Yudo HOT RUNNER User Handbook Manual
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UH-02-Aug16-ENG P 19 / 215. PROCESS ADVISERThe process of injecting plastic parts involves several areas of the technical knowledge bringing us to animmense and complex puzzle of technical definitions and parameters that can be put together in a hugenumber of different configurations.Not aiming to approach this complex subject, in this handbook we just offer some basic generic guidelines fortypical issues that involve directly the parameters set up of the hot runner.5.1. COLOR CHANGEThe process of changing color in injected plastic parts is complex and depend of many factors with bigvariation.The optimal performance is then a combination of factors that can only be achieved on the basis of a case bycase study, that has toinclude a battery of validation tests.Nevertheless there are some generic recommendations that we advise to our customers:- Whenever possible use front removable inserts. Thus the tips become accessible for cleaning.- Adjust the machine sprue diameter to the hot runner inlet diameter.- The first slot should be non coloured material.- For the color change decrease barrel temperature by 20 - 40°C and change to natural material.- Purge the barrel with natural material first, the Hot Runner system afterwards.- When approx. 95% of the purged material contains of natural material, increase the temperature ofthe Hot Runner by 30 - 50°C and continue to purge with natural material until no further improvementcan be achieved. You can also increase the injection speed from 10 to 20%.- Set temperature back to standard settings.- Start molding with new color.ATTENTION: Please observe the guidelines of the material manufacturer!5.2. GLASS FIBER- Do not stop production with the runners filled with glass fibre filled resin. Use non filled or purgingmaterial. If, for some reason, it is not possible, at least stop production with valve pin stopped in openposition.5.3. MATERIAL DEGRADATION- Respect plastic material specifications.- Check the technical data sheet of the plastic material previously to process initiation.- Residence time of the material specifications shall be taken into consideration when mold stop.- Overtime at too high temperature may cause serious problems.- Use standby temperatures according to material specifications. |
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