Machine Design

Software puts teeth into gear design

When a job calls for designing nonstandard gearing, you might crunch through the AGMA or ISO calculations or turn to one of several gear-design programs.

- Dave Huffacker


After a gearset calculation, KISSsoft software shows gears and how they mesh. This visual check indicates wellproportioned teeth and no interference of tip and root.

The presizing module lets users type in a minimal number of inputs to calculate several preliminary solutions for a gearset design. The user has selected a solution (the highlighted one) near the specified transmissionreduction ratio, with the correct number of gear teeth.

A graph from the fine-sizing module shows the distribution range of solutions.

The KISSsys module presents a 3D model of the complete internal assembly of a gearbox. Users can, for example, speed up the system to see how it operates at maximum load.

The KISSsoft 08/2005 package is a better option. The basic module handles spur and helical gears. Other modules provide a complete tool for sizing, optimizing, and rating entire gearboxes. The modules work together through one interface that provides standard calculations and a large number of sizing and optimization algorithms.

The complete software package is based on standardized methods of organizations such as ISO, DIN, AGMA, and others. The programs cover all major power-transmission machine-components including spur, helical, bevel, face, worm, crossed axis, planetary, and rackand-pinion gears and gearsets. Programs also cover shafts, axles, and bearings, along with splines, interference fits, keys, and pins. Other modules assist in selecting bolts, springs, belts, and chains and then put components into an entire gearbox and drivetrain.

The software also provides reports for documenting analyses in English, German, French, and Italian. The recent release works with SolidWorks, Solid Edge, Inventor, Catia, and Unigraphics NX3. It lets users generate a 3D model of sized gears in the CAD program.

Gear design is the software's strongest feature. The program provides many calculations for conditions such as transmission error under load (for noise reduction), proposals for gearprofile modifications, and sliding speeds, in addition to standardized methods for strength analysis. The software can be used several ways. For example, when a gearset already exists, users need only type in design details, material, and manufacturing tolerances.

Optional modules help users starting from scratch. For example, a presizing module lets users size gears for a particular transmission by typing in minimal inputs. These might include pressure angle, helix angle, nominal ratio (the reduction ratio for the entire gear set), service life, power, torque, and speed. Users also select the material of each gear from dropdown lists and select a strength-analysis method, for example, ISO 6336.

Clicking on "dimensioning" tells the software to calculate results and list several preliminary gearset solutions. Users then pick one as a starting point for further design tweaking.

The fine-sizing program lets users further tweak gearsets by defining parameters. The program then sorts all possible solutions with user-configurable filters according to design criteria such as noise, vibration, strength, and weight. It lists hundreds or even thousands of gearset solutions in text and graph form. A graph, for example, might show the distribution range of solutions on an X and Y axis.

Shaft calculations are closely tied in. The shaft module lets users type in torques and loads on existing shafts to calculate shaft stress, strength, and deflection, or slope. The software displays graphical representations of translational and rotational deflections.

Of course, if the gear train is new, the shaft geometry will be too. Users can then turn to an editor in the shaft module, define the shaft geometry using cylindrical and conical elements, pick a bearing designation from a lookup table, and select or define the material. Icons similar to those in a CAD program let users create shaft elements such as diameters or tapers from one diameter to another.

KISSsys is another useful module that lets users define the complete internal assembly of a gearbox or drivetrain. The module spreads load to various machine components, calls the core program's calculations, and presents a complete 3D model. Users can, for example, adjust the helix angle on a helical gear in the train and see the effect on the shaft and, more importantly, on each of the bearings. Users can also change speeds, shift gears, see the gears in mesh, speed up the system to see how it operates at maximum load, and so on.

The software comes from KISSsoft USA LLC, 3719 N. Spring Grove Rd., Johnsburg, IL 60050, (815) 363-8823,

Dave Huffacker is senior engineer with Dynabrade Inc., Clarence, N.Y.,

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