NUM is helping the Taiwanese machine tool company Chien Wei Precise Technology to develop innovative CNC grinding machines for manufacturing specialist gears used in robotics applications.
Based entirely on NUM’s latest-generation Flexium+ 68 CNC platform, Chien Wei’s new machines are designed to speed the production of both involute and cycloidal profile precision gears. They are believed to be the first gear grinding machines on the market that are capable of handling both types of gear profile. There are two versions of the grinding machine, one for internal gears, the other for external gears.
Founded in 1981, Chien Wei Precise Technology Co., Ltd is based in Fengshan District in southern Kaohsiung, Taiwan. The company initially specialised in precision machine tools such as vertical grinders, jig grinders and machining centres, together with co-ordinate measuring machines (CMMs). Over time, it also diversified into robotic automation systems.
Robotic systems typically use either planetary gearboxes equipped with involute gears, or cycloid drives based on a combination of a reduced epitrochoid rotor and a cycloid stator. While planetary gearboxes have been around for a long time and enjoy extensive use, cycloid drives have far fewer moving parts and offer a more efficient means of achieving extremely high reduction rates. A speed reducer with a ratio of 200:1 would typically need a chain of three planetary gear boxes with twelve moving involute gears. The same reduction ratio could be achieved with a cycloid drive using one stator and one rotor. However, cycloid gears are notoriously difficult and expensive to manufacture.
In 2015, Chien Wei decided to bring gear manufacturing in-house, by developing its own gear grinding machine. By producing its own gearboxes the company could control quality, shorten lead times and reduce costs. It would also enable it to sell gearboxes to machine builders – and possibly the machines themselves to gear manufacturers.
Chien Wei initially based its gear grinding machine on a Fanuc series 0i-MF CNC system, which it uses for other machine tools, together with Mastercam CAD/CAM software and its own CMM. But it soon became apparent that the profile complexity of cycloidal gears meant that CMM data was inadequate for controlling the manufacturing process. Another major disadvantage was that customers wishing to purchase the machines would also need to invest in an expensive CAD/CAM system and extra personnel.
According to Chien Wei’s President, Mr Lee, “We quickly decided that what we needed was a CNC system that fully supported gear grinding from the outset, so that our customers could simply input the parameters of the gear they wanted, with the CNC then controlling all aspects of the machine’s dressing and grinding processes in real-time. NUM was an obvious choice, because of its proven expertise in CNC gear grinding applications. The company was also willing to collaborate in the joint development of the CNC system, which includes an application-specific HMI (human-machine interface) and various dedicated control functions.”
The new generation of Chien Wei’s gear grinders together with NUM’s new profile grinding technology now provides the ability and flexibility to manufacture both cycloid and involute gears on the same machine.
Adrian Kiener, CSO Asia and Managing Director of NUM Taiwan, points out that this application highlights the importance of NUM’s decentralised support strategy. “By providing direct access to the CNC experts and extensive development facilities we have here in Taiwan, as well as those in many other countries around the world, we are able to provide our customers with a very fast response service that helps them shorten their time-to-market significantly. In combination with the knowledge and experience of our gear product group in Switzerland, this led to the complete package that NUM is providing. It includes the user interface, technology and calculations, as well as all the NC cycles.”
Chien Wei’s internal gear grinder is a 9-axis machine. The work piece table is mounted on a linear axis that moves axially towards the grinding wheel, which is belt-driven (due to space constraints inside the gear) and mounted on a vertical axis driven by a linear motor. As the grinding wheel spins, it is driven up and down by the linear axis, while the work piece table moves in continuously. Both flanks of the gear are ground simultaneously. The machine also handles gear dressing. During the dressing cycle, the entire tool head is moved horizontally to the right, and a symmetrical dressing disk moves along the outer shape of the grinding wheel in three sections, right/left flank and tip. Cycloids as well as involute shapes can be dressed.
The external gear grinder is an 8-axis machine. Broadly similar to the internal gear grinder in operational terms, it features a direct drive grinding wheel. Again, like the internal gear grinder, it also handles dressing. However, in this case the shape of the tooth gap can be reduced epitrochoids or involutes.
Manual correction of the gear tooth shapes is possible on either machine.
Both machines are controlled by NUM Flexium+ 68 CNC systems, equipped with NUM FS153i touch-sensitive operating panels. The application-specific HMI that has been jointly developed by NUM Taiwan and Chien Wei controls both the grinding and dressing cycles, and allows users to fully specify the required gear profile simply by entering the appropriate parameters. Graphical DXF (Drawing Interchange Format) files can be imported from – and exported to – CAD systems, and the system features a comprehensive database for grinding wheels and work pieces. The NC programs are generated entirely automatically, without any need for operator involvement.
