ORIGINAL ARTICLE A scaffolding architecture for conformal cooling design in rapid plastic injection moulding K. M. Au & K. M. Yu Received: 4 August 2005 /Accepted: 25 March 2006 / Published online: 8 June 2006 # Springer-Verlag London Limited 2006 Abstract Cooling design of plastic injection mould is important because it not only affects part quality but also the injection moulding cycle time. Traditional injection mould cooling layout is based on a conventional machining process. As the conventional drilling method limits the geometric complexity of the cooling layout, the mobi lity of cooling fluid within the injection mould is confined. Advanced rapid tool ing technologies based on solid free- form fabrications have been exploited to provide a time- effective solution for low-volume production. In addition, research has made attempts to incorporate conformal cooling channel in different rapid tooling technologies. However, the cooling performance does not meet the mould engineer’s expectations. This paper proposes a novel scaffold cooling for the design of a more conformal and hence more uniform cooling channel. CAD model for constructing the scaffolding str ucture is examined and cooling performances are validated by computer-aided engineering (CAE) and computer fluid dynamics (CFD) analysis. Keywords Conformal cooling . Scaffolding . Rapid tooling . Plastic injection moulding 1 Background on cooling channel design in plastic injection mould In recent years, rapid prototyping and tooling [1] pro- cesses have found widespread use in speeding up tooling production. These processes greatly reduce the manufac- turing cost and the lead time required for tool produc- tion. Figure 1 illustrates the difference between traditional tooling production and contempo rary rapid tooling fabrication. 1.1 Conventional cooling channel in plastic injection mould The use of conventional cooling channel [2] allo ws coolant or water to circulate within the injection mould, removing the heat by dissipation. It is the most common method of controlling mould temperature. The channel is formed by hole-drilling in various sizes as close as possible to the actual moulding area of the cavity sets. Figures 2 and 3 illustrate the conventional cooling channel in the injection mould. According to the part dimensional accuracy re- quired, the drilled holes are always machined using boring tool or drilling machine. The side wall of the mould is plugged and coolant is directed into cross bores and changed in direction. The freeform geometric cavity is surrounded by a straight-line cooling pattern. This will cause uneven cooling in the mould part. The uneven cooling will result in a tendency of several mould defects occurrence and increase the cooling time. A more accept- able cooling method is performed by the coolant flows in a pattern that closely matches the geometry of the part being moulded. 2 Conformal cooling channel in rapid soft tooling formed by copper duct Conformal cooling [4] is defined as the cooling channels that conform to the surface of the mould cavity (or core) for effectively transferring the heat from the mould cavity to Int J Adv Manuf Technol (2007) 34:496–515 DOI 10.1007/s00170-006-0628-x K. M. Au : K. M. Yu (*) Department of Industrial and Systems Engineering, The Hong Kong Polytechnic University, Hung Hom, Hong Kong, People’s Republic of China e-mail: mfkmyu@polyu.edu.hk the coolant channel. The term conformal means that the geometry of the cooling channel follows the mould surface geometry. The aim is to maintain a steady and uniform cooling performance for the moulding part. Figures 4 and 5 illustrate the geome tries of the different conformal cooling channels. From experimental results by several researchers, the injection mould cooling performance after utilizing confor- mal cooling channels can offer nearer uniform temperature distribution within the mould than the traditional cooling method. Heat can be evenly transferred or dissipated through the conformal cooling channel. Figures 6 and 7 illustrate the conformal cooling channel of direct AIM prototype tooling, designed by 3D Systems in 1997 [5]. However, the geometry of the copper duct can only partially follow the shape of the moulding part. It cannot provide a true uniform temperature distribution in the injection mould. The bending of the copper duct is limited by its diameter, mechanical strength and the size of the moulding part. Further bending of the copper duct will damage the cooling channel. It is worth to focus on the relationship between the geometry of the moulding surface and the cooling channel. The technique shown in Figs. 6 and 7 is proposed to realize the conformal cooling channel with better cooling performance. Besides, properties like thermal conductivity and coeffi- cient of thermal expansion are important in the rapid tooling process. Thermal conductivity is the quantity of heat transmitted through a distance in a direction normal to a surface with a certain area due to a temperature difference. An increase in thermal conduct ivity of the mould shortens the time required to cool down the moulding part. As epoxy is the material