There’s a lot of room for expensive errors when it comes to injection Plastic Pail Moulding. Quality issues in injection-molded products can range from minor surface defects to more serious problems that can affect the safety, performance and function of the product. They can be caused by problems related to the molding process, material use, tooling design or a combination of all three.
As an importer or manufacturer of injection-molded products, some knowledge of common molding defects and how to avoid them can help you cut costs related to unsellable goods and product returns.
Let’s look at the most common quality defects related to injection molding, what causes them and what you can do to prevent them.
MOLDING DEFECTS OFTEN CAUSED BY PROCESS PROBLEMS
Some molding defects may be difficult or costly to address. Others can be prevented by adjusting the molding process, without the need to redesign the mold tooling or replace other production equipment. You can typically avoid these defects relatively easily simply by adjusting the flow rate, temperature or pressure of your mold.
- Flow lines
Flow lines appear as a wavy pattern often of a slightly different color than the surrounding area and generally on narrower sections of the molded component. They may also appear as ring-shaped bands on a product’s surface near the entry points of the mold, or “gates”, which the molten material flows through. Flow marks won’t typically impact the integrity of the component. But they can be unsightly and may be unacceptable if found in certain consumer products, such as high-end sunglasses.
Causes and remedies for flow lines
Flow lines are most often the result of variations in the cooling speed of the material as it flows in different directions throughout the mold. Differences in wall thickness can also cause the material to cool at different rates, leaving behind flow lines.injection molding defects For example, molten plastic, cools very quickly during the injection process and flow marks are evident when the injection speed is too slow. The plastic becomes partially solid and gummy while still filling the mold, causing the wave pattern to appear.
Here are some common remedies for flow lines in injection-molded products:
Increase the injection speed, pressure and material temperature to ensure the material fills the mold before cooling
Round the corners of the mold where wall thickness increases to help keep flow rate consistent and prevent flow lines
Relocate mold gates to create more distance between them and the mold coolant to help prevent the material from cooling too early during flow
Increase the nozzle diameter to raise flow speed and prevent early cooling.
Warping is deformation that can occur in injection molded products when different parts of a component shrink unevenly. Just as wood can warp when it dries unevenly, plastic and other materials can warp during the cooling process when uneven shrinkage puts undue stress on different areas of the molded part. This undue stress results in bending or twisting of the finished part as it cools. This is evident in a part that’s meant to lie flat but leaves a gap when laid on a flat surface.
Causes and prevention of warping in molded parts
One of the main causes for warping in injection-molded plastic and similar materials is that cooling happens too quickly. injection molding defectsOften excessive temperature or low thermal conductivity of the molten material can worsen the problem. Other times mold design can contribute to warping when the walls of the mold are not of uniform thickness—shrinkage increases with wall thickness. Here are some common ways to prevent warping in your molded parts:
Ensure the cooling process is gradual and long enough to prevent uneven stresses on the material
Lower the temperature of the material or mold
Try switching to a material that shrinks less during cooling (e.g. particle-filled thermoplastics shrink much less than semi-crystalline materials or unfilled grades)
Redesign the mold with uniform wall thickness and part symmetry to ensure greater stability in the part during cooling.
We are a professional molding company, sell different design of mold, 18L Bucket Mould is one of them,welcome to visit our website.