Improving the high-speed finishing of forming tools for advanced high-strength steels (AHSS)

Forming tools manufacturers have extensively incorporated high-speed milling technology for the finishing of large punch or die tools. The main objective is to achieve a good surface quality directly form machining, without any additional, tedious, manual work. Currently, new advanced high-strength steels (AHSS) are being used for car body parts. In this case, there are two special changes related to the forming tools: a higher proportion of harder surfaces on the working area, and long try-out iterations, due to their great springback. Tempered surfaces and insert blocks harder than 60 HRC are needed to withstand the forming charges with a good working life expectancy. From this, two problems arise with regards to high-speed finishing: first, the deflection of the tool due to the cutting forces, which can produce unacceptable dimensional errors; and second, in the same finishing operation, zones with sharp changes in hardness must be machined with the same CNC program and cutting tool.