Photo courtesy DMG MORI A Revolution in Gear · PDF fileEach gear cutting process has its own benefits in terms of quality and ... Ingersoll Cutting Tools (Rockford, IL), where it

June 2014 | ManufacturingEngineeringMedia.com 49

With demand for precision gears

big and small growing across

a wide swath of industries,

along with the economy, new

innovations in gear production

technology are changing the

way some manufacturing minds think about mak-

ing gears in the first place, which hasn’t substantially

changed in decades.

In fact, these new methods of manufacturing gears,

which aim to streamline the processes of deliver-

ing high-quality gears using CNC programming and

precision cutters, may even open up the possibility for

creative new gear designs in the future.

DMG MORI says its gearMILL software solution enables a

standard lathe, mill or multitasking machine, outfitted with

standard off-the-shelf tools, to cut gears with precision.

A Revolution in Gear ManufacturingMachine manufacturers are working to streamline the gear-making process, to deliver a more highly finished gear in fewer steps

Manufacturing Engineering Staff

Gear Manufacturing

Photo courtesy DMG MORI

The traditional method of making a large volume of gears,

namely hobbing, gashing, scudding or skiving, requires

machines and tools specific to gear production and in many

cases even to the size of the gear itself—and very little else.

“A gear hobbing machine only does gears,” said Nitin

Chaphalkar, manager, Advanced Solution Development, DMG

MORI USA (Chicago, IL).

What’s more, depending on the design and material out of

which the gear is cut, these traditional gear-making processes

may require highly skilled operators and will always need

additional pre and post operations.

At the same time, however, demand is also growing for

higher quality gears with better surface quality and robust

wear performance as a greater number of higher-efficiency

gears are sought for automotive transmissions, heavy equip-

ment, airplanes, marine vessels and wind turbines.

That means more manufacturers are trying to churn out

more gears faster. While many large OEMs may be inclined

to stick with their tried-and-true manufacturing methods,

rather than make sweeping investments in new manufactur-

ing approaches, Chaphalkar estimated that about 40% of gear

production is done by job shops that are contract manufac-

turing a variety of parts and may not need to do high volume

machining of gears all the time.

For those customers doing smaller to medium batch sizes,

DMG MORI offers its gearMILL software solution that enables

a standard lathe, mill or multitasking machine, outfitted with

standard off-the-shelf tools, to deliver a highly finished gear

that is almost done-in-one and ready for heat treat.

The software, according to DMG MORI, allows complete

machining of diverse gear types in its diverse line of multi-

tasking machines. The builder has 20–25 different models of

machines that are suitable for machining various sizes and

types of gears.

The obvious benefit to this approach over, say, a hobbing

machine is that it offers flexibility for when a shop wants to

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50 ManufacturingEngineeringMedia.com | June 2014

Gear Manufacturing

machine other parts. Generally speaking, it can also offer a

higher quality finished product in pre-heat treat stage.

Essentially, the gearMILL software develops the most

ideal toolpath to create the gear with a standard machine

and tooling. “A good gear geometry is the key to everything,”

Chaphalkar explained.

Any Gear, Any Size

DMG MORI has been developing its gear solutions offer-

ing since 2006. In 2010, Sandvik Coromant (Fair Lawn, NJ)

invented the process of InvoMilling, a unique approach to

making spur and helical gears using indexable insert cutters

by slot milling and turn-milling in a path that moves the cutter

along an involute path. “It was a very new thing,” Chaphalkar

said of the method. “Nobody was doing it this way.”

So the two powerhouse companies decided to partner on

commercializing the new technology. DMG MORI developed

software that develops the toolpath based on the gear shape,

and now InvoMilling is added to hobbing and flank milling

with an end-mill as the choices customers now have to make

a gear on a multitasking machine with gearMILL.

“Now we have a broad portfolio,” Chaphalkar said. “Spur,

helical, herringbone, bevel, spiral bevel, hypoid—whatever

type of gear you have, it can be programmed and made.”

One of the main challenges in traditional gear production

is the lead time for acquiring the right hob to make a part,

which can take up to 8–10 weeks if you don’t have the right

size in stock already. But using a standard machine and tools

eliminates most of that waiting, Chaphalkar said. “You will

already have the tools most of the time. There is no waiting in

most of the cases.”

For more information on gearMILL, visit http://tinyurl.com/

dmggearbrochure or http://tinyurl.com/sandvikgearbrochure.

—Sarah A. Webster, Editor in Chief

A Deeper Look at InvoMilling

Sandvik Coromant developed its InvoMilling gearcutting

program and CoroMill 171 and 172 indexable carbide disk

cutters to provide maximum flexibility for its customers who

wanted to manufacture gears in smaller lot sizes, typically for

applications like heavy trucks, agricultural and construction

equipment. Sandvik Coromant worked initially and proved the

concept with DMG MORI, which integrated the software into

its CNC controls. InvoMilling will soon be available through

other major machine tool makers as well.

