When it comes to mass production, nothing beats injection molding. From security tapes to packaging material and even furniture pieces, plastic is ruling the work.
The bulk production of each demands more initial investment in tooling than other manufacturing methods like CNC machining or 3D printing.
However, the cost of each individual item will be much lower than it would be using conventional plastic production techniques. Because of the low unit cost, it is a practical choice for mass production.
Let’s get into the main aspects of Injection mold designing.
Foundational Design Principles
Tolerances in Injection Molding
The tolerance for error in a typical injection molding process is roughly 0.003 in. The design of the part and the resin used heavily influence the amount of shrinkage that can occur.
ABS and polycarbonate, which are both rather stable resins, have a value of 0.002 in./in., while TPE, which is more prone to degradation, has a value of 0.025 in./in.
The Thickness Of The Walls
Sink and warp are two common flaws that can be caused by improper wall thickness. It is recommended that an injection-molded component has a consistent thickness throughout.
All walls should be between 40 and 60 percent thicker than their neighbors and should fall within the resin’s suggested thickness range.
Foundational Geometry
Remove bulky walls by coring out the necessary sections. A high-quality molded component offers the same performance. Unnecessary thickness can affect the proportions of an item, weaken it, and call for additional processing.
Draft
Application of draft to mould design components is essential for preventing warping during cooling and facilitating unmolding. A correction of 1-2 degrees will do the trick in most cases.
We recommend including if there are any vertical faces. There’s a lurch of five degrees.
Offbeat Measures
A cam-operated slide that pushes a mold component into place when the mold closes. Side actions are typically employed to deal with an undercut or to make way for an unapproved outer wall.
The part is released from the mold thanks to the side action, which pulls away from it when it opens. Sometimes shortened to “cam.”
Undercuts
Interlock between the part and one or both mold halves formed by a section of the part that casts a shadow over another section. One such example is a hole punched into the side of a part perpendicular to the direction of the mold opening.
When an undercut is present, either the part cannot be released from the mold or the mold cannot be opened.
Bosses
The term “boss” refers to a protruding stud used to engage fasteners or support features of other components that pass through it.
Designing a part with excessively thick bosses increases the possibility of sinks and voids. If you want your bosses to last longer, you might want to add ribs or gussets to them.
Gates
The gate of an injection mold tool is the aperture through which resin flows to fill the mold’s interior chamber.
Ribs
Ribs are thin, wall-like structures that run parallel to the mold opening direction and provide additional reinforcement for structural elements like bosses and walls.
Ribs should take up no more than 60% of the wall thickness to avoid sinking.
Ejector Pins
After the plastic component has cooled, an ejector pin is inserted in the mold’s back side to aid in removing the part from the mold. The number of ejector pins an item needs can be reduced with careful draft design.
Logos And Text
Milling text from logos and sans-serif fonts like Text Sans will be the simplest. Our suggestion is that you choose fonts no smaller than 20 points in size and no more than 0.010 inches (or 0.015 millimeters) in depth.
Manufacturing & Design
Both the design and the manufacturability of a product need to be well thought out, as they significantly impact the product’s final price and quality. This is very important for major industries like lithium ion batteries companies or bigger packaging companies.
Thanks to the expertise of the right team, you will have a solid grasp of the critical importance of injection molding from a sales standpoint.
While a design’s creativeness and ergonomics are certainly important, a practical engineering study is frequently crucial in delivering a durable, user-friendly, and cost-effective end result.
Quality Management For Injection Molding
Since injection molding is used to mass-produce components by the thousands, if not millions, quality assurance is essential.
- Scientific molding is a method whereby the optimal setup process for an injection molding project is developed, optimized, and documented for future reference. As a result, each batch of manufactured components will be identical to the last.
- FAI stands for “First Article Inspection” and is a process used to ensure that manufactured goods are up to standards. When injection molding FAIs, we focus on quality as if it were life or death. A customer’s most important part dimensions can be specified using GD&T.
- PPAP, or the Production Part Approval Process, is a quality assessment method popular in the automobile sector. This technique ensures that a manufacturing process consistently produces a high-quality end product. The 18 different parts of a PPAP review cover everything from customer sign-off to making a sample item.
- ISO 13485 is the benchmark for the healthcare sector. Among these are operational qualification (OQ), design qualification (DQ),and performance qualification (PQ).
Conclusion
As a result of its minimal material waste and per-part cost, injection molding is typically utilized for making plastic parts at a much bigger scale. It’s a fantastic production method for many different businesses.
From healthcare, automotive, food, textiles, to even household stuff and baby gear, plastic injection molding is one of the top production methods.
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