Chamfering and Deburring gears precisely to achieve smoother gear transmissions

By Niraj M Wanikar, Chief Editor, CNCTimes.com, 2016-07-21 15:04:00

The chamfering and deburring of gears is often an undervalued process in gear production. However, it has a great influence on the usage characteristics of the work piece. Improvements in Ratings for Gear Shifting in vehicles also depends on the process used for this operation. This article explains the sophistication required in tools using plastic deformation for chamfering and rolling and cutting action for deburring.

Chamfering and Deburring Gears Precisely

Gears need to be Chamfered and Deburred with a controlled, high quality process for the following reasons :
• To avoid breakage – Excessive carburizing along the tooth edges can often cause breakage when the gear is running
• To avoid damaging gears and bearings – If burrs are not removed, they may chip off during the running cycle and cause damage to the other gears and bearings.
• To avoid poor tool life in the finishing processes
• Removal of very sharp burrs reduces the risk of tool handling injuries

Chamfering Specified on Gears is of following types : in only one or in both flanks, with a constant size along the profile, with or without chamfer in root diameter. Sometimes a further Rolling Operation is required (refer section on Rolling below)

Chamfering with Plastic Deformation / Compression Tools
Advanced Chamfering Tools use Compression (as against cutting) for creating chamfers on the edge. The pressure and the deformation of the material may modify the structure of the steel. The chamfering tool is like taper gear, with a width of roughly 10 – 15 mm, and normally is very well finished, with a surface like a mirror in order to prevent a quickly wear.
The key benefits of Chamfering with such tools are :
1. Stronger gear tooth due to better material flow; 2. Accurate Chamfer Angles

The angles of the chamfers are definite by the tool drawing, but the size depend on the rolling time and the pressure of the tool against the gear. If the contact time between the tool and piece increases, the chamfer becomes bigger.

The Pressure which defines the deformation force is generated with a pneumatic cylinder.
This method guarantees an “elastic force” that prevents some breakages. Further the Tools are Self Centering, thus guaranteeing symmetrical chamfer on both sides of the work piece.

Rolling Operation
Gears require a rolling operation after chamfering due to the plastic deformation caused by this operation and to eliminate the “burs” or swellings that form on the material. Whilst burs on the gear face may be removed by deburring tool, those on the lead remain. 

These burs, usually in the range of 0.05 – 0.07 mm, cause problems in subsequent grinding phases and actually put the grinding wheel at risk. At this point a rolling operation on the gears becomes necessary.

The Samputensili method of Chamfering-Rolling uses a common chamfering/rolling tool (Patented) and a deburring tool to complete the Chamfer-Roll-Deburr simultaneously.

Gears that are chamfered and rolled have been tested after heat treatment
1. cracks do not form in the rolled area.
2. The structure is normal and corresponds to all the structural characteristics of the material.

Tool Configuration - Options
Chamfering/Deburring tools can be organized in various configurations for different types of gears, geared shafts and sprockets.
For example, cluster gears can be processed in a single operation with multiple chamfer/deburr tools organized as shown below.

Conclusion – Precision Gear Chamfering/Deburring
Gear Chamfering/Deburring is a Key Process Technology in Automotive Powertrain for achieving smooth gear transmissions. Capability to produce strong accurate chamfers is essential. In addition for gears that are later finished, a rolling operation can be integrated with Chamfering/Deburring. Multiple Configuration options in tooling enable a solution for a wide variety of automotive gears.

About Grind Master

Grind Master launched Advanced Gear Deburring and chamfering Machine in Technical Collaboration with Samputensili of Italy in Imtex 2015. SAMP Gear Chamfering-Deburring is a reliable system used in manufacturing of Spur and Helical Gears, well recognized for its generation of Consistent Chamfering results with Patented Tooling. Samputensili is a Global Brand in Gear Industry. Grind Master is known for its expertise in Metal Finishing, Deburring and Microfinishing.

Under the Collaboration Grind Master will build Gear Chamfering and Deburring Machines using Technology and Expertise from SAMP. The machines will be marketed under a common SU-GM brand name in India, and under the SAMP brand name globally.

Grind Master has built more than 6 machines under the Collaboration to date. A further 3 machines are under manufacturing currently. These machines have been supplied to both Indian Automotive as well as International Automotive customers.

The machine uses ORIGINAL SAMP Technology to create accurate chamfering Results. The Results from SCT3 machine are clearly superior to competing technologies. It is one of the most copied but never equalled machine ! Its success is evident from the fact that it is the preferred technology for many Automotive OEMs.

 The Authors

Sameer Kelkar, Silver Medallist and Graduate of IIT Bombay, and MS in Mechanical Engineering from University of California, Berkeley, is CEO of Grind Master Machines Pvt. Ltd. Sameer has worked extensively with Collaborators SAMP Italy for Developing Advanced Gear chamfering/deburring machines for Indian and International markets.

Francesco Grippo is the Chief Technical Officer of Samputensili Machine Tools Srl. He graduated in Aerospace Engineering from the Polytechnic University of Turin, Italy. Francesco has worked for Sicmat for more than 12 years on gear shaving and gear chamfering/deburring machines, in the roles of Service Manager, then Project Manager and finally Technical Director.

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