First, the development of the large ring gear
In the late 1970s and early 1980s, due to the rapid development of heavy machinery, especially the specifications of grinding machines, cement kiln and power generation equipment, the gear ring was developed to a large modulus and large diameter. For example, in the 20th century, the largest ring gear of foreign countries is a radar antenna ring ring made by Philadelphia Gear Company with a diameter of 25 600mm. The largest ring gear in China is a self-grinding gear ring made by Shenyang Heavy Machinery Factory with a diameter of 9 660mm. Since the beginning of the 21st century, the specifications of the ring gear processing have continued to increase, and the North Heavy Industry Group has produced a grinding gear ring with a diameter of 11 559.8 mm. The processing machine for the large ring gear is mainly hobbing machine, and the gear, milling and gear shaping machine also have certain applications.
Second, the large ring gear processing technology
Generally, the large ring gears of 8.5 m or less are composed of two lobes. Due to the large modulus and large diameter, the spoke plate structure is adopted, and many deformations are often generated during processing. The general deformation form is that the ring gear is outwardly extended by the joint seam, so that the outer edge of the joint seam is elliptical deformation from the seam ring gear, and noise and vibration are generated during transmission, and the joint pin hole is not matched during installation. Therefore, the deformation problem after the processing of the large ring gear is the most serious quality problem, so solving the deformation in the large ring gear processing or later is an important factor that must be fully considered when formulating the large ring gear processing scheme. The process plan is described below.
1. Blanking and tempering on the ring gear processing technology
There are three kinds of roughing ring gear processing schemes for roughing and tempering.
(1) The first process plan: scribing → planing → scribing → drilling → pliers → drilling → pliers → scribing → car → milling teeth → scribing → drilling → pliers. This process is referred to as a single planer, a first car, and a single milling tooth. Often, due to the casting of the blank in the current month and the processing in the current month, there is no natural failure, the internal stress is not eliminated, and the machining and milling of the teeth removes a lot of metal, so that the joint seam is cracked long, the inner edge cracks small, and the outer edge cracks greatly. The ring gear is elliptical. The process of deformation is that the deformation behind the car is small, and the deformation is large when milling the teeth, that is, the edge of the milling edge is deformed.
(2) The second process plan: scribing → planing → scribing → drilling → pliers → drilling → pliers → scribing → car → pliers → scribing → planing → drilling → pliers → 镗 → pliers → scribing → car → Milling teeth → scribing → drilling → pliers. This process is referred to as secondary planer, secondary car, and one-time milling. This kind of rough car removes a part of the metal and disassembles it for 3 to 5 days to make it naturally deform, but it cannot completely eliminate the deformation. After finishing the car, before checking the teeth, the roundness of the outer circle is generally within 0.1mm, and some even reach 0.16mm. After the milling, the joint opening mouth is about 0.2mm, and the tooth thickness difference is less than 0.5mm, mainly because the deformation occurs in milling. After the tooth and after milling.
(3) The third process plan: for the maximum deformation after milling, on the basis of the second process plan, add a rough milling process. That is, scribing → rough planing - scribing → drilling → pliers → drilling → pliers → scribing → roughing → rough milling → pliers → scribing → fine planing → drilling → clamp → 镗 → clamp → scribing → fine car → Fine milling - line → drill → clamp.
This process is referred to as secondary planer, secondary car, and secondary milling. Suitable for open ring gears with poor rigidity and variability. Although the hobbing machine and the vertical gantry are added, the cutting of the tool is interrupted when the outer wheel is finished, but the quality of the ring gear can be ensured.
2. After roughing, quenching and tempering
Dash → rough planing - scribing → drilling → pliers → drilling → pliers → scribing → rough car → pliers → quenching and tempering → cut off the lacing → scribing → semi-finishing → scribing → drilling → pliers → semi-finished car → Rough milling → manual failure → scribing → fine planing → drilling → clamp → 镗 → clamp → scribing → fine car → fine milling – scribing → drilling → pliers.
This process is referred to as three-time planer, three-time car, double-milling, and secondary heat treatment. The characteristics of the process are as follows: 1 After roughing, the quenching and tempering refers to quenching and tempering after roughing. If the roughening is performed after rough milling, the hardness of the tooth top and the hardness of the root can be the same, but the production cycle is long and the heat treatment deformation is large. Rarely used. 2 The amount of rough car must be kept according to the requirements of the heat treatment process. When the rough car is used, there is a lacing (the half ring gear is used for quenching and tempering), so the inner flange cannot be roughed. 3 The ribs used for quenching and anti-deformation should be cut off by gas welding after quenching and tempering. 4 tempering cut off the ribs, each ring gear is extended outward 10 ~ 15mm, the end face deformation of about 10mm. Therefore, the final drilling joint surface must be re-marked when the hole is closed, and the two pre-holes that have been drilled are taken care of the mutual position of the two combined faces, and then the holes are reamed by the boring machine to avoid the two holes being misaligned. Cause more flat holes or enlarge the holes.
