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Shifting Gears. How to Manufacture the Perfect Pinion?

Besides the dynamic developments with respect to electric vehicles, OEMs continue to improve the internal combustion engine (ICE) with the goal to make it more efficient, reduce the CO2 emissions and ultimately reduce the cost. One supporting element to improve efficiency of ICE-powered cars and reduce their carbon footprint is the transmission. The trend of increasing the number of available gears within the transmission continues, and while this benefits the performance and decreases the consumption, it also poses a challenge for the manufacturers.

In North America, the most commonly used automatic transmission, way ahead of CVTs and double-clutch gear boxes, remains the conventional automatic with torque converter and planetary gear sets. With rising numbers of gears, the amounts of planetary gear sets is also increasing and this leads to a rapidly growing demand of pinions. When looking at the hard-fine finishing of pinions the requirements are clear: each pinion has two finish ground faces and a honed inner diameter (I.D.) to provide optimal performance over the lifetime of the transmission. The traditional production method often separates the grinding and honing, which in turn requires more workpiece handling, part buffers between machines, more floor space and more operator intervention, which may result in an inferior quality product.

Following the principle of lean manufacturing, BAHMÜLLER has developed a unique solution that addresses these issues. By utilizing a single cell, the pinion can be completely finish ground and honed while still offering a flexible production with easy changeover and high availability. The BAHMÜLLER solution finishes the workpiece in three simple steps. The 1st operation is carried out on a BAHMÜLLER Qube machine and finishes the first pinion face and rough grinds the I.D. at the same time. The workholding is specifically designed to clamp the part in the pitch line of the gear teeth in order to minimize the stock allowance for the final gear grinding and allow perfect quality. After the 1st operation the workpiece is automatically flipped by 180° and moved to the 2nd operation, which is also done on a Qube machine. Here, the remaining face of the pinion is finish ground. The 3rd and final step takes place in the Degen Vision high speed honing machine. "This unique process is capable of up to 40 honing strokes per second and utilizes just a single tool to finish hone the I.D. of the workpiece. The simplicity of the solution allows for very easy and fast changeover with superb process capability, which is an increasing demand in the automotive industry," said a company spokesperson. After the honing process an automated post-process gauging unit verifies the size of all components and provides an automated feedback loop to the machine for trend corrections.

Throughout the whole process the same coolant is utilized. This special oil was developed by ML Lubrication specifically for BAHMÜLLER and addresses the different needs of the grinding and the honing application. It enables the customer to have a single coolant throughout the manufacturing process without any concern about contamination between machines, washing, etc.

The complete internal automation is optimized for fast workpiece changing times and maximum uptime. As far as the external automation and part buffering is concerned, several solutions can be offered depending on the customer requirements and preferences.

The footprint of the cell itself is very compact with only 3 m (120") width and is suited for a scalable production within the demanding automotive industry.

For more information contact:

Bahmueller Technologies Inc.

2321-A Distribution Street

Charlotte, NC 28203


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