Bevel Gear Technology

DEBURRING – THE UNDERESTIMATEDTASK ON THE COMPONENT

Deburring or chamfering of gear teeth is gaining attention inpractical settings. And with a view to make production sequence
as efficient as possible, it is becoming increasingly important tobe able to implement the deburring tasks directly on the cutting
machine after spiral cutting. Read on to find out how complex
this seemingly simple task can turn out to be, and how a new
deburring concept provides for enhanced efficiency.

4GEARS inline 05 | 2018

Bevel Gear TechnologyW

hy are bevel gears
deburred or chamfered? The reasons
vary greatly. In bevelgears, the edge area
between the concave flank (gap) andthe component's outer contour must be
deburred in every case. That is where thebevel gear cutting tool normally exits thematerial and leaves behind a more or lessconspicuous burr. This area is extremely
sharp-edged and must be chamfered
to avoid the risk of injury. As wear on
the bevel gear cutting tool increases, aburr can also develop in the cutting area
between the convex flank (gap) and thecomponent's outer contour. This area
should therefore also be taken into account and deburred as necessary.
How complex the task of deburring
is depends significantly on the outer
contour of the component, as well ason the area to be deburred, in accordance to the user's specifications. The
outer contour can be straight in thearea of the edge to be deburred, but
it can also comprise a number of contour elements. A straight chamfer canusually be processed easily in just one
cut using a deburring tool. Complex
deburring edges typically do not allow
this. In these cases, several deburring
tool positions and cuts must instead beconsidered.

It is therefore noticeably more efficientwhen deburring takes place directly on
the cutting machine. In this case, component clamping is already quite stable, and the position of the gaps after
cutting is known and does not changeeven in the event of multiple setups.
Accordingly, the gap position does nothave to be reassigned for repeat production, which significantly decreases
the work involved in setup. If several
different deburring positions are defined for an extremely complex component contour, their assignment remainsstable and they can be sequentially
executed in the familiar clamping. The
processing times and thus the competitive capacity can be optimized in thisway. The Oerlikon C-series bevel gear
cutting machines make high-productivity cutting processes feasible – withextremely high, reproducible gear cutting quality. These machines also allow
complex deburring tasks to be realized.
The chamfer generated here can be accurately represented, and the deburring tools have a long tool life.

Deburring directly on
the cutting machine
Deburring outside the cutting machine(in a second clamping) always entails
additional component handling, inwhich the reference of the position of
the deburring edge must again be established for the deburring task. Manual deburring, by contrast, involves a riskof component damage, in addition to asignificant time factor, and is therefore
avoided in most cases.
Fig. 1: Deburring tools

Compact
High-production
deburring processes on C-seriesmachines
Efficient and economical deburring takes place directly on
the cutting machine. C-series
bevel gear cutting machinesfrom Klingelnberg enable efficient bevel gear cutting as wellas complex deburring tasks totake place in a single clamping.

Bevel Gear Technology

Compact
Simulation withthree elements
Simulations make it possible
to cope with the highly complex requirements of deburring
processes. The simulation developed by Klingelnberg covers
three elements:
1.
2.

3.

Definition of the deburring
tool geometry
Definition of the exit angleof the deburring tool cutting edge from the material
Collision and process check

Simulating highly complex requirements

however, collision analysis is often particularly important.

In bevel gear production, deburring directly on the cutting machine is alreadybeing required – and performed – withincreasing frequency. The implementation can have varying degrees of complexity and therefore suitably adapted,and varying technological approaches,
all of which must satisfy one condition:
Avoiding collisions. The risk of collision
can occur between the deburring tooland the gap, where the opposite flankcan become damaged. However, thecollision situation between the deburring tool and the clamping device mustalso be considered. This collision situation is usually less critical for deburringof ring gears. For deburring of pinions,

A simulation of this complex task makes
it possible to also analyze the penetration of the component/clamping device
with the drive of the deburring tool.
Such a simulation includes three different elements. These three elements
must be made compatible in advancewith the capabilities of the specific cutting machine:

Fig. 2: 3D view of all components
involved in the deburring task

Fig. 3: Edges to be deburred, resulting fromthe cutting area between the component envelope and the component gap

Fig. 4: Component clamped in device,
deburring tool trajectory in green

Fig. 5: Envelope contour of a clamping device
and component (red); collision range of all deburring positions (green)

1) The simulation starts with a definition of the deburring tool geometry.
The deburring tools consist of carbide
stick blades that are clamped in a holder. The stick blades can have a varietyof profile shapes, with the technological angles specifically adapted to suit

Bevel Gear Technology

requirements. To minimize setup costson the machine and reduce tool costs,
as many deburring tasks as possible areexecuted with the same deburring tool.
2) The second element includes definition of the suitable exit angle for the deburring tool cutting edge, from the material to be deburred. An exit angle must
be selected that will prevent another(secondary) burr from developing as aresult of the deburring task, which itself
is also a chip-removing operation. Boththe deburring tool geometry and themovement executed by the tool in thespace play a role here. To thoroughly analyze the deburring task, testing is necessary to determine how many different
cuts are required to completely capture
the area to be deburred. The exit angleof the cutting edge must be checked foreach of these tool positions.
When the component contour description is as precise as possible, it facilitatestargeted optimization of the deburring
tool positions. Turned part descriptions
are increasingly available in digital format. This component contour can beimported into the simulation as a contour element frequently in the form of a
Drawing Interchange file (DXF).
3) The third element is a collision andtraversing path test for the specificcutting machine. Collision testing is required with reference both to the opposite flank in the gap and to the clamping device used to hold the component
in the cutting machine. For this test, thedeburring tool trajectory is represented
in an adequate spatial expansion. Whenthe clamping device description is done
precisely, it facilitates targeted optimization of a collision-free deburring toolposition. This clamping device contour isgenerated automatically for Klingelnberg
clamping devices and can also be imported as a DXF element.