As Johnny Wu, Sales Manager for NUM Taiwan, points out, “NUM’s open architecture CNC platforms, combined with the company’s willingness to partner with machine builders in developing application-specific solutions, is a key differentiator when it comes to choosing a CNC supplier.”
CNC specialist NUM has helped the Chinese machine building company Original Point Machine Tools (OPMT) to develop an advanced 8-axis CNC machining centre capable of processing many different types of materials, including metal, ceramics, glass and cemented carbide.
OPMT is a relatively small but fast-growing company based in Fo’shan – of Guangdong Province – in south China. It is rapidly acquiring a reputation for innovative complex engineering: after developing a highly successful 4-axis milling centre for an automotive production line, it then created a compact 5-axis milling station for the dental industry.
For its latest project, OPMT was asked by Guangdong University of Technology to develop a machining centre that combined high speed laser cutting and milling capabilities. This key 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 Company and the Chinese Academy of Sciences to help with some of the complex materials processing issues.
The result is the ML125 8-axis multi-function machining centre. The machine has a dual laser head that is capable of switching between a 20 watt picosecond laser for very high speed cutting and an ultrafast 10 watt femtosecond laser for improved process quality. The femtosecond laser is capable of drilling and cutting almost any type of material, and its very short 1030 nm wavelength means that it is suitable for micro/nano processing applications.
Entirely controlled by NUM’s latest-generation Flexium+ 68 CNC platform, the ML125 machining centre has eight servo axes, two independent NC channels and fast application-specific I/Os embedded in the NCK hardware. 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 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 micrometres (0.008 mm), with a repeatability of just 5 micrometres. 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.
According to Bruce Zheng, CEO of OPMT, “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. 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 centre is now installed in a research laboratory at Guangdong University of Technology.
Innovative new software from NUM enables CNC machine tool builders and retrofitters to provide their customers with exceptionally easy-to-use machine setup and real-time control facilities for precision grinding applications.
Forming the latest application-specific addition to NUM’s FXCAM suite of CNC software, the new NUMgrind package simplifies machine tool programming for an extensive range of tasks, including external and internal cylindrical grinding, surface grinding, wheel shaping and dressing.
NUMgrind is specifically designed to simplify the creation of G code programs for CNC machine tools through the use of a highly intuitive graphical human machine interface (HMI), conversational-style ‘fill in the blanks’ type dialogues or a combination of the two. Unlike conventional CAD/CAM workstation tools for generating CNC machine tool control programs, NUMgrind is intended for use in the production environment. It enables shop floor personnel to handle everyday machining tasks such as grinding very quickly and efficiently – and the work can be easily shared amongst several people and several machines.
NUMgrind works in conjunction with embedded CNC grinding and dressing cycles and direct hyperlinks to several production files such as wheel/part data sheets, CAD files and/or other pertinent grinding production data to facilitate efficient manufacturing of a diverse range of workpieces, covering various different wheel forms and part types. It can be configured for a wide variety of machine configurations such as OD/ID Grinders, Surface Grinders, Centreless Grinders, etc.
The cylindrical grinding package includes OD/ID grind cycles for 2-Axis (X/Z) horizontal or vertical grinding machines and also offers an inclined axis capability. The dressing station can be table-mounted or rear-positioned to accommodate a wide range of machines. Standard forms or profiled wheels can be dressed with single point, double point or roller dresser. For surface grinding, NUM offers full grinding cycles for 3-Axis (X/Y/Z) machine configurations with built-in wheel dressing capabilities similar to that of the OD/ID cylindrical grinding package.
Machine production time is very efficient due to HMI pages that guide the machine operator through a step-by-step process in setting up the machine for each part. Standard dresser setup and part setup cycles prompt the user to jog the axes to specific locations on the machine in order to teach the dresser and part zero program positions. These cycles enable the user to quickly and easily calibrate their machine for a wide variety of parts and wheels.
As soon as the data entry session is complete, the program is generated automatically, stored, and made ready for execution. The result is a modular, easily modifiable program that will produce the desired grind process.
In conjunction with NUMgrind, Flexium 3D (NUM’s graphical simulation software) provides the operator with another very useful tool to further enhance productivity. Once a part program is generated through FXCAM NUMgrind, the operator can simulate the grinding cycle through Flexium 3D. The software can be configured in a variety of different ways to match many standard cylindrical and surface grinding machines. It can be used directly at the machine or as a standalone program for grinding process verification. This software gives the operator more power to ensure that the generated programs match their desired outcome before grinding occurs on the machine.
NUM’s entire FXCAM suite of CNC software, including the new NUMgrind package, is designed for use with the company’s latest-generation Flexium+ CNC platform. This platform comprises a fully modular and scalable CNC solution for a wide variety of precision machine tool control applications, and includes a Safe PLC option and comprehensive safe motion control facilities.
