Sink marks arise from the phenomenon when the surface of the molded product shrinks and becomes slightly depressed.

This may cause quality defects in the case of molded products whose outer surface is important as a product.

The following measures can be taken to solve the problem of sink marks.

(1) Measures related to molds

	1.	Slightly decreasing the cavity surface temperature.
	2.	Making the gate wider.
	3.	Making the runner size larger.
	4.	Making the sprue thicker.
	5.	Re-studying the cooling path of the mold, and increasing the cooling efficiency.
	6.	Changing the cooling structure of hard-to-cool parts to easy-to-cool parts. (Example: Baffle plate structure, cooling pipe structure, heat pipe, nests of non-ferrous metals)
	7.	Increasing the number of gates.
	8.	Changing the gate position to a thick wall part.

(2) Measures related to injection molding conditions

	1.	Making the dwelling time longer.
	2.	Setting the dwelling pressure to a higher value.
	3.	Setting the injection speed to a higher value.
	4.	Lowering the nozzle temperature.
	5.	Try increasing the value of the measure.
	6.	Try increasing the weight of the cushion.
	7.	Try changing the injection molding machine.
	8.	Replacing the reverse flow prevention ring of the injection unit.

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

	1.	Removing the thick wall parts in the molded product. (Example: Forming a recessed shape, using parts for other purposes)
	2.	Using a non-crystalline plastic.