Common Examples of Sink Marks on Plastic Injection
Posted: Mon Jan 20, 2025 10:05 am
Thick Sections Near Hollow Areas: Frequently large wall thickness variations near hollow areas cause sink marks.
Rib and Boss Features: Ribs and bosses usually lead to severe sink marks if not properly located/designed.
Parts with Variable Wall Thickness: Asymmetrical or unbalanced design having variable wall thicknesses may result in sinkage, especially when it’s not well balanced.
Large Flat Surfaces: Sink marks are common on large flat surfaces connected to thicker sections that cool slower than others.
Corners and Edges: Sink marks at corners or edges are easily visible because there is an abrupt change in thickness, which affects the component’s aesthetics.
What are the Reasons Behind Sink Marks in Injection Molded Parts?
What are the Reasons Behind Sink Marks in Injection Molded Parts?
The effect of wall thickness on sink marks
Uneven wall thickness is one of the main reasons why injection molded parts have sink marks. Sections with more mass retain heat for a longer time which results in slower france telegram data cooling than their thinner counterparts and causes an imbalance during solidification shrinkage. This variation creates external indentations, also called sink marks. The best way to reduce them is by ensuring that you keep uniformity throughout the entire piece since different areas cool down at different rates due to dissimilarities in cooling rates associated with varying thicknesses, thereby affecting both strength and beauty.
Contribution of Shrinkage towards Sink Mark Formation
Another important aspect that contributes to creating sink marks is shrinkage. When plastic cools after being injected into molds, it shrinks in volume because of solidifying. Thicker regions experience greater amounts of this reduction owing to extra retention of warmth, thus bringing about differential rates between thick and thin parts during cooling-down periods. Therefore, sections having the slowest rate change tend to exhibit the highest shrinkages, which create spaces under surfaces —— whenever these situations occur, there appear sunken regions on topographies called sinks or depressions’’. Such problems can be prevented by taking into account proper design considerations like even thickness throughout walls and locating features strategically so as to address shrinking-related defects in parts.
Rib and Boss Features: Ribs and bosses usually lead to severe sink marks if not properly located/designed.
Parts with Variable Wall Thickness: Asymmetrical or unbalanced design having variable wall thicknesses may result in sinkage, especially when it’s not well balanced.
Large Flat Surfaces: Sink marks are common on large flat surfaces connected to thicker sections that cool slower than others.
Corners and Edges: Sink marks at corners or edges are easily visible because there is an abrupt change in thickness, which affects the component’s aesthetics.
What are the Reasons Behind Sink Marks in Injection Molded Parts?
What are the Reasons Behind Sink Marks in Injection Molded Parts?
The effect of wall thickness on sink marks
Uneven wall thickness is one of the main reasons why injection molded parts have sink marks. Sections with more mass retain heat for a longer time which results in slower france telegram data cooling than their thinner counterparts and causes an imbalance during solidification shrinkage. This variation creates external indentations, also called sink marks. The best way to reduce them is by ensuring that you keep uniformity throughout the entire piece since different areas cool down at different rates due to dissimilarities in cooling rates associated with varying thicknesses, thereby affecting both strength and beauty.
Contribution of Shrinkage towards Sink Mark Formation
Another important aspect that contributes to creating sink marks is shrinkage. When plastic cools after being injected into molds, it shrinks in volume because of solidifying. Thicker regions experience greater amounts of this reduction owing to extra retention of warmth, thus bringing about differential rates between thick and thin parts during cooling-down periods. Therefore, sections having the slowest rate change tend to exhibit the highest shrinkages, which create spaces under surfaces —— whenever these situations occur, there appear sunken regions on topographies called sinks or depressions’’. Such problems can be prevented by taking into account proper design considerations like even thickness throughout walls and locating features strategically so as to address shrinking-related defects in parts.