21st Century Manufacturing Episode 1 Part 5 ppsx

Second, and equally important, the Web-based, freeform design tool incor-porated adesign rule checker for "downstream mold machining" Urabe and Wright, 1997.. By anticipating the milling

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 (inSDRC-IDEAS) was created

to check the fit of the electronics and the basic form factor The top lid was designed 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 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 aWeb-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 adesign 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 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

TABLE 2.7 Manufacturing Analysis for the Development of the TouchChip Fingerprint Device

Criteria and comments

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

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 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 and the creation of the machine codes (G&M codes) for a three-axis CNC milling

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-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

•

-Conceptual design

'-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

1E1'lII~1d"

Markel analysis,

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

the TouchChip and finally assembled to the bottom casing.Figures 2.19 through 2.24 show the device and its connections

2.10.7 Tim Analysis

Product development was thus divided into four main stages: the prototyping stage (2.5 weeks), the tooling design stage (3 weeks), the production stage (1.5 weeks), and the postprocessing stage (1.5 weeks) Details of the development processes at each stage are shown in Figure 2.26

The tooling design and machining of the mold was the most time-consuming aspect of production with a total of about 150 worker-hours.1bis task included the design of the molds, design review meetings, design iterations, and the time

con-a three-con-axis milling mcon-achine The time consumed during this stcon-age wcon-as mcon-ainly con- attrib-planning of the mold with a freeform surface

2.10.8 Conclusions from the Cas Study

1 The integrated CAD/CAM environment called CyberCut allowed a series of prototypes to be prepared in quick succession When the design was converted batch of 200 prototypes would be correct

2 The "clean interfaces" between different stages of the product develop-ment process ensured that the final mold was dimensionally correct for the final assembly processes (of PCBs, displays, etc.) so that mold rework was eliminated

3 Specifically,improving the design and mold machining process, and predicting the suitability of the final desigu of the mold, enabled a smooth "hand off' to the injection molding company (MetaJcast Engineering)

4 Elements shown on the time line could be completed in parallel because of the confidence in the decisions in the design.This reduced the overall elapsed time

of the project and avoided the need for expensive rework

Tooling Tholillj;

design machining

lnj~on ~mbly Do:bugging molding

Prototypingstage

Ilst.prototype 211~prototype

peslgn andfab.Design andfab.

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s••••

2.11 INTERACTIVE FURTHER WORK

2.11.1 Background

A manufacturing advisory service can be found at the following URL:

<bttp:l/cybercut.berkeley.edu> However, "don't try this at home" without a Java-enabled browser! Anything over a Pentium 100 should be satisfactory For a slower machine, read the instructions for work-arounds The goal is to provide an automatic way of negotiating the choices in Table 2.2 concerned with process selection 2.11.2 Tutorial

Introductory tutorials have been set up for use at <bttp:l/cybereut.berkeley.edul mas2JhtmVtutorials.btml> With a big enough screen, put the Applet on one side and the tutorial on the other

Follow the steps in the tutorial, the key aspects of which are:

• Click on Process Search

• Click on one of the attributes listed in the Facet column

• Specify a value for this attribute underneath the Facet column Note: Some Facets are selected by clicking on the choice beneath Facet List and selecting one of the options that appears Other Facets are defined through numerical entry andlor the slider bar Do not use commas (e.g a large batch size is 30000 not 30,(00)

• Go through the 11 Facets using the Get Info button for definitions

• Keep an eye on the p-renk column, making sure that tolerances are not over-specified resulting in all zero rankings

• After Process Search, next click on Materilll Search

• Repeat the same steps for Material Search

• Then, finally,click the Results Survey button to combine the two searches 2.11.3 Some Other Notes

The MAS is not a "Black Box Tool" that blindly chugs numbers It's more of an

to find out why it is being rejected Then in the f-rank column, it will show which the slider bar or choices give a nonzero rank A rank of unity is the best 2.11.4 Specific Work

Consider three domestic or industrial products and go through the selection proce-the project to date, that it should be asingle item or a component in an assembly

2.12 REVIEW MATERIAL

1 During quality assurance of a drilled hole in an aircraft component, the fol-lowing hole diameters were measured by an inspector The hole was originally

toleranced (i.e., on the drawing) at 10.000mm +0.500/-0.000.

• What is the upper specification limit (USL) and lower specification limit (LSL)?

• What is the natural tolerance (NT) for the drilling process used to make these holes? This question first involves calculating the standard deviation,(J'.

• Calculate the process capability, Cpo

• Calculate the C pkfor the process

• What does this say about therealprocess capability?

• Using the data above, define the upper control limit (UCL) and lower control limit (LCL) Do any of the holes fall outside of the control limits?

2 The new company, www start-up-compenycom, plans to market a plastic car for under $39.95,otherwise it will not sell The tool steel die costs $500,000to make Refer to Figure 2.17 to recall the steps needed to get to this die Next:

• Plot a graph below showing how this die cost gets amortized over the number

of cars sold

• If the company only had to worry about the die cost, what is a reasonable number of cars to sell?

