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Incorporating manufacturability considerations during design of injection molded multi-material objects

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Abstract

The presence of an already molded component during the second and subsequent molding stages makes multi-material injection molding different from traditional injection molding process. Therefore, designing multi-material molded objects requires addressing many additional manufacturability considerations. In this paper, we first present an approach to systematically identifying potential manufacturability problems that are unique to the multi-material molding processes and design rules to avoid these problems. Then we present a comprehensive manufacturability analysis approach that incorporates both the traditional single material molding rules as well as the specific rules that have been identified for multi-material molding. Our analysis shows that sometimes the traditional rules need to be suppressed or modified. Lastly, for each of the new manufacturability problem, this paper describes algorithms for automatically detecting potential occurrences and generating redesign suggestions. These algorithms have been implemented in a computer-aided manufacturability analysis system. The approach presented in this paper is applicable to multi-shot and over molding processes. We expect that the manufacturability analysis techniques presented in this paper will help in decreasing the product development time for the injection molded multi-material objects.

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References

  • Ahn HK, Berg M, Bose P, S.W Cheng, Halperin D, Matoušek J, Schwarzkopf O (2002) Separating an object from its cast. Comput Aided Des 34(8):547–559

    Article  Google Scholar 

  • Bakerjian R (1992) Design for manufacturability. Tool and manufacturing engineers handbook, vol. 6. Society of Manufacturing Engineers

  • Banerjee AG, Gupta SK (2006) A step towards automated design of side actions for injection molding of complex parts. Geometric modeling and processing, 2006. Lecture notes in computer science, vol. 4077, pp 500–513

  • Bryce DM (1996) Plastic injection molding. Society of Manufacturing Engineers

  • Chen Y, Rosen DW (2002) A region based method to automated design of multi-piece molds with application to rapid tooling. J Comput Inf Sci Eng 2(2):86–97

    Article  Google Scholar 

  • Chen Y, Rosen DW (2003) A reverse glue approach to automated construction of multi-piece molds. J Comp Inf Sci Eng 3(3):219–230

    Article  Google Scholar 

  • Chen LL, Chou SY, Woo TC (1993) Parting directions for mould and die design. Comput Aided Des 25(12):762–768

    Article  MATH  Google Scholar 

  • Dhaliwal S, Gupta SK, Huang J, Priyadarshi A (2003) Algorithms for computing global accessibility cones. J Comput Inf Sci Eng 3(3):200–209

    Article  Google Scholar 

  • Elber G, Chen X, Cohen E (2005) Mold accessibility via gauss map analysis. J Comput Inf Sci Eng 5(2):79–85

    Article  Google Scholar 

  • Fu MW, Fuh JYH, Nee AYC (1999) Undercut feature recognition in an injection mould design system. Comput Aided Des 31(12):777–790

    Article  MATH  Google Scholar 

  • General Electric (1960) Manufacturing producability handbook. Manufacturing services. Schenectady, New York

  • Gu Z, Zhou Z, Gao S, Shi J (1999) Determination of mold parting direction based on automatic molding feature recognition. ASME computers and information in engineering conference. Las Vegas, NV, DETC99/CIE-9199

  • Gupta SK (1997) Using manufacturing planning to generate manufacturability feedback. ASME J Mech Des 119:73–79

    Google Scholar 

  • Gupta SK, Nau DS (1995) Systematic approach to analyzing the manufacturability of machined parts. Comput Aided Des 27(5):323–342

    Article  MATH  Google Scholar 

  • Gupta SK, Das D, Regli WC, Nau DS (1997) Automated manufacturability analysis: a survey. Res Eng Des 9(3):168–190

    Article  Google Scholar 

  • Gupta SK, Nau DS, Regli WC (1998) IMACS: a case study in real-world planning. IEEE Int Syst 13(3):49–60

    Article  Google Scholar 

  • Hayes CC (1996) P3: a process planner for manufacturability analysis. IEEE Trans Rob Autom 12(2):220–234

    Article  MathSciNet  Google Scholar 

  • Hayes CC, Sun HC (1994) Plan-based generation of design suggestions. In: Proceedings of the ASME winter annual meeting, Chicago, IL

  • Hayes CC, Desa S, Wright PK (1989) Using process planning knowledge to make design suggestions concurrently. In: Proceedings of the ASME winter annual meeting, Chicago, IL

  • K C Hui (1997) Geometric aspects of the mouldability of parts. Comput Aided Des 29(3):197–208

