Plastic gears are usually produced in large numbers and therefore using an efficient injection molding process. They are often used without lubricants due to hygiene requirements or to further reduce costs. This results in wear as the dominant damage mechanism. Wear as such leads to reduced load capacity, uneven running and contamination of the environment. On the other hand, small but skillfully executed changes to the tooth form can greatly reduce this wear. The changes are largely cost-neutral, both in terms of production and quality control.

The changes in the millimeter range of tooth height, tooth thickness, profile shift or curvature are offset by modifications in the µm range for crowning, tip relief or pressure angle modification.

Reduced wear due to modified flanks

Changes are necessary and effective in both areas, and they must be considered in combination. The top right image simulates the wear for the original tooth shape, while the improvement for the modified tooth shape is visible on the right.

Like plastic gears, femurs, tiger claws and tree forks are beams subject to bending loads with a variable cross-section and a rounding. While evolution has optimized the three mechanical systems mentioned above, it is the task of the designer to do this in a shorter time for gears.

Optimized foot rounding increases service life

Figure 2 on the left shows the reduction in foot tension through the use of a maximized, position-adjusted and shape-optimized rounding.

The possibilities in design have been greatly expanded by CAE tools, but there are technical and commercial limits in production - narrow and therefore expensive shape tolerances.

A gearing engineer, equipped with specialist knowledge, the courage to be creative, the right gearing software and experience, can achieve such an improvement in an hour's work with software such as Kisssoft. The customer benefits are enormous: plastic gears can be found in cars, vending machines, kitchen appliances, water meters or washing machines, where they move sunroofs, banknotes, whipped cream, clockworks or even laundry reliably, space-savingly, cost-effectively and quietly.

Hanspeter Dinner, Director Global Sales, Kisssoft