Diseño y construcción de una máquina para cortar y doblar estribos en serie para columnas de hormigón armado

Abstract

The thesis project has been developed to prove a machine to cut and bend rebar 8 millimeters, the principal objective is create square and rectangular reinforcement bar that fulfill norm and code (NEC-11 & ACI 318S). The production will be around 200 percent more than the previous, because manual process is affected by different aspects like physical and mental fatigue. The prototype of machine was defined after several analysis of similar machines and it was approved by Engineer Freddy Alcivar, owner of project and Engineer Olger Perez, thesis advisor. Through software (Inventor & Autocad) the prototype was simulated and defined esthetically, the software technology allow to make deferent simulation on beams, columns, mechanisms and special pieces. The first chapter refers to characteristics rebar to get knowledge mechanical properties and begin with design and engineering calculation, also a short survey about similar machines, manual, semi-automatic and automatic. Second chapter are calculation to define forces and dimensions necessaries to cut and bend rebar. Main calculation is the free body diagram because here is detected the forces and reaction that create the mechanism to make the job. The results of this diagram are used to get the strength and dimension to each piece through mathematic calculations and compared with simulations. The structure of machine has columns and beams which get by expressions like factor form and slenderness. Rests of pieces are analyzed with IV combined efforts and the principal equation is flexion formula, this is used to get square, rectangular and circular section forms. A lot of pieces, parts and services like bolts, nuts, bearing and welding are calculated mathematically and compared whit books and catalog that give the same result because they are normalized. When the theoretical has been finished, begin the cost analysis to buy the material and parts, the third chapter refers to all costs necessaries to build the machine like material, inputs, labor and manufacture. The last chapter is developed from machine, its operation and movements. How to use the machine is really important to prevent accidents and to increase the life mechanism. An operations manual is described to drive this and a short preventive maintenance manual is given to repair a keep everything well before and after each job.