“We are seeing a shift in how gears are being made

because of the availability of advanced technology, includ-

ing multitask machines, even three-axis vertical machining

centers with fourth axis rotary tables, and five-axis machining

centers,” said Aaron Habeck, marketing project manager,

Sandvik Coromant.

“High-volume gear manufacturing for automotive applica-

tions like transmissions is still going to be done on traditional

hobbing machines using high speed steel. But InvoMilling

and full form disk cutters allow our customers who want to

produce gears on non-traditional gearcutting machines, the

ability to cut splines or gears. With a multitask machine, they

can machine the part in one setup using the main spindle

and subspindle to do all the turning or the milling of flats and

keyways and drill/tap holes,” said Habeck.


Gear Manufacturing

Watch Manufacturing Engineering’s Favorite Gear Manufacturing Videos at http://tinyurl.com/gearmanufacturingvideos

See us at BIGM Booth #114

The advantage of InvoMilling is that a wide range of gear

tooth profiles can be generated using a very small assort-

ment of tools. “InvoMilling uses somewhat standard prod-

ucts to cut the involute of the gear tooth by using the move-

ment of machine’s axis to generate

the involute curve, not the tool itself.

The tool typically has a straight cutting

edge and, depending on the machine

configuration, movement of the C axis

and the Y axis, generates the involute

curve,” said Habeck. “InvoMilling isn’t

going to be the fastest overall cycle

time, but for a customer who has

invested in a small assortment of tools,

a wide range of different gear profiles

can be manufactured.”

Each gear cutting process has its

own benefits in terms of quality and

cycle times that can be achieved.

“Hobbing will always be the quickest;

InvoMilling, the most flexible. CoroMill

171 and 172 cutters can achieve DIN 7

or AGMA 10 quality class, for example,

typically what our customers require.

CoroMill 171 and 172 involve easy,

straight line programming. There’s no

need for any special synchronization of

tool and part movements like that which

is required for hobbing,” said Habeck.

—James Lorincz, Senior Editor

High Chamfer Quality, One-Cut Machining

Even among those companies that

provide traditional gear-making technol-

ogy, efforts are being made to streamline.

Liebherr Gear Technology (Saline,

MI), for example, takes a fairly tradi-

tional approach, but is not afraid of

new ideas. Its new hobbing machine

for work up to 180 mm, the LC 180,

includes an integrated Chamfer Cut

unit for deburring and chamfering the

face edges. After hobbing, the Chamfer

Cut tool generates precise and repro-

ducible chamfers that are increasingly

demanded by the automakers for smoother gear engagement

and quieter transmissions.

The new solution eliminates the former main disadvan-

tage of chamfer cutting: prolonged machining time. In the


past, hobbing and chamfering took too much time at the

same setting. “We have solved this by integrating a com-

plete second machining unit for chamfer cut tools—two

machines in one, so to speak,” said Oliver Winkel, director

of Application Technology and responsible for technologi-

cal development of gearcutting at Liebherr-Verzahntechnik

(Kempten, Germany).

Chamfering no longer prolongs machining time because it

takes place in a separate unit within the same machine, while

the next workpiece is hobbed. “We know from transmission

design development that the subject of ‘chamfering’ is becom-

ing more and more important. This innovation enables the

machine to combine an already undisputed high chamfering

quality, provided by the proven Chamfer Cut procedure, with

cycle times that correspond to the demands of the automotive

industry,” said Winkel.

This technology is not limited to the auto industry. It can

be of benefit to any gearmaker whose current procedures

are too time-consuming, whose tooling costs are too high, or

those who need to take follow-up processes such as honing

into consideration.

Compared to press deburring and chamfering with finger

mills, the chamfer cut process has the lowest chamfering costs.

Anticipating further downsizing trends in the auto industry,

the Liebherr chamfer cutting technology can also generate

even smaller, more precise chamfers for transmission compo-

nents. As the importance of a reproducibly generated chamfer

increases, the smaller the gear will be.

In the industry, parts frequently do not conform to draw-

ings due to imprecise chamfering procedures. “This is espe-

cially true the thinner the gear face width becomes,” said Win-

kel. “The importance of the transmission designer being able

to calculate the limits of design feasibility is increasing, so the

chamfer is becoming more and more of an engineering factor.

Since its actual impact can now be calculated, its importance

also has increased. The ever tighter design of transmissions

is one reason why the importance of chamfer quality has

increased. It makes a huge difference in the case of a gear

from an automotive transmission that is only around 12-mm

wide, whether the chamfer is 0.5 or 1 mm—and consistently

throughout high-volume production,” said Winkel.

—James D. Sawyer, Senior Editor

Cutting Smaller Gears, Faster, Without Quality Loss

A Liebherr LC 1200 Gear Hobbing machine resides at

Ingersoll Cutting Tools (Rockford, IL), where it demonstrates

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Gear Manufacturing

Ghosted image of Liebherr LC 180 Chamfer Cut shows how

hobbing and chamfering are integrated in a single unit.

