Rack characteristics:
The tooth profile of the rack is a straight line and the normals of each point of the tooth profile are parallel. During the transmission process, the rack moves in translation and the velocity vector (i.e. the magnitude and direction of the velocity). of each point of the tooth profile is consistent. Therefore, the pressure angle at each point of the rack tooth profile is the same and its size is equal to the tooth profile angle of the tooth profile.
b. Since the tooth profiles on the same side of each rack tooth are parallel, their pitches are equal regardless of the index line, top tooth line, or other straight lines parallel to them, c i.e. P = mπ.
Common processing methods for racks include:
Milling
to land
sharpening
gear shaping
thread cutting
Later we will learn the main processes and characteristics of each type of treatment separately. Let’s start with milling today:
Rack milling
Milling gear manufacturing
Gear milling of rack gear is usually done by ordinary milling machine, and there are also special gear milling equipment. The rack is positioned in the jaws of the clamping body then tightened hydraulically. The forming cutter is installed on the main shaft of the equipment for rotation. It is driven by a servomotor and mills the rack as a whole. . During the gear milling process, a large amount of cooling oil flushes the milling area, cools the workpiece and the hob, and removes a large amount of iron shavings. The hob rises until the end of the stroke and then quickly returns to the starting point. The cooling oil is then released, the grid is removed and the second grid is installed to proceed to the next cycle.
Integrated milling gear manufacturing combines many advantages such as high dimensional accuracy, good tooth surface finish and good dimensional stability, and is widely used in small batch production of many varieties.
The following is a flowchart of the relatively traditional steering rack processing process:
The following is reference data for your reference only:
The investment in milling and gear manufacturing equipment is relatively large, asImport a milling machine from German KESEL company (request: 13522079385), equipped with various attachments and accessories, the cost is about 4 million yuan (ex-factory price)For example, if you purchase a special CNC gear milling machine from Tianjin Dingxin Chenda Precision Machine Tool Manufacturing Co., Ltd. (inquiry 15910974236), the ex-factory price is about 750,000 yuan, and a large diameter baking tray and a pair of tongs cost between 50,000 and 80,000 yuan.
To process different parts, the cooking plates and corresponding accessories must be replaced. When the workload is low, it usually takes 0.5 hours per person. It takes about 70 seconds to mill a rack, and the annual production capacity of a gear milling machine reaches 250,000 parts.
Generally speaking, if 4 to 8 types of products are processed, the annual output of a single product is between 10,000 and 80,000 pieces, and the total annual output of products reaches about 100,000 pieces. It is very economical to use the gear milling process.
The equipment is depreciated for 10 years (German gear milling machines can usually be used for 20 years). If a German KESEL gear milling machine is used and based on an actual annual production of 200,000 parts, the annual depreciation of the equipment is 400,000 euros. , and the average cost of each rack is 2 yuan. The cost of the tool holder is 60,000 yuan, and each grinding cost is 1,000 yuan. After each grinding, 1,200 teeth are milled. The milling fee for each rack is 2.4 yuan and the total is 4.4 yuan. The equipment depreciation and tool costs of the toothing process are equivalent.
Gear manufacturing using milling gear technology has the advantages of low investment, short delivery time, fast equipment lead time, high part quality and strong production capacity. It is currently suitable for product development and small and medium batch production. Companies using gear milling technology to process gear racks are the largest in China. It is relatively common, such as Shanghai Beite Technology Co., Ltd., Shanghai Geer Automotive Accessories Co., Ltd., Nexteer Automotive Systems (Suzhou) Co., Ltd., etc.
Since milling cutters are expensive and require grinding during the process, you can refer to the spindle management method for management. In order to reduce the cost of using gear milling tools, some companies first use a general milling machine and a disc milling cutter to mill a plane on the rack tooth part, leaving a margin of 0.5 to 1 mm for milling by gear milling machine. . The advantage is that it can not only accelerate the feed speed of the gear milling machine and increase the output, but also greatly increase the life of the milling cutter and reduce the operating cost of the milling cutter. The key to this process is to position the workpiece plane and then clamp it so that the milling surface is up and horizontal. If the clamp does not clamp the workpiece, it can easily cause an accident.
Daguang focuses on providing solutions such as precision CNC machining services (3-axis, 4-axis, 5-axis machining), CNC milling, 3D printing and rapid prototyping services.
