There are literally hundreds if not thousands of processes available to produce a part or product. One of the biggest challenges in Product Development is choosing which process best fits a given product.
Production quantities can vary widely depending on the product. Many medical products have production of only a few hundred units per year. For popular consumer products, production can be in the millions.
For a process to be the most efficient, it is important to match the material and production process to the production quantities and part specifications. Sometimes there are many choices, sometimes none of the choices are perfect and compromises will need to be made.
As with the prototype processes, this post will cover the most common production processes available today. This post is meant to give the reader a basic understanding.
There are a roughly a googol of documents available on-line and in books if you would like further information.
1. Injection Molding
A process that uses a metal mold to create a part.
The mold is designed with a cavity that matches the desired part. Molten plastic is injected into the mold and hardens in the shape of the part. The mold will open and the part will be ejected usually as a finished part.
These molds are very complex and molding machines are large and very expensive. However, the molding process is very fast. The result is the cost of building tooling will be quite expensive in this process, but the parts will usually be very cost effective.
- Low part cost
- Excellent part quality
- Wide range of material choices
- High tooling cost
- Part limitation due to the molding process
2. Silicone Molds
Similar to injection molding, except the tool is made from silicone instead of steel and different plastic materials are used.
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.
- Part quality and strength is very good
- Parts can be molded in just about any color or painted
- Compared to injection molding, tooling cost us much less expensive
- Part cost is much higher compared to injection molding
- Material choices are limited to thermoset type materials
3. Sheet Metal
In this method, parts and processes start with sheets of material, usually steel or aluminum. Large equipment is used to cut parts out of the sheet and form them into different shapes.
These parts are usually used for products with large flat surfaces like computer housings, cabinets and doors, and of course, automotive parts like fenders and hoods. In some cases, tooling of parts can be essentially free because sophisticated machines can create so many features in the parts. However, for custom parts like car doors or fenders, complex forming tooling is needed to press the sheet metal into specific and precise shapes.
A wide variety of materials can be used and in some cases, a combination of materials is used to get enhanced parts. One example is galvanized sheet metal: steel is coated with zinc to make the parts much more corrosion resistant.
- Large parts can be created cost effectively with often times minimal tooling cost
- Many manufacturers are available with a wide range of capabilities
- Part shape and features are limited
- Materials are somewhat limited to what is available in desired thicknesses.
This is one of the oldest process for manufacturing and still widely used today. Liquid metal is poured into a mold that has a cavity of the desired shape.
There are many ways to create the cavity, one example: a wax part is created, mold material is poured around the wax part, then the mold is heated to melt the wax out of the mold.
Many materials can be used for casting and part size ranges from small jewelry to massive pipe fittings.
- Mold cost is usually fairly reasonable
- Part cost can be very reasonable depending on the process
- Parts can be created with castings that would be difficult or impossible using other processes
- The process is labor intensive so part cost can range from reasonable to quite high
- The casting process is not a precise as other processes so oftentimes post process machining will need to be done to create higher tolerance areas in the part, which also adds cost and time.
A process that uses shaped dies and very high impact forces to form the metal into a part. Because of the repeated impact on the material, it becomes much stronger than cast or machined steel.
This is often used on tools and engine parts that have very high strength to weight ratio requirements. Post process machining is often required to finish a part into its final shape.
- Creates parts that are much stronger than other processes
- Part cost is usually higher along with tooling costs
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.
- Highly accurate and consistent creation of parts in a wide variety of materials
- There are many suppliers that can do this process, and it is one of the most common prototype and production processes available.
- 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
So, which process should I choose?
This list of processes just scratches the surface of the options that are used to creating parts and products. This can literally be a life long study that is ever-evolving.
The method you use will be determined by the specific needs and constraints of each individual project. New materials, processes and combinations are cropping up every day.
At Innovate LLC, we are always on the lookout for new developments and ways to help our customers find the best fit for their products. Feel free to reach out if you are at a decision point, and would like some expert guidance to help you make the best choice of production processes for you.
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.