Optimization of Industrial Gear box Casing Mechanical Project

Abstract—

This paper contains the study of Optimization of a three stage Commercial gearbox casing using Finite Element Analysis (FEA) Method. The gearbox casing is an important transmission component like gear and shafts. Thus the strength of gearbox casing is to be important parameter to be taken into account while designing. The 3D model is prepared by using Pro-E creo2.0 pre-processing is prepared by using Hypermesh 11.0 while FEM is solved by using Ansys 14.5 solver.
It was statically and dynamically analysed using simulation software Altair Hypermesh and Ansys. Static analysis is to find out the total amount of stresses and displacement of gearbox casing and End cover. Dynamic analysis is to find out theNatural frequency of casing. Optimization is based on Ansys Linear static and dynamic modal analysis results, which can be used to enhance the efficiency of the design process. Considering the results obtained from optimization, geometric model was modified and iterated until satisfactory results were achieved.
The process is repeated until all specified criteria are met. This process helps in finding the optimized design for the gearbox casing in which it has the best performance without any failure and with minimum Loads acting on the casing. After implementing optimization, weight of the gearbox housing will be reduced. FEA also be carried out on optimized design of the gearbox housing to check whether the optimized design is safe or not.

INTRODUCTION
The casing encloses completely different sets of gears, bearings to support the shafts. This Gear box is to reduce speed and increase torque. You’ll find them between the prime mover (i.e.: motor, gas, diesel or external-combustion engine, etc.) and also the driven equipment: conveyors, mills, paper machines, elevators, screws, agitators, etc. in an exceedingly power transmission gear system, the vibrations generated at the gear mesh are transmitted to the gearbox housing through shafts and bearings. Casing could be a part of gear box, it provides support to shaft, bearing and thence the gear loading.
It is a bimetal casting made of grey forged iron viz., FG260 and FG220. This material selection is based on the factors of strength, rigidity, cost etc. For casting, there are several factors.

optimization cad model
optimization cad model

METHODOLOGY
The problem under consideration will be modeled through four
approaches:
A. CAD Modeling
B. Finite Element Meshing
C. Boundary Conditions
D. Finite Element Analysis
E. Optimization

CAD Modeling
The Fig.shows representation of gearbox casing. The important parametric quantity while designing gear box casing is ribbing which is to attain required strength. The CAD Model of gearbox casing specification is

Length- 1435mm

Width -520mm

Height- 800mm.

The CAD model is imported into IGES file format to the FEM design software Altair Hypermesh 11.0.

Boundary Conditions
Boundary conditions can be applied to geometry, including faces, edges, curves, points, mesh points, vertices, nodes, elements or the entire model. There are various types of load applicable over gearbox casing. The Static load of transmission gear and drive shaft act on bearing hole it divide into two parts namely, Radial force and axial force on each gear have to analysis. These loads are applied to find the actual effect of stress and deformation on gearbox.

Optimization
Optimization is a process of converging onto a final solution amongst a number of possible options, such that a certain requirements are best satisfied. The objective of the optimization problem is often some sort of maximization or minimization, for example minimization of stress or maximization of stiffness. The purpose of this optimization problem is to minimize the weight of beam without exceeding the allowable stress.

CONCLUSION

  • Existing Gearbox casing weight 933 kg. Difference between Natural Freq. and Gear mesh freq. 6.7%.
  • Shape optimization Gearbox casing weight 826kg hence up to 13% optimization possible than existing gearbox. Difference between Natural Freq. and Gear
    mesh freq. 9.8% it is greater than existing design of gear box.
  • Natural frequency of casing is obtained using Ansys and compared with gear mesh frequency i.e. operating frequency. There is no resonance condition found thus the structure is safe.
  • A parametric study was conducted on casing thickness, addition of rib, increasing rib thickness.
  • The effect of varying casing thickness on the natural frequencies of the gearbox casing was not significant, as compared to increase in the weight of the gearbox casing.
  • The effect of addition of rib on the natural frequencies of the gearbox casing was significant, as compared to increase in the weight of the gearbox casing.
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