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The so-called 3D printing is actually a category of manufacturing techniques called additive manufacturing. Before we talked about additive manufacturing, let’s have a quick look on subtractive manufacturing methods. Subtractive manufacturing is easy to understand, cutting the parts out to shape the wanted forms by CNC milling, laser engraving, etc. to process on the product or on the molds for injection forming and vacuum forming. On contrary, additive manufacturing is to add up layer by layer to construct the product. Additive manufacturing methods are categorized according to the measures used to solidify the materials.

Stereolithography (SLA)

The light-activated resin will be cured into solid objects under UV light, like stone-trolls petrified under the sunlight. The UV laser will cast on selected spots in a sink of liquid resin to harden it. Multiple materials can be mixed to the resin to change the flexibility, strength or heat resistance of the object. Another technology is digital light processing (DLP) which basically shares the same theory with SLA. The difference is that the UV light of DLP is projected which will be in the form of square voxels. It causes more visible vertical accumulation which needs more finishing process on smoothing the surfaces.

Selective laser sintering (SLS)

Selective laser sintering is to sinter the powdered raw materials by laser or other electron-beams. The concept was very much like SLA but mainly used to fabricate metals. Additionally, electron-beam melting (EBM) and selective laser melting (SLM) are technologies similar to SLS. They are utilized for the demand of different structure or materials. For example, EBM is used to print Titanium for medical uses and the utilization of SLM in manufacturing with most alloys. These methods pose a great influence on metal processing. The additive manufacturing of metal is a concept change for metal processing like milling, drilling, threading and grinding.

Fused filament fabrication (FFF)

Fused filament fabrication is the 3D printing technology that most people recognized. Like squeezing whipped cream with a pastry bag, the machine extrudes melted materials through a nozzle to build up the object. Layer by layer, the material will be piled up like a crêpe cake, fused and hardened as it cooled. The applicable materials of this type of 3D printing are the most diverse among all other additive manufacturing methods. Raw materials like metal, ceramics, plastics, and compounds of binder materials.

Pros and cons

Unlike subtractive manufacturing, additive manufacturing has less material waste for tooling. Rapid prototyping is the most phenomenal characteristic of 3D printing. It can print out models that can carry out the real function of the design to test the functionality of the product during designing. It makes complex structures possible to be made without the limitations of molds. It opened up incredible possibilities to fabricating forms and structures that unachievable by traditional forming technologies. Although additive manufacturing had been developed for decades, it is relatively new and immature manufacturing technologies. There are obstacles to be overcome in massive production like removing support materials and polishing the rough surface are inevitable finishing processes.

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