    Article  Google Scholar 

  • Ishii K, Miller RA (1992) Design representation for manufacturability evaluation in CAD. In: Proceedings of the ASME computers in engineering conference, San Francisco, CA

  • Kharderkar R, Burton G, McMains S (2005) Finding feasible mold parting directions using graphics hardware. In: Proceedings of the 2005 ACM symposium on solid and physical modeling. Cambridge, MA, pp 233–243

  • Li X (2003) Geometric algorithms for automated design of multi-stage molds for manufacturing multi-material objects. Ph.D. thesis, Mechanical Engineering Department, University of Maryland, College Park, USA

  • Li X, Gupta SK (2004) Geometric algorithms for automated design of rotary-platen multi-shot molds. Comput Aided Des 36(12):1171–1187

    Article  Google Scholar 

  • Lu HY, Lee WB (2000) Detection of interference elements and release directions in die-cast and injection-moulded components. J Eng Manuf 214(B6):431–441

    Article  Google Scholar 

  • Malloy RA (1994) Plastic part design for injection molding: and introduction. Hanser Gardner Publications, Inc., Cincinnati, Ohio

  • McMains S, Chen X (2004) Determining moldability and parting directions for polygons with curved edges. In: ASME international mechanical engineering congress and exposition, Anaheim, CA

  • Menges G, Michaeli W, Mohren P (2001) How to make injection molds. Hanser Gardner Publications, Cincinnati, Ohio

  • Poli C (2001) Design for manufacturing, a structured approach. Butterworth-Heinemann, Boston, Massachusetts

    Google Scholar 

  • Priyadarshi AK (2006) Algorithms for generating multi-stage molding plans for articulated assemblies. Ph.D. Thesis, Department of Mechanical Engineering, University of Maryland, College Park

  • Priyadarshi AK, Gupta SK (2004) Geometric algorithms for automated design of multi-piece permanent molds. Comput Aided Des 36(3):241–260

    Article  Google Scholar 

  • Rosen DW, Dixon JR, Poli C, Dong X (1992) Features and algorithms for tooling cost evaluation in injection molding and die casting. In: Proceedings of the ASME international computers in engineering conference. San Francisco, CA

  • Shankar SR, Jansson DG (1993) A generalized methodology for evaluating manufacturability. Concurrent engineering, contemporary issues and modern design tools. Chapman & Hall, London

  • Trucks HE (1987) Designing for economic production. Society of Manufacturing Engineers

  • van Vliet J, Luffervelt C, Kalas H (1999) State of art report on design for manufacturing. In: Proceeding of the ASME design for manufacturing conference. Las Vegas, NV

  • Wong T, Tan ST, Sze WS (1998) Parting line formation by slicing a 3D CAD model. Eng Comput 14(4):330–343

    Article  MATH  Google Scholar 

  • Yin Z, Ding H, Xiong Y (2001) Virtual prototyping of mold design: geometric mouldability analysis for near-net-shape manufactured parts by feature recognition and geometric reasoning. Comput Aided Des 33(2):137–154

    Article  Google Scholar 

Download references

Acknowledgments

This research has been supported in part by NSF grants DMI0093142 and DMI0457058, and Army Research Office through MAV MURI Program (Grant No. ARMY-W911NF0410176). Opinions expressed in this paper are those of authors and do not necessarily reflect opinion of the sponsors.

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Authors and Affiliations

  1. Mechanical Engineering Department and The Institute for Systems Research, University of Maryland, College Park, MD, 20742, USA

    Ashis Gopal Banerjee, Xuejun Li, Greg Fowler & Satyandra K. Gupta

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  1. Ashis Gopal Banerjee
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  2. Xuejun Li
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  3. Greg Fowler
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  4. Satyandra K. Gupta
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Corresponding author

Correspondence to Satyandra K. Gupta.

Appendix A

Appendix A

The basic idea of Multi-Shot Injection Molding (MSM) is that after each material shot, the mold is manipulated in some way, with the partially completed component still inside, in order to prepare for the subsequent shot. Unlike over-molding, which requires the partially completed component to be physically removed from the mold and placed into another mold, MSM uses mold manipulation instead of component manipulation to produce the desired component. Because of this difference, MSM can greatly reduce cycle time and produce components with much more complicated geometries and interfaces than over-molding.

There are several different techniques classified under the MSM process. Based on the methods for transferring one stage to next stage, these techniques can be grouped into to the following two main categories: (1) Rotary Platen, and (2) Index Plate. Each method will be discussed below.

