TECHNICAL REPORT

Development of the GS200H5 Gear Skiving Center
Y. OOTSUKA

Production sites for the manufacture of small gear parts require processing machines with high productivity
that are flexible to various kinds of production. To meet these requirements, we have developed the Gear Skiving
Center GS200H5. The features of this developed machine include a compact machine size suitable for small-sizegear production lines, the achievement of high accuracy and high productivity through a design with high rigidity
and low thermal displacement, and the ability to conduct machining such as turning and cutting on a gear cuttingmachine. The details of these features are described in this paper.
Key Words: gear, skiving, gear skiving center, compact machine size, high rigidity, process integration

1. Introduction
An important theme for mankind at present in reducing
environmental load at the same time as achieving
sustainable development is reducing greenhouse gases.
To this end, a variety of initiatives are being promotedin each industry. The automotive industry in particular isdeeply involved with this theme and as such, is pushingahead with the development and sale of vehicles thatcontribute to energy-saving, best represented by electricvehicles (EV), hybrid vehicles (HV) and plug-in hybrid
vehicles (PHV). These vehicles are required to have ahigh level of quietness and stability when being driven,
therefore the small gear parts that make up the planetary
gear reducer equipped on vehicles are required to havehigh strength and accuracy in order to suppress noise andvibration during operation. Moreover, various initiatives
are being promoted to improve energy efficiency, suchas the downsizing and weight reduction of equipment
through the integration and combination of small gearparts.

2. Skiving Machining Method and its
Meritsprinciple behind skiving was first proposed in Germany
in 1912. In the 1970s, a technical study was also
conducted in Japan but at the time it was not developed
to the point of practical application. However, thanks
to technological advancements in recent years relating
to the fields of tools, control and processing machines,
the various issues standing in the way of realizing theskiving method were solved and practical application wasachieved. As Fig. 1 shows, skiving involves a tool tilted
relative to a workpiece, whereby both the workpiece andtool are rotated at high speeds synchronously so that thetool follows the workpiece axis to form gear teeth. Assuch, skiving means the tool has better proximity to theworkpiece than the current gear cutting method performed
on a hobbing machine as Fig. 2 shows, therefore theincomplete tooth portion of the product can be designed
short. Moreover, as Fig. 3 shows, the gear shaper basedon the back and forth movement of a tool requires its
tool relief shape to be made in the product itself. Withskiving, however, this is not necessary, therefore productdimensions can be shortened and better product strengthis achieved. Considering the abovementioned merits,
by engaging in product design assuming skiving as themachining method, it is possible to make parts lighter andmore compact than previously.

Generally speaking, the current mainstream formsof gear machining used in the manufacturing industry
require special-purpose equipment such as a hobbing
machine or gear shaper for outer teeth and a gear shaperor broaching machine for inner teeth. However, inrecent years, a style of machining known as “skiving” isattracting a great deal of attention. Skiving enables cuttingof both inner and outer teeth on a compound processing
machine that performs both turning and drilling. The62

JTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)

−Development of the GS200H5 Gear Skiving Center−

Intersecting angle
Tool
Workpiece
Workpiece
cutting speed

Actual cutting
speed

Feed direction
Tool cutting speed

Fig. 4 GS200H5 Gear Skiving CenterFig. 1 Skiving method

Largeincomplete
toothportion

Smallincomplete
toothportionHobbing

4. GS200H5 Specifications
Table 1 shows the specifications for GS200H5(hereinafter “the developed machine”). Figure 5 shows
the developed machine’s overall layout.
Skiving

Table 1 Main specifications

Fig. 2 Comparison of hobbing with skiving

Relief portion
not required

TravelReliefportion:3 to 5mm

GS200H

Gear shaping

Skiving

JTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)

Tool spindle

Workpiece axis

In 2014, JTEKT launched the GS300H, a gear skiving
center for manufacturers of small and mid-sized gearparts, then created a series in 2016 with the developmentof GS700H, which is optimal for machining large gearparts. As gear processing machines supporting not only
gear cutting, but also turning, cutting, drilling and soon, these two products contributed to the improvementof productivity through process integration and weight
reduction of gear products.
The aim of this development was to focus on themass production market for small gear parts and develop
a processing machine with a machine size suited toincorporation in a mass production manufacturing line
at the same time as offering high production capability.
Consequently, we developed GS200H5 − a gear skiving
center inheriting the process integration capacity that isa feature of the current gear skiving center series, at thesame time as being a compact machine securing highproductivity and stable accuracy.

