types of rapid prototyping - additive process

FUNDAMENTALS OF RP TYPES OF RP

SLAFDM

SLS 3D PRINTER

INPUT, METHOD, MATERIAL, APPLICATION

Figure 2.1: The Rapid Prototyping Wheel depicting the 4 major aspects of RP

Input refers to the electronic information required to describe the physical object with 3D data.

There are two possible starting points – a computer model or a physical model.

The computer model created by a CAD system can be either a surface model or a solid model.

On the other hand, 3D data from the physical model is not at all straightforward.

It requires data acquisition through a method known as reverse engineering.

In reverse engineering, a wide range of equipment digitizer, to capture data points of the physical model and “reconstruct” it in CAD system.

While they are currently more than 20 vendors for RP systems, the method employed by each vendor can be generally classified into the following categories:◦photo-curing, ◦cutting and glueing/joining, ◦melting and solidifying/fusing and

joining/binding.

Photo-curing can be further divided into categories of ◦single laser beam, ◦double laser beams and ◦masked lamp

The initial state of material can come in either ◦solid, liquid or powder state.

In solid state, it can come in various forms such ◦a pallets, wire or laminates.

The current range materials include ◦paper, nylon, wax, resins, metals and

ceramics.

Most of the RP parts are finished or touched up before they are used for their intended applications.

Applications can be grouped into:◦Design◦Engineering, Analysis and Planning◦Tooling and Manufacturing

A wide range of industries can benefit from RP and these include, but are not limited to, ◦aerospace, ◦automotive, ◦biomedical, consumer, ◦electrical and electronics products.

LIQUID BASED, SOLID BASED, POWDER BASED

Liquid-based RP systems have the initial form of its material in liquid state.

Through a process commonly known as curing, the liquid is converted into the solid state.

The following RP systems fall into this category:1) 3D Systems’ Stereolithography Apparatus (SLA)2) Cubital’s Solid Ground Curing (SGC)3) Sony’s Solid Creation System (SCS)4) CMET’s Solid Object Ultraviolet-Laser Printer (SOUP)

5) Autostrade’s E-Darts6) Teijin Seiki’s Soliform System7) Meiko’s Rapid Prototyping System for the Jewelry

Industry8) Denken’s SLP9) Mitsui’s COLAMM10)Fockele & Schwarze’s LMS11)Light Sculpting12)Aaroflex13)Rapid Freeze14)Two Laser Beams15)Micro-fabrication

As is illustrated in the RP Wheel in Figure 2.1, three methods are possible under the “Photo-curing” method. ◦ The single laser beam method is most widely use and

includes all the above RP systems with the exception of (2), (11), (13) and (14).

◦ Cubital (2) and Light Sculpting (11) use the masked lamp method, while the two laser beam method is still not commercialized.

◦ Rapid Freeze (13) involves the freezing of water droplets and deposits in a manner much like FDM to create the prototype.

.

Except for powder, solid-based RP systems are meant to encompass all forms of material in the solid state.

In this context, the solid form can include the shape in the form of ◦ a wire, a roll, laminates and pallets.

The following RP systems fall into this definition:1)Cubic Technologies’ Laminated Object

Manufacturing (LOM)2)Stratasys’ Fused Deposition Modeling (FDM)

3) Kira Corporation’s Paper Lamination Technology (PLT)

4) 3D Systems’ Multi-Jet Modeling System (MJM)5) Solidscape’s ModelMaker and PatternMaster6) Beijing Yinhua’s Slicing Solid Manufacturing

(SSM), Melted Extrusion Modeling (MEM) and Multi-Functional RPM Systems (M-RPM)

7) CAM-LEM’s CL 1008) Ennex Corporation’s Offset Fabbers

Referring to the RP Wheel in Figure 2.1, two methods are possible for solid-based RP systems.

RP systems (1), (3), (4) and (9) belong to the Cutting and Glueing/Joining method,

while the Melting and Solidifying/Fusing method used RP systems (2), (5), (6), (7) and (8).

In a strict sense, powder is by-and-large in the solid state.

However, it is intentionally created as a category outside the solid-based RP systems to mean powder in grain-like form.

The following RP systems fall into this definition:1) 3D Systems’s Selective Laser Sintering (SLS)2) EOS’s Corporation EOSINT Systems3) Z Corporation’s Three-Dimensional Printing (3DP)4) Optomec’s Laser Engineered Net Shaping (LENS)

5) Soligen’s Direct Shell Production Casting (MJS)6) Fraunhofer’s Multiphase Jet Solidifcation (MJS)7) Acram’s Electron Beam Melting (EBM)8) Aeromet Corporation’s Lasform Technology9) Precision Optical Manufacturing’s Direct Metal

Deposition (DMDTM)10)Generis’ RP System (GS)11)Therics Inc.’s Theriform Technology12)Extrude Hone’s PrometalTM 3D Printing Process

All the above RP systems employ the Joining/Binding method.

The method of joining/binding differs for the above systems in that some employ a laser while others use a binder/glue to achieve the joining effect.

PROCESS, MATERIAL, ADVANTAGES, LIMITATIONS

History:◦ Worldwide first RP-technology at all◦ Patented 1984◦ Commercialized 1988 by 3D-Systems Inc.

