Abstract

The structure and the cavity surface hardened steel mold of automobile cover is very complex. In the stamping process, the local structure bears higher extrusion stress than the type surface, which often causes local wear and even cracking. The process of multi-hardness splicing joint is applied to ensure the service life of the die according to the features of each part of the mold. The impact load caused by the repeatedly cutting in which always leads to the unevenness of cutting force in the whole process. The machining quality of the mold surface is reduced. Aiming at the ball-end milling process in mold splicing area, first, the impact behavior of tool workpiece cutting contact is analyzed. A prediction model for ball-end milling force in the splicing area is established by establishing the transient chip thickness model which considering the impact factors. Second, the experiment of cutting force measurement for Cr12MoV mold steel ball-end milling which is based on single hardness and multi-hardness are carried out to verify the model. Cross-correlation analysis based on data of milling force signal and machined surface roughness is carried out for getting the relevance of them in different processing states. Finally, the ApEn is used to analyze the nonlinear characteristics of the milling force signal at the multi-hardness splicing state. This explores the influence of the milling force on the machining quality. The experimental and analytical results show that the milling force signal exhibits more obvious chaotic characteristics in the multi-hardness stitching area than that in the single hardness region. This provides a basis for improving workpiece surface quality and improving cutting efficiency.

摘要

汽车覆盖件的结构和型腔表面硬化钢模具非常复杂。在冲压过程中，局部结构比型面承受更高的挤压应力，往往会造成局部磨损甚至开裂。根据模具各部分的特点，采用多硬度拼接工艺，保证模具的使用寿命。反复切削所产生的冲击载荷，往往导致整个过程中切削力的不均匀。降低模具表面的加工质量。针对模具拼接区球头铣削过程，首先分析了刀具工件切削接触的冲击行为。通过建立考虑影响因素的瞬态切屑厚度模型，建立了拼接区球头铣削力的预测模型。其次，进行了基于单硬度和多硬度的Cr12MoV模具钢球头铣削切削力测量实验，对模型进行了验证。基于铣削力信号和加工表面粗糙度数据进行互相关分析，得到它们在不同加工状态下的相关性。最后，利用ApEn分析多硬度拼接状态下铣削力信号的非线性特性。这探讨了铣削力对加工质量的影响。实验和分析结果表明，铣削力信号在多硬度缝合区域比在单一硬度区域表现出更明显的混沌特征。这为提高工件表面质量和提高切削效率提供了依据。