having low thermal conductivity, aluminium filler is added or mixed with epoxy. On the contrary, the coefficient of thermal expansion is the fractional change in dimension (or length) of a material for a unit change in temperature. The value decreases when aluminium filled compounds are added. Aluminium filled epoxy have a better dimensional stability than unfilled epoxy for injection moulding in RT. Table 1 indicates the coefficient of linear thermal expansion and thermal conductivity of various metal filled epoxies. Fig. 1 Difference in time between traditional and concurrent rapid tooling fabrications Fig. 2 Configuration of an injection mould with conventional cooling channel (side view) Fig. 3 Configuration of conventional cooling channel with coolant circulation [3] Int J Adv Manuf Technol (2007) 34:496–515 497 2.1 Related works in injectio n mould cooling channel design via RT techniques The advancement of SFF gives rise to the production of injection mould with intricate cooling channel geometry. Rapid tooling based on SFF technology includes RapidTool, SL, SLS or rapid casting, [8] etc. They provide significant advantages to plastic injection mould manufacturing. Much research has focused on improving the geometric design of the cooling channel via RT technologies. In 2001, Xu [9] studied injection mould with complex cooling channels based on SFF processes. He described the conformal cooling layout that can be realized with substantial improvements in part quality and productivity. He presented a modular and systematic technique for the design of cooling layouts by using 3DP. He suggested the decomposition of the injection moulded surface into definite controllable parts, called cooling zones. Then the cooling zones with the system of cooling layouts are further divided into definite cooling cells for analysis with the assistance of six design rules or constraints. He demon- strated his methodology via application to complex core and cavity for injection moulding. Figure 8 shows the green part of an injection mould with conformal cooling system design made by MIT’s 3D printing [ 9 ]. Li [10] studied a new design synthesis approach with the use of a feature-recognition algorithm to optimize the cooling system of a complex shape plastic part at the initial design stage. The plastic part model is divided from integral domain into simpler shape features. Then the individual shape feature is matched with its corresponding cooling design layout to form the mould cavity. This design synthesis technique can offer uniformity in mould temper- ature distribution. The ineffective computation time and complexity in domain part subdivision may give rise to some technical problems during the mould design process. Figure 9 illustrates the proposed conformal cooling design based on feature recognition algorithm. In 1999, Jacobs [11] described the use of conformal cooling channels in an injection mould insert. The channels are built by electroformed nickel shells. From finite element simulation, the conformal cooling channel formed by copper duct bending can increase the uniformity of mould temperature distribution. It can also decrease the cycle time and part distortion. As common injection moulding materials, such as steel, have not been included in his research, the application is only restricted to copper or nickel duct bending. Schmidt [12] investigated and generated a series of design of experiments in an attempt to evaluate and measure the benefits of conformal cooling for injection moulding. He presented an overview of the mould design methodology, cooling channel simulation and analysis, and tool product ion through MIT’s 3D Printing process. The simulation results show that conformal cooling can reduce both cycle and cooling times, and in part shrinkage. However, the mechanical strength, thermal stress of mould material and other mould defects are not taken into consideration in this work . Figur e 10 illustrates the Fig. 4 Conformal cooling channel in cavity side Fig. 5 Location of conformal cooling channel [6] Fig. 6 Conformal cooling channel formed by copper duct [5 ] Fig. 7 Bending of cooling duct evenly around the cavity wall (surrounding the ejector pin) 498 Int J Adv Manuf Technol (2007) 34:496–515 comparison between conventional and conformal cooling design for cooling simulation. Ferreira [ 13] attempted to use r apid soft tooling technology for plastic injection moulding. His work integrates rapi d tooli ng with a composi te materia l of aluminium-filled epoxy. The mould is cooled by conformal cooling channels. With the assistance of a decision matrix algorithm, a proper choice of materials and processes can be selected. The cooling layouts of the soft tooling are inserted with a bending copper duct before the epoxy filling process. However, in reality, the geometries of the cooling layouts are not fully conformed to the model. The cooling and moulding performance are affected directly with the rough metal mould surface finish. Mould defects such as flash, weld line, sink marks and low back pressure appeared and cannot be avoided. Figure 11 shows the soft RT mould with conformal cooling channel. From the above review, much research has attempted to apply SFF technologies to the design of conformal cooling channel. However, the increase in complexity of part geometries hinders the realization of conformal cooling layout fabrication in some RT processes. It is worthwhile to investigate further a more effective approach in order to obtain better cooling performances. 