Methods of reducing gear noise of radial drilling machine

In order to prevent the radial drilling machine from failing the factory test, one of the reasons is that the radial drilling machine has intermittent high noise; tested with the ND6 precision sound level meter, the low noise radial drilling machine is 72.3Db(A), which meets the factory requirements; The high noise radial drilling machine is 82.5dB(A), which cannot meet the factory requirements. After repeated testing, analysis and improvement experiments, the conclusion is that all aspects of production must be comprehensively treated in order to effectively reduce the noise of gear transmission.

1. Control the accuracy of gears: Basic requirements for gear accuracy: It has been verified by practice that the gear accuracy must be controlled at GB10995-887~8 grade, the linear speed is higher than 20m/s gear, the limit deviation of the tooth pitch, the radial runout tolerance of the ring gear, The tooth direction tolerance must be stable and reach grade 7 accuracy. In the case of reaching the level 7 precision gear, the tooth part should be reversed, and the tooth root boss should be strictly prevented.

2. Control the quality of raw materials: High-quality raw materials are the precondition for producing high-quality products. Our company's most used materials are 40Cr and 45 steel to manufacture gears. No matter what way, the raw materials must undergo strict chemical composition inspection, grain size determination, and purity evaluation after they arrive at the factory. The purpose is to adjust the heat treatment deformation in time and improve the quality of the tooth profile processing.

3. Prevent heat treatment deformation: After rough machining, the tooth blank is turned into a fine forging, which is normalized or quenched and tempered to achieve:

(1) Softening steel parts for cutting;

(2) Eliminate residual stress;

(3) Refine the grain and improve the structure to improve the mechanical properties of the steel;

(4) Prepare organizationally for eventual handling. It should be noted that during normalizing or quenching and tempering, it is necessary to keep the furnace temperature uniform, and use station appliances to heat and cool the workpieces evenly, and it is strictly forbidden to stack them together. For gears that need to be drilled to reduce weight, the drilling sequence should be arranged after heat treatment. The final heat treatment of the gear adopts high-frequency quenching of the tooth surface which makes the deformation of the part smaller; the tooth surface obtained after high-frequency quenching has high strength, hardness, wear resistance and fatigue limit, while the core still maintains sufficient plasticity and toughness. to reduce deformation. High frequency quenching of tooth surface should adopt lower quenching temperature and short heating time, uniform heating and slow cooling.

4. Guarantee the accuracy of the gear blank: The accuracy of the size of the gear hole is required to be distributed around the middle difference of the deviation value of the hole, which is set at ±0.003~±0.005mm; if it is out of tolerance and within the design requirements of the hole, it must be classified , respectively transfer to the tooth cutting process. The end face runout and radial runout of the gear blank are grade 6, which is set in the range of 0.01~0.02mm.

5. Gear cutting processing measures: The purchased gear cutting tools must be inspected and must meet the AA level requirements. After the gear cutter is sharpened, the radiality of the front face of the tool, the adjacent circumferential pitch difference of the chip flute, the maximum accumulated error of the circumferential pitch of the chip flute, and the parallelism of the front face of the cutter tooth and the inner hole axis must be checked. On the premise of not affecting the strength of the gear, increase the addendum height coefficient by 0.05~0.1m, to improve the tool addendum height coefficient and avoid gear drive tooth root interference. For gears of M=1~2, the tooth top rounding hob is used, and the rounding amount is R=0.1~0.15m. Eliminate tooth top burrs and improve tooth top interference during gear transmission. Gear cutting equipment should be checked for accuracy once a year, and repairs must be carried out if it fails to meet the requirements. The operator should also carry out self-inspection frequently, especially when the radial clearance of the machine tool spindle is controlled below 0.01mm, the diameter of the tool shaft is below 0.005mm, and the movement of the tool shaft is below 0.008mm. The installation accuracy of the tool: the radial runout of the tool is controlled below 0.003mm, and the end face runout is below 0.004mm. Gear cutting tooling accuracy, the gap between the outer diameter of the mandrel and the workpiece hole is guaranteed to be within 0.001~0.004mm. The thread on the mandrel must be ground by the thread bed under the C-top positioning: verticality ≤ 0.003mm, radial runout ≤ 0.005mm. The nut must ensure that the internal thread and the reference surface are clamped and turned at one time, and the parallelism of the washer is less than or equal to 0.003mm.

6. Civilized production: more than 30% of gear transmission noise comes from burrs and bumps. Some factories remove burrs and bumps before the gearbox is assembled, which is a passive approach. (1) For gear shaft parts, after hobbing, the teeth are immediately put on a special plastic protective cover and then transferred to the next process, and the special plastic protective cover is put into storage and shipped. (2) Carry out the honing process to reduce the roughness of the tooth surface, remove the burrs, and prevent bumps, which can effectively reduce the gear transmission noise.

7. Other materials and heat treatment and surface treatment methods are adopted: (1) Powder metallurgy forming technology can be used, and the tooth portion of the gear can be subjected to high frequency quenching after forming. (2) Graphite cast iron is used, and after gear cutting, soft nitriding treatment is performed. (3) Using 40Cr material, after gear cutting work, use soft nitriding treatment or tooth copper plating treatment. To sum up, in order to eliminate gear transmission noise, gear materials and heat treatment are essential, gear blank accuracy is the guarantee, gear accuracy is the key, and civilized production is the foundation.