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What is the cause of the screw slip of the injection molding machine?


Injection molding machines are widely used in manufacturing plastic parts of various shapes and sizes. One of the key components of an injection molding machine is the screw, which rotates and melts the plastic pellets before injecting them into the mold.  However, sometimes the screw can slip, meaning that it reverses its direction or loses its grip on the plastic material.     This can lead to defects, delays, and downtime that affect the productivity and quality of the injection molding process. In this article, we will discuss the causes of screw slip in injection molding machines and some ways to prevent or solve it.

Cause 1: Wear and Tear

Like any mechanical device, the screw in an injection molding machine is subject to wear and tear over time, especially if it runs continuously or at high speeds.The factors that contribute to screw wear include friction, corrosion, erosion, and thermal stress.When the screw wears down, its surface becomes smoother and less able to grip the plastic.To prevent or reduce screw wear, you can use high-quality materials, coatings, and lubricants that resist wear and corrosion.

Cause 2: Contamination and Blockage

Another cause of screw slip in injection molding machines is contamination and blockage, which can occur when foreign particles, moisture, or degraded plastic materials enter the barrel and clog the screw. The contamination can come from various sources, such as the pellets, the air, the water, or the environment.When the screw encounters a blockage, it may push the plastic back, twist it, or break it, causing slippage or jamming.

Cause 3: Inadequate Settings or Maintenance

A third cause of screw slip in injection molding machines is inadequate settings or maintenance, which can result in improper alignment, temperature, pressure, or speed of the screw.        For example, if the screw is too loose or too tight, it may slip or strip the teeth of the motor.        If the temperature is too low or too high, it may affect the viscosity or flow of the plastic, causing slip or burn marks.If the pressure is too low or too high, it may cause voids, flash, or short shots.        If the speed is too slow or too fast, it may affect the cycle time or the cooling of the mold.        To avoid or correct these problems, you can adjust the settings according to the specifications of the plastic, the mold, and the machine.

Screw slip is a common problem in injection molding machines that can have various causes and consequences.By understanding the mechanisms of screw slip and addressing the root causes, you can improve the performance and reliability of the injection molding process.Some ways to prevent or solve screw slip include using high-quality materials and lubricants, filtering and purging the plastic, inspecting and cleaning the barrel and the screw, adjusting the settings and maintenance procedures, and training and supervising the operators.

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