Core pull

Core pull processes using hydraulic cylinders

Hydraulic cylinders are commonly used to remove undercuts in plastic injection molding applications involving complex component geometries. The pulling cylinder strokes are used in most such cases. The initial motion requires particularly high forces since the solidified plastic still adheres to the core. This application usually requires core end position detection in order to correctly control the automatic removal and to avoid damage while the mold is closed. There is a variety of detection options that can be integrated into the hydraulic cylinder.

Our core pull solutions

Our block cylinders certainly are the most commonly used product for core pulls. They offer small and compact dimensions, flexible installation, multiple options, wide range of monitoring capabilities. 

However, the core pull unit is often overlooked. Here, the core pull guides are already integrated in the hydraulic cylinder, and the entire piston force can be utilized by the core pull. This enables much simpler mold design and space savings in many cases. As a result, either a smaller injection molding machine can be used or more cavities can be accommodated within the same outer dimensions of the mold.

Tips and tricks:

  • - Cylinders with short strokes and small piston diameters often lack a vent. If this air remains in the cylinders during operation, failures are bound to occur in many cases. 

  • A rigid connection between cylinder and core is not recommended as it may cause lateral loads and, thus, cylinder failure. We would like to refer to our couplings and the matching counter pieces from our accessories at this point.
  • A cylinder design calculation tool is available in our CAD configurator.
  • An insufficient number of sensor inputs on the machine is a common problem, especially if you need to move multiple cores that require monitoring. For this purpose, we offer a series connection box as an accessory that provides an opportunity to combine signals.

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