UBC Theses and Dissertations

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UBC Theses and Dissertations

Automatic grouping of link components for kinematic chains of multi-axis machine tools Sung, Minsi


Multi-axis machine tools are used to machine parts with complex, curved surfaces. With additional rotary axes, multi-axis machine tools have a higher risk to have collisions compared with traditional three-axis machine tools. Collision during machining often causes damages to the machine and workpiece, which in turn leads to loss of productivity and extra costs. It can occur between the cutter, workpiece, and machine. Machining simulation with moving machine axis links becomes essential to detecting collisions prior to physical machining. In order to simulate machine movements, it is necessary to attain the kinematic chain of a given machine tool and to group machine components for each link in the kinematic chain. Existing methods to group link components require many inputs from users and follow an error-prone and lengthy manual process. This thesis presents an automatic method to group link components for each machine axis of a given multi-axis machine tool. The method is able to generate the kinematic chain of the multi-axis machine tool with only basic user inputs. As the first step, interference detection by voxel modeling is used to get contact relationships between components. Link-interface features between components are then identified and used to generate the link groups. The process of generating the link groups may be accompanied with uncertainties that can result in incorrect link groups. As a result, if there is an uncertainty, the generated link groups need to be validated to be free of link collision within the travel span of each axis. If there is collision, the collision is to be resolved by examining the uncertainty causing the specific link collision. The iterative step of validation and resolution continues until no link collision exists. The link collision is detected also by voxel modeling. The output of the automatic grouping method is the kinematic chain of the machine tool and the geometric model of each link for machining simulation. The presented method has been implemented on five commercial Haas five-axis machine tools with varying configurations. Correct kinematic chains for these machine tools have been generated and ready to be used for simulation of machine movements.

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