In this post, we'll look at the multiple benefits, drawbacks, and factors to generally consider when using injection molding to prototype plastic parts, most especially for companies that are looking for custom fabrication or plastic manufacturer in Las Vegas.
What is Injection Molding?
Injection molding is a manufacturing process where molten plastic is inserted into a mold that is designed to shape that plastic into a complex shape. Once the molten plastic cools and solidifies, the mold is opened, and the part is removed.
Injection molding is commonly used to make anything from consumer goods, automotive parts, medical devices, and industrial products. Its use in prototyping is continuing to grow, especially in companies that want to events an actual production-grade prototype.
Top Benefits of Injection Molding for Prototypes and Custom Fabrication
If you look at injection molding as a high-volume manufacturing process, you might be questioning why you would want to use injection molding to prototype plastic parts, but there are some legitimate, important reasons to use injection molding to prototype:
1. Real Material Testing
One of the key advantages of injection molding compared to other prototyping methods is that most prototyping methods uses temporary or simulated materials. If you are injecting the product using the actual plastic materials you intend to use in the production run, you have the most accurate testing, whether it is acrylic, ABS, nylon, polycarbonate, FDA-approved resins, etc.
Using these materials in the prototype phase means you get actual testing with regards to durability, heat resistance, flexibility, and regulatory adherence before going to full production.
2. Precision and Repeatability
Injection molded parts generally have tight tolerances, geometries that are accurate, and good surface finishes. If your prototype is intended to fit within assemblies, or if your prototype requires mechanical testing, that level of precision can be very important.
3. Faster Product Validation
Modern tooling techniques like rapid tooling or aluminum molds allow for faster mold production, which means your prototypes can be made in days instead of weeks.
This process dramatically shortens the design cycle, moving you much more quickly from concept to market-ready.
Limitations of Injection Molding When Prototyping
Injection molding for prototypes, like any method, is not suited for all scenarios.
1. Upfront Tooling Cost
The primary hurdle is upfront tooling / die cost. Even with cheaper molds like aluminum, tooling can cost from $1,000 to over $10,000, depending on complexity.
Even if injection molding is right for you, this tooling cost may not be worth it if you are only going to produce a handful of units or if your design is still likely to change during the development process.
2. Limited Flexibility with Design Changes
Once the mold is completed, changing the design means new tooling or changes to existing tooling, which can significantly alter your timelines and budget.
In early-stage development, when it is not uncommon to go through multiple iterations, all too often with 3D printing or CNC machining, you can change and improve on your design without many limitations.
3. Not Ideal for Very Low Quantities
For quantities of less than 50 units, the per-part cost will likely be higher than using other prototype methods. Injection molding becomes more economical as your volume goes up to higher levels or if you are transitioning into small batch production.
When to Use Injection Molding for Prototypes
Injection molding is the right choice when:
- You are starting mass production and want to validate the final materials used
- You will perform real-world performance testing on the prototype
- You are close to finalizing the design
- Realism and tactile-ness are important (i.e,. funding demos, user testing, etc.)
- There are complex features or working functions in the product
All Prototyping Inputs Compared
Compared to other prototyping process options, an injection molded prototype has the following differences in inputs:
| Method | Cost | Speed | Material Accuracy | Surface Finish | Ideal For |
| 3D Printing | Low | Very Fast | Moderate | Good | Early design validation |
| CNC Machining | Medium | Medium | High | Excellent | Mechanical testing |
| Injection Molding | Higher Upfront | Fast after tooling | Excellent | Excellent | Final testing and pre-production |
Example of Manufacturing Assembly Prototype - Wearable Technology.
Imagine you are a company that is developing a wearable health tracker. You have gone through several early prototypes in 3D printing, and while they got to a good starting point, they did not represent the flexibility of the final product or any skin-safe requirements.
By switching to injection molding, you can create 100 prototypes in medical grade plastic, which allows the company to trial the prototypes with:
- Clinical testing
- User feedback
- Investor presentations
Ultimately, sorting through the durability and skin irritation testing was successful. Overall short experience went a long way to show potential investors that the product conceptually was valid and cumulated in funding the company and establishing the path to full production as a priority.
Common Materials that are Used for Injection Molded Prototypes
There are common plastics that are available to you when undertaking injection molding, to give you some perspective on the capabilities:
- Acrylic (or PMMA) - Clarity and stiffness for display parts or light parts
- ABS - Good strength and impact abilities
- Polycarbonate - Tough and heat resistant
- Nylon - Flexible and durable for mechanical parts
- TPU - A flexible plastic for wearables, or an over-molded part
If you get the right maintained material, it will act like a final product.
The problem you could run into is if you don't pick the right material, and what you hoped the prototype would behave like is different from what you would prefer.
Custom Fabrication Services That Complement Injection Molding
When you are assessing an injection mold provider, look to find a full-service plastic manufacturer that can offer more than injection molding. The value-added services may include:
- Custom Fabrication
- Plastic Bending and Forming
- Laser cutting and engraving
- Thermoforming
- CNC Machining
These services may be aimed at adding branding, finishing details, or changes that would further prepare your prototype for driving or in on-road and real-world situations.
Is Injection Molding Worth It for Plastic Prototypes?
Most of the time, yes.
If you are prepared for production, want to validate real materials, or create a presentation-quality prototype, the investment in injection moulding is worthwhile. The time savings, performance, and accurate prototype measurements & behaviour far exceed costs, especially if you intend to deliver a proven concept to market efficiently and effectively.
If you are still exploring an industry or will perform several design iterations, then save yourself the money and use more flexible, low-cost methods until you have a more certain design.
Final Thoughts
Injection molding prototypes close the gaps from concept to production part, by offering real testing benefits, quality parts, and a scalable production portal. Whether acrylics, consumer products, biomedical devices, or industrial components, injection molding can help you validate your design in real, usage-based conditions.
Before you leap, make sure to weigh the pros and cons, and consider working with an established plastic manufacturer that provides custom fabrication, has speed or efficiency, including engineering support.