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MHI Machine Tool Develops "FR Series" of Machines to Manufacture Gears for Robots
-- High Precision Machining with Two Models for External and Internal Tooth Small Module Gears for Precision Reduction Gears --

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・ Direct drive motors and other features used throughout to ensure an optimal structure for precision machining of small module gears
・ Full-fledged launch from August 2020, with unveiling at an online seminar scheduled for September

Tokyo, August 4, 2020 - Mitsubishi Heavy Industries Machine Tool Co., Ltd., a part of Mitsubishi Heavy Industries (MHI) Group, has developed new models of hobbing and gear shaping machines with highly accurate machining to manufacture precision reduction gears for robots. These new products, marketed as the "FR Series," respond to the rapidly growing need for highly precise and efficient manufacturing of precision reduction gears for robots. The full-fledged launch will begin in August 2020, with the unveiling at an online seminar scheduled for September.

The name "FR Series" is derived from "Fine Pitch for Robot, Reducer." The market expansion for industrial and life support robots in recent years has led to a sharp rise in demand for the high precision, small module (Note1) gears inside the precision reduction gears used in the joints of these robots. Two types of gears are used in these reduction gears (an external tooth gear and an internal tooth gear), and MHI Machine Tool has added to its lineup a hobbing machine to create the external gear, and a shaping machine to make the internal gear. In contrast with conventional mass-production gears typically used in the automotive industry, which have modules (gear tooth sizes) of 1-4 and accuracy requirements of ISO class 8 or 9, gears for robots require greater precision, with modules of 1 or below, and an ISO class of 3 to 6. The FR Series was specifically designed to meet these demands.

MHI Machine Tool's hobbing machines utilize direct-drive motors (Note2) for both the main spindle to which the cutting tool (hob) is attached, and the work table spindle holding the workpiece, along with advanced control technology. By limiting the machine tool error to the greatest extent possible, this system achieves a pitch error (Note3) of just 1 micrometer (μm). (Note4) Compared with precision gear cutting, accuracy has been raised three classes (from around ISO 6 to ISO 3). Also, the fast cutting speed with up to 8,000 rpm (revolutions per minute) shortens the processing time by around a third, contributing to greater productivity.

The shaping machines utilize high precision worm gears for the cutter head and work table that comprise the core components. Further, strict management values in the machine's assembly precision has raised the precision class for the gear working by two levels (from around ISO 7 to ISO 5), providing high gear precision.

MHI Machine Tool is utilizing its strength in manufacturing both gear cutting machines and cutting tools to not only offer machines to manufacture the high-precision gears used in precision reduction gears for robots, but with its comprehensive solutions for gear machining, including cutting tools to ensure optimal cutting, processing know-how, and automated systems, is contributing to the manufacturing of high-precision gears.

MHI Machine Tool completed its first hobbing machine in 1962, and over nearly six decades has continually developed new products and technologies. This track record and degree of contribution to the market has raised the company's standing, and at the end of June this year led to MHI Machine Tool being selected for inclusion in the "Global Niche Top Companies Selection 100" by the Ministry of Economy, Trade and Industry (METI). Going forward, as an industry leader, and as a manufacturer of the gear machine tools that support a wide range of industries, MHI Machine Tool will continue to lead the way in manufacturing.

  • 1Module (m) is a unit representing the size of the gear tooth. It is derived by dividing the diameter (mm) of the pitch circle by the number of teeth.
  • 2Direct-drive mechanism motors utilize the torque coming from a motor without passing through a gear box or other mechanism, in order to control driving loss due to friction, and reduce wear on parts.
  • 3Pitch error in a gear is an indicator of the spacing between the teeth of a gear and its adjoining gear. The smaller the pitch error, the smoother the gears work together.
  • 4In-house machining result with GE15FR Plus (Workpiece data: Module 0.5mm; No. of teeth 100; Torsion angle: 0°; Tooth width: 15mm)

■ Specifications of the New GE15FR Series Hobbing Machines

GE15FR GE15FR Plus
Max. workpiece diameter 150㎜ 150㎜
Max. cutting module 2.5㎜ 1.25㎜
Axial travel 250㎜ 250㎜
Radial travel 140㎜ 140㎜
Max. hob diameter 100㎜ 75㎜
Max. hob length 150㎜ 150㎜
Amount of hob shift 150㎜ 150㎜
Max. spindle rotation speed 6,000min-1
Direct drive mechanism
8,000min-1
Direct drive mechanism
Max. table rotation speed 2,000 min-1
Direct drive mechanism
1,000 min-1
Direct drive mechanism
  • The axial travel is the movement distance of the main spindle in a vertical direction, and the radial travel is the movement in a circumferential direction from the center of the main spindle.

■ Specifications of the New SE25FR and SC40FR Gear Shaping Machines

SE25FR SC40FR
Max. workpiece diameter External tooth 250㎜ 400㎜
Internal tooth 120㎜+Cutter P.C.D. 250㎜+Cutter P.C.D.
Max. cutting module 2.5㎜ 4㎜
Max. gear width 60㎜ 115㎜
Spindle stroke speed 180~1,800str/min 50~800str/min
Radial travel -60~270㎜ -125~425㎜

■ Comparison of Typical Workpieces

Conventional models FR Series
Applicable market Automotive Precision reduction gears for robots
Module
(Gear tooth size)
Around 1~4 Below 1 (Below 0.5 is standard)
Module (Gear tooth size)
Workpiece diameter Around 50~250㎜ 20~150㎜
No. of teeth Around 20~60 Around 100~250
Usual required accuracy ISO Class 8~9 ISO Class 3~6
Typical workpiece
Workpiece data
Workpiece data
Module: 2.25㎜
No. of teeth: 52
Torsion angle: 23°LH
Workpiece data

Workpiece data
Module: 0.5㎜
No. of teeth: 100
Torsion angle: 0°
Gear hobbing machines GE15FR/GE15FR Plus
Gear hobbing machines GE15FR/GE15FR Plus
Gear shaping machines SE25FR/ST40FR
Gear shaping machines SE25FR/SC40FR