Future Trends

The accuracy of processes such as stereolithography and selective laser sintering is improving as time goesby.These processes are being used more and more in the cre-ation ofthe original, first master for casting and for plastic injection molding. As con-sumer products such as stereos, cellular phones, personal digital assistants (PDAs), and handheld computers (Richards and Brodersen, 1995) begin to look more aerody-namic, there is a need to create molds that have unusual curves and reentrant shapes;

these are easy to create in SLA or S~ especially in comparison with machining.

It has nonetheless been emphasized that SFF's accuracy is poor in comparison with machining. Overhanging structures may be hard to support during fabrication, and there are problems with component warping during curing. While simple shapes might have accuracies of.ct-:25 to 75 microns (0.001 to 0.003 inch), the range for complex shapes might be as high as+1-125 to 375 microns (0.005 to 0.015 inch).

While the strength of SFF parts is today less than machined parts, new trends are closing the gap. The FDM parts made by the Stratasys machine can be formed in near full strengthABS and similar polymers. Cheung and Ogale (1998),for example, have increased the strength of photopolymers by fiber reinforcement. Also, research at Sandia Laboratories on a process called laser engineered net shaping (LENS) is permitting direct fabrication of high-strength metal molds. This and similar projects are modified versions of DTM Inc.'s SLS process.

At the same time, CA O/CA M techniques for machining are advancing rapidly.

For example, the CyberCut freeform design tools linked to open-architecture milling machines will continue to expand machining's capability (Greenfeld et al., 1989;

Schofield et al., 1998; Hillaire et al., 1998). There is a subtle point to be made here:

much of the increased activity in the SFF prototyping methods was originally prompted bythe poor communication between CAD and CNC machine tools.

During the late 1980s, stereolithography's competitive edge over machining came from the fact that the CAD model could be instantly "sliced" and then turned into laser scanning paths for rapid part production. With the CyberCut methodology and open-architecture control, the conventional machining process can be equally com-petitive from an art-to-part speed standpoint, and it continues to give the high-accuracy and product integrity qualities that it always gave.

The evidence is thus clear that the capabilities in both the machining and the SFF fields are constantly improving. It has also been noted that several of the methods such as 3-D printing with planarization, SGc, and SDM combine deposi-tion with machining "to get the best of both worlds." Perhaps in a similar way, the 3D Systems' QuickCast method uses "the best of SLA combined with the best of invest-ment casting." In QuickCast, disposable SLA patterns are fabricated with distinctly hollow internal structures. When the ceramic shells for casting are created around these hollow SLA patterns, the latter collapse inward, leaving the casting mold intact

4.7 Glossary ¹⁶³

and ready for use. This process, described by Jacobs(1996, 183-252), is gaining rapid acceptance commercially.

The issues mentioned are predominantly technical. As this chapter draws to a close, it is important to recall an earlier point from Chapter 2 that "prototypes structure the design process" (see Kamath and Liker, 1994).Physical prototypes focus the efforts of a distributed design team, especially if subcontracting is a big part of the process.

Perhaps the most important conclusion is this: each manufacturing process will playa vital role at different points in the product development cycle. SFF techniques will be more evident at the front end, machining will be more evident partway through to create highly accurate molds, and plastic injection molding will be most evident in the final high-volume production method for the consumer's product.

Once again it must be emphasized that "manufacturing in the large" is an integration of many software tools, physical processes, and market strategies.

In summary, rapid prototyping dramatically accelerates time-to-market.

• Psychologically, it focuses the attention of the members of the design team in a "learning organization" (see Chapter 2).

• Physically, it reduces the time necessary to make a full production die from hardened steel and to launch into mass production.

4.7 GLOSSARY

4.7.1 01. Casting

Low-pressure casting, often of liquid zinc, into a machined mold.

4.7.2 Electrodischarge Machining IEDM.

The use of an electrode to melt and vaporize the surface of a hard metal. Usually restricted to low rates of metal removal of very hard metals.

4.7.3 G-Codes

The standard low-end machine tool command set that gives motion, for example, G1

=linear feed.

4.7.4 Injection Molding

Viscous polymer is extruded into a hollow mold (or die) to create a product.

4.7.5 Ink-Jet Printing in 3-0

Rapid prototyping by rolling down a layer of powder and hardening it in selected regions with a binder phase that is printed onto the powder layer.

4.7.6 Investment Casting

The word investment is used when time and money are invested in a ceramic shell that is subsequently broken apart and destroyed. The original positive master that is

'84 Solid Freeform Fabrication (SFF) and RapidPrototyping Chap. 4 used to create the negative investment shell can be made by several processes. Lost-wax and ceramic mold are the two most common.

4.7.7 Laminated Object Modeling (LOM)

Rapid prototyping by laser cutting the top layer of a stack of paper, each layer of which is glued down.

