Design Tips for Optimizing Injection Molding Manufacturing
You may be wondering what injection molding is, how it works and the benefits it offers. In the guide below, we will provide clarification on some of your queries and focus on a few common examples of injection molded part defects along with their solutions.
What is The Injection Molding Process?
It refers to a manufacturing process that we at Creatingway usually use in the mass production of identical plastic components with excellent tolerances. The process essentially involves the melting of polymer granules or resins, then subjecting them to pressure to inject them into a mold where the desired plastic forms by cooling and solidification. The thermoplastic polymers that we use for the process may have colors or other additives. It has become a popular manufacturing process over the years due to its low cost of production per unit when producing high volumes. It also provides excellent repeatability and good design flexibility.
Design for Optimizing Injection Molding Manufacturing
There are a few factors that critically affect the final quality of the output and the repeatability of the process. Our team of professionals at Creatingway follows a strict set of guidelines to enable us to reap the full benefits that the process has to offer. Below is a more detailed description of the common defects in injection molding and some advanced guidelines that we follow to help us come up with top-notch parts and maintain a minimum cost of production.
Common Injection Molding Defects
Most injection molding defects arise from either non-uniform cooling rate during solidification or uneven flow of the melted thermoplastic polymer. Here are a few defects that we bear in mind when designing an injection molded part and a few of their solutions.
When certain portions cool at a faster rate than others, then the part may experience permanent bending due to internal stress. Parts that lack a constant wall thickness are more likely to experience warping.
When the interior of an injection molded part solidifies before its surface, a small recess or depression may appear on the otherwise flat surface. We call this a sink mark. Parts that have poorly designed ribs or are thickly walled are likely to experience sinking.
Small hair-like discolorations may develop when two flows meet. These knit lines reduce the aesthetic appeal of the part and may also decrease its strength. Parts with holes or abrupt changes in geometry are more likely to experience knit lines.
Plastics undergoing sinking usually apply pressure on the mold. During ejection, the walls of the injection molded part may slide and scrape against mold resulting in drag marks. It is a common defect in vertical walls that lack draft angles.
Trapped air in the mold may hamper the flow of material during injection, thus resulting in an incomplete injection mold. It is a common defect in parts with poorly designed ribs or extremely thin walls.
Design Rules for Optimizing Injection Molding Manufacturing
One of the greatest advantages of injection molding is that it easily allows us to form complex geometries, which may allow a single part to serve diverse functions. Upon production, we can later reproduce these parts at a lower cost. However, any changes that may arise later may prove to be costly. It is, therefore, crucial that you achieve the best results with the first outcome. Here are a few rules that we follow to avoid the common injection molding defects.
Use of constant wall thickness.
We strive to produce parts that have a uniform wall thickness by avoiding thick sections. This is key in avoiding warping, which is a common defect in non-uniform walls during cooling. If the need for walls with different thicknesses arises, then we try to make the transition as smooth as possible by using a fillet or chamfer. It ensures that the material flows more evenly when in the mold, thus ensuring the entire mold is full. A wall thickness ranging between 1.2mm and 3mm is a safe parameter for most materials
Hollowing Out Thick Sections
Thick sections are prone to sinking and warping. We are able to limit the maximum thickness of any section of our designs to the desired values by hollowing them out. To ensure that the hollowed section is strong enough, we utilize ribs in designing parts of equal stiffness and strength but of reduced wall thickness. Ribs also prove to be vital when we would like to improve the stiffness of a horizontal section without increasing its thickness.
Adding Smooth Transitions
There are instances when sections with different wall thicknesses are unavoidable. In this case, we use a fillet or chamfer to make smooth transitions. Similarly, the base of vertical features like bosses, ribs, and snap-fits is also usually rounded.
By following the practical guideline above, Creatingway has become a leading manufacturer of injection molded parts. If you any further inquiries, kindly contact us today.
Creatingway is concentrated on CNC machining manufacturing, prototype machining, low-volume manufacturing, metal fabrication, and parts finishing services, provide you the best support and services. ask us one inquire now.
Any questions or RFQ for metal& plastic technology and custom machining, welcome to contact us below
Call +86-0(755)-89492523 or send an inquiry to us
Welcome visit us, any metal and plastic design and machining questions, we are here to support you. Our services email address: