNC expertise and with the Xi'an Zhongke Microcrystalline Manufacturing and the Chinese Academy of Sciences to help with some of the complex materials processing issues (Figure 1).

Because OPMT already has the experience of creating NUM part programs by CAM software, for this machine, we just did the function commissioning part. I know they tested an impeller milling when the machine was still in OPMT's workshop; it was not yet tested for laser cutting. The laser system’s mirrors need to be calibrated after the machine is finally installed. Then they delivered the machine to the university in a hurry because the project verification deadline was coming.

The machine is still in test procedure in the university lab, explains Fu. We have not yet gotten the latest news from OPMT. For me, I do not think they have plans to commercialize it.

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Unlike normal laser-cutting machines, some key points of the laser system, such as laser power and mode, are not controlled by our system. The laser provider has the control solution, so we do not have the knowledge of the laser system.

The result is the ML125 eight-axis multi-function machining center. The machine has a dual-laser head that is capable of switching between a 20-W picosecond laser for very high-speed cutting and an ultrafast 10-W femtosecond laser for improved process quality (Figure 2). The femtosecond laser is capable of drilling and cutting almost any type of material, and its very short 1,030-nm wavelength means it’s suitable for micro/nano-processing applications.

Entirely controlled by NUM’s latest-generation Flexium+ 68 CNC platform, the ML125 machining center has eight servo axes, two independent NC channels and fast application-specific I/Os embedded in the NCK hardware (Figure 3).

The HMI of the ML125 machining center is based on NUM's Flexium touchscreen technology (Figure 4). Movement of the fully articulated laser head is controlled by five NUMDrive X servo drives, with high-speed interpolation between all five axes. And the CNC system provides a full real-time transport control protocol (RTCP) function.

By employing a special hollow-shaft torque motor and a linear motor drive, the dual laser head has an exceptionally high positional accuracy of 8 micrometers (0.008 mm), with a repeatability of just 5 micrometers. The associated A/C axis rotation platform has a precision rotary feed function with a positional accuracy of 5 arc minutes. The milling head uses a 40,000-rpm spindle motor, and laser cutting and milling can be performed with just one clamping operation, which further improves process accuracy.

“The requirements of the industrial processing market keep changing, which means that our machines need to be extremely flexible so that they always offer customers what they need,” says Bruce Zheng, CEO of OPMT. “Partnering with NUM helps us to achieve this; its open-architecture CNC systems are easy to integrate with third-party products such as motors, and the company is prepared to offer the long-term commitment and technical support that is necessary for successful completion of complex machine projects.”

The ML125 machining center is now installed in a research laboratory at Guangdong University of Technology.