When color isn’t evenly distributed throughout a part, appearing as streaks, swirls or patches of discolored material, you’re probably looking at color swirls. Also known as streaking, color streaks and marbling, color swirls are occasionally misidentified as black and brown streaking, so it’s important to determine which defect you’re dealing with as the first step in your troubleshooting.
If misidentified, many of the solutions to color swirls will actually exacerbate the black and brown streaking, so accurately identifying the problem is a must.
What Causes Color Swirl Problems in Plastic?
When determining the cause—and thus solution—of color swirls, the first thing you need to know is when the problem is occurring. If you’re seeing color swirls after changing from one color to another, the solution won’t be the same as random or always-present swirls.
If the color swirls only appear after changing colors or materials, the culprit probably deals with your purging procedures. Changeovers have to be done correctly or you may be stuck with color swirls for hours.
Color Swirls Troubleshooting Chart
Low back pressure
Inadequate back pressure
Fast screw speed
Hang-up in screw or barrel
Raw component issues
Low melt pressure
Found in Injection Molding Advanced Troubleshooting Guide: The 4M Approach (p. 200).
How to Prevent Color Swirls in Injection Molding
Within the molding process, you need to pay extra attention to back pressure, screw speed and melt temperature. If the back pressure is too low, the material and color concentrate won’t mix properly, leading to color swirls.
Similarly, a fast screw speed can lead to color swirls. The longer the screw rotates, the better the color mix will be, but if screw recovery is too fast, you’ll likely find good results in slowing the speed.
You could be dealing with a melt temperature that’s too low and, since the melt temperature is impacted by so many other factors, it’s important to know exactly what your melt temperature is and that it’s within the recommended range for your material.
If the issue is with the machine, check out the screw design, back pressure and possible hang-up in the screw or barrel, which can prevent it from cleaning out well during color changes. A general-purpose screw design isn’t the best option for color and material mixing, so make sure you’re using a melt-quality screw. If you don’t have enough back pressure, you’ll likely find poor color mixing, which leads to color swirls.
Color swirls emanating from material issues can be due to an incompatible material-to-concentrate relationship, which could be as simple as using a concentrate that’s intended for a different material. You could also be dealing with contamination, which can cause a host of other problems, or a raw component issue.
As one of the fastest growing scientific and engineering technologies in the world, Nanotechnology holds an incredible amount of potential, especially in the manufacturing and plastics industries. But it is also being used in fields such as bioscience, medicine, engineering, pharmacology, material sciences, and defense.
And that’s just the tip of the iceberg.
What is Nanotechnology? It involves the engineering of functional devices or systems by controlling matter on an atomic and molecular scale. Now you begin to understand the near limitless potential. Scientists now have the ability to manipulate the atomic structure of the very molecules that make up the materials in the world around us.
This enormous growth potential and set of possibilities has given industries like manufacturing exciting improvements. The very structure of materials can be changed and improved through nanotechnology. For example, the plastics industry has embraced the use of nano-materials to provide plastics with greater conductivity, increased strength, flexibility and durability, and unique surface characteristics, etc.
Other nano-scale materials can be used in thin films to make them anti-reflective, self-cleaning, ultraviolet or infrared-resistant, antifog, anti-microbial, scratch-resistant, electrically conductive, anti-stick, water-repellent and oil-repellant…the list goes on.
Our own NanoMoldCoating product is one of these innovative new polymer films that creates optimal solutions to most of the typical issues in injection molding. The coating dramatically increases production output, while reducing costs associated with manual part removal, costly mold release agents, part scrap, slow cycle times, and repetitive mold maintenance due to sticking problems.
While far from certain, the future of plastics manufacturing in the United States is showing some current trends that are worth watching closely. “Economists and analysts are watching trends in manufacturing closely, as it’s an industry that is in part driving the economic recovery in the United States.”
Here’s a good article that summarizes the most important trends including 3D printing and robotic technologies.
“The future of plastic manufacturing in the United States is far from certain, but many trends are beginning to take shape.” 3D printing and similar innovations are accelerating pace. And new production procedures are always being talked about and modified, whether that’s lean or another model.
Here’s an important article that talks about why plastic manufacturing will likely continue to be a strong yet steadily changing segment of the manufacturing industry overall.
How can you keep up with the pace? Read the full article HERE.
Plastic injection molding is extremely versatile method of producing parts and products. It is one of the preferred methods for manufacturing parts because it has multiple advantages over other methods of plastic molding. Not only is plastic injection molding simpler and more reliable, it is also extremely efficient. You should have no doubts about using this method to manufacture parts.
Here are 5 major advantages of using injection molding for manufacturing plastic parts and components.
1. Detailed Features and Complex Geometry
The injection molds are subjected to extremely high pressure. As a result the plastic within the molds is pressed harder against the mold compared to any other molding process. Due to this excessively high pressure, it is possible to add a large amount of details into the design of the part.
Furthermore, due to high pressure during the molding process, complex and intricate shapes can easily be designed and manufactured which otherwise would have been too complicated and expensive to manufacture.
2. High Efficiency
Once the injection molds have been designed to the customer’s specifications and the presses pre-programmed, the actual molding process is very quick compared to other methods of molding. Plastic injection molding process hardly takes times and this allows more parts to be manufactured from a single mold. The high production output rate makes plastic injection molding more cost effective and efficient. Typically, hot-runner ejection mold systems produce parts with more consistent quality and do so with faster cycle times, but it’s not as easy to change colors nor can hot runners accommodate some heat-sensitive polymers. Learn more about the key differences between hot-runner and cold-runner systems.
3. Enhanced Strength
In plastic injection molding, it is possible to use fillers in the injection molds. These filler reduce the density of the plastic while it being molded and also help in adding greater strength to the part after it has been molded. In fields where parts need to be strong and durable, plastic injection has an option that other molding processes do not offer.
4. Ability to Use Multiple Plastic Types Simultaneously
One of the major advantages of using plastic injection molding for manufacturing parts is the ability to use different types of plastic simultaneously. This can be done with the help of co-injection molding, which takes away the worry about using a specific type of plastic.
5. Automation to Save Manufacturing Costs
Plastic injection molding is an automated process. A majority of the injection molding process is performed by machines and robotics which a sole operator can control and manage. Automation helps to reduce manufacturing costs, as the overheads are significantly reduced. Furthermore, with reduced labor force the overall cost of manufacturing the parts is reduced and this cost saving can easily be passed on to the customer.
Furthermore, automation allows for making precise and accurate injection molds. Computer aided design (CAD) and computer aided manufacturing (CAM) allow close tolerances during the making of the molds.
The Bottom Line
Using injection molding also ensures the parts manufactured hardly require any work after the production. This is because the parts have more or less a finished appearance after they are ejected from the injection molds.
Today, plastic injection molding is an environment-friendly process. The scrap plastic generated during the production process is reground and re-used. Hence, the process generates very little waste.