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Read moreInformation and transparency. Splay marks due to burnings.
This blog on the plastic transformation sector is intended to become a portal of verified information and useful for our customers. In Colortec we are engaged in writing several posts, as a way of transmitting our specialised knowledge and experience in this business. After working closely for more than 25 years with companies from different sectors and sizes, we have gathered the main questions and common patterns when manufacturing our customers’ pieces, ensuring the requested confidentiality by our customers. We believe this may be of great help for other manufacturers and may serve as a guide in design processes and the fix of physical defects of certain pieces.
Since our first post, we are going to deal with one of the most frequent physical defects in thermoplastic injection pieces: splay marks. There are many types of splay marks with many possible causes. In this post we will write about splay marks due to burnings.
What are splay marks due to burnings?
They are caused due to the thermic degradation of plastic or colour concentrate. They appear in form of chalky or brown splay marks over the Surface of the injected piece.
What are their main causes?
- 1st Cause: Excessively high temperature in the injection machine.
- 2nd Cause: Too much time inside the injection cylinder.
- 3rd Cause: Low thermic resistance pigments or colorants.
- 4th Cause: Spindle working at a very high speed.
Solutions:
Solution to Cause 1: Lower the temperature of the machine’s cylinder, so the temperature of the plastic mass is also lowered. Reduce the injection pressure. It is important to take into consideration if the natural material has been subjected to a drying process before its processing, since prolonged exposures mat degrade the material in advance.
Solution to Cause 2: Shortening the times in the cycle may prevent the material to exceed the recommended time spent inside the machine.
Solution to Cause 3: Apply masterbatch designed with colorants, pigments or additives with better thermic resistance that may be apt for the material’s temperature processing.
Solution to Cause 4: Reduce the spinning speed of the spindle.
