Topology Optimization and Casting Feasibility of a Robot Arm

This presentation was made at CAASE18, The Conference on Advancing Analysis & Simulation in Engineering. CAASE18 brought together the leading visionaries, developers, and practitioners of CAE-related technologies in an open forum, to share experiences, discuss relevant trends, discover common themes, and explore future issues.

Resource Abstract

Oftentimes, in the design of a casting, sub-optimal structural concepts are developed which at the same time are not castable, requiring multiple and time-consuming design iterations. This paper describes a process to generate both structurally efficient and also castable parts, while reducing the overall design cycle time. The optimal structure is determined by topology optimization, reducing component mass while maintaining performance requirements. This step is followed by a design smoothing operation and then by a casting simulation to check for casting defects. To demonstrate this software driven product design and process validation, solidThinking Inspire® is used to develop the concept design and Click2Cast® for casting process validation. For the case study reported in this paper, a robot arm is considered. Concept level optimization is carried out with real field loads & manufacturing constraints. Several optimization studies are performed considering different manufacturing options and the final design selected meeting all performance targets. This final design is analyzed to investigate the casting process and any potential defects during manufacturing.
To start with the study the existing design of the robot arm is analyzed to find its performance. Further a package space is created around the existing design, considering the surrounding components. Further topology optimization is performed with the objective of Maximize stiffness with constraints on the volume, multiple concepts are generated just by changing the manufacturing constraints i.e. single draw, single draw with no-hole, split draw, extrusion and one with no manufacturing constraints at all. All these concepts are studied and it was found that the concept with no manufacturing constraints was the best, but as it was not manufacture-able the next best concept i.e split draw was selected for further study. This concept was further validated to check the stresses and displacements, it was observed that the new design was 46% lighter with the performance being equal to the existing design. Further design smoothing operation called PolyNurbs were created, which helped in getting a clean geometry.
This geometry was taken into Click2Cast and casting feasibility analysis was carried out to evaluate the filling and Solidification process. The initial iteration showed that there was some turbulence being introduced as the selected gate location was not appropriate, also the filling time used i.e. 5 seconds, was very high. So another iteration was performed by moving the gate location slightly in the X direction and the filling time changed to 2.5 seconds. The results from this iteration were quite improved, flow was observed to be very smooth by looking at the velocity plots, the temperatures plot had a uniform distribution, shrinkage porosity observed was 7.5 mm3 which was very low, the percentage porosity was also checked which was very low as well.
In this study, a design methodology is presented using an upfront design optimization and casting process simulation to reduce design cycle time and significant cost. The software used are intuitive and well-suited for product designers. Also the seamless modelling environment with finite element solver, optimization engine, and a high performance compute cluster makes it possible to run multiple design iterations very quickly.

Document Details

AuthorHiremath. P
Date 7th June 2018
OrganisationAltair Engineering, Inc


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