AdditiveManufacturing_AdvantagesAndLimitations

What are the advantages and differences of AM?

AM systems have been used by Fortune 500 companies and research teams for a decade, and major progress has been achieved in AM over the last few decades. AM is proving to be an essential element for product designers and engineers. AM users anticipate that, in the future, AM will compete with mass production systems. It proposes new alternatives in shape and function for production [13].

Traditional machine tooling or "Subtractive Technologies", as CNC equipment, that remove unnecessary material from a solid volume, have many differences and disadvantages over Additive Manufacturing, here a list of some of the most important ones:
 

 

Here is a short list of other advantages of Additive Manufacturing [37] that can be beneficial to the Aerospace industry including Cubesat development:

 

  • Complexity is free: The costs is less to print a complex part instead of a simple cube of the same size. The more complex (or, the less solid the object is), the faster and cheaper it can be made through additive manufacturing.
  • Variety is free: If a part needs to be changed, the change can simply be made on the original CAD file, and the new product can be printed right away.
  • No assembly required: Moving parts such as hinges and bicycle chains can be printed in metal directly into the product, which can significantly reduce the part numbers. Several parts under traditional machining due geometry restrictions (internal features, etc), can now be produced in a single piece using AM technologies, reducing complexity and weight.
  • Little lead time: Engineers can create a prototype with a 3-D printer immediately after finishing the part’s stereo lithography (STL) file. As soon as the part has printed, engineers may then begin testing its properties instead of waiting weeks or months for a prototype or part to come in.
  • Little-skill manufacturing: While complicated parts with specific parameters and high-tech applications ought to be left to the professionals, even children in elementary school have created their own figures using 3-D printing processes.
  • Few constraints: Anything you can dream up and design in the CAD software, you can create with additive manufacturing.
  • Less waste: Because only the material that is needed is used, there is very little (if any) material wasted (depend on the AM technology in use, in some case can be even recycled).
  • Materials properties, shades, colors: Engineers can program parts to have specific colors as also material properties in their CAD files, and printers can use a combination of materials and any color to print them (high end multimaterial color 3D printers). Progress in AM allow to even change the material properties as density, porosity and composition "on the fly", meaning during the printing process, offering unique material properties for the final part that it can be much close to the final requirements. Internal cooling is one example, usually with traditional machining, internal cooling path have geometry restrictions about where they can be machined and also in many cases adding holes to the part to access to those sections by the drilling machine (changing the properties of the part).  With AM not only the cooling channels can go to the specific areas where are needed, but we can also change the composition, density and other material properties to better adapt specific section of our part to heat or other conditions.

 

3D printers were mainly preferred in various manufacturing industries because they resulted in reduced design processes and faster prototyping. Since traditional design methods have mold-based production systems, designers and producers are not able to have the advantages of AM while using traditional methods[15].

According to Conner et al.[12], the production system is determined on the basis of three factors: complexity, customization, and the production volume (Figure 1). In general, the more complex a part is, if not impossible, the more difficult it is to manufacture with the traditional subtractive or formative means. However, in AM, complexity is essentially free[28] because the cost and time for producing a complex part is the same as that for a simple part. AM allows a lot of freedom in terms of product complexity in the manufacturing process. The following complexities are possible in AM[1]:

 

Features: “Undercuts, variable wall thicknesses, and deep channels”,

Geometries: “Twisted and contorted shapes”, “blind holes”, “high strength-to-weight ratio” geometries, high surface area-to-volume ratio designs, lattices, topologically optimized organic shapes,

Parts consolidation: Integrated parts that would otherwise be welded or joined together into a single printed part and

Fabrication step consolidation: Nesting parts that would be assembled in multiple steps if fabricated conventionally can be printed simultaneously.

 

 

AM is a computer-driven manufacturing technology and has the potential to shrink product development time and cost. It also has a potential to increase “design quality” and “conformance to use” in the view of the customers. It is seen that many small and medium-sized components can be turned from computer designs into production-quality metal parts in hours or days, instead of the days or weeks required for traditional processes. AM has several advantages over traditional manufacturing techniques as follows:

 

  • Faster, cheaper, more flexible, and easier manufacturing and design processes
  • Lower defect rate and higher quality consistency
  • Less labor
  • Less risk
  • Cleaner work shops
  • Shorter supply chains
  • Shorter lead time and reduced time to market
  • More streamlined and versatile manufacturing processes
  • Manufacturing and assembly of several parts
  • High degree of customization and low volumes
  • Eliminating of tooling
  • Accelerated new product development cycle
  • Less material waste in production steps
  • Weight reduction
  • Assembly cost reduction
  • Waste reduction
  • Production at or near the point of use

 

 

But as with any technology there are some limitations. AM technology is rapidly evolving and processes that are not possible today may become available in the next 10 years. As a result, the limitations given below are referenced to the year of 2015.

 

  • Size Limitation: Since AM processes use liquid polymers or powders comprised of resin or plaster and large size parts are more likely to have a lack of material strength, current AM technology is not capable of producing large-sized parts. At that point, the large-sized part term refers to the items such as aircraft wings and other similar parts.
  • Imperfection: Parts produced using AM processes may have rough and ribbed surface finishes. The materials used in the process may result in an unfinished look and need additional processing.
  • Cost: The cost of starting a manufacturing process including AM technology may require a costly investment. Entry level 3D printers start around USD1,000 and can go up to more than USD50,000 for more advanced models. Also for a small number of components (less than 1000 usually) AM manufacturing as FDM or SL can be cheaper than traditional plastic injection parts that require molding, but when the quantity increase they rich an equilibrium point and from there traditional plastic injection process become much less expensive than AM. 
  • Quality Control: Many AM systems do not have subsystems to monitor the manufacturing process in real time. Part-to-part and machine-to-machine variation are more likely to appear in the entire AM process. Furthermore, implementing advanced quality control requirements seem difficult in particular materials[36].
  • Materials: On the basis of recent AM technology, some materials are not usable in AM. For example, while metal used in AM is recyclable, some other materials, such as polymers, are not convenient for AM technology.
  • Software and Data Storage: It was stated in the meeting of The Royal Academy of Engineering that current software technologies and computer memories are not enough for the data used in AM processes. In addition to the machine technology needing improvements, advancements in software for future AM applications are necessary and inevitable.
  • Speed: AM technology functions more effectively with lower production volumes, as compared to higher volumes.
  • Reliability: Reliability and reproducibility are seen as an issue with current AM technologies by practitioners. Graham Bennett states that “for companies looking for a rejection rate of just a few parts per million, there is no way our technology can come close to that”.
  • Standards: The developments in AM will require higher and improved standards in AM in the future.
  • Affordability: The financial aspect of AM may be a deterrent factor for managers and owners.
  • Education: The current curricula at educational institutions need improvement in terms of teaching AM technology. While some colleges and universities have already integrated AM into the curriculum, some others are just starting.