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How to Choose Between Rapid Prototyping Techniques?

How to Choose Between Rapid Prototyping Techniques?


Today’s consumer market is becoming increasingly competitive. In order to survive and develop, companies need to develop and introduce new products faster. Thus, rapid prototyping is becoming more and more popular. It allows designers and companies to constantly test and refine product design, and develop new products in a shorter amount of time. If you are engaged in industries of automotive, medical, industrial equipment, aerospace, consumer products, and so on, you should recognize the potential of prototyping for your product design and new product development. But what is rapid prototyping exactly? Why do you need it? Are there many prototyping techniques to choose from? And which technique is the most appropriate for your project? It is of great importance to choose the right prototyping technique to make your prototyping purpose achieved.

Tuowei-How To Choose Between Rapid Prototyping Techniques

Introduction of Rapid Prototyping

It is the process of quickly mocking up the future state of a product. It allows designers to test and verify the design and collect feedback from users and stakeholders to refine it. The main idea of rapid prototyping is based on setting a direction for designers to constantly improve and iterate their designs according to more accurate feedback, thereby promoting the success of new product development.

Benefits of rapid prototyping

1. Gain Accurate and Useful Feedback

It can be difficult to explain a concept to stakeholders and customers with only papers of written information. With rapid prototyping, it is able to communicate concepts concisely and effectively. It turns ideas, images, and concepts from two-dimensional visuals to hands-on products, allowing your customers, colleagues, and collaborators to actually use and test the products and foresee what the end product looks like. It avoids the misunderstanding in the communication of ideas and helps designers and companies gain more accurate and useful feedback from customers and stakeholders.

2. Save New Production Development Costs & Risks

It allows you to test and refine your concept thoroughly and to help eliminate costly design flaws that might not be evident at the early stage. It is much more cost-effective and safer to use a small volume of prototypes to verify the design and fix issues as they arise than to wait until development is underway.

3. Create Models for Sales & Trade Show

It is not just for verifying design anymore. Many companies now take advantage of this technology to create a product model for sales and trade show, especially for those companies in the industries of industrial equipment, aerospace, medical equipment, industrial machinery, and so on. It will be difficult and expensive for them to bring their products to the exhibitions. Then making a mold is a faster, easier, and more economical way to transport and display the products.

Tuowei-How To Choose Between Rapid Prototyping Techniques-1

Types of Prototyping Techniques

1. Additive Manufacturing

Additive manufacturing, known as 3D printing, is a technique that produces mock-ups from CAD files by adding materials layer by layer, using a 3D printer. It has become a valuable asset in the world of prototyping owing to the ability to more quickly and affordably craft a testable product from a 3D file. This technique is adopted by a broad spectrum of industries, including the medical, robotics, automotive, construction, etc.

In general, it is the fastest and cheapest prototyping technology for producing a small and medium quantity of rapid prototypes. It takes less time and money to prepare the machines for production. Only 3D printers are needed, unlike CNC machining or injection molding that requires a number of large high-precision machines.

But be careful, some designs or material might not be suitable for 3D printing. Otherwise, it will be rather costly. In addition, some special surface finishes may also add cost. If the surface finish aspect is not the first concern to your project, then it is the cheapest technique for prototyping.

A great advantage of additive manufacturing is that you can make the rapid prototype directly with the final material of your product. 3D printing can process many kinds of materials. It helps save your precious time of testing other materials after the prototyping.

2. Subtractive Manufacturing

In subtractive manufacturing, the materials are not added on top of each other. It is a process by which a 3D model is constructed by successively cutting material away from a solid block of material. Thus, compared to this process, 3D printing is much more eco-friendly. The most common subtractive manufacturing is CNC machining. 

CNC manufacturing is a more precise prototyping method. It gets better tolerance than 3D printing. And using this technology, you get an excellent surface finish right away. 

However, this method is more expensive than 3D printing. Because of the expensive cost of running CNC machines, there is always a MOQ. Also, it is quite complicated to produce an intricate design. It is not suitable for all kinds of product design. For example, if you want to build a rapid prototype with hollow design, the 3D printing is more appropriate.

3. Injection Molding

Injection molding is a method to obtain molded products by injecting plastic materials molten by heat into a mold, and then cooling and solidifying them. Injection molding is typically only used for producing pre-production prototypes and for the mass production of products with complicated shapes. It takes a large part in the area of plastic processing.

This process is expensive. You won’t go through it unless you were planning to mass-manufacture a product or unless you needed to produce s moderate quantity of prototypes parts. Costs of prototyping are generally much higher when using an injection molding machining, but once you generate several hundred copies, the economy of scale kicks in.

