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Read moreBlack spots
In this second post we will focus on a very common issue that appears in injection processes: the emergence of black spots in the surface of plastic pieces. These spots are visible in the surface of these pieces and there may be many of them, as well as appear randomly, which hamper processes and threaten their efficiency levels.
What are these black spots?
They are usually small pieces of dirt or charred material that were dragged from the injection machine’s spindles or cylinders. These are incorporated as visible defects in the final piece.
Why are they caused?
- Contamination of the natural plastic material.
- Degradation of the plastic, as it is being injected in an excessively high temperature inside the machine for too long.
- Degradation of previous waste materials that were not cleaned properly and were adhered in the walls of the cylinder or in the spindle.
- Use of not suitable colorants for the kind of material that is being used.
Solutions
- Use as much non-contaminated material as possible. Conducting a visual inspection of natural chippings is an effective and simple method that can prevent these kinds of problems.
- Make sure to clean well the residues of the previous material when there are changes of materials in the same machine. We could clean the machine with the same natural material or with products with this purpose that make cleaning tasks and the change of materials easier, as the cleaning masterbatch X-999. With a 10% or 20% dose, we could achieve optimum cleaning levels in the operations involving a change of material.
