Application of RESOLUTETM Absolute Grating on Direct Drive Rotary Table

Advances in processing technology and the market's strong demand for high-quality products have prompted machine tool builders to move toward higher technology. Modern metal mold manufacturing technology is maturing, and at the same time, raw material costs are rising. Affected by many factors, the market is gradually developing in the direction of “high-speed light cutting”. The workpieces produced by the current mold technology are very close to the target size, and only need to be lightly cut to accurately reach the final size, which is much higher than the conventional processing methods. Taiwan Suichang Electromechanical Co., Ltd. (hereinafter referred to as "Suichang") foresees the advantages and potentials of the direct-drive rotary workbench (hereinafter referred to as "turntable") on the machine tool. In recent years, it has actively developed a variety of high-performance direct drive turntables. , greatly improving the precision processing efficiency and yield of related fields. Renishaw's RESOLUTE series of absolute circular encoders provide a high-performance and stable position feedback solution for Suichang's turntables using a variety of industrial serial communication protocols.

XL-80 laser interferometer with XR20-W rotary axis calibration device

Direct Drive Turntable - Future Trends

The direct drive turntable eliminates the transmission mechanism and related components required by the traditional worm gear drive turntable, and has the advantages of high speed, fast response, no backlash, low noise and compact size. In the long run, it can effectively help customers save processing time and costs.

In the past, direct drive turrets have not been truly popular due to high manufacturing costs and insufficient torque. However, in recent years, with the improvement of processing technology in related industries, the application fields of such turntables have gradually expanded. After the 4th and 5th axis turntables are installed on the traditional 3-axis machine tool, the polyhedral machining can be completed in one time, and the productivity and efficiency are fully improved. Mr. Peng Zhaoqun, General Manager of Suichang, shared his views on the development of the direct-drive turntable market. He said: "The direct drive turntable seems to me to be a 'low-speed built-in spindle', depending on the complexity of the processing, generally The speed is below 200 RPM. Compared with the high-speed spindle, the technical threshold of the turntable is relatively low, and the control of manufacturing cost is a key factor to ensure success. Taiwan's manufacturing system is perfect and has certain advantages in processing cost. Suichang has rich experience in electromechanical integration, and the stator and rotor of the motor can be completed independently. Most of the other parts are purchased from local Taiwanese companies. Our turntable has been favored by customers in the market. Working on the machine tools of many well-known smartphone manufacturers for 24 hours."

XR20-W rotary axis calibration device for turntable accuracy detection and positioning compensation

Factors affecting the accuracy of the turntable

The error of the motion control system is affected by many factors, mainly from various mechanical components, transmission mechanisms and positioning systems (gratings). Among them, the grating itself as one of the key components of the scale error, subdivision error, installation stability (affected by eccentricity, temperature and vibration and other factors) and jitter error will directly affect the overall accuracy of the system. The smaller the grating pitch, the lower the jitter and subdivision error, and the better the positioning accuracy and velocity ripple, which means the system will have smoother speed control and higher positional stability. This is especially important for equipment such as turntables that require extreme precision and stability. With a small pitch of 30 μm, a subdivision error of only +/-40 nm and a jitter error of less than 10 nm RMS, the RESOLUTE series of gratings are among the few gratings on the market that offer such excellent performance.

The error of the grating can be divided into two types: repetitive and non-repetitive: the repetitive error refers to the error from the grating itself, or the error generated after the grating is installed. The non-repetitive error refers to the bearing backlash due to the transmission system. The resulting error, as well as errors due to insufficient torsional stiffness of the connecting shaft, etc.; repeatability errors can generally be reduced by compensation, and non-repetitive errors cannot be eliminated. Closed circular gratings with bearings can produce non-repetitive errors such as joint clearance, shaft runout, mechanical hysteresis, etc. Non-contact open gratings do not have this problem, so most direct drive turrets use open gratings.

Suichang employees and Renishaw engineers take a group photo

Customized solution

As far as the current market is concerned, although the number of machine tools using industrial computer controllers is on the rise, most mainstream machine tools still use well-known traditional controllers such as FANUC, SIEMENS, MITSUBSHI, etc., because customers generally have stability against these brand controllers. More confident. General Manager Peng said: “High-speed light cutting is the future development direction of machine tool processing. Our turntable business is to provide standard and customized turntable solutions that can be connected to its controllers according to customer needs (such as controller specifications). A key component in the turntable, the diversity and compatibility of the grating specifications is an important consideration in our selection. Renishaw RESOLUTE grating products are highly compatible and cover a range of industrial communication protocols, including BISS (applicable) For industrial computer controllers, FANUC, MITSUBSHI, PANASONIC, SIEMENS, etc., the optional circular grating diameter is also very complete, which provides great convenience for our product design."

Improve product competitiveness

Suichang fully utilizes its accumulated experience and advantages in the field of motor research and development, and actively develops direct-drive products with characteristics and potential to enhance the competitiveness of its products in the market. General Manager Peng said: "One of the characteristics of the turntable we developed is cost-effective. Compared with the same type of products on the market, the specifications provided by Suichang are quite competitive. However, this also means that we must be Renishaw is one of the suppliers that can meet our needs in all aspects of design, parts procurement and production, and the company's SDRT series turntables are compact, with high torque and high response speed. Advantages, the Renishaw RESOLUTE RESA series of absolute round gratings, providing 23-bit resolution, the positioning accuracy and repeatability of the turntable can reach +/-10 arc seconds and +/-4 arc seconds respectively after compensation, the maximum speed Up to 200 RPM, IP67 protection is sufficient to meet most of the current precision light processing requirements. General Manager Peng continued: "The internal structure of our turntable has almost no extra space, so the size of the grating readhead must be light. The round scale must be hollow, and installation convenience is another important consideration; The patented cone mounting method of Sauer grating can effectively reduce the installation error and improve our assembly efficiency, and the installation is simple. It can be mastered quickly by the Renishaw engineers."

Quality verification

The sales strategy of products is important in the market competition, but in the end, the quality of the products themselves is the key to success. General Manager Peng said: “Every turntable of Suichang must undergo strict quality verification before assembly and delivery. We currently use two sets of Renishaw XL-80 laser interferometers with XR20-W rotary axis calibration device to detect The accuracy of the turntable is compensated by positioning. The machine users who are generally engaged in such light machining have high requirements for the repeatability and stability of the turntable. Renishaw's calibration equipment has an authoritative position in the international measurement industry, which greatly enhances the Customer confidence in our turntable.” Renishaw's XL-80 series of laser calibration equipment uses systems and methods that are compliant with the ISO 9000 series of international quality standards and traceable to ensure accurate calibration and quality control.

About Suichang

Suichang Electromechanical Co., Ltd. specializes in the development of various types of mechanical special motors. The product range covers servo motors, linear motors, direct drive motors and built-in stators and rotors used in various machines. The spindle motors they produce are comparable in performance and quality to similar products in advanced industrial countries such as Europe, America and Japan. At present, Suichang products have been exported to more than 30 countries and regions around the world, and are favored by customers. In recent years, Suichang has been actively developing direct-drive turntables that can be used with various machine tool controllers to cater to the future development trend of the machine tool market. .