A short shot is a phenomenon in which there is an incomplete filling in a part of the molded product.

There are two types of causes for short shots in terms of their nature. One of these occurs because, in the middle of the flow of the molten plastic, the front end of the flow gets cooled and solidifies. The second is caused, in the flow process of the molten plastic, because air traps are generated in the flow depending on the conditions of the flow.

In order to take countermeasures against short shots, it is necessary to verify which of the above two types the short shot belongs to.

n the case of short shots caused by the solidification of the front end of the flow

(1) Countermeasures related to molds

	1.	Widen the gate
	2.	Widen the runner.
	3.	Make the sprue thicker.
	4.	The cold slag well is small.
	5.	Provide a heat insulating plate on the under surface of the mold plate.
	6.	Increase the number of gates.
	7.	Change the position of the gates.

(2) Countermeasures related to the injection molding conditions

	1.	Make the plastic temperature higher.
	2.	Set the cavity surface temperature a little higher.
	3.	Try making the filling pressure higher.
	4.	Try making the dwell pressure higher.
	5.	Try setting the dwell pressure time longer.
	6.	Try increasing the charge quantity.
	7.	Try increasing the volume of the cushion.
	8.	Try changing the injection molding machine.
	9.	Replace the reverse flow prevention ring of the injection unit.
	10.	Change the tip diameter of the injection nozzle of the injection molding machine to a larger size.

(3) Countermeasures related to the design of the molded product

	1.	Increase the wall thickness of the molded product.
	2.	Provide ribs near the parts in which flow is difficult.

In the case of short shots due to air traps

(1) Countermeasures related to molds

	1.	Provide an effective air vent in the part where air traps are occurring.
	2.	Change the gate position.
	3.	Try changing the runner balance
	4.	Try making a structure in which the part with poor flow can be heated.
	5.	Try making the part with poor flow have a divided nested structure.

(2) Countermeasures related to the injection molding conditions

	1.	Try changing the injection speed and changing the flow pattern
	2.	Try changing the screw speed, and the pressure selection position.
	3.	Try making the injection speed slower
	4.	Try setting the cavity surface temperature higher.
	5.	Try setting the mold clamping force a little lower

(3) Countermeasures related to the design of the molded product

	1.	Investigate making the wall thickness of the molded product non-uniform.
	2.	Increase the wall thickness of the molded product.