Common 6 kinds of 3D printing service technology! Which one suits you?

6 kinds of 3D printing technology Additive Manufacturing (AM), also known as 3D printing, covers a range of technologies that gradually build physical parts from virtual 3D models by building them layer by layer. We list the common ones.

1. Material extrusion -FDM

The most common additive Modeling technology based on Material Extrusion is Fused Deposition Modeling (FDM), which is pushed in by heating the nozzlefilament(usually a polymer) melts and then stacks up along a predetermined path, where the filaments cool and solidify into an object. The easiest way to understand how this works is to think of it as a computer-controlled hot glue gun. Common desktop FDM 3D printers using standard materials are available with single and double nozzles, with nozzles reaching a maximum temperature of around 270°C, and more professional machine nozzles that can reach 500°C. Single-nozzle 3D printers usually use only one material for both body and support, while dual-nozzle 3D printers can print the main material of the model with a single nozzle (e.gPLA), another nozzle printWater-soluble support material, Put in warm water for 24 hours to melt (Picture 1-1) (Picture 1-2).

Picture 1-1 Additive manufacturing system based on FDM

Picture 1-2 3D model printed by dual nozzles (grey is PLA material, beige is PVA material)

There are a number of FDM 3D printers on the market that can print using composite materials, including continuous carbon fiber composite, short fiber (carbon fiber, Kevlar fiber, glass fiber, etc.) composite materials. These use wires that are either polymer mixed with a short-cut composite filler material or extruded with a continuous filament.

FDM 3D printers using metal materials have also appeared. A wire consisting of a polymer filled with metal powder (usually about 80% metal powder) is extruded to form a composite metal/polymer part (embryo piece). The embryonic parts burn off the polymer in the furnace and fuse/sinter the metal powders together to produce metal parts. Parts shrink by up to 20% of their volume during sintering, so special consideration needs to be given to the design of the part to achieve uniform and controlled shrinkage (Picture 1-3).

Picture 1-3 Support material easily removed by Desktop Metal extrusion system (provided by Desktop Metal)

One of the challenges with FDM is that the parts it produces are often anisotropic (more so than other 3D printing techniques), and the strength of the parts in the vertical Z direction is less than that in the horizontal direction (X and Y). Therefore, in general, FDM is a suitable fast fabrication process for parts that will be used in the compression state, and less so for parts in the tensile state, where the material may break and delaminate during use. It is important to note that FDM technology is improving and the problem is improving as new machines come to market.

In some applications, surface quality may also be an issue for parts printed by FDM technology. The gently sloping surfaces of the 3D models have quite a "ladder" effect. Note that the "ladder" effect applies to all additive manufacturing techniques, but is most pronounced in FDM techniques (Picture 1-4).

Picture 1-4 Step effect of extruded FDM

Typical application of material extrusion FDM:

(1) Prototype production
1) In most applications, the printed parts need a lot of post-processing to get a fine model, which can be polished, painted and so on
2) Low-cost desktop FDM 3D printers are especially good for quickly testing ideas
(2) For production
1) Fixture and fixing device
2) The application of parts in printing Z direction without tension
3) When a particular polymer cannot be formed using other techniques
4) Applications that require less surface quality and are not easily affected by anisotropy

Advantages and disadvantages of material extrusion

Materials extrude usable materials

2.Stereo Lithography Appearance -SLA

SLA (Stereo Lithography Appearance) uses an ultraviolet laser to solidify the resin layer in each slice of the model; the surface of the resin illuminated by the beam hardens. The forming platform is then lowered or raised (depending on the type of machine) by 0.1mm (if the printing layer is 0.1mm thick), a new resin layer is spread on top of the previous layer, and the next slice of the part is scanned by an ultraviolet beam, solidifying the current layer and bonding it to the previous layer. Repeat the modification process until the part is complete. SLA can make high resolution plastic-like parts.

It should be noted that the SLA requires supporting materials to support all overhangs in the part. After the part is printed, the supporting material is removed manually, and then the part is placed in a UV oven for post curing to harden the material completely (Picture 2-1).

Picture 2-1 SLA additive manufacturing system

Typical applications of SLA include:

(1) Prototype production
1) Due to the high details and surface quality, most of them are used in the production of fine prototype parts, later can be painted, electroplating, etc
2) Low-cost desktop SLA 3D printers are especially good for quickly testing ideas
(2) For production
1) Products that are not exposed to UV for a long time, such as hearing AIDS
2) Investment casting model

SLA advantage and weakness

SLA materials

3, 4, 5 powder bed melting -MJF, SLS, SLM

The Powder Bed Fusion technology includes HP's proprietary technology MJF (Multi Jet Fusion), SLS (Selective Laser Sintering), and SLM (Selective laser Melting).

1) MJF works by spraying an adhesive onto a thin layer of polymer powder particles (usually nylon) and then sinting them using an Infrared Ray heat source to build the part (Picture 3-1).

Picture 3-1 MJF multi-nozzle melt additive manufacturing system

2) SLS and SLM work by spreading a thin layer of powdered material on the forming platform, then using a laser to scan the slice of the part, the laser scanned powder will melt, then the forming platform is lowered one layer, the next layer of powder spread on the whole forming platform, and repeat the melting process, melting the current layer, Combine it with the upper layer (Picture 3-2).

Picture 3-2 SLS and SLM additive manufacturing system

These powder-based technologies are getting better and better at producing full-strength parts that exhibit relatively good isotropy in X, Y, and Z directions. There may be some anisotropy in the Z direction, but post-processing can minimize or eliminate the anisotropy if the part is well designed for the 3D printing process.

MJF and SLS can use a variety of polymers. Typical polymers include a range of polyamide plastics (nylon) and nylon with various fillers including glass, carbon fiber and aluminum, as well as high-temperature polymers such as PEEK. If designed well for the 3D printing process, plastic parts will exhibit similar properties to injection-molded parts and have the ability to make movable hinges and hold the parts together. Parts taken directly from the machine have a surface quality similar to matte plastic, and some "step" effects can be seen on slightly tilted or bent parts.

SLM can be used with metals including stainless steel, aluminum, titanium, cobalt-chromium alloy and maraging steel (tool steel). The surface quality and strength of metal parts are generally comparable to that of castings, without any voidage, bubbles or other defects. As with any cast part, metal parts need to be post-processed on a CNC machine to get a completely smooth or polished surface.

Typical applications of powder bed melting techniques include:

(1) Most applications of prototype production from display to functional prototype
(2) For production
1) Powder bed melting of polymers and metals is the most common technique used to produce industrial parts
2) Polystyrene materials are also used to produce investment casting models

Advantages and weakness of powder bed melting

Powder bed molten material