Method of defining complex geometries to transpose flow boxes into pattern equipment for the production of automotive components

#The present invention relates to the production of pattern equipment used in manufacturing, and in particular, to a method for defining complex geometries which are transposed into tooling used to produce automotive components.

#Various automotive components, for example cylinder heads, include complex geometric shapes. The production of tooling which is used to cast complex geometric shapes has required a combination of engineering design, pattern making, and casting experimentation, to produce molds which produce acceptable components.

#Typically, past methods for producing molds for complex geometries have begun in the laboratory, where clay models of the components are tested and refined. For example, a clay model of cylinder head design is engineered, and then tested and refined in the laboratory by adding and removing material to provide desired air flow characteristics. Thus, the air flow channels through such parts are not simple cylinders, but complex shapes. A "master flow box" is then made from the clay model by filling its flow channels with a compound, such as a liquid plastic or sand and adhesive mix, which hardens in the shape of the flow channels. Thereafter, the clay is removed, leaving a male mold which is placed in a perimeter mold to replicate the flow channels. A "master flow box" is then made of a permanent material, such as a plastic, poured into the perimeter mold. The master flow box is split open and the male molds removed. The master flow box is reassembled and the air flow therethrough is checked, and minor design changes made, as needed.

#FIG. 1 is a perspective view of a representative tooling master showing lines traced on the surfaces thereof in accordance with the prior art.

#FIG. 2 is a perspective view of a representative inverted B-spline drawing prepared from a design data base for area 2--2 in FIG. 1 area 2--2 in accordance with the prior art, demonstrating the effect of erroneous data entered at the boundaries between geometric and planar surfaces.

#FIG. 3 is a perspective view of a tooling master including a layer of added material and a pattern of lines traced on the surfaces thereof in accordance with the method of the present invention.

#Referring to FIGS. 1 and 3, tooling 10 having planar surface 12 and geometric surface 14 is shown with representative trace lines 16, traced with a stylus 18, indicated thereon. Position data for points along trace lines 16 is inputted with a stylus 18 into processor means 20 to produce a design data base. FIG. 1 reflects prior art methods for obtaining position data.

#FIG. 2 is an inverted "B-spline" computer-aided design (CAD) drawing 44A of a representative portion of the tooling 10 of FIG. 1 indicated at line 2--2 therein, showing the planar and geometric surfaces 12, 14 defined by a design data base obtained by prior art tracing methods. As may be seen in FIG. 2, erroneous position data was entered into the processor means 20 by the stylus 18 as it moved over the sharp boundaries 22. It has been found that rapid transitions at boundaries 22 between intersecting surfaces cause styluses 18 to enter erroneous position data. In turn, the erroneous position data produce irregularities in the CAD drawings 44A, as shown in FIG. 2.

#Reference is now made to FIG. 3 which incorporates certain additional elements and features in accordance with the present invention. The method of the present invention provides for the step of first, obtaining tooling 10 for a component having certain features. Tooling 10 has at least one geometric surface 14 and at least one substantially planar surface 12 which intersect along a boundary 22 where there is a rapid transition between the surfaces. The method next requires adding a layer 24 of material of known thickness to the planar surface 12. Adding a layer 24 of material to the planar surface 12 of the tooling 10 causes the stylus 18 to enter accurate position data defining the geometric surface 14 near the boundary 22. The step of tracing the geometric surface 14 and the added layer 24 is then performed simultaneously with the step of inputting position data related to the surface 14 and layer 24 to the processor means 20. The steps of tracing and inputting are repeated at spaced intervals to obtain accurate position data defining the geometric surface 14. The stylus 18 produces erroneous position data for layer 24, specifically its cross-sectional surface area 26 and planar surface 28 near its boundary 30. However, the method next comprises the steps of deleting with the processor means 20 the position data related to the added layer 24, which has a known thickness, and defining the planar surface 12 with the processor means 20 using a portion of the position data. The present method thereby provides accurate position data relating to the geometric surface 14 and planar surface 12 at the boundary 22.