21st Century Manufacturing Episode 1 Part 5 ppsx

74 Manufacturing Analysis: Some Basic Questions for a start-up Company Chap. 2 with standard cable connection to a computer. The top surface of the enclosure has to be smooth and ergonomic for the finger to sit comfortably on the sensing array. 2.10.3 Det_it Design At the "detail design" stage, a CAD representation (in SDRC-IDEAS) was created to check the fit of the electronics and the basic form factor. The top lid was designed to package the PCBs, single- and double-board versions, and to provide a comfort- able support for the user's finger. The base provided additional space for connection ribbon cables and a power cable. Both the top lid and the base were designed to be fastened together. 2.10.4 Prototyping The next step was to decide among the different rapid prototyping methods. It was important to fabricate a prototype that was strong enough to be structurally safe when assembled and handled during the evaluation period. At the same time, rela- tively high tolerances were needed to allow the PCBs to be securely fastened to the top lid. The strength, tolerance, and surface finish achieved by the SLA process seemed to meet these needs and was thus chosen for prototyping. An informal group of "human users" was asked to evaluate the ergonomic aspects of the upper surface. The user group recommended that a flat slope be replaced with a more contoured slope that would mirror the inside surface of the index finger. To create this more comfortable contour for finger positioning, an important decision was made. It was decided to switch to a Web-based, freeform design tool (Wang and Wright, 1998a, 1998b) to create the freeform shape on the top surface. The key issue was again time-to-market. First, it was important to have a design tool that would produce the freeform surface. Second, and equally important, the Web-based, freeform design tool incor- porated a design rule checker for "downstream mold machining" (Urabe and Wright, 1997).This software assisted the designer to create both the part and a feasible mold. By anticipating the milling process early in the design process, possible errors were eliminated, therefore accelerating the overall design-to-manufacturing time (Table 2.7 and Figure 2.22).The Web-based freeform design was rendered with the ACIS 3D tool kit (ACIS, 1996). A second prototype was then fabricated to evaluate the ergonomic freeform surface (Figure 2.23). 2.10.5 Aluminum Tooling Design After the second prototype was evaluated and modified as shown in Figure 2.24, the shape was fixed and ready for the aluminum tooling stage for the injection molding process. Again, the Web-based, freeform design tool, plus the ACIS solid modeling tool kit, was selected for the complete mold design. The mold halves for the top part of the casing are show in Figure 2.25. While designing these mold halves, some specific molding characteristics were considered as well. For instance, an enlargement factor of 1.014 was applied to the 2.10 Case Study 15 TABLE 2.7 Manufacturing Analysis for the Development of the TouchChip Fingerprint Device Criteria and comments Questions Answer Who is the customer? Conceptual design? What is the cost? (a) batch size? What is the cost? (b) accuracy and tolerances? How much quality? Delivery time? flexibility? Original equipment manufacturer (OEM) of biometric security devices for computer applications 1.Small and ergonomic 2. Simple computer interfacing 200-300 assemblies Injection molding into aluminum tooling and ABSplastic Not the final production version-s-delivery time should dominate over perfection 9 weeks Need eventually to switch to steel molds 1. A "pre-mass-production" (OEM) product prototype as an "evaluation kit" for potential customers only 2. A potential market need for such a device but the first step is to demonstrate the product to computer makers and similar equipment makers 1. Much smaller and cheaper than the current optical- based fingerprint devices on the market 2. Easy integration with current computer peripherals Product prototype as an "evaluation kit" 1. Have a direct access to an injection molding service 2. Have a direct access to CyberCut machining service Production quantity (200-300) and "prototype only" decisions merit soft aluminum tooling instead of hard_ steel tooling to save machining time and cost. "Quality" will wait until a larger batch run is needed The production prototype will be demonstrated at the Fall COMDEX computer trade show CAD/CAM software allows ramp-up to more production design to compensate for the shrinkage factor of the ABS material when it cooled down after the molding process. A "draft angle" of 1 degree was also applied to the side walls of the molds to allow for easy part-mold separation. Subsequently, injec- tion molds were fabricated on a three-axis CNC milling machine. 2.10.6 Mold Machining and Injection Molding of 250 Casings The final mold cavity designs were sent directly to the CyberCut machining service over the Internet. CyberCut is an experimental research platform for networked manufacturing. It provides a "pipeline" in which the features generated from the Web-based design tools can be analyzed for process planning, tool-path planning, and the creation of the machine codes (G&M codes) for a three-axis CNC milling machine. CyberCut also provides a detailed manufacturability check on the designs as they an: created (see Wang and Wrighl, 1998a, 1998b). The completed mold cavities were sent to Metalcast Engineering in Oakland, California, to complete the plastic injection process. The mold cavities were sand- blasted to improve the surface texture of the final product. Backing plates were machined and attached to the back of"cope"mold halves for adding the spruce, run- ners and gates, and the ejecting mechanism (see Urabe and Wright, 1997). A total of 250 casing parts were produced. The TouchChip was mounted to the top casing and a daughter board complete with cable connection was connected to lUometriclud •. - Conceptual design phase '- Detailed design phase SDRe-mEAS AIuaohoum m.W • • SLA + CyberCut Process planning formanufaeturing and setUp of machines Semiconductor PCB-rabrk:doII manufacturing ~Ie tabricadoa FIpre 2.2Z Figure 2.1 reproduced with TouchChip steps. Pipre 2.23 Stereolithography prototype. 