One of the main reasons to get in touch with experts like StepRapid is they can help you prevent a lot of problems. We have a long history of making high-quality injection-molded goods. Our engineers know how to avoid and fix any issues that may arise during the process, like injection molding failures.

There may be small flaws on the surface of the product. Some have more serious issues. These could affect the safety and how the product works. But these problems can happen with any product.

People who have a hard time creating, using, or storing materials cause these issues. Failures can be due to processing errors, materials used or storage, and design or maintenance.

Processing Issue of Injection Molding Failures!

You can often avoid injection molding failure  by changing the molding process based on the resin used and other factors. The good thing is that you can prevent these issues. 

Flow Lines

Wavy flow lines may show up in parts of the item that are very small. They might be a different color than the rest of the item, but only in these places. They don’t usually have an effect on how well things work, but they look bad and won’t be good for many consumer products. Avoid flow lines by increasing the speed and pressure of the injection and rounding corners, and moving the mold gates so that lines don’t form.

Warping

There is warping when different parts of a piece of equipment shrink at different rates, usually because it cools too quickly. We make sure this doesn’t happen with a long, slow cooling process and materials that don’t shrink.

Burn Marks

Lowering melt and mold temperatures, slowing the injection speed, and widening gas vents to let air out can help avoid burn marks caused by trapped air or too much heat.

Air Pockets (Vacuum Voids)

Air pockets are air bubbles that show up if you use too much pressure when molding. It happens when there isn’t enough plastic in the mold. As the plastic cools and shrinks, it leaves empty spaces in the mold because there isn’t enough plastic to fill them all in.

It won’t be as noticeable that there is a bubble because when the plastic touches the mold, it starts to cool first. This is called a “void.” If you see this shrinking happen on the surface, it’s called a sink defect instead.

Sink Marks

There are sometimes small depressions in surfaces that should be flat because they cool too slowly. We raise the pressure and time we hold things to make sure they cool down properly to avoid this.

Sink marks are due to the following:

• Molding conditions were not properly controlled.
• In the mold, there were some problems
• There isn’t enough raw material to make the molds.
• The structure of the plastic injection molded part is not right.

Jetting

The leading cause of jetting is the deformation of molten material that goes into the mold cavity. This can be seen as a squiggly line. Cut down the pressure to avoid this.

Weld Lines

When two or more polymer fronts come together, weld lines may form. You can prevent this by raising the temperature and injecting it at the right speed and pressure, but it can also happen.

Injection Molding Failures Due to Materials or Storage!

Injection molding failures can also happen because of the material itself. It could also be because of how the manufacturer handled the material before using it to make the item. The defects in this category can be small flaws in the look of the molded part, or they can weaken the part. They may also be dangerous because of how you use the products. The flaws include:

Discoloration

This is also known as “color streaking,” but it’s not the same thing. You get discoloration if your molded part comes in a color that isn’t what you want. You can see the discolorations in specific areas. The color of your body may change from time to time. This flaw doesn’t hurt the product’s strength, but it makes it look not good.

Delamination

Delamination is when thin layers on the surface of plastic molded parts easily separate. Delamination is a problem with injection molding that causes flaking on the surface layer. It is a problem that could make the molded part less strong.

Injection Molding Failures Due to Design or Maintenance!

When looking at injection molding failures and causes, it is also essential to think about the design of the mold. Another thing that can cause problems with molding is not taking care of the mold properly. If there are problems in the last stages, they can be costly and difficult to fix because they are so late. The most common types are the following:

Flash

The word “burrs” or “spew” can also be used to describe flash. Flash is when too much molding material is at the edge of a component, and it shows up as a bump. In this case, some materials get out of their intended channels.

They then move into the space between the tooling plate and the work surface. The injection pin is another place where some may get in as well. Even though it is a small flaw, a flash may be visible on products.

Short-Shoot

When the molten material doesn’t flow into the mold’s cavity, you have a short time to get it all in there. The molded part doesn’t come out completely after you’ve cooled down. They often show up as empty spaces on plastic shelves.

If you look at plastic forks, you might see that some of them have no prongs. There are a lot of other things that could happen. Many people think that short slots are a big flaw. It could change how your molded part looks or stop it from working properly.

Root Cause Analysis (RCA) Tools for Injection Molding Failures!

Root cause analysis is the process of finding out what caused the effects that we see or experience. In the case of failure analysis, RCA is used to find out what caused a lot of machine malfunctions or a major machine breakdown.

