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Abstract
’ Martensitic stainless steel is used in several applications including the manufacturing of scalpels,
doctor blades, kitchen knives, cutters, and razor blades. Thin sheets of the appropriate material are first hardened and tempered to get the right hardness and strength. Edges of the hardened and tempered strips are then sharpened using one or more grinding processes. The width of ground facet in some applications (e.g. razor blades) can be as small as 50 JIm.
In case of razor blades, the sharpened edge is polished and coated with a special Teflon film.
Roughness of ground surfaces (edge facets) depends on several factors such as; grinding wheel characteristics, (e.g. abrasive type, grain size, wheel grade, structure, and bond), grinding
, parameters (e.g. speed, feed ,depth of cut and cooling), machine condition, and material . characteristics. In this study, the surface roughness of micro ground edge facets of razor blades is considered. Standard razor blades are produced from a hardened and tempered martensitic
stainless strip 0.1 rom thick and 22.4 rom wide.
This study is mainly devoted to the improvement of surface roughness through optimization and
control of process parameters. Experimental work, based on the design of experiments method, is used to study the influence of operating variables (process parameters) of the grinding process on the surface quality of blade edge facets. The selected parameters were set at specified values (levels) and the effect of the change in these parameters on the produced razor blades surface quality is evaluated. The experimental work was carried out on a razor blade grind line at Lord
Precision Industries in Alexandria.
In this investigation, three main process parameters are considered. These are the abrasive grain
size (M), the grinding wheel speed (Vs), and coolant flow rate (Q). The product quality characteristics considered include, surface roughness values (Ra, Rz), surface roughness profile,
smface texture, and adhesion characteristics of the Teflon film.
The investigation proved that, through using the design of experiments approach, it is possible to
improve the surface quality in grinding of razor blade edges.
Through monitoring and control of wheel speed, coolant flow rate, and the right choice of the
grinding wheel abrasive characteristic, it was possible to improve facets roughness and adhesion
characteristics.
Additionally, problems associated with edge profile (e.g. notches, scratches, poor profile), have
also been resolved.