Tag Archives: Injection

When Is Injection Molding Used?

Custom Thermoforming, Fiberglass, fiberglass products manufacturers, injection molding, plastic injection molding, , , , , , , , ,

Injection molding is one of the most popular and efficient manufacturing processes for producing plastic parts in high volumes. It involves injecting molten plastic into a custom-designed mold, where the material cools and hardens into the final part. This method is widely used across various industries due to its ability to produce highly accurate, consistent parts with complex geometries. However, injection molding isn’t always the best choice, and it’s important to know when it excels—and when alternative manufacturing methods are more suitable.

1. When Injection Molding Is Best Suited

a. High-Volume Production:
Injection molding is ideal for high-volume production runs, where thousands or even millions of identical parts are required. The upfront costs for creating the mold are relatively high, but once that investment is made, the per-unit cost drops significantly, making it extremely cost-effective for large-scale manufacturing.

b. Complex Geometries and Precision:
If your part has intricate designs, undercuts, or tight tolerances, injection molding is the right choice. The process can produce highly detailed and complex parts with consistent quality, making it suitable for precision applications in industries like automotive, electronics, and medical devices. For example, phone casings, medical syringe components, and automotive dashboard parts are commonly made using injection molding.

c. Material Versatility:
Injection molding allows for a wide variety of materials, including high-performance thermoplastics such as ABS, polycarbonate, and nylon. These materials offer properties like impact resistance, heat resistance, and chemical resistance, making them ideal for applications where durability and functionality are key.

d. Cost Efficiency Over Time:
Although the initial tooling costs for injection molding are high, these costs are amortized over the life of the mold, especially for high-volume production. This means that once you have the mold, each additional part is relatively inexpensive to produce, making it the go-to choice for long-term, high-volume projects.

2. When Injection Molding May Not Be the Best Option

Despite its many benefits, injection molding is not always the best solution, particularly for low-volume production, rapid iterations, or when upfront tooling costs are prohibitive.

a. Low-Volume Production and Prototyping:
If you only need a few hundred units or require rapid design iterations, injection molding may not be cost-effective due to its high tooling costs and longer lead times for mold creation. In these cases, 3D printing or urethane casting might be better options. These methods allow for quicker prototyping, cost-effective low-volume runs, and easy iteration. You could also consider using 3D-printed molds for injection molding, which is an emerging trend that allows for the production of up to 200 units at a lower cost than traditional molds.

b. Large Parts with Simple Designs:
For large parts that do not require precision, thermoforming may be a better choice than injection molding. Thermoforming has lower tooling costs, faster turnaround times, and can handle larger parts like automotive panels or trays without the need for complex molds.

c. Alternative Materials (Metal or Fabrication Needs):
For parts that require higher structural strength or heat resistance than plastic can offer, metal fabrication using materials like aluminum, steel, or even composites may be a better choice. Metal stamping or CNC machining is often used when the part requires superior mechanical properties that plastic cannot provide.

Conclusion

Injection molding is ideal for producing high-volume, complex, and precise plastic parts, but it may not be the best option for low-volume, quick-turnaround, or highly iterative projects. Alternative methods like 3D printing, thermoforming, and metal fabrication offer better flexibility, cost, and speed for specific applications. Evaluating the needs of your project will help determine whether injection molding is the right manufacturing method.

At Om Raj Tech, we take pride in offering tailored solutions through our partnerships with top-tier manufacturers specializing in injection molding, thermoforming, and fiberglass (FRP & RTM). With our extensive industry knowledge and representation of expert manufacturers, we ensure that your projects are handled with precision, efficiency, and quality.

  • Injection Molding: Om Raj Tech represents Jimdi Plastics, an ISO-certified injection molding manufacturer based in Michigan. Whether you’re looking for high-volume production, precision parts, or intricate geometries, we connect you with the right resources to meet your exact specifications. Jimdi’s expertise spans industries such as automotive, medical devices, and consumer goods.

  • Thermoforming: For thermoformed parts, Om Raj Tech partners with STM Plastics, a leading manufacturer specializing in custom thermoforming solutions. Based in Kansas, STM Plastics excels at producing low-to-mid volume runs, large parts, and rapid prototypes for industries like automotive, aerospace, and packaging. Their flexibility and cost-effective services ensure that your project gets the attention and customization it deserves.

  • Fiberglass FRP & RTM: Our representation of a leading fiberglass manufacturer allows us to offer high-strength, lightweight, and corrosion-resistant parts produced through Fiberglass Reinforced Plastic (FRP) and Resin Transfer Molding (RTM) processes. Whether you need large-scale structural components or intricately detailed parts, we have the capability to deliver durable and reliable solutions for marine, automotive, and industrial applications.

Contact Us to discuss how we can provide you with expert guidance and access to premier injection molding, thermoforming, and fiberglass manufacturing services. Let us help you bring your innovative designs to life with our trusted partners and industry-leading capabilities.

Cost Model for Pricing Plastic Injection Molded Parts

injection molding, Jimdi Plastics, plastic injection molding, , , , , , , , , , , , ,

Plastic injection molding is a widely used manufacturing process for producing high-quality, mass-produced plastic parts. Developing an accurate cost model is essential for determining part prices that cover production expenses while remaining competitive. In this article, we’ll walk through the key components of a cost model for plastic injection molded parts, explaining how to calculate cycle time, injection flow rate, ejection time, and other critical factors. We’ll also explore how material costs, machine rates, labor, tooling, and overheads influence the final price.

