REMAINING LIFE PREDICTION OF MACHINE ELEMENT USING REVERSE ENGINEERING APPROACH

Abstract

Generally, any field of applied engineering is an application of scientific and mathematical principles to practical ends such as the design, manufacture, efficient operation, efficient processes and machines and maintaining the product and systems. There are two engineering techniques for making the end products using applied principles of engineering: forward engineering and reverse engineering. Forward engineering is the traditional process of moving from high-level abstractions and logical designs to the physical implementation of a system. Reverse engineering typically starts with measurement of existing object. The processing of the scanned point cloud and the reconstruction of the geometrical 3-D CAD model to exploit the advantages of CAD/CAM/CAE and rapid prototyping under reverse engineering environment. The more machine components are going under the failure due to surface wear. The wear rate is relatively high at initial stage of the rubbing surface. Critical machine elements such as such as tools, die, turbine blade, and gears tooth change their shape and size, when they pass through rubbing operation for long periods. This change in geometrical shape can be identified by reverse engineering. In the present work, a spur gear has been selected for study because of it being an imperative element in mechanical industries to transmit power and torque. Over a period of service time, surface of meshed gear changes in comparison to initial surface owing to intense wear. The 3-D laser scanner (PICZA 3-D/Roland LPX60) was used for scanning the spur gear surface geometry. The gear has been scanned before and after wear using optimal setting with scanner inbuilt tool on Roland LPXEZ studio. The scan data is collected in the form of X, Y and Z co-ordinates for multiple points in the form of point cloud data. The pre-processed data was saved as a point cloud data in ASCII file format at different height of the object. Recreation of 2-D and 3-D model using scanned data was completed successfully. The recreated curve profile before and after wear of tooth has been compared to estimate the amount of wear at various height of gear teeth in terms of removed volume. The CAD model is recreated by curves lofting together to make the 3-D solid model. The sliced based recreated 3-D physical prototype models of designed, recreated original and recreated worn-out spur gears are printed with 3-D printer Object30-Pro machine. Abstract v The solid model created from scanned data for original and worn-out gear has been imported to ANSYS Workbench 14.0. Finite element results have been obtained for design tooth recreated original tooth and recreated worn-out tooth model respectively. Further it has been assumed that the wear is on pinion tooth. For comparative study consideration, the contact stresses are also calculated by using Hertz and AGMA contact equation and bending stresses are calculated using Lewis and AGMA bending. These all bending and contact stress results have been used to calculate numbers of their service life cycles of the pinion. The necessary clearance or backlash is obtained by setting the assembly of gear pair. Using reverse engineering one can find the backlash. If backlash is more than the permitted value then center distance can be changed to incorporate this backlash. Thesis also discusses the effect of large pressure angle, effect of change in pitch circle diameter and effect of contact length variation.