3 RapidTool fabrication with conformal cooling design RT, such as RapidTool process [14] by 3D systems, has successfully applied to the production of prototype in recent years. Figures 12 and 13 indicate the workflow of the RapidTool process for tooling fabrication. The application of RT for injection mould fabrication can assess to complex metal-type prototype more rapidly than other contemporary rapid proto typing technologies. As mould cooling is one of the limiting factors in the injection-moulding cycle, cooling channel design in RT is important for controlling the production time and quality. 3.1 Laminated steel tooling (LST) Laminated steel tooling (LST) [15] is a process that is employed to produce a laminated tool made of sheets of steel from laser-based cutting technology. The process is based on sequentially combining sheets of steel layer by layer with high-strength brazed joints for the laminated injection-mould fabrication. The advantage of LST is the production of tools that have dimensional accuracy com- parable to injection moulding. The technology can give rise to produce complex geometric configuration within the injection mould. However, LST moulds are used only for low melting thermoplastics and are not appropriate for the injection-moulding process with thermosetting plastics or high-temperature glass fibre. The layered manufacturing feature of LST is capable of fabricating injection moulds insertion of conformal cooling channels into any shape or position required. Figure 14 shows the hot platening process for LST production. 3.2 RapidTool RapidTool is a proprietary process from 3D Systems (formerly from DTM) based on selective laser sintering of LaserForm powder (thermoplastic coated steel powder) and subsequent bronze infiltration. Conformal cooling channels can be incorporated into the moulds, which last for hundreds of thousands of shots of common plastic. Table 1 Mechanical properties of various metal-filled epoxies [7] Epoxy for casting resins and compounds Unfilled Silica- filled Aluminium- filled Coefficient of linear thermal expansion, (10 −6 /°C) 45–65 20–40 5.5 Coefficient of thermal conductivity, (W/(m•K)) 4.5 10–20 15–25 Fig. 8 Green parts of an injection mould with conformal cooling channel design made by MIT’s 3D Printing [9] Fig. 9 Conformal cooling design based on a feature-recognition algorithm [10] Int J Adv Manuf Technol (2007) 34:496–515 499 3.3 Copper polyamide Like RapidTool, the Copper Polyamide process is now available from 3D Systems and uses a mixture of bronze and polyamide powders and conformal cooling channels can be incorporated into the moulds. 3.4 Direct metal laser sint ering (DMLS) EOS’s DMLS process utilizes specially developed machines and multi-component metal powders (mixture of bronze or steel with nickel). The SLS process is used for sintering, but no bronze infiltration is needed. Figure 15 shows the core and cavity of inserts with conformal cooling channel designed by EOS. 3.5 Direct AIM (accurate, clear, epoxy solid-injection mould) The advancement in rapid prototyping provides the capa- bility for the development of rapid tooling for injection moulding via 3D Sy stems’ stereolithography (SL). In the SL process, a photo-curable epoxy formed resin is solidified by exposing to a UV laser beam. In order to further improve thermal conductivity, copper channels or aluminium shots can be added to the low-melt alloy mix. The proposed design of cooling channel limits the consistency of the mould surface for heat transfer. Figure 16 shows the cross section of an injection mould assembly by the SL technique. 3.6 ProMetal ProMetal is an application of MIT’s Three Dimensional Printing Process to the fabrication of injection moulds. The ProMetal system creates metal parts by selectively binding metal powders layer by layer. It uses a wide area inkjet head to deposit a liquid binder onto the metal powders. The final metal mould is obtained by sintering and bronze infiltration simil ar to RapidTool of 3D Systems. Figure 17 shows the design of the cooling channel that can be located on any position within the mould. 4 Proposed model of porous scaffold architecture for an injection mould Scaffold technique [16–20] has been widely used in the medical, bio-technological and architectural disciplines. It can offer a desirable three-dimensional interconnectivity with tough mechanical strength. The dimension can be accurately controlled by the highly repeatable solid free- form fabrication processes. The design and fabrication of various complex geometries with a porous network can be performed by various RP&T processes. Figure 18 shows a porous structure formed by the assembly of scaffold elements. A mechanical and chemical feasible three- dimensional porous scaffold architecture can be fabricated. The maturity and high resolution of various RP and RT techniques allow scaffold architectural model to be devel- oped in various applications. 