Injection Molding Machine Cam Sensing Using Magnet Sensors

Low-cost plastic injection molding machines commonly use slider cam systems to manage and sense various stages of the injection molding process, such as mold closing, injection, and ejection. These machines rely on mechanical cams to set and control parameters like the speed and position of the mold and the timing of each stage. This approach is cost-effective, simple, and widely used in smaller-scale manufacturing setups, but its effectiveness hinges on the accurate sensing of cam positions to ensure the smooth operation of the machine.

Accurate sensing is critical in injection molding for both operational efficiency and safety. Mold protect limits, which prevent damage to molds and machines, depend on precise sensing to stop operations if misalignments or even the slightest of changes such as a paper sheet within the mold are detected. Additionally, the sensing system ensures that the molding machine transitions correctly between stages, such as switching from mold closing to clamping to dosing to injection, and then to ejection. Inaccurate sensing can lead to unfilled plastic parts, machine downtime due to lack of repeatability, or even accidents. Therefore, a reliable sensing mechanism is vital for the performance and safety of the machine.

Magnet sensors provide an efficient and repeatable solution for cam position sensing in injection molding machines. Mounted behind the cams, these sensors work in conjunction with scales marked on the cams for precise adjustments. The cams are set at specific positions on the scale, and the magnet sensors detect the exact location of the slider as it moves during the molding cycle. When the slider reaches a particular position, the magnet sensor sends a signal to the machine controller, triggering the next stage of the cycle, such as mold closing, injection, or ejection. This setup ensures that the machine operates consistently and allows for easy repetition of settings for different molds.

Application Classification

Applications are classified as Position Sensing, Pulse Counting, Electromagnetic or Relay, Temperature Sensing or Magnet Biasing types. This application is classified as follows and the link gives more information on best practices to help select the most suitable AT band and matching magnet.

Position sensing Type

When an application requires the end position of a movement sensed, or the sensing of a part when it comes into a zone, or when the Continue reading -> Mar 21, 2025

Recommended Products

The Reed Switches and Sensors used in molding applications need to be robust, durable and efficient in meeting a high life expectancy. Our engineers work hard in life testing our products under various conditions, and our intention is to ensure end product durability and life. Although we wouldn’t want to restrict any of our products for use in only certain applications, the recommended products for use in this application are listed below.

M5 Threaded Sensor Cylindrical Sensor, MS-225

MS-225 Threaded Magnet Sensor drawing starFeatures10W Contact Rating. Normally Open contact. Three sensitivity bands. Sputtered Continue reading -> Dec 2, 2024

M8 Threaded Sensor Cylindrical Sensor, MS-228

MS-228 M8 Threaded Sensor Drawing starFeatures30W Contact Rating. Normally Open contact. Three sensitivity bands. Sputtered Ruthenium Continue reading -> Dec 2, 2024