Seven Skills for Reducing Defects in Processing
In order to improve the performance of the mold, many manufacturers will carry out appropriate processing of their hardware molds. Precision hardware mold processing refers to the processing of forming and billet tools, in addition to shear and die cutting molds, but in many cases, the processing defects of precision hardware molds will also be reflected after processing, leading to the decline of mold performance. The following is to share with you about the content of seven skills of precision hardware mold processing to reduce defects, welcome to read!
Seven techniques of precision hardware mold processing to reduce defects:
1. Select and dress the grinding wheel, choose white corundum grinding wheel of medium size, its performance is hard and brittle, easy to produce new cutting edge, so the cutting force is small, the grinding heat is small, the granularity is moderate, the granularity is moderate, the grinding wheel hardness is medium soft and soft (ZR1, ZR2 and R1, R2), the granularity is moderate, can reduce the cutting heat.
It is very important to select the appropriate grinding wheel during fine grinding. For the condition of high vanadium and high molybdenum of die steel, GD single crystal corundum grinding wheel is more suitable. When processing hard alloy and materials with high quenching hardness, diamond grinding wheel with organic binder is used.
In the grinding process, pay attention to dressing the grinding wheel in time to keep the grinding wheel sharp. After the grinding wheel passivation, sliding and extrusion will occur on the workpiece surface, resulting in burn on the workpiece surface and reduced strength.
2, the rational use of cooling lubrication fluid, play the cooling, cleaning, lubrication three functions, keep the cooling lubrication clean, so as to control the grinding heat within the allowed range, prevent the workpiece thermal deformation. Improve the cooling conditions in grinding process, such as using the grinding wheel oil immersion or internal cooling grinding wheel, etc. The cutting fluid is injected into the center of the grinding wheel, and the cutting fluid enters the grinding area directly to play an effective cooling role and prevent the workpiece surface burn.
3, due to the quenching stress, mesh carbonization structure under the action of grinding force, under the action of grinding force, the workpiece structure phase change, easy to lead to cracks in the workpiece. In order to eliminate the residual stress produced in the grinding process and improve the toughness, the die needs to be aged at low temperature.
4, eliminate grinding stress, can also make the mold in 260~315℃ salt bath 1.5min,30℃ oil cooling, reduce the hardness of 1HRC, reduce the residual stress 40%~65%.
5. For precision grinding dies with dimensional tolerance within 0.01mm, attention should be paid to the influence of environmental temperature, and constant temperature grinding is required. According to the calculation, when the temperature difference is 3℃, the material will change 10.8μm on the 300mm steel (10.8=1.2×3×3, the deformation per 100mm is 1.2μm/℃). Each finishing procedure should fully consider the influence of this factor.
6, the use of electrolytic grinding to improve the mold manufacturing precision and surface quality. Electrolytic grinding, grinding wheel scraping oxide film: general surface roughness is better than Ra0.16μm, grinding wheel grinding force is small, grinding temperature is low, no burr, crack, burn phenomenon, general surface roughness is better than Ra0.16μm; In addition, the abrasion degree of grinding wheel is also small, such as grinding hard alloy, the abrasion degree of grinding wheel is only 50%~100%.
7, reasonable selection of grinding amount, using radial feed less or even fine grinding way. By appropriately reducing radial feed, grinding wheel speed, increasing axial feed and other measures, the contact area between grinding wheel and workpiece can be reduced, heat dissipation conditions can be improved, so as to effectively control the rise of surface temperature.