• If it factors in some of the other costs represented in the graph.make another

"ballpark" estimate of what is a reasonable number of cars to sell

• Using a short, 50-word description, what are the total development costs that

www.start-up-company.comneeds to take into account? Add this to the man-ufacturing costs above, and then make an estimate of how many cars must be sold Note: This is not an easy task, nor is there a specific number, but it makes

3.1 INTRODUCTION

Chapter 3 discusses the general methods of design in engineering The specific focus stantly being improvedbythe rapid advances in computer power, the state of the art will change in the mere few months it takes to get this book into print However, the general principles of CAD and solid modeling should remain relatively unchanged

Chapter 4 will follow with the creation of an initial prototype and the

subse-quent manufacturing of the firstreal partfrom the prototype It may seem an unusual juxtaposition to talk about the geometric operations in feature-based design and the metallurgy of casting in adjacent chapters Certainly no other books on

manufac-turing do so.The goals of doing this are to emphasize the integration between the

var-the negative consequences ofTaylorism described in Chapter 2

In recent years, CAD design tools have been developed that can be explicitly linked in an electronic sense to rapid prototyping methods and full production Chapter 4 will describe how to "tessellate" the CAD models shown here in Chapter 3 stereolithography (SLA) process Many of these newer prototyping methods did not appear Wlli11987 Therefore, any manufacturing company that wants to be innova-tive should be constantly aware of developments in this general field that links CAD

to prototyping and then to CAM In fact, it is also much easier today to link such CAD databases to traditional processes such as machining Even lost-wax

casting-a process thcasting-at dcasting-ates bcasting-ack more thcasting-an 5,000 yecasting-ars to the casting-ancient Korecasting-ans casting-and Egyp-tians-is still in wide use because the links from design to mold making and investment casting have been radically improvedbyCAD/CAM methods

PRODUCT DESIGN, COMPUTER AIDED DESIGN (CAD),

AND SOUD MODELING

3.2 IS THERE A DEFINITION OF DESIGN?

Here are some common definitions of design that are useful but do show a rather wide range of activities Note that this list begins with a very high level artistic view

of the design world The next definition is also high level but more engineering occur as a designer begins to calculate the dimensions of the components in a spe-cific design The fourth definition is more utilitarian and concerns drawing the details The next four main sections review these four levels:

• Art related and high-level: "Design in any of its forms should be functional,

based on a wedding of art and engineering" (w A Gropius, founder of the Bauhaus movement)

• Engineering related and high-level: "Design is the process of creating a product

(hardware, software, or a system) that has not existed heretofore" (Suh, 1990)

• Engineering related and at the analytical level: "Design is a decision making

process" (Hazelrigg, 1996)

• Detailed design: "Design is to make original plans, sketches, patterns, etc."

(Webster's Dictionary)

As a result of this range of possibilities, the design community continues to

argue passionately about the definition of the word design And since the definition

seems to have a slightly different focus in its teaching methods

Some engineering schools emphasize the creative aspects of design This might mean building models or prototypes and thinking about the markets for the next-and-better consumer product Other schools are more analytical and proceed with and fatigue analysis of gears, shafts, and bearings for mechanical engineers 3.3 THE ARTISTIC CREATIVE OR CONCEPTUAL

PHASE OF DESIGN

Outside the engineering schools of a university, the word design has an even broader

designers of automobiles, living spaces, many consumer products, and clothing, the activity of design is an art form It conceptualizes creative images that are aestheti-cally pleasing

The artistic, or creative, or conceptual phase of design is a multidisciplinary

activity that considers many factors Chapter 2 discussed these factors, which include quality level, time-to-market, flexibility,and long-term growth

This "high-level" creative phase of design involves a conceptual mapping between consumer demands and physical objects Designers at this level prefer to be

Creative design should be a team effort, and the whiteboard or pencil and paper still seem to be the best toots In the Appendix it is thus recommended that the design groups create their first initial concepts with pencils on art paper that is 550 x 700

mm (22 x 28 inches) in size It provides a fluid exchange of ideas and in addition facilitates the round-table team discussion Once the design team has its vision of the analysis tools can be used for decision making among alternatives and possible opti-mization of a design

Computer aided design (CAD) programs have been developed in several for-mats and with several strategies in mind Regardless of the strategy, traditional

CAD programs have been difficult to leverage as conceptual design tools It is a

common experience that using a standard CAD system too early can actually extend the overaJl design time! 'The old cliche applies: "If you only have a hammer everything looks like a nail." Since all standard CAD programs have limits, struc-straitjacketed if new ideas have to conform to the program's logic Conceptual design should be a process that is characterized by brainstorming, market identifi-CAD program's logic

For the conceptual design of new cars and trucks, some of the newer, very

expensive computer aided styling tools do encourage the artistic spirit (see Sequin's

work at http://www.cs.berkeley.edul-sequinlCAFFEIcyberbuild.btml).However.by contrast, the majority of the day-to-day CAD packages [ProEngineer, SDRe, AutoCAD, Solidworks, etc.) fall short of the fluidity needed for full creative work

3.4 THE HIGH-LEVEL ENGINEERING PHASE OF DESIGN

3.4.1 Quality Function Deployment (QFDI

QFD is a well-known acronym for quality function deployment (see Hauser and Clausing, 1988) It focuses on the "quality versus cost" aspects of the broader CQDF issues in Chapter 2 A team of marketing specialists begins the process of OFD Cus-tomer groups are subjected to lengthy surveys that ask about their general prefer-qualities, then into design features, and finally into manufactured product character-istics (Figure 3.1a) The reader is referred to Compton's book (1997) for a more detailed analysis, but the basic steps are now reviewed

A list of desirable characteristics is first drawn up by the survey team For the polo shirt example in Chapter 2, this might be material type, fit, styling, color range, and cost An individual person being surveyed is then asked to assign a numerical value between 1 and 10 to each of the characteristics, based on the importance to that customer "Best-in-class" competing shirts from other manufacturers can also be evaluated in the survey form The survey team then collates the results from many respondents and identifies the most important customer requirements for the