Sheet Lamination

Table of Contents:

In the sheet lamination additive manufacturing process, thin sheets of material are bonded together using adhesives or a heat source to form a three-dimensional product. The sheet lamination processes are also known as: Ultrasonic additive manufacturing (UAM) when ultrasonic bonding is used to laminate thermoplastic sheets together and laminated object manufacturing (LOM) when adhesives are used for lamination.

Materials Used in Sheet Lamination

Polymers are often used but paper or metal foils are also typically processed and find application in cases where heat sensitive materials cannot be used and low costs must be realized. Almost any polymer can be used as long as it is available in thin sheet form and can be bonded by either adhesives or heat.

The main advantages of sheet lamination are:

i. Low materials cost

ii. Many substrates are available (e.g. paper, film, foil)

iii. Process does not require a closed environment

iv. High volumetric build rates

v. Allows for combination of materials and embedding components

The key disadvantages are that complex geometries are difficult to manufacture and may be less precise than other additive manufacturing methods. Many characteristics of this method are as follows:

i. Using binding materials such as adhesives or energy (e.g. ultrasonic welding)

ii. Relatively large components may be produced

iii. Possibility of low cost, easily accessible building materials such as paper, plastic film, or metal foil

iv. Bonding equipment can be easy (even by hand) or automated

v. Significant applications: Large parts, tooling

Directed Energy Deposition

Directed energy deposition methods usually do not use polymeric materials but use metal wire or powder. High energy sources, such as the laser, are directed at the material to melt and build up the product. Directed energy deposition is assumed to be a more complex and expensive additive manufacturing process, but is generally used to repair or add extra materials to existing components. Other characteristics of directed energy deposition include: Similar to powder bed fusion except material is first injected into an energy field. Common substrates are metal, metal wire, glass, and ceramics.

Strengths:

i. Can operate in open air

ii. Multiple materials can be used

iii. Large parts are possible

iv. High single point deposition rates

v. Not limited by direction or axis

Limitations:

i. Expensive equipment, lower resolutions, and reduced ability to manufacture complex parts

ii. Final machining is often required

Major applications: Repair or build-up of high volume parts (Table 1.1).

TABLE 1.1

Recap and Description of These Processes

Process	Description	Technology
Photo polymerization	A vat of liquid photopolymer resin is cured by selective exposure to light (through a laser or projector). This then initiates polymerization and transforms the exposed areas into a solid component.	Stereolithography (SLA) Digital light processing (DLP) Continuous liquid interphaseproduction (CLIP) Scan, spin, and selectively photocure (3SP)
Material jetting	Material droplets are deposited layer by layer to produce objects. Common varieties include jetting and curing of photocurable resins with UV light, as well as jetting of thermally molten materials, which then solidify at ambient temperature. This process was the origin of the term “3D printing.”	3D printing (3DP) Multi-jet modeling (MJM) Drop on demand (DOD)
Binder jetting	Bonding agents are applied selectively to thin layers of powdered material to form parts layer by layer. Binders shall contain organic and inorganic materials. Metal or ceramic powdered parts are commonly fired in the furnace after they have been printed.	Drop on powder (DOP) Powder bed printing
Material extrusion	The material is extruded by a nozzle or an orifice in tracks or beads, which are then integrated into multi-layer models. Popular varieties include hot thermoplastic extrusion (similar to a hot glue gun) and syringe dispensing.	Fused deposition modeling (FDM) Fused filament fabrication (FFF)
Powder bed fusion	Powdered materials are selectively deposited by melting together using a heat source such as a laser or electron beam. The powder surrounding the consolidated component works as a support material for the overhanging materials.	Selective heat sintering (SHS) Direct metal laser sintering (DMLS) Electron beam melting (EBM) Selective laser melting (SLM) Selective laser sintering (SLS)
Sheet lamination	Material sheets are stacked and laminated w'ith each other to form an object. The method of lamination can be adhesive, ultrasonic welding, or brazing (metals). Excessive regions are cut layer by layer and removed after the object is built.	Selective deposition lamination (SDL) Laminated object manufacturing (LOM) Ultrasonic additive manufacturing (UAM)
Direct energy deposition	Metal powder or w'ire is feed into a melt pool formed on the surface of the part where it is attached to the underlying part or layer. The source of energy is normally a laser beam or an electron beam. In essence, this process is a type of automated build-up w elding.	Laser metal deposition (LMD) Electron beam free-form fabrication (EBF3) Direct metal deposition (DMD) Laser engineered net shaping (LENS)"

FIGURE 1.7 Classification of additive manufacturing systems.