W O R K S H O P
AN INCREDIBLY
SIMPLE PRINCIPLE –
THE SECRET BEHIND
Y-AXIS PARTING
The Y-axis option has broadened the possibilities
to use rotating tools in multi-task machines and
turning centres. Now, this capability has inspired a
great innovation in one of the original missions of
these machine tool types: Y-axis parting.
Implementing this new tool and method brings
significant machining improvements in potentially
any parting operation.
Adding rotating tools to turning centres means
you can combine several set-ups in a single
machine for a more streamlined and productive
machining process. To accomplish this, turn-mill
machines were introduced in the 1990s. The initial
idea was to enable driving a milling cutter, drill or
threading tap on one or more tool positions in the
turret to eliminate limitations of polar interpolation
and other related programming difficulties. To
improve reach, an extra set of ways was added
to move the rotating tool across the spindle face.
This was accomplished by mounting the tools on
revolver sides or on its face, by installing the Y-axis
ways on a slanted bed or by using an independent
milling head. Both machine tool makers and
manufacturers soon recognised the benefits of
integrating both milling and turning operations.
Today, the Y-axis option has become a standard
THE FORCE CALCULATION PRINCIPLE BEHIND Y-AXIS PARTING.
WHILE CONVENTIONAL
PARTING
OFF TOOLS ALIGN
WITH THE X-AXIS
OF THE MACHINE
TOOL, THE Y-AXIS
TOOL HAS SIMPLY
BEEN ROTATED 90°
ANTI-CLOCKWISE
TO ALIGN WITH THE
Y-AXIS.
feature in most multi-task machines and optional
in many new turning centres.
As a potential tool breakage risks leading to costly
machine downtime or scrapped components,
parting off is a stage of the machining process
where manufacturers don't compromise on security.
To meet the high demands put on these type
of tools, the system CoroCut QD was developed
by Sandvik Coromant in 2013. While considering
how to improve this high-performing system even
further, the tool developers started looking at
these modern machines with Y-axis capacity. This
resulted in an innovation that involved more than
just the tool design but also a completely new
method: Y-axis parting.
THE Y-AXIS PARTING PRINCIPLE
The principle behind Y-axis parting is incredibly
simple. While conventional parting off tools align
with the X-axis of the machine tool, the Y-axis
tool has simply been rotated 90° anti-clockwise
to align with the Y-axis. In a conventional tool
configuration, the relatively long and slender
parting blade and holder is fed at a 90° angle into
the rotating workpiece. The largest cutting force
is generated by the cutting speed and the rest
by feed motion. The consequence is a resultant
force vector that is directed diagonally into the
tool at an angle of roughly 30°, in other words
across a very weak section of the blade. To avoid
tool breakage, this is compensated by reducing
the blade overhang and by increasing the blade
height, which in turn sometimes compromises
the usability of the tool. By turning the tip seat
90 degrees and utilising the Y-axis, the tool can
cut its way into the workpiece essentially with its
front end, which nearly aligns the resulting cutting
force vector with the longitudinal axis of the blade.
FEM analyses performed by the Sandvik Coromant
R&D team confirmed that the new solution
eliminates critical stresses and increases the
blade stiffness by more than six times compared
to conventional blade design.
To put it short; when switching to parting in the
Y-axis plane you get a beneficial direction of
the cutting force resulting in less instability and
vibration. This means you can ramp up feed rate
without losing stability or breaking the tool for an
extremely secure and productive parting process.
Simple as that.
42 May 2018