摘要: Tool deflection is severe in the micro milling process with flexible tools. Existing models usually predicted the machining errors caused by tool deflection through time-consuming iteration algorithms. This article presents an efficient method to predict the machining errors caused by tool deflection in the side-wall milling process. The concept of equivalent modulus is proposed to describe the tool deflection behavior under cutting loads. It is found that the radial cutting force at the immersion angle of π is the actual cause of the machining errors. To describe the influence of instantaneous actual cutting direction shifts in the down milling process with flexible tools, the cutter is regarded as pressing into the workpiece during the cutting process, and the total cutting load is regarded as the combination of cutting forces and the press force. The material piling up and strain hardening is included in this model. Verifications show that the proposed model can greatly save the computational time without losing prediction accuracy.