(1)Z400 and Z406 (Z-Corp, US)。 Both are based on

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jetting to bind powder materials。 Single-colored Z400 has an array of 128 nozzles (from CANON, Japan) and a layer precision from 0。075 mm to 0。02 mm, while Z406 is multi-colored, has 4 basic-colored binders that can be composed of 6 million kinds  of  colors, and each basic color has an array of 400 nozzles (from HP, US)。

(2)Quadra (Object, Israel)。 This machine integrates 3-D ink-jetting and light-curing process to photopoly- merize jetted resins in time by the UV light。 It has a vertical 60-mm array of 1536 nozzle heads, which can form a layer in 2-12 s and complete a one-inch high prototype in less an hour。 The system is of high effi- ciency,  and  the  layer  precision  can  be  as  low     as

0。02 mm。

(3)3-D 300C (Solidimension, Israel)。 It is based on LOM, and uses knives to cut plastic films and conglu- tinate them by adhesives, thus the deformation is very small。 The equipment only weighs 31 kg, and is one of the cheapest concept machines at present。

(4)Tier Print 3D (Yinhua, China)。 This is a desktop equipment, compact, is easily controlled, and needs no training。 It uses ABS plastic, cheap, of high strength and certain elasticity。 The support is intelligent, can be easily removed。

(5)Thermojet (3D System, US)。 It is based on jet- ting fused wax materials, has an array of 350 nozzles and an acceptable high forming precision。

(6)Prodigy (Stratasys, US)。 It is based on FDM, has two kinds of materials respectively for entity and sup- port。 The layer precision can be chosen as 0。175 mm,

0。25 mm or 0。33 mm。

4。3Rapid tooling and rapid moulding

Rapid tooling and rapid moulding, an important part of RPM, a new mould design and manufacturing system, is widely used in the injection molding and metal cast- ing industries。 It refers to directly create moulds with different types of RPM techniques, and then attain re- quired mechanical properties, dimensional accuracy, and surface quality with necessary postprocessing and machining。 It can rapidly get a finish mould and has a distinct advantage in those moulds that need complex flow system for cooling, compared with other methods。

(1)Rapid wood-pattern-free sand mould such as PCM, DSPC, general RP systems (GS), and Z cast di- rect  metal  casting。  PCM  was  originated  in Tsinghua

Tsinghua Science and Technology, June 2009, 14(S1): 1-12

University, China。 It completes a mould by  jetting resin or other binders onto refractory material layers such as sand and ceramic powder。 It was industrialized by Fenghua in Foshan, China。

(2)Methods based on powder metallurgy such as 3- D Keltool, launched by 3D System Corporation in US。 It fills resin-mixing tool steel powder in the middle silicone mould reversed from an SLA prototype, then bakes it to remove the binder。 A 30% porous  mould will be gotten, which would be finally infiltrated with copper and simply machined。 The precision can be   up

to 0。04 mm。 It can sustain a pressure of 20-25 kPa and a temperature of 650℃。

(3)Methods based on the deposition method such as rapid solidification process, originated in Idaho Na- tional Engineering and Environmental Laboratory, US。 It deposits a fixed thickness layer of alloy powder, ce- ramic, and polymer onto prototypes by certain deposi- tion technics like metal sputtering。 The surface rough- ness Ra can be 0。0735 mm, and the deposition rate can be 227 kg/h。

(4)Direct mould by SL。 3-D System directly formed the accurate clear epoxy solid injection mould with SL and special material。 However, this kind of mould is short-lived, and the complexity is limited。 SOUP (CMET, Japan) has a similar process。

(5)Electroforming mould。 It coats a conductive layer onto the prototype, and then places it in the elec- troforming tank to attain a metal shell at room temperature, and sinters it to remove the prototype。 Finally, after casting low melting point alloy, or resin- mixing aluminum between the mould casing and outer metal shell, the electroforming mould is completed。