3D Printing - The Essentials

Make 4 MINS read 31st Jul 2019

Seven different categories of ‘Additive Manufacturing’ processes have been identified and established. These processes brought forth ten different types of technology that 3D printers use today.

We are going to focus on the three most popular. The basics of how they work, what they are used for and the pros and cons of each technology. In a nutshell, the considerations are cost, quality, speed, capability, practicality, and user expectations.

Despite the variations of the printers, the process from design to end product follows a similar path:

1. User has access to a 3D modelling application or a 3D scanner

2. User creates a virtual design (3D model) of the object they want to print in 3D

3. User typically saves their design as a Computer Aided Design file, or CAD for short

4. User slices their CAD file before sending it to the printer

5. User uploads the sliced CAD file to the 3D printer

6. Printer reads each slice in the 2D file to create the three-dimensional object

Stereolithography (SLA)

SLA is a rapid prototyping process. Those who use this technology tend to be serious about accuracy and precision. This form of 3D printing works by exposing a layer of photosensitive liquid resin to a UV-laser beam.

Once the resin has hardened, a fraction of a millimeter of this filament is dropped down in the tank and the laser fitted in the printer continues to form layers until the design is complete.

Owing to the nature of the material used for printing with SLA printers, the end product usually has a smooth finish to it.

Pros - Accuracy and finish. Whether you are a mechanical engineer who needs to verify if the part can fit to your design, or creative person who wants to make a plastic prototype of new coming project, SLA printers do the job really well.

Cons - A downfall of SLA printing is that the object must be rinsed with a solvent after the printing completes, and even at times has to bake in a UV light to finish the curing process.

Fused Deposition Modelling (FDM)

The Ford Mondeo of 3D Printing. FDM printers build objects from the bottom up and typically need support structures if the object has overhanging parts more than a 45° angle. This form of 3D printing is the most cost-effective way for individuals and small businesses to create parts quickly and efficiently. The printers have evolved from bulky, expensive machines to smaller, faster, economical ones that have become the key components for engineering and design departments.

The great thing about this technology is that FDM can use high-performance and engineering-grade thermoplastic, which is very beneficial for mechanical engineers and manufacturers. In fact FDM is the only 3D printing technology that builds parts with production-grade thermoplastics, so things printed are of excellent mechanical, thermal and chemical qualities.

Pros - Can print items that are ready to use, e.g. plastic gears, lego pieces, and jewellery thanks to exceptional strength to weight ratio

Cons - It takes a long time compared to SLA and other alternatives. Also, Raw FDM parts can show fairly visible layer-lines on some objects. These will need hand sanding and finishing after printing.

Selective Laser Sintering (SLS)

SLS printing is when a laser is used to solidify and bond grains of plastic, ceramic, glass, metal or other materials into layers to produce a 3D object. It works like other additive manufacturing technologies in that it provides a print by building layers-upon-layers until the object is complete.

A CO2 laser beam scans the surface. The laser will selectively sinter the powder and solidify a cross-section of the object. Just like SLA, the laser is focused on to the correct location by a pair of galvos. Once the laser traces the pattern of each layer into the bed of powder, the bed lowers and another layer is traced and bonded on top of the previous.

Pros - A major benefit of SLS printing is that it does not require a support structure to produce intricate designs. Also, you can use a wide range of printing materials so its super versatile.

Cons - The need for expensive high powered lasers mean this printer is currently the preserve of professional manufacturers. And maybe Dr Evil.

At G2 we utilise all these technologies. The workshop in our design studio is veritable shrine to 3D printing technology. Contact us if you are curious about your options.

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