Tool

3. Development Aims

Feed rate

Fig. 3 Comparison of gear shaper with skiving

X axismm

470

Y axismm

360

Z axismm

B axis°Distance between spindle centermmand workpiece axis center
Distance between spindle end andmm
workpiece axis end
Height from ﬂoor to workpiece
mmaxis center
X, Y, Z axes
m/min
Rapid feed rate
B axis°/min520−220.0〜0.0−120〜240
185〜805
1 350
48
11 520Cutting feed rate X, Y, Z axes
Rapid
X, Y, Z axes
acceleration rate
Rotation speed

m/min

30m/s2 (G)6.86 (0.7)

min

−1

6 000

Output (15 min/continuous)

kW

30/25

Rotation speed

min−1

3 000

Output (15 min/continuous)kW

32/19.5(OP：33.5/28.3)

Max. workpiece dia.

mm

u220

Max. workpiece width

mm

150

A axis end-face max. moment

N・m

82.2

Tool holding capacity

tools

8 (OP：20)

Max. lengthmm

300

Max. dia.

mm

160kg

27sec

2.4Max. weight
Tool changetime

tool to tool(〜7 kg)63

−Development of the GS200H5 Gear Skiving Center−

3 000ToolControlchanger cabinet

Coolingunits

Coolantunit
Z axis process
240
620

Turning table

Tool spindle

Workpiece axis

Y axis process

360

u220

X axis process
470

2 400

3 100

Workpiece

Workpiece axis

Fig. 5 Machine layout
500

GS200H
Turning table center

Fig. 6 Minimizes work-swing

Machine footprint, mm22520

20.2
18.2

15

Good

107.2

50

Gear shaper Broachingmachine

GS200H

Fig. 7 Comparison of floor space

5. A Machine Size Suiting Workpiece SizeIn recent years, in order to increase production
efficiency per a set surface area of a production line,
a demand has emerged for small equipment suited toworkpiece size. To meet such a demand, in order to keep
the developed machine compact, the maximum fixture
workpiece installed on the workpiece axis (220mm dia.

64×240mm height) has been brought closer to the center of
the turning table rotation in order to minimize workpieceswing (Fig. 6) and this has kept the corresponding drive
axes (XYZ) processes to the bare minimum. This designpoint made it possible for the developed machines to havethe dimensions of 2 400mm in width, 3 000mm in depth
and 3 100mm in height, therefore giving it a smaller
footprint than gear-cutting special-purpose machines
such as gear shapers and broaching machines that handle
workpieces of the same size (Fig. 7).

6. High Productivity and Stable Accuracy
In order to achieve high productivity, the layout ofthe various units adopted by the developed machine wasdesigned to enable high-efficiency gear skiving. The
following describes the features of the units.

6. 1 High Rigidity Tool Spindle Unit and High
Rigidity Workpiece Axis Unit
The tool spindle plays an important role in securingmachining performance. With this in mind, we adopted
a JTEKT-made double-row cylindrical roller bearingthat offers both high damping ability and high rigidity,
which are required for the intermittent cutting thatskiving involves, and consequently improved machiningperformance. Furthermore, in regards to the workpieceaxis, we adopted a JTEKT-made angular ball bearing−1with the ability to rotate at high speeds (e.g. 3 000 min )which is necessary for gear skiving, as well as a highrigidity able to withstand intermittent cutting.

6. 2 High Performance Feed Unit
For the feed unit, we adopted a cylindrical roller slidethat is able to achieve high-speed drive while having high

JTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)

−Development of the GS200H5 Gear Skiving Center−rigidity and damping performance. The features of thecylindrical roller slide are its minimal elastic deformationand displacement relative to repetitive variable load.
It is also known for its outstanding damping ability.
By adopting the cylindrical roller slide, the feed unit
undergoes minimal position change at sudden accelerationor sudden stopping and swift positioning is possible.

6. 3 High Rigidity/Low Thermal Deformation
Platform
When designing the bed and columns that support
the moving elements of a machine tool, we performeda simulation of force transmission by utilizing FEM
analysis technology in an attempt to find the layout withthe smallest amount of part deformation due to machining
load. Moreover, to achieve stable machining accuracy
even in installation environments with varying room
temperature, we carried out repeated irregular thermal
analysis to optimize the shape and rib arrangement andfind a design which secured the appropriate heat capacity
and heat release balance. As a result, we succeeded ina design that is able to reduce the bending and warpingof the machine’s material caused by temperature change
and minimize any reductions in machining accuracy. In
addition to these efforts, by manufacturing the bed andcolumns with JTEKT’s sophisticated casting technology,
we created a highly rigid platform with high damping
performance and low thermal displacement.