3. Anti-deformation measures in the manufacture of large ring gears
In order to prevent deformation of the large ring gear in manufacturing, the following measures are usually taken:
(1) The addition of the ribs in the heat treatment process such as casting and quenching and tempering has enhanced the rigidity of the ring gear structure.
(2) Determine the reasonable amount of cutting, especially in the planing, finishing and milling processes, the amount should be controlled.
(3) Select a reasonable clamping method, and the finishing process should be slightly loosened and lightly pressed.
(4) In the thermal process, the fulcrums for furnace loading, lifting and stacking should be selected for parts that are not easily deformed.
(5) In the process lifting, the force point is reasonably selected to prevent lifting deformation.
Third, reduce the processing cost of large ring gear, improve processing efficiency
In recent years, as the number of manufacturing and grinding machines has increased year by year, the large ring gear of one of the main components on the mill has increased correspondingly. The large ring gear has a specification modulus of 16 to 40, and a diameter of 3 000 to 14 000 mm requires hobbing on the gear hobbing machine. At the same time, it also accepts a certain number of large ring gear spare parts ordering tasks every year, so the processing task of the large hobbing machine is very tight. Therefore, how to improve the hobbing efficiency of large modulus and large diameter ring gear is an important issue in manufacturing more and better medium-sized mining equipment. In terms of improving the hobbing efficiency of large hobbing machines, the use of advanced tools is better.
Tool
(1) Use a progressive hob to machine large modulus and large diameter ring gears. In order to improve the hobbing efficiency, the worker master used the "asymmetric mounting hob" method to process the large modulus and large diameter ring gear in the long-term production practice, which improved the hobbing efficiency and also adopted the tapered hob. Processing, also received good results.
The reason why these two methods can increase the amount of cutting, it is important to reduce the tooth load of the hob before cutting into the workpiece, so that the load of each tooth of the hob is uniform and the cutting is stable. Generally, the cutting of the hob is completed by the top edge and the two sides of the hob teeth. The top edges of the hobs of the hobs are different, and the load on the side teeth is the heaviest and the wear is the fastest, and the middle teeth are worn without the wear of the intermediate teeth. On the basis of this, the progressive hob is to correct the tooth height of the ordinary hob to achieve uniform load per tooth, that is, the top and side edge loads are even, which makes the cutting smooth, increases the amount of cutting, and improves the hobbing. s efficiency.
The advantages of this method: the machining of the straight toothed ring, the tool is simple to manufacture, and can be ground with a general hob. The peak load is reduced, the amount of cutting is increased, and the cutting is relatively stable. Easy to use, no auxiliary equipment is required.
Disadvantages: A progressive hob is only suitable for a certain number of teeth.
(2) Large-size large-diameter ring gear is processed by double-head, straight groove, large outer circle and large front angle gear hob. In the hobbing process, increasing the number of hobs can double the table speed and greatly improve the machining efficiency. Therefore, the multi-head hob has been widely used as a high-efficiency tool for the machining of medium and small modulus gears. When a multi-head hob is used to machine a large modulus gear, as the number of hobs increases, the number of teeth per tooth surface of the enveloping workpiece decreases proportionally, increasing the cutting load of each tooth of the hob. In order to increase the rigidity of the hob and reduce the edge of the incisor surface, the outer diameter and the hole diameter of the hob must be correspondingly increased, and the number of hob teeth (the number of chip flutes) also needs to be increased.
Shenyang Heavy Machinery Factory has designed two double-head, straight groove, large front angle and large external gear hobs with modulus m=16 and m=20 for cutting test. The hob is made into a straight groove to make the hob easy to sharpen and reduce the defects of the front edge of the side edge. The large front angle is to make the cutting light.
(3) Other efficient milling cutters. The roughing of the large ring gear can also be used with the finger milling cutter with the spiral groove and the chip breaker. The feed rate can be increased by 3 times. The foreign and domestic tool factories also manufacture the hob with the side edge of the zigzag. When the chips are discontinuous, it is easy to eliminate, the total milling resistance is small, the tool is wear-resistant, and it is suitable for heavy milling. There are also large-diameter carbide disk cutters manufactured by tool factories at home and abroad to improve the efficiency of rough milling.
2. Machine tool
The non-hobbing machine equipment performs rough machining of the large gear (hereinafter referred to as rough milling), which can alleviate the processing pressure of the large hobbing machine, protect the accuracy of the hobbing machine, and improve the working efficiency of the hobbing machine. There are many methods for rough opening. The main method is to use special processing equipment, such as boring machine, planer, etc., to machine the gear teeth.
We have summarized the following processing methods:
(1) Ordinary trampoline processing. The processing method has had practical experience in the production of the North Heavy Industry Group Transmission Equipment Branch. The Wusheng T612 boring machine was used to transform the original rack finger milling cutter: the boring tool shank for installing the modified milling cutter was designed. Solved the problem of tool installation; designed a special jacking device and loading tooling to solve the problem of splitting teeth during milling; designed the tool cooling device. Before milling the teeth, the scribing machine draws the split tooth line on the outer circle of the gear according to the pattern, and installs the card to find the right rear milling tooth. Each milling one tooth releases the card, and the jacking device micro-tops the ring gear and presses the line. Split to the next tooth, continue to mill the tooth after clamping.