4.1 Possible methods for the design of a cooling passageway The use of rapid tooling technologi es offers a compact fabrication of a complex 3D model. With the purpose of enabling the production of a cooling passageway con- formally, this section outlines the surface offsetting method for the approximation of autom atic design of cooling Fig. 10 Comparison between conventional and conformal cooling design for cooling simulation [12] Fig. 11 Soft RT mould with conformal cooling channel [13] 500 Int J Adv Manuf Technol (2007) 34:496–515 passageway with the scaffolding technique. Firstly, spatial occupancy enumeration is used to approximate the array of the whole conformal cooling passageway with scaffolding elements. Figure 19 shows the flowchart of scaffold cooling surface approximation. a) Formulation and numerical solution of conformal cool- ing passageway formed by mould surface offsetting. Offsetting method is widely applied in various applica- tions. In theory, surface offsetting [21] is defined as the locus of points that are at constant distance d along the normal from the original surface. The offset surface r 0 (u) of a parametric surface r(u) can be expressed by Eq. (1) r 0 uðÞ¼r uðÞþdn uðÞ ð1Þ Here, the surface of the mould cavity is under surface offset. The intention is to define the geometric approximation of cooling passageway with a specific offset distance d. The new offset surface will identify the location of the cooling passageway of the mould cavity. The new offset surface is then offset again with a specific distance to form the layout and size of cooling channel. Figure 20 illustrates the location of offset surface with a particular offset distance d. b) Spatial enumeration of the conformal cooling channel by scaffolding element approximation. Spatial enumer- ation is one scheme to represent the geometry of three- dimensional model. A three-dimensional solid model can be represented in a computer by decomposing its volume into smaller primitive cells, such as cuboids, which are mutually contiguous and non-intersecting. Generally, the divided cubical cells can be set at a specific resolution and models are modeled by listing the cells that they take up. Here, the cubical cells are substituted by equal-sized, porous cells or scaffold volume elements. The integer coordinate system that it induces and offers on a shape can be used for Boolean operations and volum e computations. The representa- tion of continuous variation in space can be imple- mented easily and efficiently with scaffolding models. Figure 21a shows the modeling of mould cavity surface and Fig. 21b the cavity mould half with scaffolding elements inserted for uniform cooling. c) Unionization of scaffolding elements. After the co oling passageway subdivision, Boolean unionization of con- secutive scaffolding elements will be applied to generate the whole conformal cooling passageway. The scaffold elements are combined to form the whole porous structure. Fig. 12 Workflow of DTM RapidTooL Process [27] Int J Adv Manuf Technol (2007) 34:496–515 501 Fig. 13 Workflow of common RT mould development and fabrication Fig. 14 The hot platening process for LST production Fig. 15 Core and cavity of inserts with conformal cooling channel [28] Fig. 16 Cross-sectional view of an injection mould assembly by SL technique [29] Fig. 17 CAD design and prototype of a rapid mould by ProMetal [30] Fig. 18 Numerous scaffold elements with porous structure arrangement 502 Int J Adv Manuf Technol (2007) 34:496–515 4.2 Discrete scaffolding elements formation by solid offset The positive and negative solid offset [22] of the solid primitives can be easily computed by changing the size. The c ooling passageway can be formed by unionization of the equal-sized scaffolding e lements from a negative offset. The subdivided curve is re placed b y union ization of scaffold- ing elements. Here, a cube is applied as a scaffold to speed up the processing time and smoothness of the approximated model. Connected scaffold elements can be produced to form the cooling channel which is confor- mal to the surface of the mould cavity. Th e dimen sion of the scaffoldin g elem ent is set as L a nd the edge of th e scaffolding element being used is 8 mm (based on the theoretical data of mould engineering). Figures 22 and 23 show the d imension of the scaffolding elements and their assemblies. Scaffolding element formation is shown as follows: SE ¼ S À Ã S À ðÞ ð2Þ where SE is the scaffolding element; S is the original solid box; S − is the negative offset solid from S; The unionization of the discrete scaffolding elements generates the whole cooling channel conformally. In this approach, set Z denotes the set of integers, Z 3 becomes the set of points whose coordinates are all integers in the three- dimensional Euclidean space E 3 : and a set of discrete volume data is given as a finite subset of Z 3 : A primitive of scaffolding element in Z 3 are defined. The union of the scaffold elements is based on the connectivity of