Pho

to c

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esy

Lieb

herr

Gea

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chno

logy

See us at BIGM Booth #330

Ingersoll’s indexable carbide inserts for machining large gears,

including hobs and gashing tools.

“Most of our customers can already make good quality

gears with their current equipment—but they’re trying to in-

crease productivity with no loss of quality,” said Frank Berardi,

gear machining product manager at Ingersoll Cutting Tools.

“Usually we’re taking first-time customers from high-speed

steel to carbide, and that brings a big jump in productivity

right there.”

A more recent design innovation is allowing Ingersoll’s cli-

ents to work more effectively with smaller gear sizes. “Most of

our work in gearcutting has been focused on the larger gears

used in the mining, power generation, and construction indus-

tries, to name a few—industries that generally use 8 Module

and higher,” said Berardi. [‘Module’—the ratio of the pitch

diameter in millimeters to the number of teeth—is a standard

gear measurement unit.] “Basically customers adapted our

products to their larger gears first, and then asked what we

could do for these smaller gear sizes. With our radial insert

design, we now have an answer for them.”

In recent years Ingersoll has concentrated in producing

gearcutters for the smaller gear tooth sizes, particularly in the

4–8 Module range, where Berardi says there has been a void

of indexable insert products. That size is used by customers in

the medical-equipment and large-truck industries as well as

other industries. “The challenge has always been how to pro-

duce cutters with secure insert retention in the smaller tooth

forms,” Berardi explained. “To accomplish this we developed

new concepts for indexable insert hobs, which utilize radial

mounted inserts instead of our typical tangential inserts.”

Tangentials can get down to about 6 Module. Any smaller

than that and it becomes difficult to make an insert small

enough to locate in pocket, and clamp it down and be robust,

according to Berardi. The radial mounted design can get

down to 4 Module. The tradeoff is that the radial design allows

a fewer number of indexes—however, the advantages of the

radial design more than compensates.

The radial insert design allows for a larger, more secure

insert pocket. The hobs can be made with screw-down or

clamp style inserts. Also important, the radial insert hob has

double the number of effective teeth as a tangential insert

hob of the same size. “This results in much higher productiv-

ity,” said Berardi. The hobs can be produced in single and

multiple-start versions.

—Michael C. Anderson, Senior Editor

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Gear Manufacturing

Single-Minded Modular Machining Lines

EMAG LLC (Farmington Hills, MI) offers two machines,

the VLC 250 WF and the VSC 400 WF, that can be used to

turn and hob in combination. According to the company,

there is a quality advantage to such

combination machines.

“The advantage,” said Joerg Lohm-

ann, Deputy Sales Director, Koepfer

GmbH a member of the EMAG Group

(Salach, Germany), “is that the work-

piece doesn´t have to be unclamped

between the different processes.”

Despite this advantage, EMAG

is phasing out this product family,

except, said Lohmann, “for [support-

ing] customers that already have these

machines. Some of them, however, are

even trending towards our new gear

manufacturing systems, for instance

the combination of a VL2, a VL2, a

VLC200H and a VLC100D.”

In combination these machines

become a modular multipurpose

machining line. They are still, however,

single-purpose machines. And the

reason, according to Lohmann, is that

time is money.

“EMAG has chosen to develop its

gear manufacturing system with single

technology machines,” he said, “to

offer an alternative to [combination

machines]. The hourly production cost

with single technology machines is

simply lower compared to multiprocess

machines. And in a modular system

of these machines one process follows

immediately after the other so the value

stream is optimized. Throughput times

are reduced dramatically by means of

avoiding workpiece transportation.”

EMAG has shown gear manufactur-

ing systems that perform not just the

basic metal removal operations but

which include welding and workpiece

hardening as well.

“We are developing our modular construction system

further,” said Lohmann, “and we always implement the

latest technologies on our vertical platform. The EMAG

group offers the whole process chain for green and hard

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gear machining processes. We are convinced that the

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—James D. Sawyer, Senior Editor

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Gear Manufacturing

DMG MORIPh: 855-364-6674

Web site: www.dmgmori-usa.com

EMAG LLCPh: 248-477-7440

Web site: www.emag.com

Liebherr Gear TechnologyPh: 734-429-7225

Web site: www.liebherr.us

Sandvik CormantPh: 800-726-3845

Web site: www.sandvik.coromant.com

Ingersoll Cutting ToolsPh: 815-387-6600

Web site: www.ingersoll-imc.com

Want More Information?

EMAG creates a modular gear manufacturing systems by

combining a number of single-technology machines, in

this case (from left) two VL2s, a VLC200H and a VLC100D.

Pho

to c

ourt

esy

EMA

G L

LC

Documents

Photo courtesy DMG MORI A Revolution in Gear · PDF fileEach gear cutting process has its own benefits in terms of quality and ... Ingersoll Cutting Tools (Rockford, IL), where it