In spur gear design, interference between mating gears can be a serious problem that prevents efficient work, even the spur gear system does not work.
Interference between spur gear mates can de be described as; the interference between the tip of teeth of pinion gear which is a smaller gear in spur gear mates, and the root side of teeth of the bigger gear. In the design stage, the designer must know to alleviate this issue.
The most general reason for interference between gears is the size difference between the pinion and bigger gear. If the size difference is higher than the recommended values, interference could occur. In the design stage, the designer must consider the design recommendations of the mating of spur gears.
In pinion and rack pairs, interference is the most prominent issue compared with other gear mates. Because you can think of the pinion that has an infinite pitch.
In the design or gear selection stage, you need to comply with the gear mating recommendations of the manufacturer or general recommendations about standard spur gears, to prevent interference problems.
For standards of pinion gears, there are the minimum number of teeth recommendations such as;
In general, 20 degrees of pressure angles are standard for spur gears. Also according to the number of teeth of pinion gears, some recommendations are available to prevent interference between spur gears, in terms of the number of maximum teeth used for bigger gears;
As you understand from the values above, the use of teeth numbers above 16 is common practice. Recommended maximum teeth for bigger gear increases exponentially with the increasing number of pinion teeth number.
You can face an interference problem with the existing design or machinery. All the systems can be installed, but there is an interference problem. You can do the operation called ‘undercut’ on bigger gear teeth.
Undercut prevents gear interference in a very efficient way. With a proper machining process, you give round geometry on the root of teeth.
But you need to aware that this operation decreases the strength of teeth.
There is a required strength to transmit power between gear mates. Undercut process can reduce this strength.
These are the general information about the interference problem on gear mates, which is not considered in a good way by designers generally. A good designer must be aware of these kinds of facts.
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