the chain structure. The chain structure is obtained by the vertex, edge and face connection to generate the whole cooling channel. We can define and locate the solid volume with the union of the scaffolding primitives. Let C be a Euclidean cube within the subset Z 3 : Then, we define the scaffolding elements of C as follows: – Vertices (V a ), a = 1, 2, 3 8 are labeled with (i, j, k) where i, j, k are the three plane indices, and those planes have at least one point in common; – An edge (E b ), b = 1, 2, 3 12 is drawn between two vertices if the vertices’ labels have two planes in common. The Euclidean cube primitives within the subset Z 3 develop the shape of the cooling system. The whole structure is defined by the corresponding attributes of vertices and edges of the primitives. The position of the cooling channel is tracked from the previous section of scaffolding curve approximation process. The connectivity of the scaffolding element primitives is based on the Boolean operation. Figure 24 shows the union of two consecutive scaffolding elements. The interior surfaces of the scaffolding elements will form the cooling surface for the proposed model. 4.3 Coolant flow through the scaffolding architecture The scaffold cooling syst em is desig ned with a complete coolant circulation which has an inlet, an outlet, and a pumping system. The coolant inlet and outlet are connected directly to the mould halves. Heat transfer during the injection-moulding cycle includes heat exchange originated from polymeric melt to the mould material by conduction. Fig. 19 Flowchart of scaffold cooling surface approximation Fig. 20 Surface offsetting of mouse model (mould cavity) Int J Adv Manuf Technol (2007) 34:496–515 503 Fig. 21 Schematic diagrams of the injection mould half; a Modeling of mould cavity surface; b Cavity mould half inserted with scaffolding ele- ments inserted for uniform cooling Fig. 22 Graphical representa- tion of a solid scaffolding element Fig. 23 Assembly of scaffolding elements Fig. 24 Union of two consecu- tive scaffolding elements; a Before merging; b After merging 504 Int J Adv Manuf Technol (2007) 34:496–515 The heat is then conducted from the mould material to the coolant in the cooling passageway via the scaffold cooling passageway. For the direction of coolant flow, a single scaffolding element has six faces that provide one face as the inlet and five faces as the outlet pathways for the coolant flow. Figure 21b is an example of a cavity mould half that is integrated with a scaffold cooling architecture. When the coolant inlet and outlet are connected with a high-pressure water pump and connector, a complete coolant circuit is formed. The assembly of numerous scaffolding element forms the conformal cooling surface which generates a multiple orientation passageway. The coolant flows from the inlet with high fluid pressure and run into the scaffolding architecture passageway in the cavity mould half. The coolant then brings the heat from the polymer and flows away via the outlet. As the scaffolding architecture follows the shape of the mould cavity surface, it increases the contact area of heat transfer from the poly meric melt and a near uniform cooling performance can be achieved. 5 Results of scaffold cooling performance The advent of computer-aided engineering (CAE) technol- ogy for plastic injection moulding provides a large support to injection mould design. Injection mould design simula- tion modules allow precise determination of the effective- ness of the mould cooling system at the desired mould temperature, avoiding some mould defects, and finding the desired injection moul ding cycle time. A variety of CAE simulations are performed for the proposed scaffold cooling system. Section 5.1 deals with the cooling performance analysis. Section 5.2 considers the mecha nical properties of the scaffold cooling design method for loadings during the injection-moulding cycle. Section 5.3 discusses the thermal management of the proposed method. Section 5.4 tests the effect of dimensional stability from shrinkage analysis. The CAE results illustrate the feasibility of the proposed scaffold cooling approach as for rapid plastic injection mould. 5.1 Cooling performance investigation of cooling channel by meltflow analysis Cooling performance analysis will find the temperature distribution in a plastic injection mould during the moulding process. Heat transfer will be analyzed between the plastic, the mould material and the coolant within the cooling system. An optimal cooling performance for designing the cooling system can be identified. Moreover, shrinkage and thermal stress analysis are conducted. In this research, Moldflow Plastic Insight 3.1 [23] is used to investigate the thermal effects of cooling channel design on the injection mould. The set of analysis sequence in this study is cool and flow. The parameters included injection mould pressure, maximum temperature of part, thermal stress, cooling time and volumetric shrinkage. The aims are to create uniform cooling along the circu lar cooling channel above and below the injection moulded part. Figure 25a shows the mouse model for the meltflow analysis. It consists of a thin shell with three buttons. Figure 25b illustrates the modeling of the mould cavity and core mould halves with scaffolding architecture. Figure 25c shows the opening and closing of the mould. Figure 26 shows the meltflow analysis workflow by Moldflow Plastics Insight 3.1. The procedures can be grouped into: the pre-processing step, the solver and the post-processing step. Tables 2 and 3 tabulate the specifica- tions and cooling parameters for meltflow analysis. Figure 27 compares geometric design of traditional and scaffold cool- Fig. 25 CAD models for CAE analysis;, a Mouse model; b Cross section of mould cavity and core, and c mould closing and opening Int J Adv Manuf Technol (2007) 34:496–515 505 [...]