Types of 3D Printing – An Overview and Guide

3D printing or additive manufacturing (AM) has been constantly improved and iterated upon since 1983. What type of 3D printing process has emerged victorious? In truth each process has strengths and weaknesses that suit different applications.

The start of the 3D print process is the same for all 3D printers. The process only changes after the following steps have taken place.

• Take a 3D model from 3D modelling software like SOLIDWORKS or a 3D scan.
• Save your design file so it can be sliced (usually a .STL file)
• Import your file into the software your 3D printer supports
• Orientate the file and provide support if needed
• Slice the file and upload it to the 3D printer
• 3D Printer reads each 2D slice and creates a 3D object

The last step (creating a 3D object) is where 3D printers differentiate themselves from one another.

Fused Deposition Modelling (FDM) 3D Printers

FDM is the most popular and diverse process with the best scalability. Offering printers with radically different capabilities. See the chart below for a breakdown of capabilities, applications and associated cost.

Click on the image above to learn more about the differences between industrial grade and desktop grade printers.

• The material starts off as filament on a reel and is pushed through a bowden tube
• The filament reaches the extrude head and is heated to the desired temperature
• Once the filament is at the correct temperature it is pushed through a nozzle and onto the build platform
• Using electric stepper or servo motors the printer moves the extrude head in the X, Y and Z axis
• The previous two processes over time create a 3D object which cools to become solid

Above we are talking about thermoplastic FDM however you can use pellet extruding or paste extruding processes instead of filament for ceramics and wood.

As with other 3D printing techniques the finished object needs cleaning. Depending on the printer, fairly visible layer lines can be present. You can sand and fill the finished print to create a smooth end product, with an even surface finish.

Stereolithography (SLA) 3D Printers

Streolithography is the process for precision and accuracy. If you want your model to require minimal surface finishing, be geometrically accurate and create minuscule detail with such fine detail and finish parts look as though they have been injection molded, this may be the process for you.

Since Formlabs has revolutionized the SLA 3D printer market in the last 5 years. Made possible with there vast selection of materials such as elastic and durable materials. Consequently the 3D printing process has multiplied in popularity many times over.

• The process starts from a laser that produces a thin stream of UV light
• The UV laser beam is reflected off of a series of mirrors and directed at the tank of resin
• Which in turn converts the liquid photo polymer resin into a solid 3D part one layer at a time
• Once the part has been printed, move the part from the print bed into post processing

Some post processing is recommended to get the best results. Firstly remove excess resin it is recommended that you wash the part in isopropanol liquid. Following this you cure the part using UV light. The best way to post process is with the correct equipment. Different materials require different cure times.

Selective Laser Sintering (SLS)

Selective laser sintering (SLS) is a diverse and economical process. One of the biggest draw backs that Formlabs is looking to address with the Fuse1 is the price point of these machines. Therefore expect to see the SLS market transform with the release of the FUSE 1. Certainly in the same way the SLA market transformed with the release of the Form 1&2 printers.

• The process starts from a C02 Laser (best suited for heating and fusing particles together)
• The laser passes through a scanner/mirror system to direct the laser in the correct pattern to form the desired object
• Each time a layer is completed the fabrication piston lowers and the powder delivery piston rises
• A roller then moves powder from the delivery piston to the fabrication piston

Nylon and Polyamide are typically used for the powder material from which the part is formed. The parts have strong mechanical and chemical properties, also the process itself is especially good for creating complex geometries (support structure not required). However, parts are porous after printing, some post processing is required to sand/fill the surface (Cyanoacrylate adhesive can be used for filling).

Digital Light Processing (DLP)

DLP is one of the oldest 3D printing methods around. It is similar to SLA because it also uses a photo polymer resin and UV light to cure this resin into a solid part. It differs however, in how the light is produced and directed at the part. A DLP printer uses a projector instead of a laser, able to cure one layer by projecting a UV image onto the resin.

DLP printing can result in faster print times however there are a few drawbacks against SLA. One example, is projector bleed as light can bleed from one pixel into the next resulting in lower less crisp XY axis resolution. Its also only a matter of time before a pixel in the projector will fail reducing print accuracy, quality until replacement of an expensive component. One further thing possible on SLS printers is finer control over specified areas of the part as each area is printed at a different moment in time.

Selective Laser Melting (SLM)

SLM belongs to the same family as SLA and SLS using a laser beam to form material into a solid part. The process is most similar to SLS as it also uses powder material.

SLM however melts the material rather then sintering it together, resulting in a less porous finish and increased structural reliability. The process is widely used for metal additive manufacturing applications, within aerospace, automotive and medical industries. The price point reflects this kind of application.

If your looking at metal additive manufacturing however SLM isn’t the only option check out Markforged’s ground breaking Metal X FDM printer here.

Binder Jet/Inkjet (BJ) Technology

Binder jetting uses two elements to form a solid object. One being the powdered material and the other is adhesive. Binder jet printing is great for printing sand casting molds as one of the materials that can be printed at 200-400 microns is sand.

You can 3D print other materials at finer resolutions such a metals however sand also allows for the creation of parts that are colored by the printer. In addition no support structure is required much like SLS 3D printing. Frequently binder jet printers have a large build volume too, these features all come at a high price however.

• Firstly, as with SLS, a roller is used to create a thin layer of powdered material
• The print head will selectively place adhesive and ink on the particulate to from the desired profile and colors
• The above processes repeat until the part is finished and excess particulate is removed
• Sintering may take place, highly likely if the print is some form of metal

Unfortunately parts straight off the printer don’t usually have strong mechanical properties so post processing is required, the majority of the time. For instance a metal print will be limited in strength by the adhesive holding the particulates together until you sinter the part in a furnace directly bonding the metal particulates together and making the adhesive obsolete.

Material Jetting

Material is a popular technique for creating high quality wax castings. The process as you might expect, is widely used by jewlers for making intricate wax casts that molten metal is poured into to make the complex geometries required for much jewelry.

• Firstly the wax material is heated and evenly distributed across the build platform
• Once material hits the build platform is cools and cures, this process is also assisted by a UV light
• Where complex geometries and over hangs appear a easy to remove gel is used to generate support structure
• Once removed from the build platform and the supports are removed, the part is ready for use.

Summary

3D printing is an ever evolving manufacturing process on the forefront of current technological innovation. If your thinking a 3D printer could improve your process, reduce human error and provide an intuitive hands on experience to colleagues and customers, get in contact with us, checkout the shop and subscribe to our blog. If your curious about materials available request a sample here!

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