4.7.8 Lapping and Polishing

Final finishing and smoothing of a surface that has already been machined. The surface-lapping operation is usually done on flat lapping plates loaded with diamond paste down to 0.25 microns in diameter.

4.7.9 Machining

General manufacturing bycutting on a lathe or mill; chip formation from a solid block rather than forging, forming, or joining.

4.7.10 M·Codes

The standard low-end command set for machine tool operations that are not related to x, y, or z motion of the axes-for example, M6 == call tool into spindle.

4.7.11 Near-Net Shape

Forming, forging, or sintering operations that produce an object "nearly" to its final shape so that only minor finish machining is needed.

4.7.12 Plastic Injection Molding

As "injection molding," described earlier. Note: Zinc die casting also involves "injec-tion" into dies or molds.

4.7.13 Prototyping (Prototype)

"The original thing in relation to any copy, imitation, representation, later specimen or improved form" (taken from Webster's dictionary).

4.7.14 Rapid Prototyping (RP)

A new genre of prototyping, usually associated with the SFF family of fabrication methods. Emphasis is on speed-to-first-model rather than fidelity to the CAD description.

4.7.15 Selective Laser Sintering ISLSI

Rapid prototyping by laser sintering of polymer or ceramic powders. The laser moves as a point source across the surface of the powder, first sintering the bottom slice of the desired object. A roller spreads more powder and a second layer is sintered, also fusing to the one below.

4.8 References '66

4.7.16 Shape Deposition Manufacturing ISDM)

Rapid prototyping with alternative deposition runs followed by machining runs across an object to build up complex prototypes.

4.7.17 Solid Freeform Fabrication ISFFI

A family of processes in which a CAD file of an object is tessellated, sliced, and sent to a machine that can quickly build up a prototype layer by layer.

4.7.18 Solid Ground Curing ISGCI

Rapid prototyping, also by laser curing of photocurable polymers, but done layer by layer through a photomask rather than by laser point sources.

4.7.19 Stereolithography ISLA)

Rapid prototyping by laser curing a photocurable liquid.The laser moves as a point source across the surface of the liquid, first curing the bottom slice of the object. This slice moves down on an elevator by 5U to 375 microns (0.002 to 0.015 inch), depending on desired accuracy. The nextlayer is then photocured, also fusing to the one below.

4.7.20 Tessellation

Representing the outside surfaces of an object by many small triangles, like a mesh thrown overand drawn around the object. This leads to an ".STL" file of the vertices and the surface normals of the triangles.

4.7.21 3-D Printing/Plotting

Rapid prototyping by printing/plotting thinjets of polymer onto a fixtureless base-plate followed by simple machiniug/planenzation.

4.8 REFERENCES

ACIS Geometric Modeler. 1993. Technical Overview. Spatial Technology, lnc., Version 1.5.

Ashley,S. 1991. "Rapid prototyping systems."Mechanical Engineering 34-43.

Ashley,S. 1998. "RP industry's growing pains." Mechanical Engineering 64-67.

Au, S., and P. K. Wright.1993.A comparative study of rapid prototyping technology. In Intel-ligent concurrent design: Fundamentals, methodology, modeling, and practice. ASME Winter Annual Meeting, New Orleans. Louisiana. 73-82.

Bearnan.J, 1.,1. W. Barlow, D. L. Bourell, R. H. Crawford, H. L. Marcus. and K. P. McAlea.l997 Solid freeformfabrication. A new direction in manufacturing: With research and applications in thermal laser processing. Norwell,MA: KJuwer Academic Publishers.

Berners-Lee, T.1989. Information management:A proposal. CERN Internal Proposal.

Bouldin, D., ed. 1994. Report of the 1993 workshop on rapid prototyping of microelectronic systems for universities. National Science Foundation Workshop.

Cheung, T. S., and A. A Ogale. 1998. Processing of multilayer fiber reinforced composites by 3D photolithography. In Proceedings of the 1998 NSF Grantees Design and Manufacturing Conference, Monterrey,Mexico, 557-559. Arlington, VA: National Science Foundation.

168 Solid Freeform Fabrication (SFF) and Rapid Prototyping Chap. 4

Cohen, E., S. Drake,L. Gursoz, and R. Riesenfeld. 1995. Modeling issues in solid freefonn fabrication.NSF Solid FreeformFabricationWorkshop II, Design Methodologies for Solid Freeform Fabrication, June 5--6, Pittsburgh, PA.

eutkosky, M. R., and 1. M.Tenenbaum. 1990. A methodology and computational framework for concurrent product and process design. Mechanism and Machine Theory 25 (3):365-381.

DeGarmo, E. P., 1. T. Black, and R.A. Kohser. 1997. Materialsand processes in manufacturing, 8th ed. New York: Prentice-Hall.

