Diamond grinding wheel for grinding gear

Gear is the main basic transmission component of the automobile industry; usually, there are 18–30 teeth in each car, and the quality of the gear directly affects the noise, smoothness, and service life of the car. The Gear Plus machine tool is a complex machine tool system and is the key equipment of the automobile industry.

Gear processing process:

1. Forging gear blank

2. Normalized: The purpose of this process is to obtain hardness suitable for the cutting of rear sequence gear and to prepare the structure for the final heat treatment to effectively reduce heat treatment deformation. The gear steel used is usually 20CrMnTi.

3. Turning processing: To satisfy the high precision positioning requirement of gear machining, gear blank processing all adopts numerical control lathes using mechanical clamping, not heavy ground vehicles Under the knife, realized in a clamping aperture, end face and outside processing synchronization is complete, which not only ensures the inner hole and end face of the vertical degree requirements but also ensures the size of the discrete small gear billet production in large quantities. Thus, the precision of the gear blank is improved, and the machining quality of the rear sequence gear is ensured.

4. Gear hobbing and gear shaping

5. Gear shaving: Radial gear shaving technology is widely used in the production of large quantities of automobile gear for its high efficiency and ease of achieving the requirements of tooth shape design and tooth direction modification.

6. Heat treatment: Carburizing and quenching are required for automobile gear to ensure its good mechanical properties.

7. Grinding: It mainly uses a diamond grinding wheel for finishing the inner hole, end face, outer diameter of the shaft, and other parts of the gear after heat treatment to improve the dimensional accuracy and reduce the tolerance of shape and position.

Gear processing error causes:

1. The precision of the machine tool transmission chain is not high, and vibration or impact in operation affects the instability of the machine tool transmission

2. The main shaft of the table is not in contact with the cone guide surface of the table shell. The cone guide surface is hard to contact, and the table rotates heavily. Vibration occurs during operation. Cause errors in processing.

3. Make the knife mechanism work abnormally, and scratch the workpiece surface with the knife.

4. Poor grinding quality of the gear shaper blade

5. The feed is too large, resulting in tooth cutter cutting gear that is not timely, resulting in a rough surface of gear.

6. The gear blank is not properly installed, and vibration occurs during cutting.

7. The cutting fluid is dirty or rushed into the cutting tooth groove. Gear surface quality is not qualified.

How do I choose a diamond grinding wheel for gear grinding?

1. The advantages of the spur gear and transmission are simple to manufacture, easy assembly, direct engagement without synchronizer, and direct use of deep groove ball bearings for shaft end installation, basically without axial force. The disadvantage of spur gear and transmission is that straight gear transmission stability is poor and it is easy to produce impact, vibration, and noise. Therefore, it is not suitable for high-speed and heavy-duty occasions.

2. Helical gear and transmission advantages: the helical gear meshing is gradually carried out, the tooth contact degree is large (effective meshing teeth), the load is not suddenly added or removed, so the transmission is stable, low noise, long service life, widely used in high speed and heavy duty occasions.

The disadvantage of helical gear and transmission is that when manufacturing is slightly complex, there is a lot of axial force at work, which is adverse to bearings.

Therefore, the first gear and reverse gear of the automobile gearbox are used for economy and compactness because they do not work for a long time and the speed is not high. While the other gears and rear axles have high requirements for smoothness because of high-speed operation, the helical gear is used. To reduce the influence of axial force, the gear tooth rotation offset and the manufacturing process of modified gear are adopted, so that the tooth profile with taper can reduce the bearing capacity and maintain smooth operation.

As the core technology equipment for high-precision and hard tooth surface gear processing, the application of gear grinding machines is becoming more and more popular. Generally speaking, tooth grinding is the tooth-shaped finishing process of gear parts. It is a tooth-shape finishing process that removes the finishing allowance based on completing the rough machining of tooth shape (such as hobbing and milling teeth, etc.) and heat treatment to further improve the precision and surface quality of gear.

Influence of tooth precision on tooth profile grinding:

To ensure that the grinding wheel enters the tooth groove correctly and equalizes the grinding allowance of left and right tooth surfaces, the gear grinding machine needs to carry out circumferential positioning of the parts before grinding them.

It is necessary to ensure that the center surface of the tooth groove coincides with the center surface of the sand gear tooth profile. After correctly grinding the first tooth groove, the machine tool will, in turn, separate the workpiece teeth and grind out all tooth shapes.

