3D Solid Model CAD Files Add Precision to Gasket DesignCompared to two-dimensional models, solid models are better for specific OEM gasket design applications
Today, most manufacturers of automobiles, farm and construction equipment, recreational vehicles and other gasket-using equipment apply three-dimensional (3D) computer-aided design (CAD) software to create product models. The technology allows designers to produce engine and ultimately whole vehicle designs solely on computers. By modeling in three dimensions, the designers can do electronically all the spatial fitting of components with respect to clearances and tolerances, avoiding a lot of rework on actual hardware.
Using 3D Solid Model files to design gaskets
Original equipment manufacturers' solid-modeling capabilities enable ISI engineers to design the OEMs' gaskets with more precision and confidence.
Before solid modeling, OEM designs were either two-dimensional (2D) prints or 2D CAD renderings. With 2D representations, ISI engineers could tell what shape to make gaskets, but in the absence of more information about joints, they could not go further in using CAD to completely design gaskets. However, as OEMs began putting engine and transmission designs into 3D CAD, asking ISI to design gaskets for those assemblies and providing solid models for ISI to use, ISI’s gasket designing capabilities became more powerful, too.
“With solid models, we have enough information about joints to run performance simulations with Finite Element Analysis or our internal (GMX) software package,” says Brian Lehr, the manager of ISI’s Sealing Technology Team. “Now, based on known characteristics such as bolt loading, flange stiffness, and fluid pressure, we can use CAD to design in more gasket parameters than just shape. For example, we can with confidence specify thickness, type of material, wall widths, surface coatings, etc., that will the gasket to function properly in the joint.”
Working with a variety of software packages
What ISI now gets from OEMs are 3D solid models in a variety of software packages. In house, the company has EDS Unigraphics NX, and PTC Pro-Engineer Wildfire packages. Needing a design for an oil pan gasket, an OEM using Unigraphics can simply send ISI files that include the designs of an engine block and oil pan. ISI designers can then build the required gasket geometry. For OEMs using other solid-modeling software (e.g., Solid-Edge or CATIA), ISI can perform the same thorough modeling it does with Unigraphics files if the files are converted first into a universal exchange format.
“We believe that the best of these exchange formats is one called ‘STEP file format,’” says Lehr, “and if a customer does not use Unigraphics or Pro-E 3D modeling software, we will work with them to get their solid-model files into a format we can use.” He continues, “There are two messages for fabricators in all of this. First, when we design a Select-a-Seal® gasket – or any other kind of gasket for that matter – we want to use the best information available to achieve the best possible outcome, so we would like our fabricator partners to ask their OEM customers up-front for 3D models of their application hardware. Second, if fabricators are working on their own design and do not have solid-modeling capabilities, they can still take solid model files from their customers. ISI application engineers will provide a free service to their fabricator partners who recommend ISI gasket materials – they will extract 2D CAD files of the flange surfaces from these OEM solid models and return them in a universal format (e.g. DXF).”