DeMeter, E.c.,Q. Sayeed, R. E. DeVor, and S. G. Kapoor. 1995. An Internet model for tech-nologyintegration and access part 2: Application to process modeling and fixture design.

MTAMRI Report 1995. University of Illinois.

Dutta,D. 1995. Layered manufacturing in Project Maxwell.NSF Solid Freeform Fabrication Workshop II, DesignMethodologies for Solid Freefonn Fabrication, June 5-6, Pittsburgh, PA.

Finirt, T., D. McKay, R Fritzson,and R McEntire. 1994. KQML:An infonnation and knowl-edge exchange protocol. In Knowledge buildingand knowledge sharing,editedby Kazuhiro Puchi and Toshio Yokoi. Tokyo, Japan: Ohmsha and lOS Press.

Frost,R, and M. Cutkosky. 19%. An agent-based approach to making rapid prototyping processes manifestto designers. ASME Symposium on VirtualDesign and Manufacturing.

Greenfeld, I., F. B. Hansen,and P. K. Wright. 1989. Self-sustaining, open-system machine tools.

In Proceedings of the i7th North American Manufacturing Research institution 17:281-292.

Groover, M. P. 1999. Fundamentals of modern manufacturing. Upper Saddle River, NJ:

Prentice-Hall.

Heller, T. B. 1991. Rapid modeling-What is the goal? In The Second international Con-ference on Rapid Proto typing, 242-244. Dayton, OH: RapidPrototype Development Labora-tory (RPDL), 242-244.

Hillaire, R, L. Marchetti, and P. K. Wright.1998. Geometry for precision manufacturing on an open architecture machine tool (MOSAIC-PC). In Proceedings Of the ASME Interna-tional Mechanical Engineering Congressand Exposition, 8: 605-610. Anaheim, CA: MED.

Jacobs, P. F. 1992. Rapid prototyping and manufacturing: Fundamentals of stereolithography.

Dearborn, MI: Society of Manufacturing Engineers.

Jacobs, P. F. 1996. Stereolithography and other rapid prototyping and manufacturing technolo-gies. Dearborn, MI: Society of Manufacturing Engineers.

Java, 1995, is a trademark of SUD Microsystems, Incorporated. Documentation can be found athttp://www.javuoft.com. (Also refer to 1. Gosling and H. McGilton. "The Java Language Environment: A White Paper,"Technical Report, Sun Microsystems, 1995.) Kai, C. C. 1994. Three-dimensional rapid prototyping technologies and key development areas. Computing & Control Engineering JournalS (4):20lJ...-206.

Kalpakjian, S. 1997. Manufacturing processes for engineering materials, 3d ed. MenloPark, CA: Addison Wesley Longman.

Kamath, R. R, and 1. K. Liker. 1994. A second look at Japanese product development. Har-vard Business Review. (Reprint Number 94605).

Kim,1. H., F. C. Wang, C. Sequin, and P. K. Wright.1999. Design for machining over Internet.

Paperpresented at the Design Engineering Technical Conference (DETC) on Computer Integrated Engineering, Las Vegas, NV. PaperNumber DETC'99/CIE-9082.

Kim, 1. H. 2000. WebCAD 2000: Distributed CAD tool for machining. Master of Science Thesis, Department of Computer Science, University of CalUornia, Berkeley.

4.8 References 167

Kochan, D. 1993. Solid freeform manufacturing: Advanced rapid prototyping. New York and Amsterdam: Elsevier.

Kruth, 1. P. 1991. Manufacturing by rapid prototyping techniques. Annals of the CIRP 40 (2):603--614.

Kumar, V., P. Kulkarni, and D. Dutta. 199f\. Adaptive slicing of heterogeneous solid models for layeredmanufacturing. University of MichiganTechnical Report, UM-MEAM-98-02.

Manufacturing Studies Board (National Research Council).1990. Rapid prototyping facilities in the U.S. manufacturing research community. Edited by T. C. Mahoney.

McMains, S. 1996. Rapid prototyping of solid three dimensional parts. Master of Science Thesis, Computer Science, University of California, Berkeley.

McMains, S., C.S. Sequin. and 1 Smith. 1998. SIF: A solid interchange format for rapid proto-typing. Paper presented at the 31st CIRP International Seminar on Manufacturing Systems.

University of California. Berkeley.

Mead, C, and r .. Conway.19RO. Thc F'altech intermediate form for J .SI layout description. In Introduction ro VLSI Systems, 115-127. Addison Wesley.

Mitsuishi, M., S. wansawa, Y. Hatamura, T. Nagao, and B. Kramer. 1992. A user friendly man.

ufacturing systemfor hyper-environments, In Proceedings of the 1992 IEEE International Conference on Robotics and Awomation. 25-31.

