Looking at the development trend of CNC composite internal and external cylindrical grinding machine from CIMT2015

Abstract On April 20-25, 2015, the 14th China International Machine Tool Show (CIMT2015) was held in Beijing China International Exhibition Center (New Hall). The theme of CIMT2015 is "New Normal•New...
On April 20-25, 2015, the 14th China International Machine Tool Show (CIMT 2015) was held in Beijing China International Exhibition Center (New Hall). The theme of CIMT 2015 is “New Normal•New Development”. This theme accurately and vividly reflects the characteristics of China's machine tool industry development and industrial market, reflecting the background of CIMT 2015. The major grinding machine manufacturers all over the world participated in this exhibition. Now, a brief review of the CNC precision universal cylindrical grinding machine, ie the composite cylindrical grinding machine, which is representative of this exhibition.

1 Introduction of main exhibits (1) S41 CNC precision universal cylindrical grinding machine of UNITE GRINDING Group STUDER
The S41 is the latest generation of CNC universal cylindrical grinding machines launched by the company in 2011. In May 2014, the UNITE GRINDING annual grinding seminar introduced a new shape. The machine is equipped with many advanced technologies. The bed material is Granitan® artificial granite. The guide system StuderGuide® for longitudinal and lateral slides is directly die-cast on the bed and covered with a patented wear-resistant Granitan® S200. The guide rails ensure the highest possible accuracy over the full operating speed range, ensuring excellent linear accuracy of 0.003 mm over a measuring length of over 950 mm, and high load carrying capacity and excellent shock absorption. High-precision CNC axis drive with linear motor, ultra-high-speed B-axis direct drive, repeat positioning accuracy less than 1 arc second, with a wider choice of wheel frame configuration.

The machine is equipped with a universal workpiece head frame for both live spindle grinding and two tip grinding. It can be equipped with a specially designed chuck type workpiece head frame for grinding applications for chuck clamping. It can also be configured. Direct drive workpiece headstock, mainly used for live spindle grinding of heavy workpieces and high precision C-axis grinding applications. Among them, the direct drive workpiece head frame design structure can also directly install a high-precision measurement system on the spindle.

The machine comes standard with a spring tailstock that is clamped by a spring tailstock sleeve and can be tapered for loading workpieces up to 150 kg. It can also be equipped with a hydraulically operated tailstock to increase the pressure of the top, so that the weight of the two tip-bearing workpieces reaches 250kg. It can also be equipped with a synchronous tailstock. When grinding a series of workpieces, when grinding the full length of the workpiece, it is particularly cost-effective to use the synchronous tailstock when the conventional tailstock driving method cannot be used.

The machine uses the FANUC 31i CNC system, and the user interface software Studer WIN creates a stable programming environment and ensures the machine's efficiency. The functions of grinding online measurement, machining process control, sound control monitoring and automatic wheel balance can be integrated into the operation interface, thus ensuring standardized programming under different systems.

(2) Harding Grinding Group KELLENBERGERKEL-VERA CNC Precision Universal Cylindrical Grinder
The machine has a center height of 300 mm and a tip distance of 750 mm. The maximum workpiece weight of the two tips is 250 kg. The CNC system is HEIDENHAIN GRINDplus 640. At the exhibition, the coordinate grinding function of the B-axis of the direct-drive grinding wheel frame and the C-axis of the direct-drive live spindle head frame was demonstrated.



Interpolation grinding waist hole
The machine tool is a cast iron bed, the wheel frame feed X axis and the table moving Z axis and the wheel frame rotating B axis are closed hydrostatic guides. The grinding wheel frame can be equipped with various specifications of grinding heads: universal type, diagonal type, front and rear arrangement type and mass production type. The B axis of the exhibit is a direct drive of torque motor. The headstock can be configured with standard, chuck and direct drive types. The roundness of the workpiece is 0.4μm and optional 0.2μm. C-axis non-circular grinding with HEIDENHAIN round grating, exhibits water-cooled direct drive head frame, chuck capacity of 320 Nm, maximum 250 kg. The tailstock adopts a dense bearing support sleeve with a taper fine adjustment function.

(3) Harding Grinding Group HG-U100 0 CNC Precision Universal Cylindrical Grinder
The center of the machine is 190 mm high with a tip distance of 1000 mm and a maximum workpiece weight of 100 kg at both tips. The CNC system is FANUC 0iTD. The machine tool is a precision universal cylindrical grinding machine designed by KELLENBERGER of Switzerland and the JONES & SHIPMAN company of the Harding Grinder Group. It is specially designed for the Chinese market. The ultra-precision grinding function was demonstrated at the show.

