Additive Manufacturing vs. Traditional Methods
The term additive manufacturing (AM) refers to industrial production methods that use digital design data to create objects by adding together layers of material. Many subscribe to the theory that AM is positioned to replace all forms of manufacturing in the very near future. It’s important to remember that today’s products are manufactured using a wide variety of processes and materials. Successfully adopting additive manufacturing and creating a return on investment (ROI) in doing so involves carefully evaluating whether or not there is an AM technology that’s the right tool for the job. Given the speed at which AM is evolving it’s also important to re-evaluate this on a regular basis.
The first step it to understand additive manufacturing’s strengths and weaknesses before comparing it to other technologies or processes.
Additive Manufacturing’s Strengths
· Freedom of design / ability to create objects with complex geometry
· Rapid iterations without retooling
· Supply chain efficiencies
· Reduced waste
· Reduced inventory
· Mass customization
Additive Manufacturing’s Weaknesses
· High material costs
· Questionable material strength in some cases
· Post processing is often required
· Workforce isn’t trained to leverage its strengths
Additive Manufacturing vs. CNC Mills and Lathes
Strengths: Additive is able to create complex geometries that CNC simply cannot. A great example of this would be conformal cooling channels that follow the curve of a cylindrical injection mold. Another strength is that AM equipment is simpler to operate than traditional CNC. Additive also generates less waste. Desktop additive machines that produce plastic parts are typically smaller and less messy to operate than traditional CNC equipment
Weaknesses: Traditional CNC equipment can produce most simple objects much faster than current AM solutions. Traditional CNC materials typically retain most, if not all of their original properties and are therefore stronger and less porous than the parts produced by some AM processes. Traditional CNC materials are less expensive, widely available and there is a greater variety available. When it comes to working with metal, traditional CNC machines are currently far less expensive than metal AM equipment. To date traditional CNC equipment is more dimensionally accurate and has better surface finishes, particularly in the case of metal AM.
We have seen additive manufacturing widely and successfully adopted vs. CNC in the production of prototypes, particularly ones made out of various plastics. We are now seeing a lot more metal AM solutions on the market. Prices for both equipment and materials are dropping rapidly so we think it’s safe to say that in the near future there will be a lot more metal AM prototyping. As for production runs of actual parts, AM is starting to have success vs. CNC when it comes to small, complex metal parts. In the aviation sector there have been a number of high profile examples of this. AM has also been successfully used for custom or “one-off” parts such as jigs and fixtures in the automotive and general manufacturing sectors. In many cases the end result was a jig or fixture that was far more accurate, lighter and easier to use. High value, complex objects are also likely to migrate to being manufactured via AM. Dies with conformal cooling are a good example of this.
Over the next couple decades additive will continue to take market share away from CNC, particularly when metal additive becomes faster and less expensive.
Additive Manufacturing vs. Injection Molding and Die Casting
Strengths: Additive Manufacturing can produce complex geometries that traditional injection molding and die casting equipment can’t. Additive Manufacturing doesn’t require molds or tooling thus reducing start up costs substantially (tens of thousands of dollars in some cases) as well as saving the time required to have molds made (3 to 6 weeks is not uncommon). Objects that are created using AM can be revised from one print to the next with no tooling costs thus allowing for mass customization – this is not feasible with molding or casting.
Weaknesses: Traditional Injection Molding and Die Casting cycle time are between 15 and 30 seconds per part and multiple parts can be extruded at once allowing for production of hundreds or thousands of parts per hour. Die cast and injection molded parts often have surfaces that require no further finishing in terms of smoothness or colour – this is often not the case with AM. Injection molded and die cast materials tend to retain their original properties better than parts manufactured via AM. There are a wide variety of materials that are readily available for both die casting and injection molding.
The greatest advantage that AM has over injection molding or casting revolves around the time and expense to create dies. Additive is a far superior way to produce prototypes. In some cases it makes sense to create beta test runs in very low quantities using additive depending on the mechanical and cosmetic requirements of the end product. AM also offers the ability to customize products that might otherwise have been mass produced in some cases. Some of today’s fastest and most robust AM solutions are changing the game and allowing for the cost effective production of thousands of parts, particularly if they are small. HP’s Multi-Jet Fusion is a good example of this.
Additive if poised to have a great impact on injection molding and die casting as a direct competitor in the coming decade. Faster equipment is one reason. New players such as BASF entering the materials market are another key factor. Perhaps the most important change agent will be the designers of tomorrow embracing additive’s ability to create complex geometries.
