Building Prototypes? Here are Your Options.

Prototype processes continue to evolve, practically on a daily basis. Depending on the product and development needs, there are several options and each has its advantages and disadvantages. We will cover most of the processes available today and have used every one at one time or another.  

This blog is meant to give the reader a basic understanding of the processes; if we tried to go into full detail on all of the available prototype processes, we could literally write a book, or two.  

One interesting note about prototypes vs production processes. It is possible to create parts with some of these prototype processes that are not possible in higher volume production processes. This is valuable for a couple of reasons:

  1. You can quickly build models to see how things function or feel without having to worry about how it will be manufactured.
  2. This process allows for more creative options and if the volumes are low enough, selling parts using this process might be a viable option.

The disadvantage is, just because you can make the part using one of these processes, doesn’t mean you can make the part in higher volume production without some potentially huge cost impacts.

On the other hand, with the trend of small volume manufacturing and more customized products, some of these lower volume processes are being used for production more and more.  

Process Options

SLA (Stereolithography Apparatus) – is a process that uses a laser to cure liquid material.  The laser will very quickly move over the entire cross section of part to cure a layer. Each layer is built onto the next to create solid wall sections, and finally a full part.   

  • Advantages: This process produces a very good resolution, or surface finish and dimensional accuracy. Usually the material is milky white and can be painted if needed.
  • Disadvantages: The material strength is not production quality. Materials are getting better every day but this is mainly used for testing how parts fit together, size and shape, etc.

SLS (Selective Laser Sintering) – is a process similar to SLA except it uses powder instead of liquid. The laser will cure the powder material layer by layer to build up to a solid part.  

  • Advantages:
    • This process can produce very strong parts since it basically melts powder versions of engineering materials.
    • Many different material options are available centering around Nylon.
    • Carbon, glass, and aluminum can be added as well as other materials to give the part unique properties.
    • Flexible parts can also be produced to create a rubber type feel to the part.  
  • Disadvantages:
    • The parts usually have a rough texture and are not as dimensionally accurate as SLA parts.  

DMLS (Direct Metal Laser Sintering) – is a process similar to SLS except it uses metal powder instead of plastic powder. There are a wide variety of material choices including aluminum, stainless steel, Inconel and titanium.  

  • Advantages:
    • Parts are strong, durable and accurate and can produce shapes not possible using other manufacturing processes.
    • Parts can be used for prototypes or production.
  • Disadvantages:
    • This is a slow and costly process.

FDM (Fuse Deposition Modeling) – is a process that extrudes a very fine line of plastic material in rows and columns on a layer, then layers are build up one by one to create the full part. This is how most of the 3D printers are creating parts. You can use many colors and materials with this process and even switch colors to get multi color parts or assemblies.

  • Advantages:
    • You can chose from a variety of materials and colors and the cost of getting a personal machine is fairly low.
    • With higher quality machines, you can get parts that are almost as strong as molded parts.
    • Common materials to use are ABS, Polycarbonate, Nylon, and a very strong material called Ultem.
  • Disadvantages:
    • Usually the part quality is not as high as other process, but it is getting better all the time.

Silicone Molds – are very cost effective molds that can be used to make multiple parts from each mold. You start with a pattern that is usually made from the SLA process. Silicone is poured around the pattern to create the mold. When the silicone is cured, plastic material is injected into the mold and can create 20-50 parts before the mold wears out.

2 part ‘thermoset’ materials are used for this process which set up and cure with time, like Urethane, since you can not use high heat or pressure in these molds. Part quality and material strength is very good with these materials and there is a wide range of durometers available. In general, the durometer of a material is how flexible it is. Rubber has a lower durometer than hard plastic.  Some low volume products use this process for their production parts, like medical product housings.  

  • Advantages:
    • Part quality and strength is very good, and they can be molding in just about any color or painted.  
  • Disadvantages:
    • Part and tooling cost is not as economical as other prototype processes.
    • Material choices are limited to thermoset type materials.

Polyjet – is basically an inkjet printer that will layer the ink on top of the previous layer to build up the material and create a part. It will product a very high quality part with fine details, and can even combine materials in one part to produce parts that have hard features and soft touch features on the same part, like an overmold.  

  • Advantages:
    • High quality parts with complex geometries.
    • The ability combine soft and hard materials in the same part.
  • Disadvantages:
    • There are many materials and colors available including clear, however, these are not engineering materials.
    • This should only be used for high quality presentation models or for testing form and fit.  

CNC (Computer Numerical Control) – is basically cutting parts out of solid blocks of material. This process can be used for prototypes and production manufacturing. In it’s very basic form, this is a milling machine whose movement is controlled by a computer.  

Once the shape or part is designed in CAD, that part can be fed into the CNC machine and it will cut that shape out of a block of material. There are many cutting tools that can be used and depending on the capabilities of the CNC machine, it can move in many different ways to create the part.

You can CNC many different materials like metal, plastic, wood, just about anything that can be machined. This is generally a very high tolerance process meaning the parts that are cut are very accurate with little production variation.  

  • Advantages:
    • Highly accurate and consistent creation of parts in a wide variety of materials.
    • There are many suppliers that can do this process.
    • It is one of the most common prototype and production processes available.
  • Disadvantages:
    • This is not a cheap process.
    • There is programming that needs to be done to the part in preparation before it can be CNC’d.
    • The CNC machines are very costly to purchase and operate.

Hard Models – are generally used for looking at shape, size, ergonomics, and aesthetics. An example of this type of model would be a laptop computer made out of solid material. It would not function but would be painted to look exactly like the production model.

The design team could then see how it looks, how it feels when using it, how it might fit into a bag or briefcase, how it might compare to other products in their line or against competitors. This is a very useful process when every detail needs to be considered and production volumes will be high.  

  • Advantages:
    • This is done at the very beginning of the design process.
    • Helps to evaluate many design alternatives.
  • Disadvantages:
    • This model will look like a real product but will not function other than simple hinges, etc.
    • Because this is usually a very high quality model, it is generally quite costly.

Foam Models – are parts and assemblies created out of simple cheap foam. They are very quick and simple to create and are intended to get a quick idea of size and shape. They are very helpful at the beginning of the design phase and to evaluate many models at the same time.

Quite often, design firms may create 10’s or even 100’s of foam models in the iteration process to help finalize the shape and size.  

  • Advantages:
    • Quick test of size and shape.
  • Disadvantages:
    • This is just the start of the process, many details will still need to be developed.

Breadboard Models – is a generic term for a very basic model to test a concept. This could be made of wood or cardboard or anything that the designer or engineer can find to build and test a design concept.

This might be a small mechanism that is part of an overall product or the whole product to see how big it is, how it fits into your hand, how heavy it might be or any number of factors that can be determined with a physical part. This process is very useful to quickly test many ideas in physical form.  

  • Advantages:
    • Usually cheap made from existing parts, or parts of other products, with basic assembly for quick evaluation.
  • Disadvantages:
    • Very basic prototype that focuses on a small aspect of the design.
    • Again here, many details left to develop.

These are exciting times in the product development world for making 3d objects. Designers, engineers, inventors and even kids can design and create their own ideas and make them in their own home. Legos and clay used to be the basic building blocks of 3D design, now there is practically no limit to what you can create.

Daniel TagtowDaniel Tagtow – Partner

Dan has been with Innovate for more than 15 years and in Product Development for 25+.

He is passionate about product design with a background in both Industrial Design and Mechanical Engineering. Dan enjoys pushing SolidWorks’ and its surfacing tools to their limit to give his clients the very best possible product.

Have a question or comment for him? Dan is pretty easy to find over on LinkedIn.


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