Rotary cutting as an alternative method in the processing of electrical steel strip: Geometric and kinematic determination of the process setup

Abstract

Improving the efficiency in production is always the aim. In many applications, where progressive stamping approaches the technological limits, rotary cutting is successful. Relevant applications to name are the processing of paper, card boxes, packaging and simple perforated steel profiles. The main limiting factors of the stamping technology are the accelerations and decelerations in sheet feed and stamping motion. In contrast rotary cutting is a continuous process which leads to greater speeds and higher output. While performing the electrical steel strip between two cylindrical tools in stamp and die arrangement, the laminations are being cut out. Rotary cutting in the manufacture of laminations is a great challenge and a research topic at the Bavarian Technology Center for Electric Drives at the FAU. This paper provides the main technological differences between progressive stamping and rotary cutting regarding the process structure. Furthermore the geometric and technical parameters of the rotary cutting process are described mathematically. Finally the correlation of process parameters are identified.

Rotary Cutting of Electrical Steel Laminations – A Contrast to Traditional Stamping

“…The most important parameter is the circumferential speed vc, which results from the circumference d·π and the number of revolutions n. [4] = • •   By means of (4), the resulting speed in x-and y-direction can be calculated. All equations for the different speed components can be found in [3]. [4] Since the speed of the lower sheet surface is faster than the upper one, there is a sheet speed difference ∆vsheet [4].…”

“…Thus, the punch also describes cycloid curves on the steel strip. [4,5] According to Figure 1 and [3], the conventional stamping process differs significantly from rotary cutting process through the following points:…”

“…This value is varying during the cutting process and depends on the circle diameter d, the sheet thickness s, the angle of impact α and the entry angle β. According to [3], the immersion depth ∆y is: [4] …”

“…Thus, the length of line in action ls and length of the contour in action lc are getting small. [4] According to [3], the angle of impact for equal diameters is defined by (1). …”