Data processing: generic control systems or specific application – Specific application – apparatus or process – Product assembly or manufacturing
Reexamination Certificate
1998-09-14
2001-06-12
Cuchlinski, Jr., William A. (Department: 3661)
Data processing: generic control systems or specific application
Specific application, apparatus or process
Product assembly or manufacturing
C700S196000, C700S197000, C264S040100, C264S045300, C264S045500, C264S045900, C428S326000, C072S271000, C073S054280, C073S054350
Reexamination Certificate
active
06246918
ABSTRACT:
BACKGROUND OF THE INVENTION
This invention relates generally to a profile extrusion die and more particularly to a system and method for providing die swell or draw down (hereinafter die swell/draw down) information for designing a profile extrusion die.
Typically, a die designer uses experienced-based rules to derive a profile extrusion die design. After deriving the profile extrusion die design, the designer implements the design in an extrusion process. The designer then evaluates the design to determine if the die land length, die opening thickness, and die opening width produce the desired profile dimensions. If the dimensions do not have the desired profile dimensions, then the die is re-cut and implemented in another extrusion process. Usually there is many iterations of cutting and then changing the die before deriving a die design that yields the desired profile dimensions. This design methodology requires a lot of work and time and a tremendous amount of experience-based data. In addition, the designer must modify the die every time the dimensions change or when the extrusion process uses a new plastic resin. These situations also involve more time, work and money. As a result, the designer is reluctant to work with new plastic resins, which hinders the introduction of these resins into the profile extrusion market.
U.S. Pat. No. 5,608,637 discloses a semi-empirical die design methodology that enables a designer to readily design a die that shapes products having varying dimensions and products made from different types of resins. In U.S. Pat. No. 5,608,637, a designer uses a viscoelastic computer software package to provide a representation of a product made from a resin material and shaped by a die. The representation illustrates a relationship between die swell of the resin, shear rate of the resin through the die, and the ratio of die land length of the die to die opening thickness of the die. The designer uses the representation to determine instances where the ratio of die land length to die opening thickness minimizes die swell of the resin. The designer then studies the flow rate effect on die swell for experimental dies in an extrusion process and obtains experimental data therefrom. U.S. Pat. No. 5,608,637 arranges the representation and the experimental data into die design charts and the designer uses the charts to determine profile dimensions of a desired profile extrusion die.
A drawback with U.S. Pat. No. 5,608,637 is that the methodology provided in this patent uses an extruder to develop the die design charts for a particular resin. Using an extruder to develop die design charts is expensive and time consuming. Typically, the extruder needs about two to three gaylords of resin to generate a sufficient number of data points. In addition, the extruder has a tendency to introduce errors at different locations. For example, shear rate measurements and melt temperature control at the extruder die are questionable. The errors produced by the extruder result in the die design charts having inaccurate die swell/draw down values. Therefore, there is a need for a methodology that can provide die swell/draw down information for profile extrusion die design that is simpler, faster, and more accurate than the information provided by an extruder.
BRIEF SUMMARY OF THE INVENTION
In a first embodiment of this invention, there is disclosed a system for generating die swell/draw down information of a polymer resin material. The system comprises a rheometer comprising a barrel for receiving the polymer resin material and a piston for packing the resin material in the barrel as a function of a shear rate setting. A slit die, coupled to the rheometer, generates an extrudate as the piston packs the polymer resin material. A puller mechanism coupled to the slit die, pulls the extrudate at a plurality of draw rates. A processor determines the die swell/draw down information from thickness measurements obtained from samples of the extrudate at each of the plurality of draw rates and the shear rate.
In a second embodiment of this invention, there is disclosed a method for obtaining die swell/draw down information of a polymer resin material with a rheometer having a slit die and an puller mechanism coupled thereto. The method comprises specifying a shear rate setting for operating the rheometer. After specifying the shear rate setting, the next act is filling the polymer resin material into a barrel of the rheometer. After filling the polymer resin material into the barrel, the next act is packing the polymer resin material in the barrel with a piston moving as a function of the shear rate setting. The next act is using the slit die to generate an extrudate as the piston packs the polymer resin material in the barrel. After generating an extrudate, the next act is pulling the extrudate at a plurality of draw rates with the puller mechanism. The next act is collecting a sample of the extrudate at each of the plurality of draw down rates. After collecting a sample of the extrudate, the next act is measuring the thickness for each sample of the extrudate obtained at each of the plurality of draw down rates. The next act is determining the die swell/draw down of each sample of the extrudate as function of the thickness measurements, the plurality of draw rates, and shear rate.
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Chan et al., Integration of Computing Techniques for Plastics Extrusion Die Design, IEEE., Apr. 1990, pp. 37-42.*
“A New Design Procedure for Profile Extrusion Dies” by P. Hurez, et al, Polymer Engineering and Science, Mid-March 1996, vol. 36, No. 5, pp. 626-635.
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Dunton Thomas Paul
Saraiya Gopal Rameshchandra
Teutsch Erich Otto
Wang Hsin-Pang
Breedlove Jill M.
Cuchlinski Jr. William A.
General Electric Company
Goldman David C.
Marc McDieunel
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