7. Condder product .• • Potential new synergies/, Nut product START 1E1'lII~1d" Markel analysis, •••••••••••b System assembly -, Plastic-proclucts\ manufacturing • • ••.• , Metal-product'! manufacturing Computer -c-; manufacturing Rapidprototyping and design changes \ Business pl~ C •••••2511 •••••••••••b Who is the _ customer? ~CIdp ._do Technical invention [...]... anufacturin specifics 3.1a Evaluation of requirements According to r~~~7.:er 3.1b (1- 10) ~c:~~~~~ class Relative numerical ranking of requirements Rank ordering c00~g)or Easy to read 9 9 18 2 Easy to understand 10 9 19 1 Easy to carry/handle 6 7 13 5 Good aesthetics 4 8 12 Content relevant to cours 9 6 15 3 Reasonable price 7 7 14 4 Good resale value 5 5 10 8 Freedom from errors 5 6 11 7 5 Figure J.t The... Mantyla, © 19 95 Reprinted by permission of John Wiley & Sons Inc.) 4 ParaUel(line 3 line 5) • Line B parallel to line 5 • Line2 acirculararc,tangenttolines! and 3 • Line4 orientedatatoline3 • Line 1 horizontal and length b • Line 5 perpendicular to 1 aod length a Product Design, Computer Aided Design (CAD), and Solid Modeling 88 Chap 3 Constantl/d Figure 3.4 Parametric scaling of a soft drink can 3 .5. 2 Design... object into unique variations from one original Consider a simple aluminum can for soft drinks (figure 3.4) Rather than specify that the dimensions are 12 0 millimeters (4. 75 inches) high and 62 millimeters (2 .5 inches) in diameter the ratio 4.7 51 2 .5 == 1. 9 might be used The height and diameter are then described in proportion to each other without specific dimensions being used Then the model can be... constrained on these inner, more engineering-like dimensions Another example from Shah and Mantyla (19 95) is shown in Figure 3.3: • Line • Line • Line • Line • Line 3 is parallel to line 5 2 is a circular are, tangent to lines 1 and 3 4 is oriented at 0: to line 3 1 is horizontal and length b 5 is perpendicular to 1 and length a A more sophisticated development of such constraints is parametric modeling This... analysis (FEA) 3 .5 .1 Constraint-Based Design and Parametric Modeling Rather than build up a model with specific dimensions, it is often useful to create constraints between certain features or lines Consider the simple cover plate to a regular domestic light switch Using the U.S standard dimensions as an example, the 3 .5 The Analytical Phase of Design 87 outer dimensions of the plate are usually 11 2 X 68 millimeters... Wire frame using the AutoCAD package (Section 3.8) • Constructive solid geometry (CSG) using the AutoCAD package (Section 3 .10 ) • Destructive solid geometry (DSG) using the SolidWorks package (Section 3 .11 ) 3.8 First Tutorial: 91 Wire Frame Construction Top Handle Front Base Back F1pre 3.6 Virtual reality joystick (from a student group led by Ryan Inouye) The three tutorials show the characteristics of... Design for Assembly, Manufacturing, Environment {DFA/M/EI and the software packages give manufacturing and environmental feedback to the designer or design team Ideally, designs can be modified early in the design process to improve manufacturability and decrease environmental impact New techniques to analyze a particular design for its manufacturability include the design for manufacturing and assembly... routine consumer products the goal of a design is to make money, and more is better (Hazelrigg, 19 96) With "making money" as the main objective, the designer might choose material properties in such a way that "an occasional failure is acceptable"; for example, 3.4 parts per million might be acceptable (Figure 2 . 15 ) In such circumstances, the consumer might be temporarily disappointed by a product failure... effectiveness" as the main design goal In Figure 3 .5, this means that the two curves should move apart on the x axis leaving no possibility for a failure zone Figure3 .5 A frequency distribution for predicting the strength ofa design It shows the inevitable spread in material properties on the right and loading stresses on the left (courtesy of James Stress due Siddall ,19 70) to loading Yield stress of material... errors 5 6 11 7 5 Figure J.t The mapping process in QFD and Compton's (19 97) example for a textbook (from Engineering Management by Compton, © 19 97 Reprinted by permission of Prentice-Hall, Inc., Upper Saddle River, NJ) Figure 3,1b is Compton's hypothetical example for a textbook This ranks the topics from "easy to understand" as number 1, down to "good resale value" as number 8 In another matrix, these . at 10 .000mm +0 .50 0/-0.000. 1 10.042 11 10 .022 2 10 .029 12 10 .030 3 10 .0 31 13 10 . 012 4 10 .029 14 10 .048 5 10 . 011 15 10 .099 6 10 . 054 16 10 . 0 15 7 10 .0 25 17 10 .023 8 10 .0 31 18 10 .034 9 10 .047 19 10 .042 10 10 . 016 20 10 . 053 •What. understand 10 9 19 1 Easy to carry/handle 6 7 13 5 Good aesthetics 4 8 12 5 Content relevant to cours 9 6 15 3 Reasonable price 7 7 14 4 Good resale value 5 5 10 8 Freedom from errors 5 6 11 7 Figure J.t The. weeks Prototypingstage Ilst.prototype 211 ~prototype peslgn and fab.Design and fab. 1& quot;asU w••• s•••• 2 .11 Interactive Further Work 79 2 .11 INTERACTIVE FURTHER WORK 2 .11 .1 Background A manufacturing advisory