Key Components of a Plastic Injection Molding Cost Model

A comprehensive cost model involves understanding the full production process, from the initial injection of molten plastic to the ejection of the cooled part. The following sections break down each part of this process, providing formulas and methodologies to estimate costs accurately.

1. Cycle Time Estimation

Cycle time refers to the total time required to produce one part and consists of three main phases:

  • Injection time: The time it takes to inject molten plastic into the mold cavity.

  • Cooling time: The time required for the part to cool enough to be ejected from the mold.

  • Ejection time: The time taken to eject the cooled part from the mold.

This formula captures the core components of the injection molding process and helps you estimate how long each part takes to produce. Let’s explore how to calculate each part of this formula.

Cycle Time formula

a. Injection Time Calculation

The injection time is influenced by the volume of the part, the machine’s injection speed, and the material’s viscosity.

  • Part Volume: The volume of the plastic part being produced, measured in cubic centimeters (cm³).

  • Injection Flow Rate: The speed at which molten plastic is injected into the mold, determined by machine settings and material properties.

Plastic Injection Molding: Injection Time Formula

Factors affecting injection time:

  • Machine capacity: Larger machines can inject more material at once, increasing the flow rate.

  • Material viscosity: High-viscosity materials, like polycarbonate, are more resistant to flow, resulting in longer injection times.

  • Part geometry: Thin-walled or complex geometries slow down the injection process, as they require more precise control to prevent defects.

Injection Time Calculation Formula Example

For example, if the part volume is 50 cm³ and the machine’s injection flow rate is 25 cm³/sec, the injection time is:

b. Cooling Time Calculation

Cooling time is often the longest part of the cycle and is crucial to ensure the part solidifies properly without defects like warping.

Injection Molding Cooling Time Calculation

Where:

  • Wall thickness is the thickness of the part’s walls (in cm).

  • Thermal diffusivity constant (a) is a material property indicating how fast heat spreads.

  • T_mold, T_material melt, and T_ejection are the temperatures of the mold, the material in its melted state, and the material when it is ejected, respectively.

This formula is useful for estimating how long the part needs to stay in the mold before it’s solid enough to eject. The thicker the part, the longer the cooling time.

For a wall thickness of 0.2 cm, assuming the material is ABS (a = 0.00015 cm²/sec), with mold, material melt, and ejection temperatures of 50°C, 230°C, and 90°C, respectively, cooling time might result in approximately 15 seconds.

c. Ejection Time Calculation

Ejection time refers to the time required to remove the cooled part from the mold cavity. This includes the mechanical time taken by the ejector pins or air systems to push the part out of the mold.

  • Ejection Delay Time: Time for the mold to open and prepare for part removal.

  • Mechanical Ejection Time: Time for the ejector pins or other mechanical systems to push the part out.

Ejection time is generally short, usually between 1 and 5 seconds, depending on the complexity of the part and the number of ejector pins used.

Factors affecting ejection time:

  • Part geometry: More complex shapes require more careful ejection to avoid damage.

  • Mold design: The number and placement of ejector pins, as well as the presence of undercuts, influence ejection time.

  • Material shrinkage: Materials with high shrinkage can contract around the mold, making ejection slower and more difficult.

For example, if ejection delay takes 1 second and mechanical ejection takes another second, the total ejection time would be 2 seconds.

2. Material Costs

Material cost is a straightforward calculation, based on the weight of the part and the cost per unit weight of the material.

Material costs vary depending on the type of plastic (e.g., ABS, polyethylene, polycarbonate) and the supplier. Material costs should also account for any scrap or waste generated during production.

3. Machine Rate

The machine rate is the cost associated with running the injection molding machine, calculated based on the machine’s hourly rate and the cycle time.

  • Machine Hourly Rate: The operating cost of the machine per hour, which includes energy consumption, depreciation, maintenance, and overhead.

  • Cycle Time: Total time (in seconds) to produce one part.

Example for machine rate calculation

4. Labor Cost

Labor costs are associated with machine setup, operation, and quality control. These are usually calculated on a per-part basis by distributing the operator’s hourly wage across the cycle time.

Labor costs can vary depending on the level of automation. Highly automated processes will require less direct operator involvement, reducing labor costs.

5. Amortized Tooling Costs

Tooling refers to the mold used to shape the plastic part. Molds are a significant initial investment, so tooling costs are amortized over the total production volume.

Amortized tooling cost example

6. Overhead Costs

Overhead costs cover expenses such as plant utilities, administrative costs, machine downtime, etc. These costs are typically spread across the entire production and calculated per part.

7. Profit Margin

Finally, the profit margin is added to cover the company’s profit expectations. This is usually a percentage markup on the total cost.

Injection Molding Profit Margin Calculation

8. Final Cost Model Formula

The final price of the part can be calculated by summing all the cost components:

Cost Model total price calculation of injection molded component

Conclusion

Developing a robust cost model for plastic injection molded parts involves understanding each phase of the injection molding process, from cycle time calculations to labor, material, and overhead costs. Accurate tracking of factors like injection flow rate, cooling time, and ejection time is crucial for estimating production time and costs. With a comprehensive model in place, manufacturers can ensure competitive pricing while covering production expenses and achieving desired profit margins.

However, many injection molders quote based on wrong assumptions, often adding hidden buffers or overestimating certain factors, which unnecessarily inflates the quote. Rely on Om Raj Tech and our manufacturer to provide a quote with precision—no unknown buffers—giving you accurate, transparent, and precise quotes every time.

Contact Us