The generative approach:◦ Production of parts by addition of material instead of

removal (like for example by cutting,etc)◦ Layer-by-layer build up >>bottom-to-top<<◦ Easy manufacture of undercuts, complex structures,

internal holes 

Realization by Stereolithography◦ Local solidification of a light-sensitive liquid

resin (photopolymer) using an UV laser◦ Scanning of the cross-section areas to be

hardened with the laser focus.

Layer – by – layer curing of a liquid photopolymer by a laser

Control of laser by a scan-mirror system

Process steps◦ Lowering of table by the thickness of one layer◦ Application/leveling of liquid resin◦ Scanning with laser◦ Again lowering of table

Supports◦ Needed for manufacture of undercuts◦ Build up with part similar to a honey-bee-structure

Process chain of SLA

Process chain of SLA (Cont..)

Only photopolymer of different qualities available ◦temp.-proof, ◦flexible, ◦transparent etc)

High part complexity High accuracy Support structure required

Part size: 250x250x250 mm3 to 1000x800x500 mm3

Accuracy: 0.05 mm Facility costs: 50 000 – 605 000 US$

PROCESS, MATERIAL, ADVANTAGES, LIMITATIONS

Melting of a wire-shaped plastic material and deposition with a xy-plotter mechanism

Characteristics◦Limited part complexity◦Two different material for part and

support

Thermoplastics ◦ABS, ◦Nylon, ◦Wax etc)

Fabrication of functional parts Minimal wastage Ease of support removal Ease of material change

Restricted accuracy – filament diameter 1.27mm

Slow process Unpredictable shrinkage Part size: 600x500x600 mm3

Accuracy: +/- 0.1 mm Facility costs: 66 500 – 290 000 US$

PROCESS, MATERIAL, ADVANTAGES, LIMITATIONS

TYPE 1◦Produced by 3 D Systems, USA◦Developed & patented by Univ of Texas,

Austin ◦Material: only technology directly process

thermoplastic, metallic, ceramic & thermoplastic composites

◦Model: sinter station 2000, 2500 & 2500plus, Vanguard

TYPE 2◦Produced by EOS, Germany◦First European for plastics, & manufacturer◦Capable to produce 700 x 380 x 580 (mm)◦First worldwide system for direct laser sintering◦Model: EOSINT P – thermoplastic ( eg nylon ) EOSINT M – metal EOSINT P 700 – plastic

Local melting/sintering of a powder by a laser Direct: the powder particles melt together Indirect: the powder particles are coated with

a thermoplastic binder which melts up Characteristics

◦ High part complexity◦ Many materials available◦ Burning out of the binder and infiltration might be

required◦ Relatively high porosity and surface roughness◦ Usually no supports needed

Wax Thermoplastics Metal Casting sand Ceramics

TYPE 1 (3D System)◦ Good part stability –precise controlled

environment◦ Wide range of processing materials – nylon,

polycarbonates, metals etc◦ No part supports required – material as support ◦ Little post-processing required - blasting &

sanding◦ No post-curing required – model solid enough

TYPE 2 (EOS)◦ Good part stability –precise controlled environment◦ Wide range of processing materials – polyamide,

polystyrene, metals etc◦ No part supports required or only simplified support –

reduce building time ◦ Little post-processing required – good model finishing ◦ High accuracy – low shrinkage & in separation building◦ No post-curing required – model solid enough◦ Built large part – large build volume (700x380x580)

Part size: 250x250x150 to 720x500x450 mm3

Accuracy: +/- 0.1 mm Facility costs: 275 000 – 850 000 US$

TYPE 1 (3D System)◦ Large physical size of the unit – need big space. ◦ High power consumption – high wattage of laser for

sintering.◦ Poor surface finish – use large particle powder

TYPE 2 (EOS)◦ Dedicated systems – for plastic, metal & sand only. ◦ High power consumption – high laser power for

metal sintering.◦ large physical size of unit – use large space

PROCESS, MATERIAL, ADVANTAGES, LIMITATIONS

Produced by Z Corporation, USA Core Technology invented & patented by MIT

Materials: starch & plaster formulations Model:

◦Z 400 – entry level & education◦Z 406/ 510 – Color Printer builds◦Z 810 - large build volume

Local bonding of starch powder by a binder using an ink jet (patent of MIT)

Characteristics◦ Very high building speeds◦ Easy handling◦ Binder available in different colors◦ Infiltration necessary◦ Ideal for fast visualization

Process steps◦ Spread a layer of powder◦ Print the cross section of the part◦ Spread another layer of powder◦ Parts are printed with no supports to remove◦ Refer z corp.doc

Starch powder (Z Corp.) Other manufactures offer systems for ceramics or metals

High speed – layer printed in seconds Versatile - used for automotive, aerospace,

footwear, packaging, etc simple to operate - straightforward No wastage of material – can recycle colour – enable complex colour scheme

Part size: 200x250x200 mm Resolution 600 dpi in x-y-direction Facility costs: 49 000 – 67 500 US$

Limited functional parts – models are weak limited materials – starch & plaster-based

only poor surface finish – need post-processing