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Optimal thermal design of compression molds for chopped-fiber compositesPresented at the second world Congress of Chemical Engineering, Montreal (October 1981). (1981)

Barone, M. R. ; Caulk, D. A.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 21 (1981), S. 1139-1148

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ISSN: 0032-3888

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Because heat is convected by the motion of material in the cavity of a compression mold, the time-averaged heating load on the cavity surface is nonuniform. In rapid production of large, thin parts, this can lead to large variations in cavity surface temperature when the mold is heated by the usual uniform distribution of heating lines. In this paper, a new method is developed for optimizing the mold heating design so that this nonuniform heating requirement can be satisfied with a minimum variation in cavity surface temperature. Oil heating is considered specifically, but the method can also be used for stream or electric heat. The optimal position and power supply for each heating line in the mold is determined by combining mathematical programming techniques with an analysis of the steady temperature field in the mold. The nonuniform heating load on the cavity surface is represented by a time-averaged steady heat transfer coefficient calculated from the transient temperature distribution in a polyester sheet molding compound as it fills the mold cavity. The design method is applied to an example mold for a large flat panel. At a one-minute cycle, the optimal heating design dramatically reduces nonuniformity in cavity surface temperature compared with a conventional distribution of heating lines. The optimal design is remarkably simple, uses only conventional equipment, and involves only half the customary number of heating lines. Nevertheless, it still has sufficient flexibility to adjust for changes in cycle time without sacrificing uniformity in cavity surface temperature.

Additional Material: 8 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pen.760211705

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2

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Optimal thermal design of injection molds for filled thermosets (1985)

Barone, M. R. ; Caulk, D. A.

Stamford, Conn. [u.a.] : Wiley-Blackwell

Polymer Engineering and Science 25 (1985), S. 608-617

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ISSN: 0032-3888

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics

Notes: Since the cure rate of injection molded thermosets is usually very sensitive to cavity surface temperature, spatial variations in these temperatures can lengthen the necessary cure time for the entire part and cause distortion and residual stress in the molded article. This problem is addressed in the present paper by combining an optimization algorithm with a quasi-steady heat conduction analysis in the mold to determine the heating line positions and operating temperatures that minimize the spatial variation in cavity surface temperature. The method is applied to an example mold for a flat panel of uniform thickness, using two different gate locations. At a one-minute cycle, the optimal designs for each gate location dramatically reduce the variation in cavity surface temperature compared with corresponding results using a conventional heating system. These results are made more significant by the fact that the optimal designs use considerably fewer heating lines. In spite of their simplicity, the optimal designs still have enough flexibility to adjust to a changing cycle without sacrificing uniformity in cavity surface temperature.

Additional Material: 16 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pen.760251006

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3

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Optimal arrangement of holes in a two-dimensional heat conductor by a special boundary integral method (1982)

Barone, M. R. ; Caulk, D. A.

Chichester [u.a.] : Wiley-Blackwell

International Journal for Numerical Methods in Engineering 18 (1982), S. 675-685

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ISSN: 0029-5981

Keywords: Engineering ; Engineering General

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mathematics , Technology

Notes: The position, size and surface temperature of circular holes inside a two-dimensional heat conductor are optimized to produce a minimum variation in surface temperature over a portion of the outer boundary. This problem, whic arises in thermal desing of moulds and dies, resembles those encountered in structural shape optimization because the internal geometry of the heat conductor depends on the design variables. In this paper, some of the traditional difficulties associated with shape optimization are overcome by analysing steady heat conduction with a special boundary integral method developed for two-dimensional regions with circular hole. This approach eliminates the need to regenerate a finite element mesh over the interior of the region each time the geometry is changed during the design process. It also increases the efficiency of the analysis by reducing the number of unknowns in the numerical discretization of the region. Since the objective function depends only on the boundary temperatures, there is no need to determine temperatures in the interior.The analysis method is applied to two problems arising in optimal thermal design of compression moulds. These examples show that the number of holes choson for the design strongly affects their resulting optimal arrangement as well as the ultimate uniformity of the cavity surface temperature.

Additional Material: 5 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/nme.1620180505

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4

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Kinematics of flow in sheet molding compounds (1985)

Barone, M. R. ; Caulk, D. A.

Brookfield, Conn. : Wiley-Blackwell

Polymer Composites 6 (1985), S. 105-109

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ISSN: 0272-8397

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: Experiments utilizing charges constructed of black and white sheet molding compound (SMC) reveal the basic kinematic mechanisms controlling the flow of the fiber-filled compound in compression molding. The experimental results show that SMC deforms in uniform extension within individual charge layers, with slip occurring at the mold surface and, for slower closing speeds, also between the layers of SMC. When the mold closes rapidly, the charge extends uniformly through its thickness, with all slip concentrated at the mold surface.

Additional Material: 12 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pc.750060208

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A boundary element analysis of flow in sheet molding compound (1988)

Barone, M. R. ; Osswald, T. A.

Brookfield, Conn. : Wiley-Blackwell

Polymer Composites 9 (1988), S. 158-164

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ISSN: 0272-8397

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: A new boundary element method has been developed for analyzing the flow of sheet molding compound (SMC) during compression molding. The boundary element equations can be used to determine the velocities on the perimeter of the charge. Successive flow front configurations are then generated by a simple explicit updating procedure. This approach was used to predict the flow front progression for elliptical, rectangular, and L-shaped charges. Comparisons with experimental data for elliptical and rectangular charges were encouraging. The fact that it was possible to obtain reasonable agreement for charges with different shapes and thicknesses lends support to the underlying flow model. Furthermore, valuable insight regarding knit line formation was acquired by analyzing the L-shaped charge. Results from the boundary element analysis showed that the initial thickness of the charge has a pronounced effect on knit line development. Even though there is considerable industrial experience in making SMC parts, the important role of charge thickness on knit line formation appears to have been largely overlooked. Prior analyses gave no indication of this effect because they were based on lubrication models that were independent of charge thickness.

Additional Material: 5 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pc.750090210

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6

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Experimental verification of an optimal thermal design in a compression mold (1986)

Barone, M. R. ; Caulk, D. A. ; Panter, M. R.

Brookfield, Conn. : Wiley-Blackwell

Polymer Composites 7 (1986), S. 141-151

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ISSN: 0272-8397

Keywords: Chemistry ; Chemical Engineering

Source: Wiley InterScience Backfile Collection 1832-2000

Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics

Notes: A production sheet molding compound (SMC) mold for an automotive hood outer panel was instrumented with 64 thermocouples to measure cavity surface temperatures along two cross-sections in each mold half and regulate the supply of steam to each heating line. The positions and temperatures of each heating line in the mold were optimized using an in-house computer program to produce a minimum spatial variation in cavity surface temperature during steady cyclic molding. Provision was also made to heat the mold conventionally so that optimal and conventional heating could be directly compared in the same mold. While maintaining a 78 s overall molding cycle, the conventional heating system eventually produced a 10°C temperature variation on the cavity surface. This, in turn, led to serious resin undercure and severe difficulties in removing the part from the mold. When the optimal heating design was substituted in place of the conventional system, the surface temperature variation was reduced to less than 3°C and the problems experienced with conventional heating disappeared. For the most part, the measured temperatures in these experiments agreed with the results of the computer analysis to within 1°C.

Additional Material: 24 Ill.

Type of Medium: Electronic Resource

URL: http://dx.doi.org/10.1002/pc.750070303

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