Taking a product from concept to reality is an intricate, expensive and time-consuming process. It’s not easy and there is a high degree of risk involved.
Engineering is only part of the process of successfully bringing a new product to market, and prototype production is only part of the larger engineering process.
It is, of course, a very important part.
Getting the prototype right can and often does determine the viability of a new product. It doesn’t, unfortunately, guarantee success. Do it right and the product might succeed. Do it wrong, however, and the project will struggle just to stay above water.
CAD design of child-safe bottle. (Image courtesy of Creative Mechanisms.)
The process of prototype production has many steps. It typically starts with the product design, which is done with computer aided design software (CAD). Once the product is designed, we then move to the engineering-for-production phase.
Pre-production prototypes can be generated partially or completely with three principal technologies: computerized numerical control (CNC) machining, 3D printing and injection molding.
Initial vs. Pre-production Prototypes
Just as there are different production techniques for different parts, there are different prototypes for different purposes.
Initial prototypes are very useful for proof-of-concept presentations and fundraising while pre-production prototypes are designed for product testing and consumer research prior to mass manufacturing.
Pre-production prototypes typically start as initial prototypes which are developed further as the production process gains momentum.
Let’s discuss prototype production by the two distinct phases we just identified:
Developing the initial prototype
Every project starts out with an initial prototype. The initial prototype is a physical model of the final product, typically (but not always) created in a plastic resin that’s different than the final production part.
ABS plastic is typically used if the prototype is 3D printed while a variety of plastics can be used if the part is CNC machined.
Production of the initial prototype involves three distinct steps:
1. CAD and Engineering
Frequently, clients with a concept for a part or product seek outside engineering support to develop drawings in 3D CAD software. SolidWorks, for example, can be used to craft a digital 3D model with the required dimensions.
Design starts by defining project requirements. These are often provided by the client, or they may be developed by the engineering prototype supplier. In either case, once the perfect 3D digital model is developed, it’s time to translate it into a physical model.
2. Prototype Production by CNC or FDM
In order to finalize a design, the design file is used to program CNC or Fused Deposition Modeling (FDM) processes. FDM is one of several available technologies known collectively as “3D printing.” The FDM machine builds parts by adding thin layers of ABS plastic on top of each other according to computer instruction.
CNC is an alternative way of developing a prototype; it is achieved by automated machining rather than the ‘building block,’ additive manufacturing method of FDM.
Which method is best for a given application depends on which process best reproduces and realizes the design and engineering of the particular project: some parts are better machined while others are better printed.
3: Evaluate the Prototype and Refine SolidWorks
Typically, three or four prototypes are made per project. In most cases, the digital model has to be tweaked because some things aren’t apparent until a physical prototype is made – the physical dimensions or other parameters may need adjusting.
In cases where major changes are made to the digital model, it’s necessary to print or machine another prototype. This iterative process may be repeated several times until the perfect prototype is obtained.
Pre-production prototypes
The initial prototype is often a necessity if one is trying to provide a working proof-of-concept to investors. It can also be a very useful final prototype for smaller scale production efforts.
However, for products intended for larger scale mass-manufacturing, pre-production prototypes (also known as injection molded prototypes) are a prudent step in the development process.
Initial prototype for child-safe bottle. (Image courtesy of Creative Mechanisms.)
The concept behind pre-production prototype development is to provide exact replicas of what will become the final product using the actual production material.
This is essential for product testing and/or consumer research before trying to bring the product to market.The process involves the creation of an injection mold typically used to produce 300-1000 replicas of the prototype part.
Pre-production prototype development can be thought of in three simple steps:
1. Engineering For Mass-Production
Before a mold is started, a mold engineer has to design it so that the mold cavity fills evenly, will be completely empty of air, and will cleanly eject the parts.
Once again, special software is used to optimize the mold design and to run simulations of injection mold cycles to identify any areas in the mold that are at high risk of producing a preventable defect. Read here for 10 commonly made injection mold defects and how to fix or prevent them.
In a good shop, engineering for mass-production is a cooperative effort between the design engineers and the tooling/production engineers. Open communication early in the engineering process is crucial to adjusting the design of the parts in order to optimize not only performance, but also the tooling, molding, and assembly of the product.
2. Mold Design & Construction
This is where the mold is drawn and all of the mold details are determined.
Pre-production prototype injection molds are different compared to production molds.
In actual production, manufacturers need the ability to produce many times the capacity of prototype injection mold tools, so the focus at this stage is not the volume of parts produced, but how fast a mold that can produce a few hundred parts can be made.
A pre-production mold is a precursor to a production mold because experimentation is too costly to be carried out by designing production tools. Frequently a pre-production mold will have the same number of cavities as the production tool. Often the production mold is much more complicated (more internal cavities).
An increase in cavitation is most typically prevalent in the consumer goods market. Instead of making one shampoo bottle cap or one breath mint case at a time, for example, producers will make 16 or 24 at a time (sometimes even more).
3. Prototype Injection Molding
Once the prototype injection mold is built, the plastic parts are shot in an injection molding machine or “press”.
Typically, 300-1000 parts are created for the purposes of product testing and consumer research. This is particularly relevant for heavily regulated industries that require FDA approval, medical trials, UL certification, MIL-spec, consumer product safety commission (CPSC) approval, or child resistant testing.
In the event that the tests of the injection molded prototypes come back with insufficient data and/or negative feedback requiring iteration, the part or device is redesigned, the mold updated and/or recreated and a new run of prototypes made.
An Example of the Initial Prototype Development Process:
To demonstrate the initial prototype development process, Creative Mechanisms created a short video of a self-assigned design project. The task and project requirements are self-derived because most client work in the prototype development business is subject to Nondisclosure Agreements that do not allow for public distribution.
The example project requirements included the following:
Design a child safe bottle to hold solids (such as pills) that could be dangerous to children. The prototype needs to be a novel design not currently on the market. Additionally, the bottle needs to function as a flip-top cap that utilizes a living hinge mechanism to open and close.
Living hinge mechanisms complicate prototype development because they necessitate that both 3D printers and CNC machines are used for the project. 3D printers are typically the quickest way to generate a quick prototype while CNC machines are the only machine capable of creating a living hinge (a piece of plastic no thicker than 0.005 to 0.010 inches). For more on living hinge prototype development read here.
Watch the video below to see the initial prototype development process from start to finish:
The prototype development process is designed to produce both working proofs of concept and final replicas of the manufactured product. If done properly, you will optimize your design while identifying and correcting mistakes before they present themselves during final mass production processes.
Executed properly, the prototype development process is an indispensable part of engineering a new product for market.