What Are Some Of The Considerations For Injection Molding:
Before you endeavor to produce a part via injection molding consider a few of the following things:
Case Study: Using A Plastic Injection Mold To Create A Gutter Cleaning Tool
Recently, we had an entrepreneurial client come to us with an idea for a plastic part. He had jury-rigged an innovative gutter cleaner from parts he bought at a local hardware store. On his own, he produced about a dozen gutter cleaners. But he needed to scale his production to make the product commercially viable. He came to our team at Rex Plastics to find out whether plastic injection molding was right for his design.
After reviewing the hand-made prototype, we recommended that he use injection molding for the following reasons:
- The plastic part was smaller than 40g.
- The client needed to manufacture more than 1000 plastic parts per year.
- The plastic parts wall thickness was uniform.
- The plastic part could be made from a thermoplastic material.
- The function of the plastic part was more important than its aesthetics.
- The client could wait several months before starting mass production.
We were able to design a mold for the gutter cleaner, build a prototype, tool the mold, and begin production in just a few months.
Today, the client purchases thousands per year, and order quantities for his gutter cleaner are climbing steadily.
Reducing Injection Molding Costs
The cost of the mold is largely defined by the complexity and the amount of time it takes to produce it. We advise adhering to design for manufacturing principles to drive down part costs with injection molding.
The cost of producing the mold can be reduced by applying the following design guidelines:
Evaluate the CAD model to determine its feasibility before undertaking an injection molding project. Eliminate potential bottlenecks such as steep angles, undercuts, and other complex geometries.
Evaluate the models design to eliminate unnecessary features. This reduces the molds size and the material used to develop the model.
Apply a core cavity approach that simplifies the design of Side B of a mold. The core cavity approach involves sinking the wall cavities into the mold base, thereby reducing the need to mold steep draft angles while improving surface finish.
Embrace the use of self-mating parts to reduce the need to create multiple molds when one universal mold can be used to achieve similar results.
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Products That Can Be Produced Using Injection Molding
How Does Plastic Injection Molding Actual Work
Plastic is molten within the machine used for the injection molding and is then injected into the mould under high pressure.
Afterwhich, the material is cooled down, it solidifies and is then released by opening the two halves of the mould.
This technique, therefore, allows the production of a fixed-sized pre-defined plastic product.
For this reason, in order to facilitate the process, the parts used within the injection molding process need to be designed very carefully by either a qualified designer or specialised engineer.
Afterwhich, a tool-maker needs to create the mould, according to the design, usually using materials such as steel or aluminium.
So, the injection molding process actually can be sub-divided into three phases:
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Automotive Plastic Injection Molding: The History
In the early days of the automotive industry, cars were made almost entirely of metal, which meant they were clunky and extremely heavy. However, the industry became advanced and the plastics market erupted in the 1940s and 50s. Therefore, automotive manufacturers began to experiment with plastic car parts in their production.
In the 1970s, manufacturers rolled out the first cars with plastic decorative elements. Later in the 80s, they also introduced more functional parts like plastic headlights, bumpers, and fenders.
In the early 2000s, automotive manufacturers unveiled the first plastic structural components for cars, which had the advantage of being more lightweight than their metal counterparts, unlocking improved fuel efficiency and cheaper production. Today, injection molding is now a dominant production method for manufacturing plastic car parts in the automotive industry.
Ability To Produce Detail/complex Geometry
With the right tool design and a scientific molding approach to process optimization, injection molding can help manufacturers produce highly complex, detailed plastic parts in large volume with virtually no deviation.
The key to consistency is reliance on the comprehensive data collection and analysis techniques at the center of scientific molding, as well as the engineers trained in the process. Specialization is required to accurately develop and document the specifications, settings, and steps required to create a tightly controlled and repeatable manufacturing process. When done correctly, impressive details and geometries follow, such as those pictured below:
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Injection Moulding Quote: Protoquote With Design Analysis
Product designers and engineers can upload a 3D CAD model online at any time to receive an interactive ProtoQuote® with free design for manufacturability analysis and real-time pricing information within hours. The DFM analysis helps eliminate potential problems like sink, challenging undercuts or walls that are too thin or thick. Once a part design is ready and a quote approved, production begins almost immediately. Upload a part today for a ProtoQuote with design analysis.
Needing to solve difficult tooling and design issues? Shut-offs are a design element that help engineers solve this. Read more about incorporating shut-offs into your mould design.
Why Molding Material Matters
Choosing the wrong material can lead to premature component failure and consequences ranging from inconvenient to extremely costly. Contact Valencia Plastics today to begin your free expert consultation and learn more about material selection and other factors that dictate the success of your plastic molding project.
