Prototyping Processes
Every prototype you build should start by questioning “What is its purpose?” You can use that to select the best way to fabricate it, balancing cost, quality, and speed. At Touchstone 3D, we have a long history of prototype design and fabrication, and can help you get the right prototype at the right time.
When most people think of prototyping, they think of 3D printing. It has become the poster child of rapid prototyping. However, there are several other prototyping methods and you can save a lot of time and money by selecting the right one method for your specific goals.
Getting Started - The CAD Model
In this day and age of digital fabrication, the CAD model is key to being able to produce anything. This virtual model serves as the "blueprint" for your design and is used to create prototypes, renderings, and manufacturing documentation.
Creating the CAD model is often more expensive or time consuming than the actual prototype, depending on who is making it.
3D Printing
3D Printing is considered additive manufacturing. You start with nothing and add material to create your object. This process is perfect for hard to create geometry and quick, iterative prototyping. It also lends itself to other prototyping processes like making mold tools or patterns.
It does have some limitations. Some of the biggest challenges are: material properties, production speed, part size, and machine maintenance.
Compared to other processes, there are very few material options out there for 3D printing, and no way to produce production like rubber. A single part takes hours or even days to create, compared to seconds for injection molding and minutes for resin casting. Many printers are restricted by build size, which causes parts to have to be pieced together. And 3D printing machines require significantly more maintenance than other production machines, causing increased labor costs and machine down time. This can be a major challenge for anyone considering buying their own printer.
There are many different types of 3D printers and printing techniques out there. We’ll cover the highlights here to give you a brief introduction to the tradeoffs of each technology in terms of materials, resolution, speed, quality, and cost.
Resin Casting
Also known as urethane casting, silicone casting, or RTV casting. This process involves the creation of a low cost, low yield silicone mold tool (0-50 units). The mold tool is then hand shot with a 2 part resin to fabricate a part. Each part should be nearly identical to every other part that comes out of the mold tool, although there can be small defects that may require hand finishing. This process is ideal when you need very specific material properties or need many parts with a custom finish. It’s also great for simulating injection molded parts for field testing or low volume production.
Laser Cutting & Etching
Laser cutting is fantastic for custom sheet goods. We use our 50W laser to cut acrylic, polycarbonate, rubber, and wood up to 0.25” thick all the time. This method can also be used to simulate die cutting. It’s great for cutting fixtures, gaskets, and even etching logos and labels. One of the down sides is that the cut edges tend to have some melting, burning, or charring due to the heat of the laser. There are also some restrictions on what materials you can and can’t cut otherwise you risk damaging the equipment or producing harmful gasses.
Machining
Machining is one of the older fabrication methods and can be done by hand or with computer programming. It is very precise and great for use with plastics and metals. It is a subtractive process which may limit what geometry can be formed and may result in significant material waste. When using CNC machining, typically the first part costs the most due to the programming involved, and then additional parts are cheaper after that. Machining can be time consuming, but is great for high precision parts with production grade materials.
Vacuum Forming
Also known as thermoforming. This process involves creating a pattern or tool that is loaded into the machine. Then a sheet of plastic is heated and the tool is pressed into it. As the tool starts to engage, a vacuum is turned on, which draws the plastic down around the tool. Vacuum forming is a great option for sheet parts with simple geometry. It is commonly used to create packaging. It requires a small tooling cost, similar to resin casting, but does allow the use of production grade thermoplastics. Patterns and tools can be made quickly by 3D printing, but can also be machined or made by hand.
Painting & Finishing
Custom paint and finishes can make all the difference on high quality, tradeshow prototypes. By using a combination of sandpaper, fillers, and paint, you can make even the lowest of resolution 3D prints look like a production grade part. Slow and steady wins the race; moving too fast on finishing or painting can easily cause you to have to start over. As a general rule of thumb, try to limit how much finish work has to be done as the cost is largely all labor and can become pretty expensive. We’re happy to help you figure out the best fabrication approach to meet your goals and minimize the amount of finish work needed.
Moving Forward
Now that we've covered general product development terms and prototyping processes, we'll head next into the design phase and cover what needs to happen to get you off on the right foot.