Injection molding is among the most effective production methods, but its accuracy depends on the mold design. Slight design problems can result in expensive production downtime and low product quality.
Studies show that defects in injection molding can be attributed to design issues. Bad design decisions slow production and produce poor quality, such as warping, sink marks, or uneven surface texture.
The key design tips for injection molding
In this blog, our experts will dive into key design tips for injection molding. Let’s begin.
Maintain Uniform Wall Thickness
One essential requirement for injection molding to succeed is a constant wall thickness of a particular component. If the thickness of a portion of the material is uniform, the material moves smoothly through the molding cycle, and the part is again more dependable and accurately formed.
Wall thickness can vary throughout a specific structure, resulting in uneven cooling, warpage, or intrinsic stresses. To prevent such problems, it is advisable to maintain a uniform thickness across the design. Due to the raw materials used, walls are generally produced to a 2-3mm range.
Incorporate Appropriate Draft Angles
A draft angle is a slight taper applied to the vertical walls of the part. It helps prevent the part from sticking to the mold during the ejection process. Without enough draft, parts may experience surface damage or get stuck, leading to delays or defects.
The draft angle is usually estimated to be between 1 and 2 degrees; however, it depends on the part’s material and design complexity. Correct draft angles mean less pressure is applied, making part-making smoother and more efficient.
Avoid Sharp Corners
Any point on an injection-molded part with prominent corners might show several problems, such as unsuccessful material flow and enhanced stress points that may result in cracks or weak points in the final part. Since material flow and part strength depend on the design, it’s always recommended to blunt sharp corners with fillets or radii.
Design Efficient Cooling Channels
Efficient cooling channels must exist to shorten the cycle time and uniformly cool the parts formed during the injection molding. These channels are essential to prevent defects such as warpage or unequal shrinkage because the part is cooled on all its surfaces.
These channels need to be located as close to the part as possible, especially if it has a thickened diameter, to cool it faster. Advanced techniques, such as conformal cooling channels, can optimize heat distribution and reduce overall production time, leading to better part quality and cost savings.
Plan for Proper Gate Placement
This is the key to gate placement because locating a gate is influential in determining the flow of material to the mold and the quality of the end part. The gate is the entry point of the molten plastic into the mold, and it is an important area because it affects the part’s appearance, strength, and use.
Strategically placing gates helps avoid issues such as weld lines, air traps, and uneven filling. Factors such as part geometry and material flow must be considered when selecting gate locations.
Minimize Undercuts and Complex Features
They can significantly complicate the IM process, requiring the creation of secondary molds or the incorporation of special tools such as slides and lifters. This process is costly and time-consuming.
Reducing undercuts and avoiding some complexity of features in the mold ensures that it is relatively cheap to produce and that manufacturing is easier. In case of conflicts with molding parameters, consider redesigning the part so it can be fed through normal molding processes; otherwise, opt for other designs, like inserting molding or movable cores.
Optimize Rib and Boss Design
Optimizing rib and boss design is crucial for adding strength to a molded part without compromising its appearance or functionality. To avoid creating sink marks on the opposite side, the ribs should be about half the thickness of the wall.
Placing ribs at the right angle and symmetrically helps improve part rigidity without causing material flow issues. Similarly, bosses which are used for screw placement or reinforcement should be reinforced with ribbing and designed to prevent warping.
Properly designed ribs and bosses enhance the part’s overall strength while ensuring efficient molding and minimizing defects.
Consider Material Selection Early
Evaluating the material before designing is essential to realize the desired functionality and performance of the molded part. The choice of material also impacts parameters such as shrinkage ratios, strength, thermal stability, and the overall design of the part and the molding cycle.
For instance, some materials may need a certain wall thickness or longer cooling time to avoid some defects. Early material selection ensures that the part meets functional and aesthetic requirements while minimizing production costs.
Implement Proper Venting
Venting is critical to creating a passageway for air gases and other substances to be liberated from the mold cavity during injection molding. A lack of vents can lead to defects such as burn marks, inadequate filling, or unnecessary pressure buildup.
Vents should be strategically placed at the highest points of the mold where air accumulates, and their size should be carefully controlled to avoid material leakage.
Plan for Tolerances and Fits
Planning for tolerances and fits is crucial to ensuring your injection-molded parts assemble correctly and function as intended. Tolerances indicate the deviation of the part’s dimensions. Therefore, accurate tolerance design aids in determining the fit between the parts.
Smaller tolerances lead to increased cost and a high scrap level, while more general or large tolerances lead to poor part performance. As with nearly all manufacturing processes, one must find the right fit to meet the molding process requirements.
Conclusion
Mold design decisions should consider several aspects that affect part quality, manufacturing, and costs. This helps increase productivity and decrease the chances of defects in the product produced in the actual molds.
If you require professional advice and mold design services, then Go4 Mould is the best option. Our Design professionals are always here and ready to turn your visions into reality with delicate and accurate precision. Call us today and start your project with us now!