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When It Comes To Injection Molding Can Learn A Lot From Extrusion
admin 1 | Feb 21, 1999
|The quality of the melt has a lot to do with the quality of the final part, yet because it’s harder to measure, it’s harder to control-and too few people bother. Here’s what that quality control can do.|
|In screw design, the longer the metering section, the better the injection rate at the same backpressure. As backpressure is reduced, efficiencies improve even more. Applying more backpressure is commonly done in molding to fill out the mold, but backpressure is a poor substitute for proper screw design.|
Dray believes the injection unit is the foundation of the molding process, yet he says it has generally been overlooked, and the process technology involved in the injection unit has been disregarded. “The current screw design technology used is from the 1950s,” he says. “In the 1950s, ’60s, and ’70s, the extrusion industry revolutionized process technology. The motivating force was the advent of measuring and monitoring equipment that could accurately describe product quality.”
L/D Lessons to be LearnedIn a technical paper Dray has authored, “Screw Design In Injection Molding,” he details the impact of screw design on extrudate quality and the need for injection molding machines to incorporate systems capable of accurately monitoring extrudate quality and screw performance, systems that have long been standards in the extrusion industry. “In injection molding, the measuring is more difficult, but not impossible,” says Dray.
Full Injection Molding Material List
We hope this brief overview helped you to understand some of the most popular injection molding plastic types, their properties and applications. Please note that we can work with you to modify all of these materials with lubricants, glass fibers and UV stabilizers to suit your unique project needs.
Here, you can check out our full material list for plastic injection molding. You can also explore the most common injection molding defects and their solutions in our recent article. Ready to collaborate with us on your next manufacturing project? Request a free quotetoday!
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Advantages Of Injection Molding For Automotive Applications
Injection molding is an established production process in which automotive mold manufacturers inject molten plastic materials into a mold cavity. The melted plastic then cools and hardens, and the manufacturers extract the finished part. Though the mold design process is critical and challenging , injection molding itself is a reliable method for producing solid plastic parts with a high-quality finish.
Here are a few reasons why the process is beneficial for automotive plastic parts production:
Plan For Dimensional Deviations
Speaking of warping, you need to accept that its a natural part of subjecting materials to extremely high temperatures and cooling them down. If you need an extremely high degree of dimensional accuracy for your injection molded parts, this warping is something you will need to anticipate. Every resin behaves differently, so you may need to print your mold multiple times before you can get this right.
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Benefits And Limitations Of Injection Molding
Injection molding is an established manufacturing technology with a long history, but it’s constantly being refined and improved with new technological advancements.
Below is a quick rundown of the key advantages and disadvantages of injection molding to help you understand whether it’s the right solution for your application.
Benefits of injection molding
Injection molding is the most cost-competitive technology for manufacturing high volumes of identical plastic parts. Once the mold is created and the machine is set up, additional parts can be manufactured very fast and at a very low cost.
The recommended minimum production volume for injection molding is 500 units. At this point economies of scale start to kick-in and the relatively high initial costs of tooling have a less prominent effect on the unit price.
Almost every thermoplastic material can be injection molded. This gives a very wide range of available materials with diverse physical properties to design with.
Parts produced with injection molding have very good physical properties. Their properties can be tailored by using additives or by mixing together different pellets to achieve the desired level of strength, stiffness or impact resistance.
This means that hundreds of identical parts can be produced every single hour.
Limitations of injection molding
Embed Metal Rods Or Supports
If you plan on using the same mold for a hundred or more cycles, consider adding hollow channels on the edges of the mold. Placing metal rods in these channels greatly increases the robustness of the mold. It also reduces the warping of the plastic material during the repeated heating and cooling cycles, ensuring that dimensional accuracy is preserved longer.
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Materials Used In Blow Molding
Our blow molding capabilities extend to small and large parts using single or multi-part molds, including both air needle and blow pin models. The exact techniques used for a given project depend largely on the complexity and desired physical characteristics required by the design. The material selection process can be similarly complicated and often requires professional guidance for optimal results.
Design For Injection Molding
There are several factors that may affect the quality of the final product and the repeatability of the process. To yield the full benefits of the process, the designer must follow certain design guidelines.In this section, we outline common defects of injection molding and basic and advanced guidelines to follow when designing parts, including recommendations for keeping the costs to a minimum.
