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How to choose hobbing cutter for gear hobbing machine?

2018/11/15 18:53:05 Viewers:
Gear is a wheeled mechanical part that transfers torque by meshing of teeth. By driving with other gear mechanical parts, it can realize the functions of changing speed and torque, changing direction of motion and changing form of motion. Because of the advantages of high transmission efficiency, accurate transmission ratio and wide power range, gear mechanism is widely used in industrial products. Its design and manufacturing level directly affects the quality of industrial products. With the continuous development of productivity, gear transmission is developing towards the direction of high speed, heavy load and high precision. More and more gear transmission uses hard tooth surface gears with high load-carrying capacity and good pitting resistance. The following is a brief introduction of the tool selection method for the hobbing machine.

First, the advantage of hard tooth hobbing technology.

(1) For high-precision grinding gear, hard tooth surface hobbing can replace rough grinding process with high efficiency, remove the heat treatment deformation of gear teeth, leaving a small and uniform margin for grinding, thus greatly improving the grinding efficiency.

(2) For honing gear, arranging hard tooth hobbing before honing can remove heat treatment deformation to achieve the necessary accuracy, and then honing, in order to give full play to the honing process finishing advantages, make up for the shortcomings of hobbing processing.

(3) For hardened gears with common accuracy, carbide hobs can be used directly to finish hobbing to ensure gear processing accuracy at the lowest cost, which has more technical and economic significance for large and medium-sized gears.

Two. Factors affecting the accuracy of hobbing technology

There are two main reasons that make it difficult to improve the tooth profile accuracy further. One is the poor stability and transmission stiffness of the hobbing machine. The other is that there are some difficulties in manufacturing high-precision carbide hobs, especially the hobs with large negative rake angle change greatly after re-grinding. Therefore, it is necessary to carefully design and calculate the structure and parameters of hobs, analyze the tooth profile accuracy after re-grinding and put forward improvement measures.

Three, carbide hob design

The characteristics of hard surface hobbing are: high hardness of workpiece, intermittent cutting process and thin cutting layer. In the process of cutting, the cutter bears large impact load, high cutting temperature and strong friction. Therefore, the requirements for impact toughness, wear resistance and heat resistance of cutting tool materials are very high. The material has high wear resistance, and high temperature carbides such as lithium carbide are added to improve the impact toughness and wear resistance of the blade to obtain good cutting performance. Its main structures are integral, clamp and welding.

(1) integral carbide hob

The advantage of this method is that the rigidity is strong and the precision is high, but the cemented carbide which is limited by the whole pressing process and is expensive in wear and tear is more.

(2) clamped carbide hob

The clamping structure is complex and the clamping reliability is poor. Especially when processing large modulus hardened gears, the extrusion force on the tooth surface is large and the alternating effect is significant, so the clamping requirement of the blade is high.

(3) welded carbide hob

The utility model has the advantages of simple structure and high connection strength, and the cemented carbide blade is sintered and the material is saved. However, the crack caused by welding stress is always a factor of product quality instability, so higher welding technology is needed.

Four. Selection of precision gear cutting oil:

(1) Silicon steel is a relatively easy-to-cut material. Generally speaking, in order to make the finished products easy to clean, low-viscosity gear cutting oil will be selected on the premise of preventing burrs. cnc machining

(2) When choosing gear cutting oil for carbon steel, the better viscosity should be determined according to the processing difficulty and degreasing conditions.

(3) Because galvanized steel and chlorine additives will react chemically, we should pay attention to the possibility of white rust when choosing gear cutting oil, and the use of Yida Borun sulfur-type special gear cutting oil can avoid rust problem, but after processing, we should degrease as soon as possible.

(4) Stainless steel generally uses gear cutting oil containing sulfur-chlorine compound additives, which ensures extreme pressure processing performance and avoids burrs and cracks on the workpiece.