Versatility in deburring tasks depends on
the number of available machine axes.

Testing of this deburring task and thecollision check can be tailored to suitthe circumstances, such as, machine
concepts and machine sizes of individual machine types.

Machine axes determine flexibility
For spiral bevel gear production, there
are different machine designs on themarket. Various deburring options areavailable, depending on the design. In
terms of deburring versatility, the numberof available machine axes always plays animportant role. Depending on the component size and clamping device concept, the available traversing paths also
influence the deburring task options.
Compared with older models, new machine generations have a significantly
increased range of functions with regard to deburring. This development
is reflected in the fact that in modern
concepts, great emphasis is placed on
the capability to thoroughly implement
deburring tasks.

A variety of methods forcomponent deburring
Deburring facets can be generated indifferent ways – and combinations arealso possible. These include:
For Klingelnberg's horizontal cutting
machines with only four axes available
for the deburring task, the single-cut

THE MACHINE
MAKES THE
DIFFERENCE
Realization of complex deburring tasks in one clamping
Efficient deburring
Shorter processing times
Optimized competitive capacity

Bevel Gear Technology

method is used. The tooth root can also
be deburred by turning the component
in the final position of deburring.

Fig. 6: Action of the deburring blade cutting edge at the tooth root andfinal shape of the deburring edge after a single cut

Fig. 7: Contour generated with five different positions of the deburring toolFig. 8: Contour generated with many different positions of the deburring tool

The numerable-cut method can be
employed on Klingelnberg machineswith a vertical machine concept andthe capability to use six simultaneously
controlled NC axes. Here a contiguousedge is deburred through several cuts
located one after the other in the heelarea. Fig. 7 shows the result of five selected positions. These are necessary
because the tooth flank has an extremely pronounced curvature in the profile
direction, which is offset by three cuts,
and because there is a peculiar contourchange on the back cone of the component. This requires an additional, extremely steep cut. Lastly, the gap rootis deburred with a tightly-turned final
cut. Between each deburring position,
the tool is withdrawn from the gap andre-situated for the next position with afeed movement.
The many-cut method can also be
employed on Klingelnberg machineswith a vertical machine concept andthe capability to use six simultaneously
controlled NC axes. A contiguous edge
is deburred through innumerable cuts
located in close proximity to each other.
The special thing about this method isthat the deburring tool does not lift out
from one position to the next – rather, it
executes every deburring position alongthe edge directly with a rapid feedmovement. The cutting is performed
primarily by the tool tip radius.

New coupled movement optimizes thecollision curve

Fig. 9: Comparison of the two possible coupling situations for the same deburring task

All of the component deburring methods presented are based on a principleof continuous motion. This has theadvantage of extremely short auxiliaryBevel Gear Technology

times, and therefore a short deburring
time overall. This continuous operation
principle requires a coupled movementof the rotation of the deburring tool
axis and the component axis.
All familiar coupled movements used so
far for deburring are set up in such a
way that the component flank moves
toward the deburring blade. This movement requires a specific spatial expansion relative to the trajectory of the deburring blade. In a number of deburring
tasks, however, this spatial expansionof the trajectory relative to the collisionsituation is a key challenge.
Klingelnberg has therefore developed away to create this coupled movement
so that the component flank moves
away from the deburring blade. Thespatial expansion of the trajectory forthis coupling relationship has a significantly different form and requires considerably less space. Collision-criticaltasks can therefore be performed withmuch better results using this deburring
principle.

METHODS FOR COMPONENT DEBURRING
Single-cut method
Horizontal cutting machines with four axes
Oerlikon C 27, C 42 and C 60 bevel gear cutting machines
Numerable-cut method
Machines with vertical machine concept and six NC axes
Oerlikon C 29, C 30 and C 50 bevel gear cutting machines
Many-cut method
Machines with vertical machine concept and six NC axes
Oerlikon C 29, C 30 and C 50 bevel gear cutting machinesimportant the capability to implement
the deburring tasks directly on the cutting machine after spiral cutting has
become for customers. It also clearlyshows the highly individual approachtaken by companies such as Klingelnberg in response to special customer
requirements from the market.

Compact
New deburring
principle – evenmore efficient
Collision-critical tasks are
performed with far better results thanks to a new coupled
movement of the component
flank and the deburring blade.

Conclusion
The seemingly simple task of performing deburring tasks on a cutting machine can turn out to be quite complex.
This is evident in the variety and diversity of ways deburring can take place
on a cutting machine – and also in the
difficulty of reliably determining processparameters such as risk of collision. The
simulation option developed by Klingelnberg provides valuable support in thisrespect: The machine settings determined during the simulation can beloaded directly on the cutting machine,
removing all obstacles to manufacturing real, burr-free components.
The fact that more versatile solutions
are being offered and demanded withincreasing frequency reflects just how

Dipl.-Ing. Karl-Martin Ribbeck
Head of the Bevel Gear Competence Center,KLINGELNBERG GmbH