In order to be competitive in the markets of today, more and more companies try to make their production more effective by automation. Consequently more money is invested in robots and the operability of the robots becomes increasingly important. Undetected faults may result in damages, both to the robot itself and to the operator, which make detection and prediction of faults important.The gearboxes responsible for controlling the motions of the robots are essential for their functionality. In order to increase the understanding about them this project focuses on creating a model of the stress distribution inside a gearbox.First, the geometry of the gearbox is measured and digitalized using a vernier caliper, a protractor, a ruler and the CAD-program Solid Works. Then the geometry is imported into the finite element program Samcef. In Samcef, the interaction between the parts in the gearbox is modeled and a dynamic simulation of the stresses inside the gearbox during a robot cycle performed.Since there are almost no experience about Samcef at ABB SECRC, part of the project is to evaluate the program and comment the experiences received when using it.Two main power transmission steps are identified, modeled and simulated. They are merged together into a big model where both steps are present. This model consists of all the essential power transmission inside the gearbox, from input to output. The load applied is a rotational movement on the input axle during a robot cycle.
Contents
1 INTRODUCTION
1.1 PURPOSE
2 INDUSTRIAL ROBOTS
2.1 CLASSIFICATION OF ROBOTS
2.1.1 Classification by coordinate systems
2.1.2 Classification by control method
2.2 MAIN COMPONENTS OF A ROBOT
2.3 ROBOTIC APPLICATIONS
2.3.1 Current applications
2.3.2 Future applications
3 GEARS
3.1 TYPES OF GEARS
3.2 KINEMATICS OF GEARS
3.3 GEAR TOOTH GEOMETRY
3.3.1 Involute profile
3.3.2 Cycloidal profile
3.4 POSSIBLE FAULTS
3.5 THE GEARBOX IN THIS PROJECT
3.5.1 Included parts
3.5.2 Basic power transmission
4 ESTIMATION OF LIFE TIME
4.1 NABTESCO LIFE TIME FORMULA
4.2 MODIFIED FATIGUE LIFETIME THEORY
4.3 THE FINITE ELEMENT APPROACH
5 SAMCEF
5.1 GENERAL LINE OF WORK
5.2 CALCULATION METHOD
5.3 BOUNDARY CONDITIONS USED IN THIS PROJECT
5.4 REMARKS
6 MODELING APPROACH
6.1 MODELING OF THE CIRCULAR MOVEMENT OF THE RV GEAR
6.2 MODELING OF THE CONTACT BETWEEN THE RV GEAR AND THE ROLLERS
6.3 MODELING OF DISC AND CASE MOVEMENTS
6.4 REACHING THE FINAL APPROACH
6.5 REMARKS
7 THE FINAL APPROACH
7.1 THE CAD MODELING
7.2 THE FINITE ELEMENT MODEL
7.3 RESULTS
7.4 REMARKS
8 DISCUSSION AND CONCLUSIONS
8.1 FUTURE WORK
9 REFERENCES
APPENDIX A – THE FORMULAS FOR CREATING THE CYCLOIDAL SHAPE
Author: Persson, Johan
Source: Linkoping University
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