PRELIMINARY EXAMINATION OF THE FRACTURE SURFACES OF A COLD CUTTING TOOL
The objective of failure analysis is to determine and explain the causes leading to premature failure.The final objective of failure investigation is suggesting measures that can be taken in order to prevent or minimize the chance of failure in the most economical way . Failures can be attributed to any one or a combination of causes such as improper material selection, design, processing and fabrication, operation, repair and maintenance and exposure to hostile environments not designed for. A failure investigation of mechanical components may follow specific techniques.
This paper studies the failure of a cold cutting tool. A die was produced for cutting envelope packages in the pharmaceutical industry. The die is part of a cutting machine and is located in an assembly including a roller. A strip of the medical product and its packaging material, which is cut at the required size, pass through the machine. High cutting precision is required, as this process defines the shape and dimensions of the package and also the medical product dose. The tool failed during the production process on the machine it was designed for, thus stopping the manufacturing process. The failure was initiated by a crack that began at the point of a diameter change of the tool body in the attachment part, where the tool was fastened to the rest of the machine.
The results refer to preliminary examination of the component’s fractured surfaces. The preliminary examination is usually the first step in the analysis of failures . In some cases, the causes of destruction may become apparent at this stage. In such a case, the results could lead to immediate actions, aimed at avoiding similar situations.
The following were carried out: collection of background data on the manufacturing site, fabricating and service history, selection of production samples, design and dimension control, visual inspection of the parts and macroscopic examination of the fractured surfaces. The paper presents conclusions on the the state of the fracture, crack origin and type of the fracture, crack propagation, the existence of cracks, type of cracks where they are visible and presents the principal causes that led to the premature failure of the die. The paper may be of interest in providing information on extending the viability of the product.
 DAS A.-K., ''Metallurgy of Failure Analysis'' ,Types and Characteristics, edited by Mc Grow-Hill Companies, New York (1997), p.67
 NAUMANN F.-K., '' Failure Analysis, Case Histories and Methodology’’, ASM, Metas Park, Ohio (1983), p.6.