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#033 Key Aspects of Textured Finishing

Category : Technical Information
March12, 2010

Since the textured surface finishing of molds for plastic injection molding is done after completing all of the mechanical forming operations and polishing work, if the appearance is not equal to the desired quality, it is necessary to correct it, or if the damage is so high as to make correction impossible, it is necessary to prepare the mold again. In order to complete the mold within the budget according to the schedule that was planned, it should be understood that textured finishing is a final process that has a high risk. In order to reduce the risks caused by defects in textured surface finishing, it is very important to pay attention to the following aspects.

(1)The cavity surface which has to be texture finished is polished carefully using sand paper or abrasive powder thereby removing micro cracks or deformed surface layers caused by machining.
(2)For the cavity material, select a steel that has a low probability of having material defects such as voids (air bubbles), inclusion of impurities, inclusion of carbides, etc.
(3)Do not carry out texture finishing on parts that were repaired by welding (because it will cause striations).
(4)Make the heat treatment of the steel, the cutting direction, and the rolling direction as identical as possible.
(5)When processing the side surface of the cavity, set the draft as large as possible.
(6)When carrying out processing on the side surface of the cavity, make the wall thickness of the molded product thick and intentionally make the shrinkage large.
(7)Adopt a cooling structure that makes it easy to carry out temperature control of the cavity surface, and use a cartridge heater structure.
(8)In some cases, a better finish is obtained if the processes are changed so that machining operations are made after texture finishing.
(9)Since the visual appearance of the textured finish even changes depending on the type of the molded material, coloring, and amount of glass fibers mixed in, etc., select the type and depth of a textured finish taking into account the importance of past data.

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