You’ll use your detective skills to figure out: what happened, why it happened, and how to make sure it doesn’t happen again.

There are a lot of root cause analysis tools one can use to figure out what the problem is and come up with a way to fix it.

Pareto Chart Technique

A Pareto chart shows how often things go wrong and how they all add up. Italian economist Vilfredo Pareto noticed that almost all frequency distributions he looked at had the same thing in common. There is a huge difference between the number of failures and their effects on people.

He said in any system, 80% of the results (or failures) are caused by 20% of possible reasons, and the rest causes the rest.

People use the Pareto principle as the rule’s name (some know it as the 80-20 rule). You can see this skew between cause and effect everywhere, from how people get rich to when machines don’t work.

The 5 Why Analysis

Sakichi Toyoda came up with the original method for finding the root cause of problems at Toyota factories. It’s called 5 Whys. It’s like a child who wants to know why everything is the way it is.

Ask “why” over and over again until you find the real reason for the problem, then stop. You can keep going through this process until you reach a point where you don’t need to ask “why” again. That is when you should have found the root of the problem.

If you ask and answer five more “why” questions, you should be able to figure out the real reason for most problems. This is why it’s called a “5 why” study.

Fishbone diagram (Ishikawa diagram)

In the Japanese shipbuilding industry, Kaoru Ishikawa used quality control techniques to make sure he did his work right. This led to the Ishikawa method for root cause analysis. The shape of the diagram that comes out looks like a fishbone, which is why it is called a fishbone diagram. This diagram is based on the idea that many things can lead to a failure, event, or effect.

The 5 M framework from the Toyota Production System uses RCA and the Ishikawa method. They are:

• Machines
• Man/mind power
• Material
• Measurement
• Methods

The problems or issues are added at the far right end, the location of the fish head. Across the bottom of this picture, you can see what caused the problem. The effects and causes are written on the fish bones representing each of the 5 M. Repeat the process until you convince everybody that you identify the root cause.

Failure mode and effects analysis (FMEA)

FMEA is a way to look for the root cause of a machine or system’s problems before they happen. This way, you can prevent them from ever happening in the first place. So it’s not just one thing.

It’s a mix of reliability engineering, quality control, and safety engineering, so it’s not just one thing. If you look back at how things have been, you can figure out what will happen in the future.

To use FMEA, you need a group of people from different places. As a group, you will need to be very clear about the scope of the study to each other. Everyone who works on the system, process, or design does their best to make sure everything is right.

Is it thought about what each system is used for? Is this important? And how does it work? Ideas about what could go wrong are many. Looking at how things like this haven’t worked in the past can also be looked at.

Failure modes are looked at to figure out which RPN they have. This way, we can figure out what each failure mode could do.

One can fix this if the failure mode has a higher RPN than the company is used to. There are ways to make this work. You can change one or more of the things shown in the picture above.

Fault tree analysis (FTA)

Fault tree analysis is a way to figure out why things don’t work. It uses Boolean logic (AND, OR, and NOT) to determine what caused things to fail. It tries to figure out how faults and parts of a machine are connected to make sense.

One uses a logical OR operator if two causes have a logical OR combination that has an effect when they are put together. This means that a machine can break down both when it is in use and when it needs to be repaired.

If two things have to happen at the same time for the fault to happen, it is called logical AND. To show you this, let’s say a machine only fails when someone pushes the wrong button, and the relay doesn’t work, which is called a logical AND relationship. It is shown with the Boolean AND symbol.

Summary for Injection Molding Failures

Injection molding failures can be dangerous because of how you use the products and what materials are used. There are many different ways to look for and fix problems with molded parts. Root cause analysis is the process of finding out what caused the effects we see or experience. A Pareto chart shows how often things go wrong and how they all add up. If you ask and answer five “why” questions, you should figure out the real reason for most problems.

This is why it’s called a “5 why” study. The Ishikawa diagram is based on the idea that many things can lead to a failure or event. Fault tree analysis is a way to figure out why things don’t work. It uses Boolean logic (AND, OR, and NOT) to determine what caused things to fail. To use FMEA, you need a group of people from different places to agree on the scope of the study.

StepRapid can help you avoid and fix any issues that may arise during the molding process. Injection molding failures can be due to processing errors, materials used or storage, and design or maintenance. The company has a long history of making high-quality injection-molded goods. A number of different factors can cause injection molding defects. These include small flaws in the look of the molded part, or they can weaken the part.