Rapid Prototyping –  The Next Level Detail

So you’ve read our ‘Rapid Prototyping – A Beginners Guide’, and now we understand why Rapid Prototyping is important, and what the basic types of testing are.  We know that we can commission a ‘looks-like’ or a ‘works-like’ prototype, and we understand what a ‘Proof-of-Concept’ model looks like and that our end goal is to achieve a production-quality prototype that will precisely replicate our final manufactured product.

So let’s dig a little deeper and understand the different elements within Rapid Prototyping, to understand which would be the best fit for the project we have in mind.  Here’s our breakdown of the techniques available in Rapid Prototyping:

Electronics

If you need to prototype electronics for your product, you will need to consider what questions you are trying to answer. Every time you create a new prototype you should have a well-defined set of questions that will be answered by creating the prototype.

If you have broad questions about whether your product will even work, or whether it will solve the intended problem, then you may be wise to begin with an early ‘works-like’ prototype, using something like the Arduino development kits or SteamVR Tracking HDK.

Nearly all electronic products require either a microcontroller or a microprocessor, both of which are fundamentally computer chips that run programs. Microcontrollers are less complex and less expensive, but also less powerful. Unless your product requires high-speed computer processing capabilities, then a microcontroller is likely to be most suitable. We estimate that about 75% of the product ideas we see, are best served with a microcontroller.

Using a microcontroller simplifies the electronics design; they are known as System-On-a-Chip (SoC) solutions. This means in addition to the Central Processing Unit (CPU), a microcontroller also includes memory (RAM and ROM) and other peripherals, all embedded on a single chip. Some microcontrollers are available with more complex peripherals built-in such as a Bluetooth, Wifi.

Custom Printed Circuit Board (PCB)

Eventually, in order to achieve a production quality prototype, you will need to move beyond a development kit, in order to create something closer to your desired end product. Whilst a development kit Proof-Of-Concept prototype is great for showing the fundamental concept of the product, it will be a number of steps removed from the fully functioning product you will want to take to market.

If there are no considerable questions about your product’s functionality then you could move straight to designing a custom PCB – this is where most large companies developing products start, as this is usually the fastest route to market. Be aware however, that this is not usually the cheapest option; without a lower cost POC prototype, you will miss out on key learnings about your new product, meaning you may require a greater number of revisions to your production-quality prototype.

So how do you prototype using a a custom Printed Circuit Board (PCB)?  There are two main steps when creating a custom PCB, so let’s look at the process for each stage:

1) Producing the Bare PCB

The process begins with a laminate core made from woven glass epoxy, which serves as an insulator between conducting layers, providing physical strength to the board.  Single-sided boards consist of one laminate core with a copper layer on one side. Double-sided boards consist of a laminate core with copper layers on each side. Multiple layer boards consist of a stack-up of alternating copper layers with laminate core layers. Most boards will use 2, 4, 6 or perhaps 8 conducting layers.

The layout design for each conducting copper layer is laser plotted on film and a light sensitive chemical Resist is applied. The copper layers are then exposed to high intensity ultraviolet light which shines through the film. This light hardens the “resist” layer over any copper traces and pads.

The copper layers are then processed through a chemical solution which removes any of the “resist” layer which wasn’t hardened by the ultraviolet light. This leaves hardened “resist” material only over the desired copper traces and pads. Another chemical is then used to remove any exposed copper not covered by “resist”. The hardened Resist layer is then removed, leaving only the desired copper to form the traces and pads.  A lamination process is used next to bond all of the layers together to form the stacked PCB.

Holes are drilled through the PCB stack-up to form vias which are used to connect signals on different layers. Any holes for through hole components are also drilled. However, it’s generally best to only use Surface-Mount Technology (SMT) components to minimize your soldering costs.

Copper is next deposited onto all exposed metal surfaces including the inner walls of any holes. Additional copper is electroplated onto all exposed copper surfaces.

2) Soldering the Components

Now that the bare PCB is complete the next step is to place and solder all of the electronic components. Robotic equipment called a pick-and-place machine uses a vacuum system to pick up the components and precisely place them on the PCB. Solder paste (a sticky mixture of solder and flux) is used to temporarily hold the parts in place.  Finally, the boards are put through a reflow oven which melts the solder paste to form a permanent electrical connection between the component and the PCB pads.  And now you have a complete PCB.

