First, the process analysis of shaft parts
Precision forming technology is used to replace traditional cutting technology. Because the gear in the reduction shaft not only bears great instantaneous bearing capacity, but also has centering function, it requires high coaxiality and mechanical strength, and plastic forming is difficult, so effective technological measures need to be taken. According to the structural characteristics of the parts, we determined the technological process of the reducer shaft as follows: blanking → peeling → spheroidizing annealing → positive extrusion → upsetting → tooth forming → finished product.
Second, the mold design and manufacture
Because the precision of precision forming parts depends on the precision of the forming die, the design of the die should not only formulate a reasonable forming process scheme, but also comprehensively consider the follow-up process and other matters according to the structural characteristics and precision requirements of the parts. The designed die not only requires simple and practical structure, easy replacement, but also convenient manufacture. The female die bears almost all the extrusion force, which can be dispersed among the stress circles of each layer to avoid collapse failure caused by stress concentration. In order to meet the requirements of long life and high precision of the die, the die should be made of materials with high strength, wear resistance and small deformation.
Third, the choice of strong shrinkage molding oil
Due to the poor plasticity and high strength of the materials used in shaft parts, attention should be paid to the properties of the oil when selecting the cold heading forming oil for precision cold heading. The extreme pressure and anti-wear performance of strong shrinkage molding oil is not enough. In this process, the oil film breaks under the action of high temperature and high pressure, and the punch directly contacts with the die, causing damage. The solution is to add vulcanizing extreme pressure agent to the existing formula system according to the engineer's suggestion; Or use special strong shrinkage molding oil to replace non-special oil products such as rapeseed oil and engine oil.
Four, process test and mass production
(1) blank annealing In order to reduce the deformation resistance of the blank and improve the plasticity of the metal material, it is necessary to properly anneal the blank before forming to improve the internal structure of the metal blank.
(2) The blank preparation determines the blank blanking size according to the principle that the size and shape of the product parts and the metal volume are unchanged. Through a series of methods such as forward extrusion, upsetting and reducing extrusion, the blank is made into a blank with a similar shape to the finished product.
(3) Lubrication of the blank The lubrication of the blank surface is an important process of plastic forming. The surface lubrication of blank has great influence on the surface quality of formed parts and the life of die. When the metal is plastically deformed with special cold heading oil, the friction resistance can be greatly reduced, the service life of the die can be prolonged, the surface roughness of the formed parts can be reduced, and the use requirements of the plastic net forming process can be met.
(4) During the process test and batch production process test, the mold should be carefully assembled to ensure the dimensional accuracy of the formed parts. After repeated process tests, the process parameters were improved in time, and all the indexes of the reduction shaft manufactured by precision forming met the requirements.