In order to prevent the gearbox from not passing factory testing, one of the reasons is that the WPEDA40-70,WPEDA50-80,WPEDA60-100,WPEDA70-120,WPEDA80-135 gearbox has intermittent high noise; Tested with the ND6 fine sound level meter, the low noise reducer is 72.3Db (A), meeting the factory requirements; The high noise reducer is 82.5dB (A), which cannot meet the factory requirements.
After repeated testing, analysis, and innovative experiments, the conclusion drawn is that comprehensive management of all aspects of consumption is necessary in order to effectively reduce the noise of gear transmission.
1. The fundamental requirement for gear accuracy
After theoretical verification, the gear accuracy must be controlled within the GB10995-887-8 level, with a linear speed higher than 20m/s for gears. The tooth pitch limit fault, radial runout tolerance of the gear ring, and tooth orientation tolerance must definitely reach a stable accuracy of level 7. In the environment of reaching level 7 precision gears, the teeth should be reversed and the root protrusion should be strictly prevented.
2. Control the quality of raw materials
High quality raw materials are a condition for consuming high-quality products, and a certain company uses the largest amount of materials 40Cr and 45 steel to manufacture gears. Regardless of the route taken, the raw materials must undergo rigorous chemical identification, grain size determination, and purity evaluation upon arrival at the factory. Its goal is to adjust the deformation caused by heat treatment in real-time and improve the quality of tooth profile processing.
3. Prevention of heat treatment punishment deformation
After rough machining, the gear blank is transformed into a precision forging and subjected to normalizing or quenching and tempering treatment to achieve: (1) hardening of steel parts for cutting processing; (2) Eliminate residual stress; (3) Refine grain size and improve structure to enhance the mechanical function of steel; (4) Prepare structurally for ultimate punishment. It should be noted that in the punishment of normalizing or quenching and tempering, it is necessary to adhere to the uniform temperature of the furnace, as well as to accept station equipment, so that the workpiece is evenly heated and cooled, and it is strictly prohibited to stack them together. For gears that require drilling to increase the weight, the drilling sequence should be arranged after the heat treatment punishment.
The ultimate heat treatment punishment for gears accepts high-frequency quenching of tooth surfaces that cause less deformation of the parts; The lost tooth surface after high-frequency quenching has high strength, hardness, wear resistance, and fatigue limit, while the core still adheres to sufficient plasticity and toughness. To eliminate deformation. The high-frequency quenching of the tooth surface should accept lower quenching temperature and shorter heating time, uniform heating, and slow cooling.
4. The accuracy of the tube gear blank
The accuracy of the size of the gear hole is required to be set at the center difference of the hole's defect value, ranging from ± 0.003 to ± 0.005mm; If it exceeds the tolerance and falls within the scope of the hole plan requirements, it is necessary to classify and identify the transition to the gear cutting process.
The end face runout and radial runout of the gear blank are of level 6, set within the range of 0.01-0.02mm.
5. Gear cutting processing pace
Outsourced gear cutting tools must be inspected and must meet the AA level requirements. After grinding the gear cutting tool, it is necessary to check the radial nature of the front edge of the tool, the adjacent pitch difference of the chip groove, the maximum accumulated deviation of the chip groove pitch, and the parallelism between the back of the tool tooth and the axis of the inner hole.
Under the condition of not affecting gear strength, improve the tooth top height coefficient by increasing by 0.05-0.1m, improve the tool tooth top height coefficient, and prevent gear transmission tooth root interference. Gears with M=1-2 receive a tooth tip rounding cutter, with a rounding amount of R=0.1~0.15m. Eliminate burrs on the tooth top and improve the interference of the tooth top during gear transmission.
Gear cutting equipment needs to undergo an accuracy inspection once a year, and maintenance is necessary if it fails to meet the requirements. Operators should also conduct self checks frequently, especially when the radial clearance of the machine tool spindle is controlled below 0.01mm, the tool shaft diameter jumps below 0.005mm, and the tool shaft moves below 0.008mm.
Device accuracy of the tool: The radial runout of the tool is controlled below 0.003mm, and the end face runout is controlled below 0.004mm. The accuracy of the gear cutting fixture, the clearance between the outer diameter of the spindle and the workpiece hole, is within 0.001~0.004mm. The thread on the spindle must be ground by a thread machine under Class C positioning: verticality ≤ 0.003mm, radial runout ≤ 0.005mm. The nut must be clamped with the internal thread and the reference plane in one operation, and the parallelism of the washer should be ≤ 0.003mm.
6. Civilized consumption
More than 30% of gear transmission noise is caused by burrs and bumps. Some workshops take the initiative to remove burrs and bumps before disassembling gearboxes. The author advocates the following approach: (1) For gear shaft parts, after gear hobbing, immediately cover the teeth with a common plastic cover and proceed to the next process, and bring the common plastic cover into storage and shipment. (2) The honing process is carried out to reduce the roughness of the gear surface, remove burrs, and prevent bumps, effectively reducing the noise of gear transmission.
7. Acceptance of other materials and heat treatment punishment, appearance treatment punishment methods
(1) Powder metallurgy molding skills can be used, and the gear teeth can be high-frequency quenched after molding.
(2) Accept ductile iron, gear cutting and processing, and then carry out soft nitriding treatment punishment.
(3) After receiving 40Cr material and gear cutting work, accept the punishment of soft nitriding or copper plating on the teeth.
