Hsiang S, McGorry R, Bezverkhny I
Liberty Mutual Research Center for Safety and Health, Hopkinton, MA 01746, USA.
Ergonomics. 1997 Apr;40(4):476-90. doi: 10.1080/001401397188107.
Knives are used in industry, and particularly on meat packaging assembly lines, where a premium is placed on the speed of cutting. One consequence of this is that knife design and selection has been based on the speed of cutting as the most significant measure of a knife. In industry the cuts that knives make vary in difficulty with many factors such as thickness, contour, and temperature of the material being cut. These factors may change the speed with which these cuts are made. According to Taguchi's methods, a robust design is one that maintains high performance while remaining insensitive to changes in its environment. This means that a robust knife design would enable an employee to cut not only with as much speed as possible in one particular cutting scenario, but also with a consistently high speed in as many cutting scenarios as possible. An experiment with various knife designs was evaluated with Taguchi's method. Ten subjects cut outlined clay patterns in 15 min with each one of nine different knives. The nine different designs were generated from the following combinations; three grip sizes (44.4, 50.8 and 63.5 mm), three coupling angles between the grip and the blade (0, 45 and 90 degrees), three blade heights measured from the middle of the blade (10, 13 and 15 mm), and three blade lengths (85, 125 and 155 mm). Eight conditions of cutting material were used to generate 'noise'. They are combinations of temperature of the clay to be cut (from temperature (R) approximately 25 degrees C, frozen for 1 h (F) approximately 5 degrees C), thickness of the clay to be cut (15 and 25 mm), and orientation of the work surface (0 and 30 degrees). The result shows that the knife design of 63.5 mm grip size, 0 degree coupling angle, 13 mm blade height, and 85 mm blade length provides the highest number of cuts, the knife design of 50.8 mm grip size, 45 degrees coupling angle, 15 mm blade height, and 85 mm blade length gives the highest signal to noise ratio. The shorter blade (85 mm) is suggested by both designs, but the two designs are different in the other three variables. Further analysis of the noise variables shows that lowering clay temperature significantly reduces cutting speed. Although there is more than one design that can resolve changes in clay thickness and clay orientation, a 15 mm blade height is the only design insensitive to the clay temperature change.
刀具在工业中使用，尤其是在肉类包装流水线上，在这些地方，切割速度至关重要。由此带来的一个结果是，刀具的设计和选择一直以切割速度作为衡量刀具的最重要指标。在工业中，刀具进行的切割因多种因素而难度各异，比如被切割材料的厚度、轮廓和温度。这些因素可能会改变切割的速度。根据田口方法，稳健设计是指在保持高性能的同时，对其环境变化不敏感。这意味着稳健的刀具设计能使员工不仅在一种特定切割场景中尽可能快地切割，而且在尽可能多的切割场景中都能保持持续的高速切割。用田口方法对各种刀具设计进行了一项实验。十名受试者用九种不同刀具中的每一种在15分钟内切割勾勒出的黏土模型。这九种不同设计由以下组合产生：三种握把尺寸（44.4、50.8和63.5毫米）、握把与刀片之间的三种连接角度（0、45和90度）、从刀片中部测量的三种刀片高度（10、13和15毫米）以及三种刀片长度（85、125和155毫米）。使用八种切割材料条件来产生“噪声”。它们是待切割黏土的温度（从约25摄氏度（R）、冷冻1小时（F）约5摄氏度）、待切割黏土的厚度（15和25毫米）以及工作面方向（0和30度）的组合。结果表明，握把尺寸为63.5毫米、连接角度为0度、刀片高度为13毫米且刀片长度为85毫米的刀具设计切割次数最多，握把尺寸为50.8毫米、连接角度为45度、刀片高度为15毫米且刀片长度为85毫米的刀具设计信噪比最高。两种设计都表明较短的刀片（85毫米）较为合适，但在其他三个变量方面两种设计有所不同。对噪声变量的进一步分析表明，降低黏土温度会显著降低切割速度。虽然有不止一种设计可以解决黏土厚度和黏土方向的变化，但15毫米的刀片高度是唯一对黏土温度变化不敏感的设计。