(2) Planer processing. Using the bullhead planer to remove the front workbench, redesigned the base that can be angled, designed a special planer; set the planer to 4~5m high, and dig 4~5m deep pit at the front end, and need to draw the split teeth before processing. Line and tooth line, when the workpiece is placed in the pit during processing, when the card is firmly fixed, the tool is turned by the crane to rotate the workpiece through a certain angle, and then the base of the planer is used. Finding the rear planer, this method is slower and less efficient, but it can reduce the amount of allowance, and can also process large modulus and large diameter ring gear.
(3) Band saw processing. The processing method is designed and manufactured by some factories and mines by a band saw machine and a clamping tool. In theory, it is possible to process gears of infinite diameter; the processing speed is fast. However, due to the blisters, pores and uneven hardness of the blank, the band saw is damaged and the cost is high and the loss is large. This method has not been widely promoted and used, and the uneven amount of the hobbing machine causes the hobbing machine to have a large cutting amount.
(4) Special boring machine processing. The method is improved by the ordinary trampoline processing method, the common trampoline is removed from the workbench, the lateral moving guide rail and the servo motor are added, and the compound motion can be used to conveniently process the straight tooth and the helical tooth ring; since the spindle motor power is improved, Properly increase the cutting speed, the processing speed can be faster than the ordinary trampoline.
(5) Simple milling machine. The machine tool used in this method is a self-made machine tool of a manufacturer. It has the functions of a hobbing machine other than hobbing. It can also divide the teeth and differentially machine the helical gear through the hanging wheel. The workpiece can be processed to minimize the amount of work. Finishing can be done with a forming cutter. The table can carry 30t, and an auxiliary table and auxiliary support can be added to machine larger workpieces. The machining speed is improved because no manual teething is required. The tool uses an aluminum high-speed steel spiral groove finger milling cutter, which saves tools when machining.
(6) Comparison of rough milling machine tools, as shown in the attached table:
3. φ11559.8mm large ring gear rough milling machining
The “3.8 million t/year lava series beneficiation project of the expansion project of Dahongshan Iron Mine of Kunming Iron and Steel Group Co., Ltd.†is a design technology transfer project for semi-autogenous mill and overflow ball mill with Fowler.
The large gear on the MZS8848 semi-autogenous grinding machine is manufactured and processed by the Transmission Equipment Branch of Northern Heavy Industry Group Co., Ltd.
MZS8848 large ring gear on semi-autogenous grinding machine, parameters: modulus m=36 (corresponding to diameter of 0.706), tooth width b=950mm, diameter=11 559.8mm, number of teeth z=316, helix angle=8°, pressure angle =25°, full tooth depth = 81 mm. Material: ZG45CrMo, quenching and tempering hardness 241 ~ 286HBW. Processing accuracy level: 8 levels. The large gear adopts a 4-valve structure, and the spoke adopts a double-spoke box-type structure. The half-gear adopts dumbbell pin positioning and high-strength bolt connection between the joint faces, and the ring gear adopts helical teeth, which has large bearing capacity, stable transmission and noise. Small and other characteristics.
Instead of the 12m vertical hoisting machine on the trampoline, instead of the 14m hobbing machine rough milling, it can reduce the occupation time of the 12m vertical car and the 14m hobbing machine, reduce the processing cost and improve the processing efficiency.
In order to process the 4-lobed φ 11 559.8mm helical gear ring gear, it is necessary to take processing measures to complete. The key to rough milling on a trampoline is how to ensure single-segment accuracy and ensure helix angle. The three boring machines are used for rough milling of each lobes at the same time, and the accuracy of the single-division teeth is the same, and it is more difficult to ensure that all the helix angles are the same.
After repeated research and determination of the processing technology, the three-cylinder super large diameter, large modulus, long tooth width ring gear was used to carry out the roughing and rough milling process simultaneously with three boring machines, ensuring the four petals on the MZS8848 semi-autogenous grinding machine. φ 11 559.8mm helical tooth ring gear processing progress, after roughing the ring gear, the finishing tooth is finished in the 14m gear hobbing machine (see attached figure). Through the fine milling test, it was proved that the rough milling technology of the four-lobed φ 11 559.8mm large ring gear on the trampoline was successful. The gear has been installed on the MZS8848 semi-autogenous mill in Dahongshan Iron Mine, Yunnan Province, and it works very well.
Fourth, the conclusion
This paper introduces several processing techniques of large modulus large diameter ring gear, analyzes the advantages and disadvantages of various processes, and summarizes the anti-deformation measures of large ring gear in manufacturing, as well as the method of reducing the processing cost of large ring gear and improving the processing efficiency. The company can make reference in the process of formulating the large ring gear processing [this article is the fund project: the national "high-end CNC machine tools and basic manufacturing equipment" technology major project (2010ZX04014-091)].
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