An indirect impact will be the use of additive to create the molds used in molding and casting. As additive improves and becomes less expensive it will decrease the cost of dies and allow for complex geometry related improvements such as conformal cooling channels. It should also shorten turn around times for dies considerably.
Additive Manufacturing vs. Sand Casting and Investment Casting
Strengths: Additive Manufacturing can produce complex geometries and fine detail that sand casting and investment casting can’t. Additive Manufacturing doesn’t require patterns, molds or tooling thus reducing start up costs substantially (tens of thousands of dollars in some cases) as well as saving the time required to have molds made (3 to 6 weeks is not uncommon). Objects that are created using AM can be revised from one print to the next with no tooling costs thus allowing for mass customization – this is not the case with casting.
Weaknesses: For large, simple objects traditional sand casting and investment casting are far faster and less expensive than current AM technologies once the patterns have been created. In the case of investment casting once a mold has been prepared to create lost wax patterns parts can be cast in large volumes faster and less expensively than AM technologies. There are a wide variety of materials that are readily available for both sand casting and investment casting.
At this time additive is not poised to directly replace the casting of large objects such as man hole covers, particularly when producing large quantities. Metal AM machines are typically too small and too expensive to operate. Where it can have an impact is in the creation of patterns. Large FDM printers are being used for this when near net shape is acceptable. Even when the final shape is very important FDM patterns can be employed and then the casting can be machined to the net shape as required. A yacht propeller manufacturer is using this process.
Additive equipment has been developed to create sand molds. By creating the mold this way the need for a pattern is eliminated, thus saving time and money. The trade off is that printing molds via additive manufacturing is slow. In the case of short run castings, particularly one offs, AM is still much faster and less expensive than traditional methods. For high volume it doesn’t make sense – yet.
Investment casting is being impacted in a number of ways as well. If the run is very small and the objects are small as well then metal AM can compete directly. AM using “castable” materials can also create investment casting patterns for lost wax casting. This has been adopted commercially for the production of jewellery. It allows for mass customization and eliminates the need for injection molds. Another indirect way to impact investment casting is to use AM to create the molds required to create high volumes of wax patterns. Finally for simple objects the ceramic molds into which the metal is poured can be created directly using an AM technology developed in 2013 by Olivier van Herpt.
Additive Manufacturing vs. Forming/Stamping
Strengths: Additive can produce complex geometries that forming and stamping can’t. Additive doesn’t require dies. Additive produces less waste than stamping.
Weaknesses: Once dies have been created stamping is faster and less expensive than Additive Manufacturing. Stamping can create very thin objects which AM typically cannot.
Comparing additive manufacturing to metal forming/stamping is a little like comparing apples to oranges. Additive’s main strength is the ability to create complex 3 dimensional objects. Stamping often creates parts that have very simple geometry. Metal AM is currently only cost effective when creating small objects. In the automotive sector stamping is used to create body panels that are quite large and thin. At this point the two technologies do not appear to be competitors. In the case of creating stamping dies, a novel technique was demonstrated in China recently whereby large stamping dies were created out of resin using an SLA process and then coated in metal for production purposes. This doesn’t appear to have hit the market commercially yet but it does look interesting for short run production of replacement part.
Additive Manufacturing vs. Joining/Welding
Strengths: Additive can produce complex geometries and fine detail that joining/welding can’t
Weaknesses: Joining/Welding can create very large objects very quickly. Joining/Welding typically already has very little waste. Joining/Welding often requires very little equipment and that equipment is typically quite inexpensive by comparison to industrial AM equipment. There is a very large skilled workforce readily available for Joining/Welding
Again comparing Additive Manufacturing to Joining/Welding isn’t very logical at this point in time. Welding typically creates large objects, that’s just not where AM’s strength lie.
Today’s Additive Manufacturing technologies are excellent tools for creating rapid prototypes as well as high value, highly customized parts. Additive is of greatest value when it can eliminate the cost and time required for dies or molds.
In the future AM will continue to change the manufacturing landscape in new and impactful ways. As Additive Manufacturing becomes faster and less expensive it will allow for reduced parts inventory as replacements can be printed on demand, on location. As engineers and mechanical designers embrace additive’s ability to create complex geometries parts that are lighter, have less components and last longer will become commonplace throughout all industries, not just aerospace. As new materials are introduced AM will be able to create a wider range of products that match or can replace OEM parts. Conversely, as supply chains become optimized OEM parts that are traditionally manufactured will be designed with AM replacement parts in mind.
If you are involved in CNC machining or any kind of molding/casting you should keep a close eye on Additive Manufacturing and constantly be looking for ways to use it to improve your bottom line.