Additive Manufacturing

Manufacture for plastics and metals, usually via 3D printing

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What is Additive manufacturing?

Additive manufacturing (or AM) is a method of manufacture for plastics and metals, usually via 3D printing. It has revolutionised industrial production by enabling lighter, stronger parts and systems to be created.

The process of Additive Manufacturing uses CAD software or 3D scanners to guide machinery in creating an object, adding material one layer at a time using little more than the required amount of raw material per layer. AM adds material to create an object, as opposed to ‘subtractive’ or more traditional means of manufacturing, where an object is created by removing material into a given shape.

Is additive manufacturing the same as 3D printing?

3D printing is the best known phrase that describes many Additive Manufacturing technologies, however this buzz-word came about when cheaper entry level machines became available on a wide scale. Before then, the only term used was ‘rapid prototyping’ or RP which refers to the primary use of AM machines which was a method of making prototypes quickly. Therefore AM could be referred to as 3D printing in a manufacturing capacity.

Uses of Additive Manufacturing in today’s manufacturing environment

As it stands Additive Manufacturing will never be capable of mass manufacture (eg to satisfy the demand for 300M plastic Coca-Cola bottles per day) as it cannot compete with traditional manufacturing techniques in terms of speed or cost at high volumes.  That being said, there are many cases where AM is the best choice. Some examples of its uses are as follows:

  • Customisation

Additive Manufacturing unlocks new possibilities for customisation because it does not require expensive tooling. Invisalign were one of the worlds first to utilise AM in the production of their teeth alignment product. They produce thousands of “similar, but uniquely different” aligners, each one tailored to each unique customer. https://www.youtube.com/watch?v=vsR0_wTR2a8 

  • Assisting with prototyping/product development

Manufacturers are able to quickly produce several prototypes before committing to final production, enabling effective user testing and consumer feedback exercises to be carried out in order to develop and improve the design during the process. MNL have been helping designers and R&D divisions of companies at all stages of product development for almost 50 years. For an in-depth look into the many MNL services available throughout product development try here. 

  • Low Volume Manufacture

Additive manufacturing for low volumes has been used for a few years now. It is difficult to say a quantity at which AM is the best choice. 

There are many factors to be considered when deciding to use AM over more traditional methods. Some of the factors that influence the decision making are as follows.

  1. Quantity
  2. Complexity of design
  3. Size of components
  4. Material choice
  5. Timeframes available
  6. Surface finish requirements

In general AM produces parts with a layering process and as such are not always suited to aesthetic pieces. Often these lines or layers can be used as a desired feature making the process suitable or, more recently, parts may be produced with “texture” on the surface to hide the layer effect. In cases where aesthetics are important and numbers are suitably low then finishing techniques are possible to improve the look. You can read more about uses of Additive Manufacturing here.

Benefits of Additive Manufacturing

  • Cost effective
    AM makes prototyping more cost effective than traditional prototyping process.
  • Large reduction in time-to-market
    Prototyping using AM is significantly quicker than more traditional processes. This can lead to a reduction in time-to-market, which in turn leads to more sales, in particular over your competitors.
  • Energy and material efficient
    AM’s process of strategically adding layers of material on top of each other until the bespoke part is created means that overall waste from the AM process is minimal. 
  • Consolidate different parts within assemblies
    Parts that previously required assembly from multiple pieces can be additively manufactured as a single object which not only can provide improved strength and durability, but can also save time and material costs.
  • Lighten the weight of your parts with complex lattice structures
    Lattices and other intricate structures are often impossible and costly to create using traditional manufacturing methods. Redesigned components with lattice structures manufactured using AM can provide a lightweight solution over standard parts without compromising on strength or durability. Perfect for weight saving in the Aerospace and Motorsport industry.
  • Less design constraints Additive manufacturing is fantastic for any unusual or complex component shapes which can be difficult or unachievable to manufacture using other processes.

Additive Manufacturing technologies and materials

Additive Manufacturing technologies can be broadly divided into these different types:

Sintering, SLS, DMLS, DMLM, EBM

Sintering in general takes a powdered form of the chosen material and fuses the powder particles together layer by layer using heat. The process builds components with thousands of such layers being sintered together to form the desired shape.

