1.4.4 Preparation before injection molding
Preparation before forming may include many things. Such as: materials processing performance test (determination of plastic flow, moisture content, etc.); raw materials, dyeing and processing of pre-selected grain; aggregates warm and dry; insert the cleaning and preheating; test mode and barrel cleaning and so on.
22.214.171.124 Pretreatment of raw materials
According to the characteristics of plastic and feeding conditions, usually in response to raw material before forming the appearance and performance testing process. If the plastic used for the powder, such as: polyvinyl chloride, and dry ingredients should be mixed; if the products have color requirements, you can add the right amount of coloring agent or masterbatch; supply of aggregates often contain different levels of water , flux and other volatile low molecular weight compounds, especially those with moisture, water is always a tendency to exceed the processing of plastic allowed limits. Therefore, must be dried before processing and measurement of water content. Sensitive at high temperature polycarbonate water requirements of the moisture content of 0.2% or less, or even 0.03% to 0.05%, so commonly used vacuum oven drying. Has to be properly dry and sealed plastic to prevent plastic from the air and then the loss of moisture and drying effects of the hopper can be used for this purpose drying room for the injection molding machine to provide continuous hot, dry material, to streamline operations, keep clean, improve quality, increase in injection rate are favorable. The added material drying hoppers generally the injection molding machine with a feeding amount of 2.5 times per hour.
126.96.36.199 Insert the preheating
Injection molding products for the assembly and strength requirements, the need of embedded metal insert products. Injection molding, placed in the cavity of the cold and hot metal insert with plastic melt cools, the metal and plastic shrink significantly different rates, often around the inserts have a great internal stress (especially as polystyrene rigid-chain polymers of ethylene and other more significant). The existence of such internal stress cracks around the insert, resulting in significantly reduced performance products. This can be a large selection of thermal expansion coefficient of metal (aluminum, steel, etc.) for the inserts and the inserts (especially a large metal insert) to warm up. Also, when designing products around the insert arranged in a large thick-walled and other measures.
188.8.131.52 barrel cleaning
The beginning of a new injection molding machines purchased before using, or need to change products in production, the replacement of raw materials, change the color or find a break in the phenomenon of plastic, injection molding machines are required to clean or take apart and wash barrel.
Washing machines generally use the heating cylinder tube cleaning method. Cleaning materials in the plastic materials (or plastic recycled material.) For heat-sensitive plastics, such as the existence of PVC material, can be low density polyethylene, polystyrene and other materials for cleaning the transition, then the processing of new materials replacement of cleaning materials transition.
184.108.40.206 Selection of release agent
Release agent is easy to make plastics material ejection. Zinc stearate applies in general outside the plastic polyamide; liquid paraffin used for polyamide plastic is better; silicone oil is expensive, cumbersome to use, less use.
Should be controlled using the amount of release agent, try to use less or no. Excessive spraying will affect the product appearance, color decoration on the products also have adverse effects.
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