Hanjiang Machine Tool Design S7720B CNC Worm Grinder for Precision Machining

陕西汉江机床有限公司副总经理 余建旬
Yu Jianxun, deputy general manager of Shaanxi Hanjiang Machine Tool Co., Ltd.

Shaanxi Hanjiang Machine Tool Co., Ltd. is a leading manufacturer of precision thread grinders invested by the state in 1969. It is a large-scale backbone enterprise of machinery industry. It mainly produces precision thread grinder series, worm grinder, special special machine, precision measuring instrument, high precision CNC precision machine tool and rolling function. Parts and other products.

Hanjiang Machine Tool Co., Ltd. has more than 2,300 employees, including nearly 300 senior and intermediate technicians. The company has a national-level thread grinder research institute, a Shaanxi rolling functional component research institute, and more than 70 scientific research achievements at the provincial level. Many products have filled the gap in the country.

Develop new grinding machines to meet user needs:

In order to improve the machining precision, processing efficiency and automation of the worm grinder, our company's worm grinder has stronger market competitiveness and operational advantages. Our company has developed SK7720A, SK7732×15, SK7732×20, SK7732×30 and SK7763×40 and other CNC worm grinders, the above products have been widely used in the domestic reducer industry since they were put on the market. Their performance has been affirmed by the majority of users, and many problems have been received from users. The technicians have carried out these problems. Many improvements have been made to continuously improve the series of worm grinders.

With the increasingly fierce competition in the market, various manufacturers have higher requirements for the interchangeability of their products and the accuracy of the tooth profile. For this reason, many users have requested that our company adjust the screw angle of the CNC worm grinder grinding wheel frame manually. It is a servo axis. In addition, domestic users purchase Taiwan's series of CNC worm grinders, the screw angle adjustment is servo axis, according to sales reflects many users are very satisfied with this function, in order to further meet the user's requirements, so that our CNC worm grinder function More perfect, and at the same time in the market competition in an invincible position, the development of the spiral lift angle servo servo adjustment SK7720B CNC worm grinder is very necessary.

SK7720B数控蜗杆磨床
Figure 1 SK7720B CNC worm grinder

Features and advantages of SK7720B CNC worm grinder:

SK7720B CNC worm grinding machine is shown in Figure 1. The thread movement of the machine tool is formed by the linkage of the headstock spindle rotary servo motor and the longitudinal motion servo motor of the table. The main part of the machine tool is mounted on the strong cast iron bed, and the machine control console is installed in front of the bed. The table motion is moved along the rolling and sliding hybrid rails (ie, the V-shaped rail is a sliding rail, the flat rail is a rolling rail), and the wheel carrier moves along the rolling rail.

The grinding wheel spindle component is mounted on the grinding wheel drum, and the SIEMENS built-in AC synchronous motor directly drives the grinding wheel spindle to realize the high-speed turning motion of the grinding wheel. By modifying the numerical control system parameters, the grinding wheel speed can be adjusted to ensure the constant speed of the grinding wheel. The grinding wheel spindle is supported by high-precision rolling bearing, which has the advantages of high rotation precision and high rigidity, and is easy to maintain.

The adjustment of the helix angle of the grinding wheel spindle is realized by the rotary motion of the grinding wheel of the grinding wheel frame. The rotary motion is servo control, and the AC servo motor is driven by the high-precision indexing rotary table, which is convenient to adjust and has high accuracy.

The grinding wheel frame is equipped with a numerical control grinding wheel dresser. The two CNC axes of W and V are interlocked and interpolated. The grinding wheel driven by the servo motor is used to trim various grinding wheel profiles, and the finishing precision is high.

The rotary motion of the headstock spindle, the longitudinal movement of the table, the lateral feed motion of the wheel carrier, the vertical movement and horizontal movement of the wheel dresser, and the rotary motion of the dresser diamond roller are all driven by an AC servo motor. The grinding wheel is driven by the SIEMENS built-in AC synchronous motor.