According to Steven Schilling, General Manager of NUM Corporation in Naperville, Illinois, “The concept behind FXCAM software is to provide a straightforward, easy-to-learn programming method. Our new NUMgrind package includes cycles for a wide variety of cylindrical and surface grinding operations. The OEM or retrofitter receives a control system with a complete, world-class grinding solution built-in, which eliminates the need for any additional software that can take years to develop”.
NUM will be presenting new developments in CNC hardware and software technology at the FMB. NUM is a globally active company that covers the complete spectrum of mechanical engineering in the field of CNC, from automation to programming and electronics.
NUM will be presenting a host of latest generation CNC products at the FMB. This includes new models within the well-known NUMgear portfolio of CNC gearwheel production solutions, like a highly flexible electronic gear function which provides exceptional accuracy even at high cutting speeds, a new conversational user interface for circular and surface grinding – with 3D simulation – and the most recent version of the MTConnect corporate interface which simplifies the integration of CNC machine tools and production software from third-party providers.
Here the new NUMmill control solution will be exhibited for the first time, which should be particularly interesting to manufacturers of CNC milling machines and retrofitters of control units. It is available as a completely scalable control system and is suitable for a wide range of precision milling applications in markets that are as diverse as machining, wood processing, plastics and high-precision processing.
NUMmill represents a comprehensive, ready-to-use solution and offers an extensive package of preset cycles ranging from simple concentric drilling operations to drilling and thread-cutting, pocket cycles and complex copy milling cycles. And all that comes with 3D simulation for pre-process verification.
NUM has launched an advanced control solution for CNC milling machines that features a highly intuitive conversational style user interface. Known as NUMmill, the CNC hardware and software provides a fully scalable control system and is supplied as a complete ‘off-the-shelf’ package.
- provides simple conversational style user interface for CNC milling machines
- fully scalable control system suits wide range of precision milling applications
NUMmill is designed specifically for CNC milling machine manufacturers and control retrofitters. It offers an extensive suite of canned cycles, ranging from simple centre drilling, boring and threading to pocket cycles and complex profile milling cycles. All with 3D simulation for pre-process verification. The package is suitable for a wide range of precision milling applications in markets as diverse as metal cutting, woodworking, plastic, and high precision machining.
Based on NUM’s market-leading Flexium+ modular CNC platform, NUMmill is typically configured with 3 or 4 linear axes and a single rotary axis, though it easily scales to suit any size and type of milling machine application. All motorised axes are equipped with high performance brushless servo motors, controlled by NUM’s latest-generation NUMDrive X digital servo drives. The NUMmill software features an exceptionally easy to understand graphical user interface which employs an interactive, conversational style dialogue to radically simplify machine operation. In fact, it is so simple to use that end-users can operate machines without any prior knowledge of ISO code programming techniques.
NUMmill Windows-based software provides graphical shop floor programming screens that depict the tool, the workpiece and all associated setup data in a concise and unambiguous manner. The operator is prompted to fill in the appropriate data fields presented by the human-machine interface (HMI), after which the machine control program is generated entirely automatically and then stored, ready for execution. On-line help files and step-by-step video tutorials are included for ease of operation. This conversational style programming helps to save considerable development time, as well as significantly reducing the learning curve for new operators.
NUMmill is supplied as a complete, ready-to-run package that includes the Flexium+ CNC system, software, and a 19-inch touch-sensitive machine control panel, together with all necessary drives and motors. The system is also equipped with NUM’s MTConnect interface, which simplifies the integration of CNC machine tools with third party manufacturing software.
In addition to a large number of canned cycles, the NUMmill software provides functions for material removal of basic pockets; these can be defined as circular, oblong, reticular and square. The hole pattern definitions can use a wide variety of geometries, including Arc, Cover Patter, Drilling with Rotary Axis, Grid, Pitch Circle, Row, and Single Points. Milling operations can be performed on circular, oblong, rectangular and square pockets. The drilling cycles that can be performed on hole patterns include Centre Drill or Chamfer, Peck, Chip, Counter Bore, Tap, Ream-Feed Out, Bore-Dwell/Feed Out, Bore-Stop/Rapid Out, Thread Chase, and Taper Threading.
The NUMmill system also provides measurement and probing cycles, to help users meet precision and quality targets, as well as full 3D simulation with collision monitoring for pre-process verification.
The Flexium+ architecture also offers machine designers, builders and retrofitters an easy means of implementing functional safety. Available as a build-to-order option for all Flexium+ CNC systems, NUMSafe includes a safety PLC, safety input and output (I/O) modules, digital servo drives with built-in safe motion monitoring facilities, and compatible brushless servo motors. NUMSafe is a system-wide architecture that puts functional safety features precisely where they are needed, thereby reducing the number of components and wiring, which simplifies design and most importantly saves time in implementing ‘safe motion’ functions.