The rotary platen type process contains two identical cavities mirrored across the centerline of the platen which coincides with the axis of rotation. The stationary platen contains two corresponding cavities with differing geometries. In essence, the rotary platen accomplishes the task of switching the partially completed component between molds for each stage. This eliminates the need for manually changing molds via hand or robot. For this type of MSM, the core for both material stages is exactly the same while the cavity is different. This has been shown schematically in Fig. 4. The process, as illustrated in a more details in Fig. 12, can be described as follows:

  1. 1.

    The first shot of material is injected out of both barrels into their respective cavities of the mold (not shown). This step produces one partially completed component (of material A), and discarded piece composed entirely of material B (in the form of cavity B). This is the initial step that occurs only when a production batch is first being started. After the transient period has passed and the machine is producing good components, steps 1–4 are cycled until the production run ends.

  2. 2.

    The cycle starts with the nth partially completed component (composed of material A) rotated into position for the second shot (material B) (Fig. 12a).

  3. 3.

    Simultaneously, a shot from barrel B and a shot from barrel A are injected into cavities 1 and 2, respectively (Fig. 12b). The shot from barrel A produces another separate, partially completed component, referred to as the “(n + 1)th component”. The shot from barrel B flows around, over, under, and/or onto the partially complete nth component, completing it.

  4. 4.

    The mold is opened by shifting the rotary platen to the left, and the finished nth component (Fig. 12c) is ejected. Steps 1–3 are repeated until the desired nth component of the batch is completed.

Although Fig. 12 only shows a two-material rotary platen machine, it is possible to accommodate more materials. Three-shot and four-shot injection molding machines are also available to manufacture three-material and four-material objects, respectively. Normally, depending on how many different materials there will be, the rotary platen can be rotated by 90°, 120°, or 180°. Special molding presses are required to provide the rotation needed for the core side.

The equipment setup for the index plate MSM process is similar to that of the rotary platen process, with the addition of an extra piece: the moving platen at the far left. Instead of a stationary platen and a rotating platen, index plate molding uses a central rotating plate sandwiched between two platens. The index plate performs the function of switching the partially completed components between molds. Unlike rotary platen MSM, in indexing plate MSM, both the core and cavities for each material stage are completely different. The only common mold piece between stages is the index plate. This has been illustrated in Fig. 13. The process is described as follows:

  1. (1)

    The first shot of material is injected out of barrel B into cavity 1 of the mold. This step produces a partially completed component, referred to as the “first component”. This is the initial step which occurs only when a production batch is first being started.

  2. (2)

    After the desired cooling period, the mold is opened by shifting the core side to the left (Fig. 14c). The index plate then rotates by 180° (Fig. 14e) and shifts to the left to close the mold (Fig. 14a).

  3. (3)

    Simultaneously, a shot from barrel B and a shot from barrel A are injected into cavities 1 and 2, respectively (Fig. 14b). The shot from barrel B produces another separate, partially completed component, referred to as the “second component”. The shot from barrel A flows around, over, under, and/or onto the partially complete first component, forming the final product.

  4. (4)

    The mold is opened again, and the finished first component is ejected (Fig. 14d). Steps 2–4 are repeated until the desired nth component of the batch is completed.

Index plate MSM is more complicated than rotary platen MSM and requires more mold pieces. This complexity further increases the mold cost and cycle time, but it also allows more complicated objects to be manufactured.

Multi-shot molding also requires careful control of the mold temperature at all times so that any moving or rotating components can function properly. For instance, if a brass slide or core lifter is incorporated into a steel mold, the temperatures have to be controlled so that the slide/lifter will not lock up or jam due to different coefficients of thermal expansion between the two metals.

Over-molding is a process, which uses multiple molds to produce a multi-material component. In essence, the first material is injected into a mold by means of standard single material molding techniques and then moved to a different mold where the second material can be injected to combine with the first material. This has been schematically shown in Fig. 15.

As with all MMM processes, it is desirable to use appropriate materials in over-molding to control the degree of adhesion between two materials. If articulation is desired then incompatible materials should be used. If bonding is desired, then compatible materials should be used. If bonding is required, the time in between changing molds also has to be controlled so that the first material is not given too much cooling time. The semi-finished component can be transported to the second mold either manually or robotically.

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Banerjee, A.G., Li, X., Fowler, G. et al. Incorporating manufacturability considerations during design of injection molded multi-material objects. Res Eng Design 17, 207–231 (2007). https://doi.org/10.1007/s00163-007-0027-9

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