The designers and operators of rubber extrusion molds face a hard job of obtaining a material that naturally flows quickly through thick sections and away from thin edges, to obtain a low and uniform retracement of the formation that allows the overall local velocity distribution. The goal is to achieve a unified relaxation ( So stable) Products at the end of the extrusion line. This method minimizes the unnecessary length changes and curvature of the extruded product during storage. The rubber mold design can be divided into two steps: * control the flow inside the mold and give the required speed distribution at the Mold outlet; And * determine the size profile of the mold outlet to provide the desired product by properly considering the expansion, drop and distortion downstream of the mold surface. This paper discusses two ways to control the flow inside the mold, including: * mold surface relief as a way to achieve balanced flow, especially in the thin part of the mold; And * provide insight and guidance in mold interior design using finite element simulation. The simulation is also used to \"reverse calculate\" the mold opening shape from the specified profile to explain the distortion in the so-called reverse calculation. These topics include the mold design section of the short course on rubber extrusion technology held annually (ref. 1). The traditional practice of surface elimination of molds is to be very effective in establishing a uniform speed at the outlet of the mold, however, there is a bad trend, it will cause the rubber to flow into the adjacent thick part from the thin part most needed by the mold. In the schematic diagram behind- Rest assured mold in Figure 1 (top) , Rubber flows perpendicular to the dotted line, representing a constant pressure from high to low pressure. The flow of particles represented by points is far away from the thin outer edge of the mold, towards a thicker central part, as shown by the solid arrow. With the face- Rest assured mold in Figure 1 (center) , The flow of rubber from high pressure to low pressure is biased towards the thin outer edge, as shown by the point and arrow. As shown in Figure 1, the extrusion sample of low elastic rubber has a tear edge of the rubber squeezed through the back Rest assured mold and smooth edge of the surface-relieved die. [ Figure 1 slightly] Use of the face- Relief mold was checked in tire side wall application with backrest Discharge and discharge (straightcut) Die as a comparison (refs. 2 and 3). Schematic diagram of relief mold after tilting ( The back of the mold cut at a fixed angle); Linear face relief ( Local mold opening ground proportional to the mold opening gap) And the secondary surface relief ( Local mold ground proportional to the square of the opening gap) As shown in figure 2. The expression related to the local mold L and the local mold opening thickness H is determined (1)L/[L. sub. max]= [(H/[H. sub. max]). sup. p] Back relief was imposed on the remaining 10mm of the land. After three iterations, the back of the mold ( As shown on the left side of figure 8) The speed profile shown on the right side of this figure is given. With this back relief, the outlet speed of the mold surface is much more uniform. However, the calculated shape of the downstream extrusion profile shows a slight distortion with the specified shape. To correct this distortion, a reverse algorithm (ref. 8) Used to change the opening of the mold surface, as shown in Figure 9. The reverse algorithm takes the specified product shape and works backwards to determine the mold opening that will give the specified shape. As shown in Figure 10, the released mold profile and the die head. [FIGURES 7-10 OMITTED] The insight gained from simulation representative molds, combined with experience and intuition, can be widely used in molds of products with similar shapes. Simulation is also a quick way to test the feasibility of a new design concept without interfering with production mold work or bundling manufacturing extrusion lines. The computer simulation does not eliminate the mold test, but the starting point of the first test is expected to be closer to the final design, especially if the simulation correctly identifies the design that handles subtle problems such as the deformation of the mold downstream. References (1. )J. F. Stevenson and J. S. University of Wisconsin rubber Extrusion Technology Research Institute2003). (2. )C. -C. Lee and J. F. Stevenson\'s face \"Relief strategy for profile mold design,\" intern. Poly. Proc. 7, 186 (1992). (3. )C. -C. Lee and J. F. Stevens, \"evaluating mold design strategies through simulation and experiments\", SAE paper 880027, SAE International Conference and Expo, Detroit (1988). (4. )Y. Rubin, L. Fondin, T. Marchal, T. Burton and A. Goossens, \"numerical balance of extrusion dies: validation study of wind and rain seal profiles for TPV cars\", International Rubber Conference, Prague (2002). (5. )C. Reese, \"using mold modeling to improve the manufacturing process of extruded silicone rubber\", 52 Antec proceedings, p. 94 (1994). (6. )D. A. Andrejewski, \"Polyflow: paper on the design of reverse mold/core shaft for high consistency silicone rubber\", Association of Plastic Engineers308 (1997). (7. )E. Cavka and T. \"Pipe seal- \"4 th International Esaform conference on material forming, Liege, Belgium (2001). (8. )V. Legat and J. -M. Marchal, intern \"mold design: implicit formula for counter-problems. J. Numer. Method fluid, 16, 29 (1993).
