As part of the product design process, one of the questions we will ask is – what material(s) should we use to build our prototype, and subsequently commercial product? Commercial Off-the-shelf (COTS) components aside, the chassis, casing and many internal parts are usually not available off the shelf, and have to be custom designed and fabricated.
From my point of view, the choice of material(s) must meet three main objectives:
1. Can the material(s) fulfill the functional needs of the product?
The choice of material(s) must first and foremost fulfill the product design requirements, so that the prototype is able to perform the job that it is designed for. Some points under this category are:
a) Weight, Strength and other Physical Properties – Is there certain material properties that we have to adhere to in the design requirements? For example, is the product designed to be operated from a benchtop or floor with a weight limit? Or is the product meant to be physically integrated into a bigger system, and there are constraints on the material strength and operating environment? Does the part need to be of a certain hardness and must be able to be surface treated against corrosion? By probing into the physical properties required, we can narrow down our choice of material(s).
b) Dimensional Tolerance – Ensure that the material(s) (and it’s corresponding manufacturing process) can support the dimensional tolerance levels required for your product. For example, optical and photonics applications typically require tolerance levels of ±0.05mm or smaller, where semiconductor applications can demand even more stringent levels of ±0.01mm or smaller. Dimensional tolerances affect how well parts will fit in a build in a system, and ultimately translate to the level of product performance. For instance, if the tolerance requirements of optical lens mounts are not met in a laser imaging device, this can have a detrimental effect on the SNR and image quality, which will greatly impact product functionality.
c) Safety Standards – If your product needs to comply with safety standards and certification, such as in areas like electromagnetic and fire safety, this will probably also play a part on the choice of material, e.g. does the casing or chassis have to be non-metallic for electrical insulation, or does it need a flame-retardant coating?
2. Can the material(s) improve the perceived value of my product?
Not wholly relevant in all industries, but aesthetics does play an important role in products with significant human interaction. Correct choice of material(s) can significantly improve the perceived value of your product. I mentioned “perceived” because ultimately, a very strong perceived value will greatly help influence the customer’s decision to commit to a purchase.
a) Build Quality – Build quality will help give the customer the impression that the product that he or she is going to purchase is a well made, durable and reliable one, which helps to instill confidence in your product. Assume there are two devices with identical functionality and form, but built with different materials for their bodies: Device 1 feels flimsy to the touch and the walls could flex easily under slight pressure, while Device 2 feels solid to the touch, and is even able to sustain bumps or knocks without any noticeable physical changes. As a potential customer, which of these devices will you choose to buy?
b) Finishing – In addition to build quality, finishing also contributes to the perceived value of the final product. For example, besides being scratch and corrosion resistant which are functional requirements, colour anodizing can help improve the product appeal. Plastics can be given wood-like or leather-like finishes to give that extra “human touch”. Think about the types of finishing that would be good to have from the customers’ point of view, and if the material(s) support these.
3. Can I reduce the manufacturing cost associated with this material(s) in the long run?
This is not very critical during initial prototyping, but do keep this in the back of your head as we look at the long run. During our initial prototyping stages, demonstrating a working concept and subsequently a functional prototype subject to user trials are our key priorities. Once we have proved the concept and established that there is a commercial value and practicality for the market, it is time we look at the manufacturing cost of each unit we are producing. Once the product achieves commercial production status, manufacturing costs will directly influence revenue and profit, and the survival of the startup business.
a) Types of Manufacturing Processes – Some manufacturing methods comprise of a considerable “setup” cost upfront – like fabricating the die used for casting metal enclosures, or to fabricate the mold cavity which is to produce plastic component using injection molding. Such processes are intended for large volume production, where the setup cost will be spread across a large production quantity and thus will be economical for the unit production cost. However, for low volume production, such as producing parts for a handful of prototypes, this will not be cost effective. On the other hand, CNC (Computer Numeric Control) machining and 3D printing do not need dies or molds, and are ideal for low volume work – and can support a large variety of materials: CNC machining can work on many types of metals (and alloys), plastics, composites and even wood. 3D printing has the ability to work with plastics and metals, can be quicker but CNC machining can usually achieve much higher dimension tolerancing.
b) Low volume VS High Volume – This holds true for practically all manufacturing processes – producing in bulk will lead to economies of scale, and subsequently a lower per unit cost of production, which directly translates to higher profits assuming everything else stays constant. Another benefit of a larger volume order – Vendors will tend to pay more attention to your needs and treat you with greater importance, which would lead to a better client-vendor relationship. (It also means that it may become easier to negotiate certain terms and requests when the need arises!)