Cam Indexing Mechanism Gears for Packaging Machinery

Client Background#

A packaging machinery company produces high-speed packaging machines. The transmission gears of the cam indexing mechanism on these machines were damaged frequently, which affected production efficiency and turned gear replacement into a recurring maintenance task.

Problem Analysis#

• Original gear material 40Cr quenched and tempered, with insufficient hardness for this application.
• High-frequency start-stop impact loads are large.
• Gear service life was only 3 months.

In a cam indexing mechanism, the gears are loaded each time the mechanism indexes, so the loading is not continuous but repeated. With frequent starting and stopping, the tooth surface and especially the tooth root see impact loads over and over again. When surface hardness is not sufficient to match that loading, the teeth deteriorate well before the rest of the mechanism does — which is what happened here, with gears being replaced every few months while the surrounding parts remained in service.

Solution & Process#

The three measures below were applied together — material, accuracy and tooth root — because no single change alone would have addressed both the surface loading and the fatigue behaviour at the root.

1. Material upgrade: changed to 20CrMnTi, carburized and hardened to HRC 58~62, so that the surface can resist the repeated contact and impact loading.
2. Gear grinding process: accuracy improved to DIN 6 grade, giving more consistent tooth contact and a more even spread of load across the tooth.
3. Tooth root strengthening: tooth root shot peening to improve fatigue strength. In this type of application, failure usually starts at the tooth root under bending stress, so strengthening that region addresses the point where the damage begins rather than only the surface where it becomes visible.

Result & Feedback#

• Gear life extended from 3 months to 18 months.
• Equipment downtime reduced by 80%.