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Pros And Cons Of Injection Molding
Since injection molding is a very scalable and repeatable process, the end result is that you get identical parts in high volumes. If you are manufacturing critical parts that need high quality and consistency specifications, or if your brand reputation demands consistency in the product, then injection molding can help you achieve those goals at scale. Injection molding can also match any physical properties desired because there are a large number of plastic compounds available to inject into the mold. Lastly, injection molding is a relatively more environmentally friendly process than some other manufacturing processes. There is a low amount of scrap produced in the process of injection molding, and depending on the type of plastic used, the remaining material or scrap material can be crushed, re-melted, and re-used again.
Though injection molding has its benefits, there are some downsides as well. Injection molding is an expensive process at the beginning. One has to first design and prototype the product. Once that happens, the next step is to design and prototype the mold. After certain testing and iterations, the final mold is prepared. All of the testing, iterations, and mold creation takes a reasonable amount of time as well. Secondly, injection molding machines have size limits. Hence, if your manufactured item is large or complex, then you may need to create multiple pieces and then fix them all together to get the final product ready.
Tip #: Fit Multiple Parts In One Mold
As we saw in a previous section, fitting multiple parts in the same mold is common practice. Usually, 6 to 8 small identical parts can fit in the same mold, essentially reducing the total production time by about 80%.
Parts with different geometries can also fit in the same mold . This is a great solution for reducing the overall cost of assembly.
Here’s an advanced technique:
In some cases, the main body of 2 parts of an assembly is the same. With some creative design, you can create interlocks points or hinges at symmetrical locations, essentially mirroring the part. This way the same mold can be used to manufacture both halves, cutting the tooling costs in half.
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Why Working With An Experienced Injection Molder Matters
In order to truly leverage the benefits of plastic injection molding, its important that manufacturers seek out experienced custom injection molders that know how to maximize efficiency and overcome any design or process issues that might arise.
Having the best equipment, technology, and materials will only get you so far its having the best, most experienced injection molding engineers and tooling partners that will really make a difference in your lead times, costs, and final quality.
Before deciding on an injection molder for your project, ask these key questions:
- Does the molder have in-house engineering expertise?
- Do they have scientific molding and overmolding capabilities?
- Do they have in-house tooling design and maintenance capabilities?
- Do they have robust QA/QC and testing procedures?
- Do they understand the complexities of my industry and the nature of my products?
If you can answer Yes to those questions, you know youll be choosing an experienced partner you can trust to deliver the quality, value, and expertise needed to affordably produce complex injection-molded parts. Read more in our guide, How Injection Molder Partnerships Influence Project Costs. Click the button below to download your copy now
What Plastic Is Used For Injection Molding
Plastic part manufacturers most commonly use thermoplastics for injection molding. Thermoplastics are polymers that turn into molten under high temperatures and solidify under cool temperatures. Unlike thermoset plastic material, which burns if it is reheated, you can heat and cool the thermoplastics multiple times before it degrades beyond use.
Youll most often see thermoplastics in plastic pellet-form for injection molding purposes. You can mix plastic pellets with colorants, recycled material, and even glitter or other specialty additives.
The most common types of thermoplastics are:
- Polyethylene is one of the most versatile plastics to use for injection molding. Polytheylenes high ductility, tensile strength, impact resistance, low moisture absorption, and recyclability make it an ideal material for plastic containers and bags.
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Tip #: Stick To The Straight
Side-action cores and the other in-mold mechanisms can increase the cost of tooling by 15% to 30%. This translates to a minimum additional cost for tooling of approximately $1,000 to $1,500.
In a previous section, we examined ways to deal with undercuts. To keep your production on-budget, avoid using side-action cores and other mechanisms unless absolutely necessary.
Typical Products Made With Plastic Injection Molding
Plastic bottlesare the most common product manufactured by the billions each year, ranging in multiple shapes and sizes. Typically, the plastic bottles used to hold potable water and other drinks are made from polyethylene terephthalate , because the material is both strong and light.
Electronic housings are also quite commonly fabricated with injection molding services. Used in devices such as remote controls, computers, televisions, medical equipment, and other consumer electronic components, housings are all produced by injection molding process. Injection molding services can manufacture any custom plastic enclosures for practically any application and sizes.
Toys: Imagine a building material which is lightweight, durable, and doesnt corrode it comes in many sizes and colors and is designed for easy precise assembly. The Lego brand of building block recognized by all is made of firmer plastic granules which are heated until liquefied and then injected into metal molds in which the plastic cools and solidifies into a studded brick or other shape. But whats important is that each brick and component is accurately molded so theyll all fit together. Its a precision product available in many colors, shapes, and sizes.
Household: Molded closures, containers, components, and drinkware are just a few of the common items that can be custom fabricated with injection molding.
- High-end Trash and Recycling Receptacles
- Vending Machine Components
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