Additive manufacturing, not only used in rapid prototyping, embraces applications in many industries nowadays. The rise of additive manufacturing technology is a revolution in industrial manufacturing. The industrialization of additive manufacturing technology means faster time-to-market, more manufacturing flexibility, better product quality, and higher productivity.

1. Definition of additive manufacturing

Additive Manufacturing, also known as 3D printing, uses materials accumulation as the basic principle, and combines CAD/CAM technology with different energy sources, in contrast to the traditional subtractive manufacturing and molding process.

Combining computer-aided design, material processing, and forming techniques, additive manufacturing creates solid objects based on digital model files through the layering of specialized metallic materials, non-metallic materials, and medical biomaterials through software and numerical control in ways such as extrusion, sintering, fusion, light curing, and jetting.

Compared with the traditional processing mode, additive manufacturing is a bottom-up processing method through material accumulation. Its characteristic is that it produces products from scratch, which makes it possible to manufacture complex structural parts that were not possible in the past due to the constraints of traditional manufacturing methods.

2. Value of additive manufacturing technology

The value of additive manufacturing technology lies in the following aspects.

A. Product design

(1) Simplify and standardize the assembly process of products via additive manufacturing rapid prototyping.

2) Reduce the size of parts and products.

3) Reduce the installation effort.

B. Manufacturing process

1) Reduce the number of parts by more than 50%.

2) Reduce the welding work by about 50%.

3) Reduce the complexity and steps of assembly.

4) Shorten the lead time.

C. Business value

1) Accelerate product launch.

2) Adjustable design changes.

3) Simplify product maintenance and reduce service costs.

Compared with traditional production models, additive manufacturing has a more stable cost variation. The cost per part remains constant regardless of the complexity of the product or the volume of orders. At the same time, additive manufacturing technology itself is rapidly developing. For instance, HP's Multi Jet Fusion 3D printer can print tens of thousands of small-sized plastic parts. The cost is much lower than that of the traditional plastic injection process. Metal additive manufacturing equipment is also evolving rapidly, with significant productivity and product quality improvements enabled by laser technology.

Additive manufacturing technology is also driving changes in the entire industry chain, mainly in the below ways.

1) Reducing the mold manufacturing processes, including plastic molds, die castings, and tooling.

2) Reducing the processes of the parts supply chain, which will eliminate the bull-whip effect of inventory.

3) Significantly reduce the cost of mass production, making it easy to achieve the real single-piece flow.

These changes will impact the whole business model, which can strongly support the personalized and customized operation mode. It will be easier to achieve the innovation of end-user-oriented product function and service model, and the whole industry chain collaboration will be easier.

3. Three typical additive manufacturing methods

A. Laser Sintering

Laser sintering is a technique for forming objects by sintering material one layer at a time, using a fast-moving mirror controlled by a computer. After one layer of sintering finishes, the table moves down to sinter another layer of the material.

If the material is photosensitive resin, the process is called Stereo Lithography Appearance (SLA), the most widely used additive manufacturing rapid prototyping method.

If the material is ceramic, metal powder, or plastic, the process is called Selective Laser Sintering (SLS). Any unused powder can be recycled for the next print run. All un-sintered powder remains intact and becomes the support structure for the physical object. Therefore the process does not require any other support. In contrast, manufacturing methods such as FEM and SLA require a support structure. 

B. Material Extrusion Molding (FDM)

Material Extrusion Molding, also known as Fused Filament Deposition (FDF), involves heating and melting a filamentary hot-melt material and extruding it through an extrusion head with a microscopic hole. The extrusion head can be moved in the X-axis direction, while the table can move in the Y-axis direction. The nozzle can squeeze out the hot-melt material that will be randomly fused to the previous layer by keeping the hot-melt temperature higher than the curing temperature and the forming part temperature lower than the curing temperature. After a layer finishes, the table drops in predetermined increments equal to the thickness of a layer and then continues fusing wire deposition until the entire solid shape completes.

The materials are usually various plastics such as ABS, PLA, PP, PC, etc. Most of the 3D printers on the market with low processing costs are of this type.

C. Powder Jetting (3DP)

The powder jetting process is similar to inkjet printing in that the nozzle jets liquid resin onto the powder processing table to cure it. Multiple liquid resins can be injected to form parts with different material properties.

The 3DP process is similar to the SLS process which uses powdered materials for printing, such as ceramic and metal powders. 3DP differs from SLS in that the material powders are not sintered together, rather the cross-section of the part is printed on top of the material powder with an adhesive (e.g. silicone) through the nozzle. Parts bonded with adhesive are less strong and require post-processing.

Laser Powder Deposition (LPD) is commonly applied for processing metal materials. The metal material is deposited on the surface by a nozzle and laser-sintered to form the object.

Note:

This article was translated and edited from a Chinese book called Intelligent Manufacturing Digital Additive Manufacturing, edited by Zheng Weiming and others.