Causes and Remedies of Sink Marks In Injection Molding

Are you an injection molder plagued by pesky sink marks? Then you’re in the right place! In this blog, we’ll examine why these deep blemishes can appear and most importantly, how to treat them. We’ll tell you everything from what exactly a sink mark is to how much it can potentially set back your project. 

By the time this blog post is finished, if there’s any hint of a potential sink mark near your injection molded part – fear not! You will be armed with tips and tricks for avoiding or remedying them in no time. Stay tuned for all that plus more on causes and remedies of sink marks in injection molding.

What’s Sink Mark In Injection Molding?

Have you ever heard of sink marks? It’s the dreaded and frustrating enemy of the plastic injection molding process. Sink marks are created when there is insufficient flow balance between different sections in a part. Basically, during the cooling process, some portions within a part may cool faster than others, resulting in unequal shrinkage. This can cause divots or shell-like caves on the surface of your part. Thankfully, there are remedies; such as controlling gate sizes and locations and altering resin to reduce melting points combined together can help reduce or even prevent sink marks from happening — so think ahead and act fast to steer clear of these pesky pitfalls.

Fix Sink Marks In Injection Molding:

Remedies to sink marks in injection molding might sound like a tricky fix, but they don’t have to be! Removing sink marks is as simple as making adjustments to the molding machine. Adjusting things like the melt temperatures and cooling times can help you achieve the desired look. 

Furthermore, reducing the plastic feed rate can also help reduce sink marks. Not all injection molds need tweaking though, so don’t worry if your mold remains resilient to these remedies.

Causes and Remedies of Sink Marks In Injection Molding:

It’s no surprise that sink marks in injection molding can be a total pain to deal with. Sink marks occur when the plastic part is cooled too quickly and the outside is hardened before the inside, resulting in an uneven surface. 

So what causes this and what can you do about it? First of all, causes could include insufficient material in the area affected by shrinkage or improper design of injecting gate where the plastic enters. Remedies, thankfully, are more plentiful. 

You could try decreasing the wall thickness of your parts or increasing its gate size to allow for a better flow of plastic resin inside. Or maybe modify your process parameters such as reducing mold temperature while maintaining proper cooling time. In summary, understanding why sink marks happen and learning some potential remedies will help ensure a more successful outcome with your injection molding projects – no one wants to unearth a batch full of sunken disasters.

The Cause And Avoidance Of Sink Marks On Plastic Injection Molded Parts:

Avoiding sink marks on plastic injection molded parts is no small feat. Why? Because when thin walls of injected plastics cool at different rates, sink marks can form. These sick sinks are what nightmares are made of, but there is still hope! Remedies such as reducing the injection velocity and temperature, using a higher melt quality resin, or increasing the cavity wall thickness—where applicable—can solve this issue before it sets in.

Plastic injection molded items frequently include shrink marks. By utilizing design best practices, we hope to assist product designers in reducing the negative consequences of sink marks. Based on our knowledge of mold manufacture, we believe we can make helpful recommendations even though they could be unavoidable in some circumstances.

Why do they occur? Sink marks develop as hot, liquid resin cools and contracts in distinct ways. Your product will shrink more as it comes into touch with the tool wall if it has a considerably uneven distribution of mass. Here is some advice that will help you make design selections.

Conclusion of Remedies of Sink Marks:

Sink marks are one of the most common cosmetic defects in injection molded parts. But don’t despair, there are a number of remedies that can be employed to help reduce or eliminate sink marks. The key is to work with your molder to determine the root cause of the problem and then employ the appropriate remedy. With a little bit of effort, you can say goodbye to sink marks and hello to beautiful, blemish-free injected molded parts.