Critical Factors Should Be Considered in Selecting Prototyping Methods

The requirement for a rapid prototype varies in so many ways as each project, product, and design elements are different. Choosing the right rapid prototyping method is critical to the success of a prototype as each prototyping technique has its own compromise in terms of cost, speed, material, fidelity level, and development stage. Here are some key factors that should be taken into consideration seriously when you choose a prototyping technique for your project:

1. Purpose

Rapid prototypes are created for purposes which will vary in different stages of new product development. Each stage of new product development has unique requirements for prototyping.

The first stage is the communication and discussion of design ideas within a team. At this stage, an early mock-up of the concept is required for the clear and accurate demonstration of a design idea to others. In this case, you can choose either CNC machined mock-up or 3D printed model.

The second stage is the conceptualization of design. At this stage, the broad outlines of function and form of the new product are articulated. Then you can choose the 3D printed rapid prototype to get a feel for the shape and size of the product. If your products or parts are metallic, then CNC machining is your best bet.

The third stage is the embodiment of the design. It is the stage that you need to explore the functionality of your new products fully. At this stage, functional prototypes are required for testing, and the details are of great importance. You may also need more than one rapid prototype as there may be some changes and modifications. Then it is worth considering vacuum injection molding and high-resolution 3D printing.

The final stage is the detailed design stage. Any rapid prototype made during this phase is most likely used as the proofing of pre-production. In this case, the injection molding process is most preferred.

2. Fidelity

If you want to make a mock-up, choosing the right fidelity is essential to saving your time and money while achieving your prototyping purpose. Fidelity refers to how closely the prototype resembles the final solution. 

A low-fidelity rapid prototype only has essential characteristics of the end or targeted product. Low-fidelity prototyping is a simple and quick way to translate an idea or design to a testable product. But only some of the visual attributes of the final product are presented. The main purpose of making a low-fidelity prototype is to test functionality, rather than the visual appearance of a product. If your products, your customers and stakeholders value more on the functionality than the appearance, low-fidelity prototyping is recommended. It is more economical and faster to produce through 3D printing or CNC machining.

A high-fidelity prototype is in closest resemblance to the final design in terms of details and functionality. Teams usually make high-fidelity prototypes when they have visual designs of the product and when they want to test the customers’ preference for the product’s appearance. This type of prototype is also right for demonstration in exhibitions. It gives customers a clear picture of what the final product looks like and how it is supposed to work. An excellent high-fidelity prototype is more convincing. If you emphasize a lot on high precision, low tolerance, and superior surface finishes, then you should choose CNC machining or injection molding. 

3. Materials

Material selection also plays an essential part in determining the right prototyping technique. If some quality and performance aspects of your product, such as the surface finish, durability, are linked to special material properties, then additive manufacturing might not be the best choice. 3D printing is suitable for processing Nylon, PLA, ABS, ASA, TPU, as well as metal materials of aluminum, stainless steel, titanium, Inconel; CNC machining is for ABS, Nylon, polycarbonate, PEEK and metal parts of aluminum, stainless steel, titanium, brass; injection molding is only suitable for plastics materials and Nylon material.

4. Quantity 

How many prototypes you need to make is essential as well. Some rapid prototyping techniques are only cost-effective for small quantity. For plastic prototypes, 3D printing is appropriate for producing both low quantity and medium quantity. CNC is also suitable for producing a medium quantity of prototypes but limited to those with a simple design. Otherwise, 3D printing and injection molding are more appropriate. For processing metallic prototypes, injection molding is not suitable. 3D printing is recommended for producing a small number of metallic prototypes. In other cases, CNC machining is more preferred.

5. Spend & Speed

Time and money needed to get the rapid prototype manufactured should also be considered in the selection of the prototyping method.

3D printing might need some post-processing time, but it is relatively quicker and cheaper. Injection molding requires less or no post-processing, but it takes much more tooling cost. The cost of CNC machining is proportional to the complexity of the design. In addition, the overall cost of injection molding or CNC machining is also closely linked to the quantity because of the expensive machine running cost.

In Conclusion

All these types of rapid prototyping methods have their unique advantages in certain cases. Bearing in mind the above five key factors when you decide on the type of prototyping tool. New product development always involves making prototypes to test and verify idea and design. But the quality of testing and feedback, as well as the following modification will highly depend on how good your prototype is. Choosing the correct technique is vital to your new product development success.

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