Software

Software prototyping is an opportunity for the Software Engineer to get an idea of what the final product will look like before additional resources, such as time and money, are invested into finalising the product. Prototyping gives the Software Engineer the opportunity to evaluate the product, ensure it’s doing what is intended, and determine if improvements need to be made.

Often, the software prototype is not complete. Sometimes, only certain aspects of the program are prototyped, such as the elements of key concern which are critical to the success of the product, or areas where the user interface may be tricky – this may be an area which poses the most questions for the development team.

Enclosure/Case

3D printing is an additive prototyping process that adds material to create the desired shape. The term 3D printing is a broadly used term that refers to various prototyping technologies.  There are 3 types of 3D printers to consider.  Let’s explore what each of these printers does and how they differ:

Fused Deposition modeling (FDM)

This is the most affordable method of 3D printing and is therefore the most common technology used for home 3D printers. This technology can produce prototypes with a moderate amount of detail.  The FDM printers work by feeding plastic through a heated nozzle. The material is melted and deposited layer by layer, with each layer fusing to the layer below it. FDM printers are limited in the fine details they can produce.

Stereolithography (SLA)

An SLA printer is able to provide a finer, highly accurate level of detail, so when considering a complex prototype, an SLA printed prototype is recommended. This process is used mainly on high-end, home 3D printers and by professional prototype shops. This type of 3D printer works by curing resin with light. The light hardens the liquid resin layer by layer in a process called photopolymerization.

SLA printers also produce a much stronger prototype because the layers are chemically bonded together. Prototypes produced by an SLA printer tend to look more professional than those created with FDM printers.

A good strategy for many entrepreneurs is to purchase a low-cost, FDM based, 3D printer for producing early prototypes. Once the appearance and strength of the 3D printed prototype become more important, you can move to using a professional prototype shop with SLA printers. This strategy will save you money and speed up development for many products.

Selective Laser Sintering (SLS)

An SLS system uses a laser to sinter (i.e. harden) powder materials layer by layer to form the desired shape. A big advantage of SLS is it can be used to create metal prototypes. SLS is too complex for home 3D printers so it’s only an option when outsourcing to a professional prototype company.

CNC (Computer Numerical Control) Machining

The opposite of an additive process; CNC is a subtractive process. As the name implies a subtractive process removes material to form the desired shape. The process starts with a solid block of plastic or metal. Material is then carved away to form the final sculpted prototype.

One of the primary advantages of CNC machining compared to 3D printing is that you have much more flexibility in regard to the material used. Not only can you create prototypes from plastic or metal, but you can select very specific plastic resins which precisely match the material you will use for mass production.

Injection moulding

3D printing is fantastic at producing tens of parts. However, it’s not practical for producing hundreds or thousands of parts. Ultimately, injection moulding will be necessary to replicate your product’s enclosure in higher quantities, if you are taking your product to mass market.

As the name suggests, the injection moulding process starts with the creation of a mould. Moulds are machined from metal; the hardness of the metal determines the mould’s lifetime and cost. For prototyping, or early production, aluminium moulds are generally the best choice. Aluminium moulds typically cost a couple thousand dollars each and can produce up to about 10,000 parts.

The mould forms two halves that are held together as hot, molten plastic is injected at high-pressure into the mould. The high-pressure is necessary in order to produce fine details in the part. Once the plastic cools and solidifies, the mould is opened and the part is removed.

Most designs will require significant modifications in order to prepare them for injection moulding. Whereas 3D printing can reproduce just about any shape you can imagine, injection moulding has strict design rules that must be followed.

Be sure whoever designs your enclosure understands injection moulding, otherwise you are likely to end up with a product that can be prototyped but not manufactured in high volume.

Next Steps…

We hope this blog series on how Rapid Prototyping works has been helpful and insightful.  If you still have any questions on what your specific project needs are, or you are now unsure which elements are most suitable for you, please do get in touch with our team at Conficio Product Design.

Our expert team are on hand to understand not only the potential of your new product, but also your ultimate end goal.  Our team will help you understand the questions that will need answering in order to get your new product to market and can advise you on your next steps for best success.

So feel free to use and abuse our collective years of experience and expertise to help navigate you to a successful product test and launch!

Drop us a line at contact@conficio.design or call us on 0117 313 1458.

Comments 1

  1. Pingback: Rapid Prototyping - A Beginners Guide - Conficio

Leave a Reply

Your email address will not be published. Required fields are marked *