The Concept Of Direct Gear Design

Direct gear design refers to an alternative method of analysis and design of involute gears. The operation uses condition and performance parameters to conceptualize the design. Various steps involved in the process is common for most part of mechanism and machines (eg. crankshaft, rods, etc). It is mainly driven by specific application needs, when technical and market performance of the product is critical. It used mostly for the custom gear drives such as molded cast, powder and forged gear. Other examples include the mass production of gears for critical and extreme applications like automobile, aerospace and racing gear transmission.

 

The concept of direct gear design is not new. Ancient engineers successfully used the method to design standard gears. They exactly knew the specifications for design parameters including desired gear ratio, center distance and power sources. These parameters were used to define diameters, number of teeth and shape for each gear. Gear and tooth geometry were defined first. A streamlined gear manufacturing process was than applied to finish the direct gear design into final products.

 

In brief, direct gear design is an application driven gear development process with prime emphasis on performance optimization and cost reduction without concern of any predefined tooling parameters. It provides complete tooth profile optimization which result in maximum contact and bending stress reduction. The stress reduction is transformed to higher load capacity, reduced size and weight, extended life, reduction of vibration and noise, higher efficiency and reliability.

 

The comparison between traditional gear design and direct gear design will provide the readers with much better understanding of the subject:

 

Traditional Gear Design	Direct Gear Design
Design Based on defined standards  and fabrication process	Design Based on the application and  performance needs of the equipment
Advantages Requires low tooling inventory Standardized tooling makes  the process much simple	Advantages Unlimited design specifications can  be considered The stress level reduction allows to optimize performance  for any application
Disadvantages Gear with limited (standard) performance	Disadvantages Requires custom tooling
Applications Gears box with standard or  interchangeable gear set Low production machined gears Mechanical drive prototyping	Applications High performance and custom  gear drives Plastic and metal injection molded gear Powder metal gears High production machined gears