The machine tool is a cast iron bed, the wheel frame is a roller linear guide block, and the workbench is a flat-V plastic guide rail. The grinding wheel frame is equipped with two outer grinding wheels and one inner grinding wheel. The CNC B-axis is automatically indexed, and the rat tooth plate structure is adopted, which is 1 degree. The head frame adopts a dead-life dual-purpose top structure with a clamping accuracy of 0.5 μm. The tailstock allows for fine adjustment of the taper. A fixed wheel dresser can be installed on the rear side of the headstock and a diamond wheel dresser.
(4) Japan SHIGIYA company GSU-30B-75 CNC universal cylindrical grinding machine
The machine is a universal cylindrical grinding machine developed with the concept of “simple operation and high-precision grinding”. The maximum grinding diameter is 300 mm, the tip distance is 750 mm, and the maximum workpiece mass is 150 kg. Section 31i. The biggest feature is that the numerical control rotation of the grinding wheel frame adopts the direct drive method to realize the installation and configuration of nine kinds of grinding wheels. The grinding wheel frame adopts the closed static pressure guide rail, and the head frame adopts the direct drive to realize the CX axis interpolation grinding.

(5) Taiwan Daguang Evergreen Co., Ltd. OCD-3265M3 multi-spindle head cylindrical grinder
The machine table has a maximum diameter of 320 mm, a tip distance of 650 mm and a maximum workpiece weight of 150 kg. The automatic rotation of the wheel frame is driven by a servo motor, and the rat tooth plate is positioned with a minimum resolution of 0.0003 degrees and a repeating positioning accuracy of 1 arc second. It is equipped with three grinding wheels: 510×50 straight grinding wheel, 510×75 oblique grinding wheel and inner grinding wheel. The numerical control system adopts FANUC numerical control system.

2 CNC universal cylindrical grinding machine is the development trend of composite internal and external cylindrical grinding machine
(1) The grinding wheel frame is diversified and enriches the grinding function. The grinding wheel frame can be realized from the original single straight grinding wheel, single inclined grinding wheel and single inner grinding wheel to the general-purpose, diagonal type, front-rear type and mass production type grinding wheel. It can also be CBN grinding wheel for high-speed grinding. Medium and small batches of various inner and outer rounds and even large batch grinding.

(2) The automatic indexing technology of the B-axis of the grinding wheel frame is improving day by day. The B-axis drive is manually 2.5 degrees from the initial ratchet, automatically 1 degree indexing to the servo motor drive worm and worm gear continuous indexing, to the current torque motor direct drive, circular grating direct detection. Bearings from YRT rolling turret bearings to closed hydrostatic guides are now available.

(3) Precision CNC universal cylindrical grinding machine table and grinding wheel guide generally adopt static pressure guide rail or exclusive technical guide rail to ensure grinding precision and vibration resistance. The cylindrical grinding head bearings are basically made of exclusive high-precision dynamic pressure sliding bearings.

(4) The head frame configuration is diversified, and the torque motor direct drive live spindle head frame is generally added. Generally, the universal head frame is a dead-end top, a live spindle head frame and a direct-drive live spindle head frame. The spindle is supported by a high-precision rolling bearing, and the roundness of the card grinding is generally 0.4 μm and the maximum is 0.2 μm.

(5) The tailstock is generally equipped with a taper fine adjustment function to meet the requirements of high-precision grinding adjustment.

3 Conclusion
From this exhibition, the CNC universal cylindrical grinding machine technology is improving day by day, and the technology is in full swing. Switzerland's STUDER and KELLENBERGER are world leaders, and their S41 and KEL-VERA UR-RS300/750 represent the highest level. Japan's SHIGIYA company GSU-30B-75 is also a high-end grinding machine, but there is still a gap between STUDER and KELLENBERGER products in terms of configuration diversity and technical maturity. The KG33 assembled by STUDER and the HG-U1000 assembled by Harding in China are all products developed for the Chinese market, and the pressure on domestic and foreign cylindrical grinding machines manufacturers is relatively high. The OCD-3265M3 multi-spindle head cylindrical grinding machine developed by Taiwan Daguang Evergreen belongs to the catch-up entry-level composite internal grinding machine. Domestic and foreign round grinder manufacturers have a large gap between Europe and Japan in the technology of composite internal and external cylindrical grinders, and they need to make great efforts to catch up.

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