Selective Laser Sintering (SLS) is the process where plastic powdered material is heated by a computer controlled laser beam. Powdered nylon was one of the first materials to be used by this process. A few other materials are available such as polypropylene and others with various different fillers being used. The most common being glass filled nylon. SLS parts are durable, due to using real plastic materials. Parts are free from supports as the surrounding powder does that job. Surface finish is better than FDM, but not as good as SLA. The process takes place at elevated temperatures, and as such certain shaped components can suffer from warping.

Direct Metal Laser Sintering (DMLS) is the process whereby a laser sinters layers of metal powder so that the metal particles weld to one another. DMLS is ideal for detailed parts production especially for lightweight components in aerospace and motorsport. Material choice is wider than plastics, but unlike the plastic variant, supports are required. Metal supports require machining to remove them and as such design for manufacture is required to minimise these occurrences.

Melting – Direct Metal Laser Melting (DMLM) and Electron Beam Melting (EBM)

Direct Metal Laser Melting (DMLM) and Electron Beam Melting (EBM) are known as melting Additive Manufacturing technologies. These methods fully melt the materials during the process, instead of just sintering, leading to greater strength. DMLM uses a laser to completely melt each layer of metal powder, while EBM uses high-power electron beams to melt the powders. Both these AM technologies are ideal for manufacturing dense and non-porous objects. 

Stereolithography (SLA)

Stereolithography uses a process called photopolymerisation where a computer-controlled UV laser beam is fired onto the surface of a vat of photopolymer resin. The UV laser sets off a chemical reaction turning the liquid resin solid. Successive layers, bonding to the previous one building up the component being produced. Support structures are required to prevent solid parts drifting away in the liquid. Stereolithography is the oldest 3D printing methods and was the first process developed for rapid prototyping. There are a limited number of material choices, often being suitable for prototyping purposes rather than production. This technology produces parts with the best surface finish of all.

Fuse Deposition Modeling (FDM)

FDM also known as fused deposition modelling is the most widely available form of 3d printing. It is an additive manufacturing technology that selectively deposits molten plastic to build parts layer by layer building from the bottom up. Before printing begins, the modelling software slices the 3d cad file, and it creates an extrusion path that the nozzle will follow.

FDM works by heating and extruding a thermoplastic filament. The 3d printer heats the thermoplastic to a semi-liquid state and deposits it in ultra-fine beads along the extrusion path. Where support or buffering is needed, the 3d printer deposits a removable material that acts as scaffolding. When your 3d print is finished, the user either dissolves the supports attached to it in a solution of detergent and water or simply breaks them off.

FDM has the largest choice of materials with hundreds on offer. Surface finish is generally the poorest of all the technologies and the slowest too.

Binder Jetting 

Binder Jetting is a family of additive manufacturing technologies, Utilising materials such as metals, sand and granular form ceramics where a binder is selectively deposited onto the powder bed, bonding these areas together to form a solid part one layer at a time.

Binder Jetting can be within various applications, including the fabrication of full coloured prototypes and the manufacture of low-cost 3D printed metal parts.

There are a variety of materials used for Additive Manufacturing including thermoplastics, metals, ceramics and biochemicals. In general the choices for materials are significantly lower than for injection moulding, however, the choice is getting larger week by week.

    Materials 

    Plastics

    Thermoplastics are the most commonly used Additive Manufacturing material typically used in the FDM process. These include Acrylonitrile butadiene styrene (ABS), polylactic acid (PLA), polycarbonate (PC), and for temporary support structures before being dissolved; Water-soluble polyvinyl alcohol (PVA). Each material can be used in a variety of applications and comes with different advantages.

    Metals

    Additive Manufacturing can utilise many different metals and metal alloys. Titanium, stainless steel, chrome, aluminium, copper and nickel-based alloys are available as powdered form for AM, as well as precious metals like gold, silver, platinum and palladium. 

    Ceramics

    Ceramics including zirconia, alumina and tricalcium phosphate have all been used in AM. In addition, new classes of glass products can be created by alternating layers of powdered glass and adhesive.

    Biochemicals

    Silicon, calcium phosphate and zinc are biochemicals used in AM. These are primarily used in healthcare applications to support bone structures as new bone growth occurs. Bio-inks fabricated from stem cells are being researched to allow the production of complex tissues for surgical implants.

    As there are many different processes under the AM umbrella which give way to differing pros and cons of each technique and material it is not always clear cut as to what is the best choice for manufacture. Our expert team at Malcolm Nicholls Ltd can advise the best Additive Manufacturing technology based on your specific requirements.

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