Welcome!

Basically, open-loop molding machines are not capable of this since open-loop molding machines cannot decouple 1st stage filling from 2nd stage packing. These machines lack closed-loop, injection velocity control and inject using pressure control instead. As a result, the screw speed decreases as the screw moves forward, resulting in an inconsistent shear rate from shot to shot. On these machines, the best approach is to fill and pack the part during 1st stage.

More posts about this topic can be found below:

Documenting Open-Loop Processes…

Processing With Older Injection Molding Machines…

-Andy

The mean is the average of measurements within a particular sampling. This value equals the sum of all the numbers in a sampling divided by the number of values in the sample. For example: the mean of numbers 1.1, 1.1, 1.1, 1.3, 1.4 would be 1.2

The median is the middle measurement within a sampling. This value is determined by lining up all the different measurements and the middle number is the median. For example: the median of numbers 1.1, 1.1, 1.1, 1.3, 1.4 would be 1.3

The mode is the most commonly occurring number within the measurements. This value is determined by adding up how many times each measurement occurs and choosing the value with the highest frequency. For example: the mode of numbers 1.1, 1.1, 1.1, 1.3, 1.4 would be 1.1

In an ideal distribution, all three values should be the same. For example: For the numbers 1.1, 1.2, 1.2, 1.2, 1.3 the mean, median, and mode all equal 1.2.

-Andy

For the silver streaks, I suggest you ensure the material is properly dried. A dewpoint meter or moisture analyzer should be incorporated to ensure the material is dry enough for processing. It is also advisable to pull the screw and clan both the screw and barrel to ensure there is no buildup contaminating the material. It is also advisable to use a temperature probe to ensure the material temperature is at the manufacturer’s recommended setting.

As for the short shots, you may need to develop a more robust process better capable of handling variation. for more on this, please consider reading the following:

Since the system can adjust the screw speed to maintain a desired lbs/hr setpoint, it can be considered gravimetric. The precision of he setpoint is not high since it has to take intermittent weight measurements as the hopper needs more material. This rate of consumption is then reevaluated each time the hopper is refilled. As a result, the system is a true closed-loop gravimetric system with a relatively long lag time.

-Andy