PurposeTo calculate the volume deviation between a CAD model and built‐up part in 5‐axis laminated object manufacturing employing direct slicing with first‐order approximation.Design/methodology/approachIt is proposed here that the deviation between the CAD model and the built‐up part, which is normally calculated as a linear dimension in specific 2D sections of the CAD model, be treated as a volume (as it actually is), for higher accuracy in subsequent calculations. An algorithm has been developed and implemented for identification and calculation of volume deviation, considering all possibilities.FindingsIt has been conclusively shown that volume deviation consideration results in improved feature recognition and less approximation.Research limitations/implicationsIncrease in complexity of the CAD model leads to a considerable increase in the volume deviation computation time. Future research in this area would focus on optimization and calculation of the slice heights based on volume deviation.Practical implicationsCalculation of volume deviation would help eliminate the loss of intricate features in a complex surface and thus improve feature recognition. Slice height calculations based on volume deviation would reduce the deviation between the actual model and the built‐up part.Originality/valueA new method has been developed for the calculation of volume deviation that could be implemented in the rapid prototyping software packages so as to build prototypes with higher accuracy.
A solid bluff object produces a recirculating wake region immediately behind it when subjected to flow separation under a steady flow condition. Similar phenomena can also be observed for a porous body. However, unlike the solid object the porous body allows some part of the flow to go through it. A consequence of this flow penetration in porous objects is, the wake behind the body may get reduced in size and detach from the body. The wake even may disappear at some value of the porosity parameter (Darcy number). In this brief article, we compute the critical values of the porosity parameter for complete disappearance of the wake region behind two-dimensional porous bodies of circular and square shapes. A regime diagram is constructed to show the regions of wake formation, its detachment and finally its disappearance around circular and square shaped porous bodies. The critical value of the porosity parameter increases with increasing Reynolds number, and it is found greater for the square body in comparison to the circular one. The study provides a quantitative estimation of how the porosity plays a significant role in demarcating the flow characteristics around porous objects.
This paper aims at automatic generation of optimal sequence of machining operations in setup planning by Genetic Algorithm (GA) based on minimizing the number of setup changes and tool changes, subject to various machining precedence constraints. The GA has been reconstructed as the method of representing an operation is not as simple as assigning it a binary digit as in case of a chromosome in traditional GA but it has to be a distinct real number. Accordingly, the GA operators had to be modified. At the end of each GA cycle, there might be chromosomes having high fitness values but not conforming to constraints. Moreover, due to randomness of GA, the conformable chromosomes might tend to get lost. In order to minimize such losses, the elitist model is used for selection of chromosomes. Furthermore, a special subroutine has been developed to check the chromosomes for conformability and modify/repair those that violate the constraints.
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