Evaluation of cutter path strategies and orientations when high speed milling hardened AISI H13 work tool steel
The use of High Speed Milling (HSM) for the production of moulds and dies is becoming
more widespread. Critical aspects of the technology include cutting tools, machinability data,
cutter path generation and technology. Much published information exists on cutting tools and
related data (cutting speeds, feed rates, depths of cut, etc.), however, relatively little
information has been published on the evaluation of cutter paths for this application.
Most of the research work is mainly focused on cutter path generation techniques. Works with
regard to cutter path evaluation on tool wear and tool life, surface integrity and relevant
workpiece machinability characteristics are scant. Therefore, a detailed knowledge on the
evaluation of cutter path strategies and orientations when high speed rough and finish milling
is essential in order to improve productivity and surface quality respectively. The present
work deals with some aspects related to the evaluation on the machinabiltiy of hardened AISI
H13 hot work tool steel of 52 Rockwell Hardness C scale when high speed rough and finish
milling using designated cutter path strategies and orientations.
A literature review has been carried out to identify the various geometrical forms that are
commonly utilised and common cutter path strategies presently employed in the mould and
die industries. A review on the cutter path strategies and techniques is identified and classified
according to the rough or finish milling stage. The selection and evaluation techniques
notably feed rate, cutting tools and cutter path strategies and orientations are presented.
Machinability criteria in terms of tool life and tool wear, cutting forces, tool wear and
vibration signatures, cutting temperature and chip formation are reviewed. Last but not the
least, surface integrity analysis on machined hardened steels are detailed and reviewed.
The experimental work was divided into three phases. The first phase dealt with the
investigation by employing high axial depths of cut (10 mm < Ai <20 mm) on three main
cutter path strategies when rough milling hardened steels. In the second phase, the spotlight of
the research was on finish milling an inclined workpiece surface using different cutter path
orientations through machinability assessments in order to identify the optimum cutter path
orientation. In the final phase, the effect of various cutter path orientations on workpiece
surface integrity when finish milling hardened steels was investigated.
The experimental results for Phase 1 revealed that in general where higher material removal
rates, shorter machining time, longer tool life and higher volume of metal removed were of
concern, raster cutter path strategy was the most favourable at all axial depths of cut
employed. In Phase 2 when finish milling at an inclined workpiece angle of 75 0, tool life was
highest when employing a downward cutter path orientation. On the other hand, upward cutter
path orientation would be preferred where low workpiece surface roughness was concerned.
In the final phase, surface integrity analysis revealed that upward cutter path orientation in
particular the single direction raster vertical upward orientation was the most preferred in
achieving optimum component life.