Contour Analysis of a Worn Gear Using 3D Profilometry

A gear is a rotating machine part that transmits torque by meshing with another toothed part. It is a key mechanical component widely used in a variety of industrial applications, such as automobile, machinery and many others. In order to effectively change the speed, torque, and direction of a power source, gears possess several shapes to achieve different drive mechanisms, including but not limited to spur gears, helical gears, skew gears, bevel gears, hypoid gears, crown gears and worm gears.

Manufacturing of high precision gears requires stringent quality control, in order to obtain the best operational conditions and energy efficiency. Surface defects on the gears may lead to negative impact on the gear mesh quality. Moreover, during the service time, wear and tear takes place, creating surface defects such as dents and cracks in the gears that may result in decreased power transmission efficiency and potential mechanical failure. An accurate and quantifiable tool for surface inspection is needed. Unlike a touch probe technique, the NANOVEA Profilometer performs 3D surface measurement of the sample without touching, making it possible to precisely scan samples with a complex shape, such as gears of different geometry.

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The false color view of the gear sample surface is shown in Fig. 2. The height variation and machined patterns on the top surface of the sample can be observed by the change of color. The gear consists of two sections: a center ring and the outer cogs.

The contour analysis of the worn gear is presented in Fig. 3. It shows that the inner ring possesses a radius of 2.56 mm. The outer cogs have been deformed and worn after long term wear and tear during the service period. The tips (top land) of the teeth have a distance of 6.35 mm to the center of the gear. The shape of a tooth on the right of Fig. 3 was altered: the angle between the two shoulder faces is changed from above 50° to 43.4°. By setting up a tolerance limit value, the analysis software can automatically determine which and how many cogs have been worn out, allowing users to make a quick and accurate decision whether to replace the gear.

The roughness and uniformity of the gear surface play an important role in ensuring its quality and functionality. The 3D non-contact surface scan determines the surface finish quality with high precision. Fig. 4 presents the surface morphology of the gear sample at a high magnification. The surface roughness values are calculated and summarized in Table 1.

In this application, we have showcased that the NANOVEA ST400 3D Non-Contact Profilometer performs surface contour analysis on a worn gear sample. The capacity of high resolution scan enables users to measure the detailed morphology and tiny surface features. Moreover, it can pick up any undesired defects including chipping or cracks on the gear surface. The detailed contour analysis provides a useful tool to determine whether the new mechanical parts fall in line with manufacture specifications, and to evaluate the failure mechanism of the worn components.

The data shown here represents only a portion of the calculations available in the analysis software. NANOVEA Profilometers measure virtually any surface in fields including Semiconductor, Microelectronics, Solar, Fiber Optics, Automotive, Aerospace, Metallurgy, Machining, Coatings, Pharmaceutical, Biomedical, Environmental and many others.