Ⅰ. Ensuring the quality of raw materials

The materials commonly used for manufacturing gears are 40Cr, 20CrMnTi, 40CrNi and other alloy steels and 45 steel. In order to ensure the quality of raw materials, we adopt the method of fixed point purchase, the purpose of which is to facilitate timely adjustment of heat treatment process, control heat treatment deformation and improve the quality of tooth processing.

II. Prevention of heat treatment deformation

After rough machining or finishing forging, the tooth billet must be normalized to eliminate internal residual stress; normalization or tempering treatment, must maintain the uniformity of the furnace temperature, while using the station fixture, so that the workpiece is uniformly heated and cooled; try to use cyanide treatment, which is lower than the carburizing quenching temperature, small deformation, and cheaper than nitriding or carburizing, for cyanide treatment equipment, must be used to drip-feed UNIC gas carburizing nitriding furnace; part of the high-frequency quenching and cyanide treatment of gears can also be converted to soft nitriding process, in order to obtain high hardness values and thicker white bright layer.

III. Improving the machining accuracy of tooth blanks

(1) improve the machining accuracy of the gear hole: gear hole size accuracy, shall be distributed around the middle of the deviation value of the hole, generally set at ± 0.003 ~ ± 0.005mm, if the excess difference and within the design requirements of the hole, must be transferred to the gear cutting process respectively, in order to take measures; at the same time, the straightness of the hole must be controlled within 0.003mm.

(2) control the billet end runout and radial runout: the billet end runout is the item that directly affects the tooth to tolerance, when processing the two end faces of the billet, must ensure that the parallelism is within 0.01mm, and then fine boring on the tooling to ensure the hole to the end runout tolerance; when cutting the tooth, must be 100% rounding by the table, to ensure the radial runout tolerance of the tooth ring.

IV. Measures in tooth cutting process

(1) Gear tools: ① All the gear tools purchased are inspected and must meet the requirements of AA grade, and gear tools that fail to meet the requirements must all be finely sharpened.

②The gear tools are all titanium plated to improve tool durability, improve wear on the top part of the tool teeth and prevent excessive rounding of the gear roots.

③ Gears with m=0.3~0.8 use top cutting hob; gears with m=1~2 use tooth top rounding hob, rounding amount R=0.1m~0.15m.

④Improve tooth top interference during gearing by increasing the tooth top height factor by (0.05 to 0.1) m without affecting the strength of the gear; improve the tool tooth top durability to avoid tooth root interference during gearing.

(2) gear-cutting process: ① gear-cutting equipment by the motorized office once a year to check the accuracy of the failure to meet the requirements must be overhauled, especially the machine tool spindle radial clearance must be controlled at 0.01mm or less, tool shaft diameter jump 0.005mm or less, tool shaft runout 0.008mm or less, tool diameter jump control at 0.003mm or less, end jump 0.004mm or less.

②The clearance between the outer diameter of the mandrel of the gear-cutting tool and the hole of the workpiece must be ensured within 0.001-0.004mm; the threads on the mandrel must be positioned under the two tops and ground by the thread grinder to ensure a perpendicularity of ≤0.003mm and a diameter jump of ≤0.005mm; the workpiece and the tightening nut must ensure that the inner threads and the reference surface are clamped and turned at once, and the parallelism of the washers must also be ≤0.003mm.

③The machined gear parts must be measured by a dedicated inspector for the items Fw, Fr, Fi″, fi″, Fβ and Ff.

V. Processing after heat treatment

(1) For soft nitriding and high-frequency quenching of gear holes in the teeth, the method of releasing the quantity before heat treatment and then researching the holes after heat treatment is used to ensure machining accuracy and reduce production costs.

(2) For cyanide-treated gear holes, all holes are ground using the indexing circle positioning and Archimedes helix locking process.

VI. Insist on civilized production

According to information, more than 30% of gear transmission noise is caused by burrs and knocks. In order to solve this problem, we have taken the following measures: all gear parts are transferred using station jigs after machining; after gear shaft parts are hobbed, they are immediately transferred to the next process with plastic tubes and shipped with plastic sleeves; cyanide treated gear parts are subject to liquid sandblasting treatment and a simultaneous honing process to remove burrs and improve the surface roughness and machining accuracy of the tooth surfaces.

As a result of the effective measures, the unit produced by the military, civilian gearboxes in each delivery inspection, gear transmission noise indicators are all up to standard, the general praise of the user side. After years of mass production practice has proved that these measures are desirable, the effect is obvious.