Prototype Injection Molding

A custom plastic part may go through several design stages as it evolves from an idea to reality. A 2D drawing of the part provides a baseline for creating a detailed 3D CAD model rendering of the part to be manufactured. After custom plastic parts have been clearly illustrated and may seem ready for production, there may be some very good reasons to consider prototype injection molding (making injection molded prototypes) before going into mass production. The following considerations will help you in determining your prototyping needs.

Producing real injection molded prototypes are usually a good idea if your parts have functional features that require very close manufacturing tolerances or appearance features that are critical to the desired overall look of the product.

Injection Molded Prototypes vs 3D Printed Prototypes

Recent news heavily features the advent of 3D printing technology as a solution for many prototype injection molding applications. Real world plastic injection molding can still be the best alternative for most prototyping scenarios in many cases. You should be aware of each prototyping method’s strong points to understand which is best suited for your application.

In a supporting role, 3D printing is sometimes useful to correct early design flaws and help visualize a finished product. But one clear benefit of using prototype injection molding is gaining manufacturing experience and knowledge that can be applied when starting to prepare for production . Testing the chosen production material along with the injection mold design offers the manufacturer a preview of any potential problems that may arise in future production.

Prototypes with 3D printing

No tooling required
Average lead times from 5 to 15 days
Good for very low quantities
Does not reveal real manufacturing challenges

Prototypes with injection molding

Low cost tooling
Average lead times from 10 to 45 days
No quantity restrictions
Does reveal actual manufacturing challenges

Prototyping Prevents Hazardous Design Errors

Design problems that are not apparent in a 3D model or printed model can create delays and subsequently added production costs. Developing a prototype injection molding solution for your custom plastic part can help you to avoid some of these common mistakes before production begins:

Mistake #1

Surface and appearance defects

Computer models and 3D printed models are not 100% representative of real-world plastic molded parts. Injection molded parts often have surface and appearance flaws that can only be fully discovered through real injection molding. Many of these flaws, such as, sink marks, flow lines and gate imperfections can be addressed after prototyping.

Mistake #2

Non-uniform or unreasonable wall thickness

Many production failures of injection molded parts are the result of part designs with non-uniform or wall thicknesses that are either very thick or very thin by good injection molding standards. Plastic molded parts that require any of these conditions for proper function should always be prototyped by real-world injection molding to understand the production challenges that may lie ahead.

Mistake #3

Incorrect gate type or location

Proper gate placement and gate type on a plastic molded part ensures the mold cavity can be filled evenly and the plastic can be held under pressure long enough to produce parts with consistent quality. Testing the results of a proposed gate type or location on a custom molded part can only be done through prototype injection molding.

Mistake #4

Critical dimensions, warp and material shrink

Injection molded parts designed with dimensionally tight tolerances in order to perform properly are very good candidates for prototyping. All plastic materials and molded parts shrink and even deform after they are removed from the mold during injection molding.

The amount that a plastic part will shrink or warp depends on many factors, such as, the plastic type chosen and a wide variety of mold design and processing factors. The best way to gain insight on how repeatable a plastic part will be on tight dimensions is through real injection molded prototypes.

Prototype Injection Molds vs Production Injection Molds

Unfortunately, in the injection molding industry there are very broad assumptions and cliché names for plastic injection molds. Many of these assumptions and category names for molds are not only untrue and misapplied, but they also confuse engineers and buyers of custom molded parts. Perhaps the most misinformed assumption that resides in our industry is that there is a clear and well-defined difference between a prototype injection mold and a production injection mold. That is incorrect and we can expand on this by giving you some commonly used mold types along with the real scoop about each of them:

Rapid prototype injection molds

Any mold within this category is available at considerably less cost than traditional injection mold tooling. This cost assumption is considered true most of the time. But, any mold that is manufactured by “rapid prototyping” should be assumed as made by 3D printing and 3D printed molds have a very narrow set of advantages. With their relatively quick manufacturing time, they offer a cost-effective way to test a basic design but should only be used for extremely low quantity molding. In most cases, a prototype injection mold made from aluminum is a much better choice for near the same cost.