The mother screw and the transverse feed screw of the machine tool adopt high-precision ball screw. The support bearing of the lead screw and the spindle bearing of the head frame and the spindle bearing of the grinding wheel frame adopt imported high-precision bearings to ensure high precision and stability. .

The machine tool is controlled by the CNC system, which can realize the automatic indexing of the workpiece in the axial and radial directions, with high indexing accuracy and reliable operation. The Z, X, W, V, C, and A axes all use a gapless transmission system, eliminating the reverse error in the drive chain.

The machine adopts a fully enclosed casing and is equipped with an imported oil mist processor, which reduces the pollution of the working environment caused by the oil mist generated by the machine grinding, and is beneficial to the health of the operator.

Design principles for machine tools:

(1) Design basis: "GB/T9601-2006 general technical requirements for metal cutting machine tools" and "JB/T9925.2-1999 worm grinder technical conditions" and "Q/HJ003-2000S CNC thread grinder series product manufacturing and acceptance technology condition".

(2) Borrow the parts of the company's thread grinder series as much as possible to achieve product generalization and standardization.

(3) Use the mature and reliable structure of the company's CNC thread grinder as much as possible to ensure the possibility of success.

(4) It is preferred to use mature hydraulic components to ensure the performance and accuracy of the machine.

Grinding precision and processing case of grinding machine:

This machine is an eight-axis CNC worm grinder. It is suitable for machine tool manufacturers and other machinery manufacturers to grind various cylindrical worms with a length of 750 mm and a diameter of 200 mm, such as ZA, ZN, ZI, ZK and ZC1. The worm can also be used to grind the lead screw. The FAGOR 8055i/POWER-M CNC system can be configured, and the SIEMENS840 D sl CNC system can also be configured upon request.

Using this machine to grind the worm, the precision that can be achieved is: Z = 1 ~ 2, 4 levels; Z = 3 or more, 5 levels.

用SK7720B数控蜗杆磨床磨削蜗杆的加工案例
Figure 2 Processing case of grinding worm with SK7720B CNC worm grinder

Figure 2 shows the machining case of grinding the worm with the SK7720B CNC worm grinder. The worm has a modulus of 4, a head count of 1, and a lead of 12.566 mm. The grinding accuracy is: 1 The limit deviation of the axial pitch: ± 0.003 6 mm. 2 Limit cumulative deviation of axial pitch: ±0.006 7 mm. 3 Tooth shape error: 0.005 6 mm. 4 screw radial runout error: 0.005 6 mm. 5 thread surface roughness value Ra = 0.32 μm.

The precision of grinding the trapezoidal lead screw with the S K7720B CNC worm grinder is 6 grades. When grinding the Tr50×5 trapezoidal lead screw, the precision achieved is: 1 within the screw 2π: 0.004 mm. 2 over 25 mm length: 0.007 mm. 3 over a length of 100 mm: 0.008 mm.

4 over 300 mm length: 0.011 mm. 5 on the full length of the screw: 0.016 mm. 6 The total length of the upper and lower diameter of the screw is changed by 0.01 mm. 7 lead screw middle diameter jump: 0.008 mm.

Conclusion:

The main components of SK7720B CNC worm grinder adopt the mature component structure of our company's same series of machine tools, shortening the design and manufacturing cycle, saving the manufacturing cost of the machine tool and reducing the risk of machine tool trial.

For the processing demand of CNC worm grinder, research and development of high-efficiency CNC worm grinder, solve the problem of design and manufacture of domestic precision, high-efficiency, CNC worm processing equipment and key component design and manufacturing technology; master the high-efficiency worm machining machine with independent intellectual property rights Manufacturing Technology. The product has reached the advanced level of similar foreign products in terms of processing precision and processing efficiency, and has realized the localization processing of high speed and precision worm. With the successful production of this product, it has been favored by the majority of users. It has been widely used in China's reducer industry and auto parts industry, and exported to overseas, the economic benefits of the product are also reflected.

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