█ The cause of increasing materials costs.

1. An injection-molding industry still has not come up with standardized production management of following elements, which is why this industry has lagging productivity.

1)       Environmental temperatures (Cooling water/Interior temperature)

2)       Mold temperature

3)       Injection pressure

4)       Oil temperature

5)       Resin heating temperature

6)       Change of cycle time

2. When one has to produce many different products under none-standardized production management, the efficiency of an injection-molding machine will decrease definitely.

Machine’s working rate by multiple models and little production: 56%

Types of reject (Overall reject average: 24%)

1)       Un-molded reject rate: 63%

2)       Weld line reject rate: 18%

3)       Flow mark reject rate: 9%

4)       Gas foaming & black spot others: 10%

3. Analysis contents

Above conditions 1), 2), 3), occur when mold temperature is kept too low and the cold water of chiller, cooling tower is continuously flowed into the mold without temperature control.

Gas foaming at 4): occur if resin heating temperature is too high.

Black spot: occur when crushed products are greatly used or screw, cylinders are worn and unclean and resin heating temperature is high.

█ The factors of low productivity

1.       The time to set molding conditions in accordance with mold temperature takes 50 – 120 minutes and machine’s working rate drops as well as inferior products are made in the beginning.

2.       Owning to multiple models and little production, which arouse decrease of machine’s working rate and many rejected products.

3.       An atmospheric temperature, or cooling tower temperature vary with weather change of summer and winter, day and night, and it causes a change of mold temperature, disturbing constant quality of goods.

4.       If an injection-molding stops because of disorder of mold and the machine, decrease of machine’s working rate and initial inferior products.

5.       When an operator leaves working site, an injection-molding machine comes to stop, and mold temperature drops and making defected products.

6.       The amount of water and pressure flowing into the mold are changing by the differences of machine’s working rate at factory and mold temperature is not only changed with difference of heat exchange capacity but also quality differs.

7.       Bad bent happens with the deviation of mold temperature on fixing, moving unit and either method that delay to prevent the bent it will drop the quality and productivity.

8.       If user fills with the resin with excessive injection pressure at low mold temperature, production will be stopped or life span of the mold will be shortened due to the mold damage and wearing.

9.       If injection pressure is high, the density of resin gets high and products’ size becomes long, weight comes heavy, which arouse to spend a lot of and inferior products.

10.   Cooling capacity will be better when water pressure gets low but heat exchange cannot be normal. So cooling water flow system should be improved so that it can have maximum cooling effects and high productivity.

In final analysis, quality of products is decided by mold’s temperature.