Investigation into Hand Scraping: A Microanalysis

Abstract

Hand scraping is a manual surface finishing process that, despite its low productivity and high cost, is still applied in many industries because of its advantages concerning accuracy and tribology. In the presented microanalysis forces, movement patterns and tool orientation of individual hand scraping strokes were measured using a test stand, specifically designed for this purpose. It utilizes a camera, a three dimensional dynamometer, and an inertial measurement unit (IMU). The results show the basic characteristics of hand scraping. Typical courses of relevant quantities like cutting force, passive force, clearance, and directional angle are shown. In addition, the movement pattern of the tool during individual scraping strokes is analyzed. This research aims to contribute to a later implementation of automated scraping. The conducted research creates a base for future research regarding different scraping methods and achieved results.

Macroanalysis of Hand Scraping

“…In general, worker "S" applied higher cutting forces than worker "J" did. However, the forces were lower than those presented in [9] where the worker exceeded cutting forces of 100 N. Moreover, cutting forces of the "Western" scraping style seem to be lower than those used in the Japanese kisage scraping style presented by [8] where 300 N were exceeded in "rough cutting". However, kisage cutting forces are significantly reduced for the finishing passes, which cannot be observed in Figure 5.…”

“…Table 1 lists the main components of the test stand and their main specifications. In order to simultaneously acquire forces, positions and angles during scraping a special test stand was used as introduced in [9]. Apart from the camera, the setup is shown in Figure 2.…”

“…Additionally, characteristic values of the material ratio curves were calculated according to ISO 25178 [15] as depicted in Figure 3. As shown in [9], hand scraping is usually executed in individual rows as sequences of scraping strokes. Usually, the cutting direction takes place in an angle directional φ of 30° to 45° to the Figure 3.…”

“…As shown in [9], hand scraping is usually executed in individual rows as sequences of scraping strokes. Usually, the cutting direction takes place in an angle directional ϕ of 30 • to 45 • to the workpiece edge.…”

“…Fuji et al [8] provide an exhaustive insight into the motion patterns and cutting forces occurring in an Japanese scraping style, named "kisage". A respective investigation on the Western scraping style was presented by Oßwald et al [9] in a so called microanalysis. However, no research has been conducted yet on the processing strategy and procedure that workers use to work a surface.…”