... materials (P20, H13 and A6 ) being tested The results indicate that the variation in mould temperature from 328 to 483 K have no significance in thermal stress and thermal strain The mechanical strength of these tool materials can withstand the vast change in mould temperature during the plastic injection moulding process The scaffolding architecture of injection mould can maintain the mechanical stability... cooling passageway for heat to be carried away from the injection mould Contemporary CCCs are characterized by offering nearuniform cooling with consistent heat transfer Better cooling can be achieved with less residual stress initialized defect formation during injection moulding Compared to the existing cooling channel systems design, the scaffold cooling system provides even better cooling for injection. .. being carried out within a period of time via the cooling passageway The flow can be classified into turbulent flow and laminar flow Coolant temperature at lower or higher degree can provide various heat capacities for the heat transfer The larger the contact area of the cooling passageway for heat transfer, the greater the region to achieve uniform cooling Thermal conductivity is the quantity of heat,... Contact area Thermal conductivity of mould material Coolant selection Coolant circulation within the injection mould 7 Conclusions In this paper, a novel approach using uniform-sized scaffolding architecture is proposed for conformal cooling design This method is aimed at providing a more uniform cooling surface for the injection moulded part With proper selection of mould material, the scaffolding. .. (A6 ) Int J Adv Manuf Technol (2007) 34:496–515 Fig 27 Geometries of two different cooling channel design; a traditional cooling and b scaffold cooling Fig 28 Performance of maximum mould temperature between a traditional cooling and b scaffold cooling Fig 29 Performance of incavity residual stress between a traditional cooling and b scaffold cooling Fig 30 The performance of volumetric shrinkage between... withstand the injection mould pressure and locking pressure during mould opening and closing The mould designed can perform with stable dimensions and hence the cooling performance The uniformity of the injection mould cooling can then be maintained with a high efficiency and part quality can be ensured 6 Discussion Straight-drilled cooling channel and conformal cooling channel (CCC) systems provide a cooling. .. COSMOS/FloWorks is used [26] A CAD model of the cavity mould half with internal scaffolding architecture, coolant inlet and outlet is designed and analyzed by internal fluid flow analysis Figure 36 illustrates the CAD model of scaffold cooling architecture for COSMOS/FloWorks analysis By setting the boundary conditions of inlet mass flow rate Fig 44 a Strain and b deformation of tool steel A6 at solid structure... injection moulding The cooling channel matches further to the cooling surface Extra uniform cooling can be provided and extended to region that is always ignored due to restrictions in traditional machining process For the proposed scaffold cooling system, the cooling surface provides a more uniform heat exchange system as the cooling covers the whole cavity surface The surface area of the cooling region... structure can offer additional mechanical strength so as to withstand the force and stress experienced during the injection moulding cycle A genuine uniform cooling, pressure drop performance and thermal distribution can be optimized by CAE and CFD analysis In the simulation results, the cooling performance indicates that the scaffold cooling technique can offer a more uniform thermal distribution with minor... Fabrication, pp 51–56 13 Ferreira JC, Mateus A (2003) Studies of rapid soft tooling with conformal cooling channels for plastic injection moulding J Mater Process Technol 142:508–516 14 Pham DT, Dimov SS (2001) Rapid manufacturing: the technologies and applications of rapid prototyping and rapid tooling Springer, Berlin Heidelberg New York 15 Bryden BB, Pashby IR (2001) Hot platen brazing to produce laminated . ORIGINAL ARTICLE A scaffolding architecture for conformal cooling design in rapid plastic injection moulding K. M. Au & K. M. Yu Received: 4 August. computer-aided engineering (CAE) and computer fluid dynamics (CFD) analysis. Keywords Conformal cooling . Scaffolding . Rapid tooling . Plastic injection moulding 1 Background