In this paper, according to the characteristics of gear parts processing technology itself, combined with the experience summarized in the process of actual process planning, the main problems that should be paid attention to in the process planning of shaft gear parts are systematically introduced, as well as the determination of blank size and rough and fine machining of gear teeth in the process planning of gear parts. In this paper, the compilation process of the technological regulations for shaft gears is introduced, and the problems that should be paid attention to in the compilation process are described in detail.
1. Determination of Processing Technology for Shaft Gears
1. Determine gear blank
When determining the size of the blank, it is necessary to consider whether the processing allowance can meet the technological requirements, especially when carburizing and quenching gears and non-carburizing surfaces adopt the "allowance protection" method, the value of "allowance protection" should be taken into account.
2. Rough Machining Gears
The purpose of gear roughing is to remove the machining allowance, to determine the benchmark for semi-finishing, and to roughen the gear teeth at the same time. Gear roughing should select a good reference, the determination of the reference has a great influence on the distribution of processing allowance of each machined surface and the relative position of machined surface and non-machined surface.
When roughing, chemical heat treatment of parts - non-carburized surface protection methods in carburizing process should be considered. Generally, there are copper plating protection method and residual protection method. The former is non-carburized surface protected by copper plating, carburizing and quenching are carried out simultaneously, then the copper layer is removed, and there is no carbon layer on the copper plated part. The latter is to leave enough processing allowance on the non-carburized surface (greater than the depth of carburization), carburize completely when carburizing, then go to the carburized surface without carburizing, and then quench.
Rough processing chooses hobbing. When determining the thickness of hobbing indexing circular teeth, it is necessary to consider the carbon layer thinning during grinding. Generally, the one-sided grinding allowance is not more than 0.2mm. Because hobbing and grinding teeth are not based on the same processing standard, the jump of gear tooth profile should be limited in hobbing, so as to avoid the inconsistency of the remaining allowance during grinding, resulting in uneven penetration layer on the tooth surface and reducing the wear resistance of the tooth surface.
3 .Heat Treatment Gears
In order to meet the requirements of the design drawing, heat treatment is usually carried out after rough processing of gear body and gear teeth, such as carburizing, quenching, cyaniding and nitriding of gear teeth, in order to improve the mechanical properties of materials and meet the requirements of use. The gear of hydraulic pump is carburized and quenched.
4. Semi-finish Machining Gears
Semi-finishing mainly completes the processing of secondary surface and prepares for the finishing of main surface. Semi-finish machining mainly includes turning, grinding and revision of finishing benchmark. Carburizing and quenching of gear with residual protection in Carburizing and quenching are divided into two processes, in which the semi-finishing of removing residual protection is required.
5. Finishing Gears
The finishing of gears is divided into the finishing of the wheel body and the finishing of the gear teeth.
(1) Finishing of the wheel body. The finishing of gear wheel body mainly includes the finishing and finishing of Parts'precise surface, the rolling, inserting and broaching of internal and external splines on gears, the grinding, milling and turning of threads, the milling and inserting of keyway, the milling of process flat table, the drilling and reaming of alleviating holes, etc. These processes are mostly arranged before the finishing of bearing outer circle and gear teeth (grinding).
(2) Finishing of gear teeth. The accuracy of high precision gears is mostly 6-7 grades, the highest is 5 grades. According to the gear accuracy grade, grinding is often used in the finish machining of spur gear. When grinding teeth, appropriate cutting parameters should be selected to avoid grinding burns and cracks.
6 NDT
Nondestructive testing is generally required in gear design drawings. Gear parts are usually inspected by magnetic particle inspection. The process of magnetic particle inspection is usually arranged before the end of mechanical processing and final inspection.
7 Inspection Procedure
Inspection process plays an important role in ensuring product quality, finding waste products in time and stopping processing. In gear technological regulations, besides final inspection after all parts are processed, intermediate inspection is usually arranged:
(1) Before and after heat treatment and surface treatment by the parts sending unit;
(2) Some dimensions are not easy to measure after all the processing of gears. For example, the hollow slot in the inner hole of axle gears can be inspected in the middle after the processing of hollow slot, and this part of dimensions will not be inspected in the final inspection.
8 Surface Treatment Processes
After passing the gear inspection, in order to meet the requirements of anti-rust and wear resistance, the surface of gear should be treated by bluing, oxidizing phosphating, copper plating and silver plating to meet the requirements of anti-rust and wear resistance.