MOSIS, 2000. University of Southern California's Information Sciences Institute-The MUSIS VLSI Fabrication Service.http://www.isi.eduhnosisl.

NSF. 1994. Solid Preeform Fabrication Workshop J. New Paradigms for Manufacturing, Arlington VA.

NSF. 1995. Solid Freeform Fabrication Workshop II. Design Methodologies for Solid Freeform Fabrication, June 5--6, Pittsburgh, PA.

Richards, B., and R. Brodersen. 1995. InfoPad: The design of a portable multimedia terminal.

In Proceedings of the Mobile Multimedia Conference, 2. Bristol, England.

Sachs, E., M. Cima, J. Bredt, A. Curodeau, T. Fan, and D. Brancazio. 1992. CAD-casting: Direct fabrication of ceramicshells and cores by three dimensional printing.Manufacturing Review 5 (2):117-126.

Sachs, E., N. Patrikalakis, D. Boning, M. Cima, T. Jackson, and R. Resnick. 2000. The distributed design and fabrication of metal parts and tooling by three dimensional printing.In Proceed-ings of the 2000 NSF Grantees Design and Manufacturing Conference. Arlington, VA: Univer-sity of British Columbia and National Science Foundation.

Sarma,S., and P. K. Wright. 1996.Algorithms for the minimization of setups and tool changes in "simply fixturable" components in milling.JourfUll of Manufacturing Systems 15, (2):95-112.

(Also see S. Sarma,S. Gandhi, and P. K. Wright.1995. Reference free part encapsulation: A universal fixturing technology for rapid prototyping by machining. In Concurrent Product and Process Engineering. 1:339-351.Anaheim, CA; MED.).

Schey, J. A. 1999. Introduction to manufacturing processes. New York: McGraw-Hill.

Schofield, S., F. C. Wang, and P. K. Wright. 1998. Openarchitecture controllers for machine tools part 1: Design principles,part 2: A real-time, Quintic spline interpolator.Jownef of Man·

ufacturing Science and Engineering 120:417--432.

Smailagic,A., and D. P. Siewiorek. 1993.A case-study in embedded system design:The VuMan 2 Wearable Computer. IEEE Design and Test of Computers,56-fJ7.

Smith, C, and P. K. Wright. 1996. CyberCut: A World Wide Web baseddesign to fabrication tool. Journal of Manufacturing Systems 15 (6):432-442.

'68 Solid Freeform Fabrication (SFF) and Rapid Prototyping Chap. 4

Smith, D. 2000. 3DP prototyping at Motorola. Personal communication.

Sundararajan, V., and P. K. Wright. 2000. Identification of multiple feature representation by volume decomposition for 2.5 0 components. Transactions af the ASME. Jou17UIl of Manu-facturing Science and Engineering 122 (1): 280-290.

University of California, Los Angeles (UCLA). 1994, University Extension, Department of Engineering, Information Systems, and Technical Management, Short Course Program,Rapid Prototyping:Technologies and Applications.

Weiss, L. E., E. L. Gursoz, F. B. Prinz, P, S. Fussell, S. Mahalingam, and E. P. Patrick. 1990. A rapid tool manufacturing system based on stereolithography and thermalspraying. Manufac-turing Review 3 (1):40-48.

Weiss, L. E., and F. B. Prinz. 1995. Shape deposition processing. NSF Workshop II. Design Methodologies for Solid Freefonn Fabrication, June 5-6, Pittsburgh, PA.

Weiss, L. E., R. Merz, F. B. Prinz, G. Neplotnik, P. Padmanabhan, L. Schultz, and K.

Ramaswarni, 1997. Shape deposition manufacturing of heterogeneous structures. SME Journal of Manufacturing Systems 16:239-248.

Weiss, L. E., and F. B. Prinz. 1998. Novel applications and implementations of shape deposition manufacturing. Paperpresented at the Naval Research Conference.

Woo, T. 1992. Rapid prototyping in CAD. Computer AidedDesign 24:403--404.

Woo, T. 1993. Rapid automated prototyping:An introduction. Industrial Press.

Wright, P. K., D.A. Boume,J.A. E. Isasi, 0. C. Schatz, and J 0. Colyer. 1982. A flexible manu-facturing cell for swaging. Mechanical Engineering 104 (10):76-83.

4.9 BIBLIOGRAPHY

Benett, 0., ed. 1996. Developments in rapid prototyping and tooling. Mechanical Design Pub-lication Ltd. London: Bury-Saint Edmunds.

Koenig, D. T. 1987. Manufacturing engineering:Principles for optimization. Washington, New York, and London: Hemisphere Publishing Corporation.

In document 21st Century Manufacturing - P. Wright (2002) WW (Page 169-175)