Control of mechanical load in milling process

This is the third article in a series discussing the application of metal cutting tools and the loads generated during the machining process. The first article focused on basic metal cutting concepts in turning operations, as well as the relationship between tool geometry, feed rate, and mechanical loads. The second article analyzed the impact of tool positioning and tool path on mechanical loads in milling operations. This article continues to explore milling and explains how the selection of tools and cutting parameters affects the generation, absorption, and control of heat in interrupted cutting conditions typical of milling operations.

The Heat Challenge: Metal cutting generates temperatures as high as 800 to 900 degrees Celsius in the cutting zone, where the cutting edge deforms and removes the workpiece material. In continuous turning operations, heat is generated in a steady, linear manner. In contrast, the teeth of a milling cutter intermittently engage and disengage with the workpiece material, causing the temperature of the cutting edge to alternately rise and fall.

The components of the machining system absorb the heat generated during metal cutting. Typically, 10% of the heat goes into the workpiece, 80% into the chips, and 10% into the tool. Ideally, the majority of the heat is carried away by the chips, as high temperatures can shorten tool life and damage the machined parts.

The different thermal conductivities of workpiece materials and other machining factors can significantly affect the distribution of heat. For example, high-temperature alloys have poor thermal conductivity. When machining workpieces with poor thermal conductivity, the amount of heat transferred to the tool increases. Additionally, machining harder materials generates more heat than machining softer materials. In general, higher cutting speeds increase heat generation, while higher feed rates enlarge the area of the cutting edge affected by high temperatures. Dual-spindle machining center.