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. Improvement in rating 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
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
Types
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 stronger gear tooth due to better material flow and accurate chamfer angles. The angles of the chamfers are definite by the tool drawing, but the size depends on the rolling time and the pressure of the tool against the gear. If the contact time between the tool and piece increase 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.
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
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
- Cracks do not form in the rolled area.
- 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 (See Figure 10 Simultaneous Operation on 2 gears)
Conclusion
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.