6. 4 Control Technology Supporting Skiving
Skiving requires the high-speed, high-accuracy
synchronous control of tool spindle and workpiece axis
rotation. As such, the developed machine is equippedwith a high accuracy, high resolution encoder in its tool

Machiningprocess

spindle and workpiece units, as well as adopts a JTEKTmade CNC unit, TOYOPUC-GC70, with a track recordin gear skiving control, for its controller. By adding
the functions necessary for skiving to the TOYOPUCGC70, it has become possible to achieve high speed, highaccuracy synchronous control. Moreover, creating an NC
program for skiving is extremely difficult due to the needfor synchronous control of three axes or more. As such,
this CNC unit was given a simple programming feature
to enable users to create gear skiving programs simply
through entering data such as gear specifications, toolspecifications and cutting conditions.

7. Process Integration with a Gear Skiving
Center
Generally speaking, gear cutting machines such as
broaching machines and hobbing machines do not havemagazines or tool changers. In contrast, the unit layoutof the developed machine is based on that of a machining
center but designed as a compound processing machinewith both a tool changing function and gear machining
function, therefore it is capable of supporting processes
other than gear cutting. Figure 8 explains using workpieceand process examples. Conventionally, machining of
this part comprised the five processes of ①turning, ②hobbing, ③gear shaping, ④chamfering and ⑤drilling.
Then, in order to achieve these processes, equipment orspecial-purpose machines for each process were required.
Meanwhile, the developed machine accomplishes all fiveprocesses in a single machine. This makes it possible tocomplete several processes on a workpiece in just one
operation of the chuck, thus eliminating the machining
error created when the workpiece is loaded and unloaded

Turning

Hobbing

Shaping

Lathe

Hobbing machine

Gear shaper

Chamfering

Drilling

Conventional

Machiningequipment

Machiningprocess

Turning＋Skiving (gear cutting)

Chamfering machine Machining center＋

Chamfering ＋

Drilling

・Improved machining accuracy(single-chuck machining)・Smaller equipment footprint(increased space efficiency)

New
technology

Machining equipment

Gear skiving center GS200H

Fig. 8 Example of process integrationJTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)65

−Development of the GS200H5 Gear Skiving Center−

Processing conditions
Sizemmu149×24

Material−

SCM415Module−1.5Intersecting angle°

Spindle rotation speedmin

Workpiece axis rotation speedmin

Workpiece(ring gear)

Feed rate

20−12 159−11 666

Roughingmm/min

416

Finishingmm/min

283

ResultProcess timesec19

Tooth profile accuracy

μm

5.5

Tooth trace accuracy

μm

6Fig. 9 Example of machining ring gear

between processes and postural changes, and ultimately
securing stable machining accuracy. Moreover, byintegrating the processes, the standby time between eachprocess is eliminated, thus the net machining rate in theproduct manufacturing cycle is improved. The time taken
for the gear cutting process has been shortened due toreplacing ②hobbing and ③gear shaping with skiving. In
addition to the above-mentioned merits, the developed
machine also offers a smaller footprint and reduced initialinvestment due to a smaller number of equipment being
required. In this way, promotion of process integration
will make it possible to reduce the scale of productionlines and enable a transformation to flexible production
equipment.

References
1)
2)

H. Ohtani: JTEKT ENGINEERING JOURNAL, No.
1012E (2015) 85.
H. Ohtani: Development of Energy-Saving Machine
Tool, Int. J. of Automation Technology, Vol. 11, No. 4(2017) 608.

8. Machining Examples
As an example of the machining capable by thedeveloped machine, Fig. 9 shows the results of machining
a module 1.5 ring gear. This machining result gives anaccuracy equal to or less than Level 7 in the accuracy
level scale defined in JIS B 1702: 1998 (with 0 being
highest accuracy and 12 being the lowest accuracy)commonly necessary in the roughing process of gear
cutting in mass production lines.

9. Conclusion
The developed GS200H5 fulfills the needs of manycustomers by maintaining the process integration ability
characteristic of gear skiving centers at the same time
as offering high accuracy, high productivity and spacesaving merits. Moving forward, JTEKT will constantly
stay on top of market trends so that we may continue
offering our customers attractive products.

Y. OOTSUKA**

66

Machine Tools Development Dept., Machine Tools &Mechatronics Operations Headquarters

JTEKT ENGINEERING JOURNAL English Edition No. 1015E (2018)