A Maximum of Gear Quality with Hobbing

Gear hobbing is the most productive and economic way to produce gear teeth profiles on a outer diameter. For the gear cutting process, the hob cutter and the gear are building a pair similar to a worm shaft and a worm gear. To produce the required gear profile the hob cutter with a geometric defined cutting edge, is cutting with an interrupted generating cut.

The superior characteristic of the gear hobbing is the extreme high flexibility. With the basic rack tooth profile, different work pieces with any amount of teeth, different profiles and helix angles, can be produced. This is usually done with the axial hobbing process. With this process the hob cutter is shifted axial to the work piece axis. Work piece and hob cutter are intersected based on the lead angle and helix angle.

Gear hobbing is one of the core technologies in gear manufacturing. The quality achieved in this process has a high influence on the following processes such as gear grinding and gear honing. A maximum on gear quality is achieved with the so called two cut strategy. In combination with an integrated chamfering and deburring operation, the optimum process chain can be accomplished: roughing – chamfering/deburring – finishing. This process does not leave a secondary burr on the work piece, opposite to the single cut process with a following chamfering deburring process. The two cut process is the fundamental requirement to avoid damage of the honing tool after the work piece is heat treated.

With the patented Felsomat main spindle configuration the complete process chain can be done in one setup; the result is highest work piece accuracy and shortest cycle times. This is only possible with a two spindle machine: the loading and unloading is done in parallel to the machining. The machine is almost constantly cutting chips. Remarkable is that the complete process chain on this machine is done with the environment friendly dry cutting and therefore reducing the cost per work piece even more.

Felsomat has established a new bench mark in terms of productivity and quality. With an extreme stiff and good damping machine design, as well as high dynamic spindle concepts with high torque and high rpm, the use of high performance cutting material such as solid carbide cutters is possible. The use of such cutting materials allows for a up to 50% higher cutting speed compared to standard coated high speed steel tools. Higher productivity means less machines for a given production volume resulting in lower cost for personnel and energy.

With an intelligent shift strategy it is possible to use the complete length of the hob cutter and thus lower the tooling cost even more. With this strategy the finishing segment on the tool is used for the roughing process after it is worn out for the finishing process.

The newest trend in gear manufacturing is the finish cutting of the teeth profile in the green state of the work piece, followed by a low distortion heat treat process. The Felsomat FHC gear hobbing machine platform are prepared very well for this process.