If the circumferential positioning of the workpiece is not accurate before grinding, the size of the grinding amount on both sides of the tooth groove will be uneven. Serious grinding wheels will directly impact the tooth surface and grind the workpiece into waste or even cause the loss of precision of the machine tool.

The circumferential positioning deviation will directly affect the tooth margin of subsequent grinding, so the actual grinding must be considered according to the side with the large margin, increasing radial feed times, and thus reducing the machining efficiency.

In addition, the uneven allowance will cause the allowance on one side of the actual grinding layer thickness to be greater than the theoretical value. For carburizing or nitriding heat treatment of hard tooth surface gear, because the surface hardening layer is very shallow, the actual grinding thickness increase will lead to the finished parts of tooth surface hardness decreasing, resulting in a quality problem or affecting the performance of the part.

Grinding wheel selection:

The selection of grinding wheel mainly considers abrasive, particle size, hardness, bonding agent, and so on.

Abrasive: The grinding wheel abrasive selection is mainly related to the material heat treatment method and hardness. The grinding wheel should have high hardness, wear resistance, heat resistance, and toughness, as well as sharp corners for cutting metal.

Super hard abrasives: mainly natural diamond, artificial diamond, cubic boron nitride, etc., general grinding of high-hardness, brittle materials At the same time, diamond abrasives can also be used as grinding wheel dressing tools.

Corundum and ceramic abrasives are recommended for carburizing and hardening gear tooth surface grinding.

Particle size: Particle size refers to the size of the grinding wheel grain size. The smaller the size of the grinding wheel grain, the smaller the particle size. On the contrary, the larger the particle size, The selection of grinding wheel size is directly related to the machining time and the roughness of the tooth surface during gear grinding.

Application conditions for coarse grain grinding wheels:

Coarse-grained grinding wheels are selected for grinding under the following conditions:

(1) parts with high toughness and low hardness.

(2) Materials with poor thermal conductivity and easy to burn.

(3) When the feed quantity is large.

(4) When the roughness of the tooth surface is not high, that is, on the premise of meeting the roughness requirements, coarse-grained grinding wheels should be selected as far as possible.

(5) When the contact area between the tooth surface and grinding is large, a grinding wheel with a larger particle size should be selected to prevent excessive heat generated during grinding from grinding burns.

Fine grain grinding wheel applicable conditions:

Under the following circumstances, a finer-grain grinding wheel is selected for grinding:

(1) During tooth surface grinding, the retention of the forming wheel is improved to ensure higher grinding tooth precision.

(2) when the roughness of the tooth surface is higher.

(3) Grinding parts with a smaller tooth surface modulus.

The grinding wheel with a grain size of 46~80 should be selected for the carburized and hardened gear during grinding, which can increase the contact area between the grinding wheel and the tooth surface and reduce the roughness of the tooth surface. At the same time, the grinding wheel should have a certain chip tolerance space to ensure chip removal and heat dissipation performance.

Hardness: The hardness of the grinding wheel refers to the degree of difficulty for grinding grains on the surface of the grinding wheel to break or fall off from the bond under the action of the axial and radial forces of the machine tool when the grinding wheel rotates at a high speed during gear grinding. The general principle for selecting a soft grinding wheel is as follows:

(1) To increase the grinding contact area, a soft grinding wheel can be used to process gears with low hardness.

(2) For tooth surfaces with low thermal conductivity and material sensitivity to thermal temperature, the soft grinding wheel is selected.

(3) When the linear speed of the grinding wheel is high, the soft grinding wheel is used.

(4) To improve grinding efficiency, a soft grinding wheel can be selected.

The general principle for selecting a hard grinding wheel is as follows:

(1) When the grinding tooth surface is in a discontinuous state, a hard grinding wheel should be selected.

(2) To maintain better grinding accuracy, the hard grinding wheel was selected. When carburizing and hardening gears are grinding, the grinding wheel with medium hardness is selected.

Bonding agent: A bonding agent is an abrasive material bonded together. The strength, impact resistance, and heat resistance of the grinding wheel mainly depend on the type and nature of the bonding agent of the grinding wheel.

For carburized and hardened gear grinding, the vitrified diamond grinding wheel should be selected.