While machining width is an important factor of the machining time of freeform surface finishing operations, in reality the kinematic capability of the machine tool is usually the bottleneck of achieving higher feed speed and optimal machining time. The purpose of this paper is to conveniently (and approximately) determine the optimal cut direction considering the speed kinematic capability of the machine tool, without having to compute the actual tool path. We propose a mathematical instrument, called Machine Kinematic Metric (MKM), to easily evaluate infinitesimal machining time on a freeform surface based on machine kinematic consideration. It's a tensor field similar to the metric tensor in differential geometry. MKM is integrated over the part surface to approximate the cut-direction-dependent total machining time, and used to determine the optimal cut direction that minimizes the machining time. To validate the accuracy of the prediction using MKM, we apply the method and compute the machining time at every direction with one degree apart and derive the optimal cut-direction. The computation is performed on two examples: a simple freeform surface and a complex die face model. We then use a commercial CNC emulator software from Huazhong CNC to precisely simulate the machining time in distributed cut directions (five degree apart) for the two models. We find that the optimal cut direction determined from CNC simulation is consistent with the prediction from the proposed method. It validates that the proposed method is a convenient and economical tool to approximately determine the optimal cut direction based on machine speed kinematic capability.
This paper presents current research results that concern the generation of foot bio-models for performing finite element analysis for footwear design evaluation and optimization. The foot bio-models produced so far include complete geometric models of the foot bones along with their corresponding material properties. For the generation of the bones geometry a dense set of CT scan data is utilized. Four different approaches for the reconstruction of the corresponding 3D surfaces are presented and discussed. A preliminary FE analysis for simulating foot/ground interaction has been carried out to assert the performance of the chosen material type and properties. Finally, a cloud infrastructure is introduced to provide to the end-users a web-based interface for performing simulation scenarios concerning foot/footwear and foot/ground interaction.
Transferring CAD data between heterogeneous CAD systems is a challenge because of differences in feature representation. A study by the National Institute for Standards and Technology (NIST) performed in 1999 made a conservative estimate that inadequate interoperability in the automotive industry costs them $1 billion per year. One critical part of eliminating the high costs due to poor interoperability is a neutral format between heterogeneous CAD systems. An effective neutral CAD format should include a current-state data store, be associative, include the union of CAD features across an arbitrary number of CAD systems, maintain design history, maintain referential integrity, and support synchronous collaboration. This research has focused on extending an existing synchronous collaborative CAD software tool to allow for a neutral, current-state data store. This has been accomplished by creating a Neutral Parametric Canonical Form (NPCF) which defines the neutral data structure for many basic CAD features to enable translation between heterogeneous CAD systems. The NPCF’s for a few key features have been implemented in a synchronous collaborative program and work between the NX and CATIA CAD systems. The 3D point, 2D point, 2D line, and 2D spline NPCF’s will be specifically presented. Complex models have successfully been modeled and exchanged in real time and have validated the NPCF approach. Multiple users can be in the same part at the same time in different CAD systems and create and update models in real time.
Collaborative CAD promises to solve the major design challenge facing industry relating to interoperability and design sharing: translation between heterogeneous CAD systems. Translation issues alone account for upwards of $1 billion in costs for the US automotive supply chain. With collaborative CAD, parts and assemblies can be viewed and edited simultaneously by multiple users in geographically diverse locations, without the need to manually export and send models as neutral files. In order to attain interoperability between CAD systems, a neutral format is used to pass data between clients. By expanding the traditional neutral format to include interfaces, the object hierarchy more closely resembles the hierarchy employed by native CAD systems — allowing more feature information, and thus design intent, to be preserved. The interface method also enforces referential integrity in the neutral representation of CAD objects by limiting the type of objects to be referenced to valid objects. Corrupt and invalid data can be caught and corrected before being transferred to other users viewing the CAD model.
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