High Speed Machining Precision Tooling - Indobiz.biz

ecipe for manufacturing indexable
carbide inserts that deliver the desired
performance characteristics is a function
of the ratios among base components. In
its simplest form, to increase an insert’s
toughness (its resistance to fracture), the
binder content-to-powder ratio is raised.
To create a harder cutting material, the
ratio is lowered, with more powder and
less binder, which vmakes the cutter
grades of carbide substrates refl ect
a sliding scale between the extremes
of toughness and hardness, which are
matched to a given application.
Mixing the binder and powder is a
critical step in the manufacture of
indexable insert tools. Like a “heat”
in steel production, each batch of the
recipe for a given base grade is carefully
controlled for consistency.
After mixing, the “batter” is pressed
into a shape. The pressing process
uses insert molds to impart the insert
shape and some of the geometry, such
as chipbreakers, onto the now “green”
insert.
In addition to the conventional pressing
technology used by most insert
producers, there is a successfully
developed method of injection molding
inserts as well. This gives the user the
ability to mold complex inserts much
closer to a fi nal shape and complete
forms that would be almost impossible
by conventional technology. In turn, it
reduces the amount of grinding required
to achieve a fi nished geometry and
speeds the throughput.
The details of this process are
proprietary, but consist basically of
adding a compound to the binder/
powder mix so it can fl ow under pressure
through gates into a closed mold cavity.
This fl owable material is also extruded
into tooling blanks that become the basis
for some of the company’s solid carbide
products. In the next manufacturing
step, which is sintering, this additional
compound vaporizes leaving no trace in
the fi nal insert grade.
Sintering is the last processing step
before a green insert blank becomes
the rugged carbide substrate that shops
are familiar with. Using the cake-baking
analogy, this step represents the oven.
Under a vacuum at high temperature, the
green insert is heated until the binder
plasticizes, enabling it to fl ow around
the grains of powder fi lling the voids.
Upon cooling, the binder and grains are
chemically and physically linked into a
uniform matrix.
On The Shop Floor
Out of the oven, the inserts are ready
to be machined to their fi nal shapes,
geometry and precision. The shop fl oor
refl ects this rationalization concept.
The grinding department is arranged
in rows of autonomous cells. Four of
these cells are operated by one person.
Each cell is built around a DMG milling
machine converted to grind inserts. In
the machine spindle, an arbor is used
to hold various superabrasive wheels
and brushes allowing all of the grinding
operations to be performed in sequence
without changing wheels.
An automated load/unload system shall
be designed and feeds the machine
tools. As a fi nished insert is removed
from the work zone, it passes through a
laser gaging system that checks critical
dimensions. This cellular concept is
duplicated at every manufacturing
company nowadays.
While the cells are not dedicated to a
specifi c cutting tool product, they are
tooled to accommodate like families
of inserts. It should have several types
of cells to accommodate various insert
parameters. The production schedule is
made up to run similar jobs sequentially,
which simplifi es change-over from one
insert to another. Generally, only the
material handling devices and gaging
units need to be physically adjusted.
To do own insert coating it shall use a
PVD (physical vapor deposit) system.
Inserts to be coated are fi rst cleaned in
an automated (no-touch) batch washing
system. The clean inserts are assembled
into racks for placement in the coating
chamber. Three different coatings can
be used individually or layered.
1. Precision 1 : To expedite the grinding process,
an arbor with various wheels and brushes is used
in the grinding cell. The arbor is supported by a
dual contact V-flange connector
2. Precision 2: In addition to sintering its own
inserts, the company also uses a PVD process to
coat various insert grades. The racks on the left
are shown prior to coating, and the racks on the
right have been processed.
3. Precision 3: Insert grinding is arranged in
cells. These are comprised of converted milling
machines set up to grind inserts. Load/unload and
inspection is automated, enabling one operator to
oversee four cells
indometalworking news Vol. 2 / 2008 13