D-10-IMM Evaluation

The best order is a single part with crazy qty. requirement, manufacturer only need to do same thing every day and keep making money. To meet the order’s requirement, manufacturer needs to prepare a big land/plant full of same equipment and molds. It means all equipment have same model/specification/even manufacturing date, so does the molds. During the mass production, each set of molding equipment and mold’s output are same at every moment, so does the raw material’s property.

BUT, this kind of situation is almost doesn’t exist in the real world. The forecast could change, the land/plant/equipment/molds require investment and time for preparation. The plant has various injection molding machine (IMM) and molds to produce different parts. All these variations are what manufacturers needs to overcome in daily basis.

One question that high quality molding manufacturers may ask themselves every day during arranging production schedule, “Where shall I perform the production?? Which equipment shall be assigned to perform such production??”

Knowing the equipment performance in the plant well could be helpful to answer the question. Here discuss a test to evaluate IMM’ performance, manufacturer can arrange the production according to each part requirement and assign the most suitable equipment for the same. It helps production schedule become more efficient.

The test requires a standard mold equipped with in mold pressure sensor system (see more in D-4,), and run the mold on every (same model/spec.) IMM in the plant with standard procedure and molding parameter. Through the data collected in the test to understand each IMM’ performance, and this can help manufacturer to arrange production more smoothly.

Following are the information to be collected during the test:

  • Cavity pressure data
    The data dot (the pressure value captured by sensor at specific moment) collected during the molding process could consist a graph, the profile of the graph demonstrates the cavity pressure change during each cycle.
  • Part weight
    It represents the amount of plastic being injected into mold cavity.
  • PD data
    This is a record of injection molding process which stored in IMM. This step focusses on feedback data of each shot.
    Cycle time: the time required for a single molding cycle
    Plasticize time: the time required for injection unit to melt enough qty. plastic
    Injection time: the time required for IMM to perform the injection phase
    Cushion: the plastic remains inside injection unit after each molding cycle
    Peak pressure: the highest-pressure value captured by IMM during each molding cycle
    Switchover pressure: the pressure value by IMM at switchover position
    Barrel melt temperature: the temperature captured inside injection unit
  • Response time
    The peak pressure value feedback from IMM generally happens at the switchover position during molding pressure, and it is very much (30~50%) higher than holding pressure. The screw movement inside injection unit has a rapid change during this transition, the time required for stabilization between switchover to start of holding phase is response time.
    Note: Less the response time stands for better IMM performance.
  • Speed linearity
    This step gives several different injection speed inputs into IMM in different molding cycle and record the actual injection speed (feedback value from IMM). Draw a graph consisted of input/ feedback injection speed, the correlation of both is speed linearity.
    Note: Higher the correlation stands for better IMM performance.

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