Production Injection Molds

Beware of “production injection molds”. Engineers and buyers within the injection molding industry blindly specify that production injection molds should be made from steel. The first assumption of most any injection molding company is that production injection molds are made from steel. As mentioned above, the proper reference between a prototype injection mold and a production injection mold should not be the metal that it is made from. A production injection mold should be designed and constructed to accomplish the fastest cycle times, the highest quality parts, and the longest tooling life possible no matter the metal that it is made with!

Aluminum Molds For Prototype Or Production!

There is an old school stigma that any plastic injection mold made from aluminum should be considered a prototype mold with a limited tool life. That is incorrect. Customers often ask, “Can you build an aluminum prototype mold for me?” The answer of course is “sure we can build an aluminum prototype mold for you, or we can build you an aluminum production mold.” The point is that the type of metal used for building the mold does not determine if it should be considered a prototype mold or a production mold. The difference between a prototype aluminum mold and a production aluminum mold is the mold design! If the mold is designed with a single cavity for a very specific purpose of making a limited number of prototypes it will be designed for that purpose. Likewise, it can also be designed with one or multiple cavities and all the features required for mass production.

Prototype Injection Mold Designs

The design features of a prototype injection mold should try to represent the basic design intent of a future production mold within a budget. Using the intended gate location and type, ejection locations and other important tooling features can help designers and engineers discover any manufacturing challenges. Be cautious of prototype injection molds that are constructed using 3D printer technologies. 3D printed prototype molds are not representative of true production injection molding conditions.

The prototype injection mold should:

Incorporate the intended gate type and location on the part.
Be made from mold materials that can test the intended mold temperatures during processing.
Have the ability to keep up with the production-intended cycle times.

Get Production Quality Prototype Injection Molds as Fast as 10 Days!

MSI Mold’s team of experienced tooling engineers and injection molding technicians can guide you for your specific custom plastic part prototyping needs. We can:

Eliminate design risks before building production plastic injection molds
Deliver production quality parts from production grade materials
Provide superior quality over 3D printed parts
Reduce unseen final costs to your injection molding project
Satisfy low volume introductory production needs

Affordable Prototype Injection Molds Built In-House

Through our plastic prototyping services we can offer you the same options that exist for long term production projects:

A large plastic material selection
A variety of standard or custom colors
Insert molding or substrate overmolding
Assembly of your injection molded parts
Pad printing and other part decorating

For a fast start to your project, use our plastic prototyping services! For more information on prototypes, plastic injection molding, custom injection molding, insert molding, and more contact us today. We are the a leading injection molding supplier in the USA.

Benefits Of Prototyping Plastic Parts

Rapid prototype injection molding is a preferred method that not only helps engineers and designers confirm part quality, but also delivers real-world parts that can be market-tested before designs are considered finalized. In addition to design verification and structural validation, you can use rapid prototype injection molding to help finalize tooling designs for your long term production runs. Rapid injection molding greatly benefits buyers of products with strict appearance requirements and functionality early in product launch phases. Before you spend extra on production tooling, contact MSI Mold for a quote rapid prototype injection molding. Other benefits of making prototype plastic parts before full scale manufacturing begins include:

Faster & More Reliable Product Launch: Many products fail to succeed for many reasons, including costs and price miscalculations, lack of market testing, and worst of all—product failures. Rapid prototyping and market testing can reduce these challenges before a product launch.
Better Product Functionality & Appearance: When products are judged aesthetically based on engineering drawings and visualizations, they often fail to impress in real-world production scenarios. You can also field-test a prototype sample for functionality and aesthetics.
More Efficient Design Process: A prototype can actually help shorten the overall engineering and design review phases of a new product. And, when you have a prototype plastic part in hand, you can easily convince its market viability to stakeholders.
Reduced Tooling Costs: When manufacturers don’t prototype, they often have to rework their production tooling. If you opt for rapid prototype injection molding, you’ll find and address any challenges before you make expensive production molds.

Prototype Injection Molding