Dimensional and Geometric Deviations Induced by Milling of Annealed and Hardened AISI H13 Tool Steel

José Luiz S Ribeiro,Juan Carlos Campos Rubio,Alexandre M Abrão,Steve B Diniz

doi:10.5923/j.materials.20120201.03

José Luiz S Ribeiro, Juan Carlos Campos Rubio + Show 2 more

Open Access

https://doi.org/10.5923/j.materials.20120201.03

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Abstract

The principal goal of this paper was to investigate the influence of tool grade, cutting speed and feed rate on the dimensional (length, diameter and radius) and geometric (parallelism and angularity) deviations obtained after milling AISI H13 hot work die steel in both annealed and hardened conditions using three indexable insert grades: two coated tungsten carbides tools and one cermet tool. The results indicated that lower dimensional deviations were obtained for the external features when up-milling the softer material. Tool grade did not seem to drastically affect external dimensional errors. The dimensional deviations for the internal features were lower when up-milling the hardened steel. The cermet tool was re- sponsible for tighter tolerances when milling the annealed steel, whereas the PVD-coated tungsten carbide tool gave the best results when machining the hardened steel. The parallelism results indicated that tighter tolerances were obtained when milling with the PVD-coated carbide tool. Finally, the angular deviation was lower when down-milling the annealed material with the cermet tool.

Highlights

The quality of moulds and dies subjected to milling is critical to the final cost of these products due to the influence of milling on subsequent finishing and polishing operations
The results indicated that the milling force components tended to decrease as the rake angle was elevated; it appeared that the helix angle should not exceed 45–50° when cutting hardened materials to avoid an increase in the force components
The results indicated that the dimensional deviations increased with feed speed, the findings concerning the type of fixture were not conclusive

Summary

Introduction

The quality of moulds and dies subjected to milling is critical to the final cost of these products due to the influence of milling on subsequent finishing and polishing operations. Better quality rough and semi-finish milling operations result in shorter finishing and polishing cycles and lower manufacturing costs. Toh[1] presented a survey of the principal strategies used to optimise both productivity and surface quality when milling hardened die and mould materials at high speeds. Contour milling is the most common approach employed when roughing to achieve higher metal removal rates associated with less machining time. A number of factors must be taken into account, such as mould or die features, cutter geometry, the radial depth of cut and the cutter path strategy. The use of adaptive machining to maintain a consistent cutting load by changing cutting speed and feed rates may result in an improved surface finish, longer tool life and higher productivity

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