This master’s thesis focuses on analysis of time consumption of machining process, the basic units of operating costs of production,optimization and subsequen tapplication to specific part. It is a turning shaft in two operations, named roughing and finishing turning. The aim is to find the optimum combination of life time of cutting tool and cutting speed, which is the main criterion for optimization in terms of minimum production cost or a maximum of productivity.

This work deals with operating production costs in machining process and further optimalization. In the first chapter, individual costs items which are related to machining process are specified. These cost items are quantified and total production costs are acquired. Optimalization of operation production costs are described for criterion of minimal production costs and criterion of maximal productivity are described in next chapter. Practical part of this work is focused to apply each individual criterion in practical example. There is CD with programs attached to this work. The goal is to find optimal combination of cutting speed, sufficient life time of cutting tool and suitable cutting technology so that chosen criterion can be acceptable.

The precision of machining systems is ever increasing in order to keep up with components’ accuracy requirements. At the same time product variants areincreasing and order quantities are decreasing, which introduces high demands on the capability of machining systems. The machining system is an interaction between the machine tool structure, the process and the control system and is defined in terms of capability by the positional, static, dynamic and thermal accuracy. So far, the control of the machining system, in terms of static and dynamic stability is process based which is often translated into sub-optimum process parameters and therefore low productivity.This thesis proposes a new approach for control of the machining systemwhich is based on the capability to control the structural properties of themachine tool and as a result, controlling the outcome of the machining process.The control of the structural properties is realized by carefully designed Joint Interface Modules (JIMS). These modules allow for control of the stiffness and damping of the structure, as a result of tuning the contact conditions on the interface of the JIM; this is performed by control of the pre-load on the interface,by treatment of the interface with damping enhancing materials, or both. The thesis consists of a presentation of the motivation behind this work, the theoretical basis on which the proposed concept is based and a part describing the experimental investigations carried out. Two prototype JIMs, one for a milling process and one for a turning process were used in the experimental investigations that constitute the case studies for examining the validity of the proposed concept and demonstrating its applicability in a real production environment. / <p>QC 20140611</p> / EU FP7 POPJIM

<p>Carbon fiber bending during Carbon Fiber Reinforced Plastic (CFRP) milling is an important factor on the quality of the machined surface. When the milling tool rotates, the fiber first contacts the rake face instead of the tool edge at a certain cutting angle, then the fiber is bent instead of being cut by the tool. It causes the matrix and the fiber to fall out, and the fiber is broken from deep inside the machined surface. The broken fibers are pulled out as the tool rotates, which is known as pull-out fibers. The machining defect is the main cause of deteriorating the quality of the machined surface. To reduce such machining defects, it is important to predict the carbon fiber bending during CFRP milling. However, it is difficult to determine a point where fiber bending occurs because the fiber cutting angle changes every moment as the tool rotates. Therefore, in this study, CFRP milling simulation was performed to numerically analyze the machining parameters such as fiber cutting angle, fiber length, and the magnitude of fiber bending according to the different milling conditions. In addition, the deformation of the matrix existing between carbon fibers is predicted based on the fiber bending information obtained through simulation, and matrix shear strain energy model is developed. Also, the relationship between the matrix shear strain energy and machining quality is analyzed. Through verification experiments under various machining conditions, it is confirmed that the quality of the machined surface deteriorated as the matrix shear strain energy increased. Moreover, this study analyzed the fiber cutting mechanism considering bent fibers during CFRP milling and proposed a method to identify the type of machining mechanism through machining sound analysis. Through experiments, it was verified that fiber bending or defects can be identified through machining sound analysis in the high-frequency range between 7,500 Hz and 14,800 Hz. From the analysis, the effect of different chip thickness in up-milling and down-milling on fiber bending was investigated by analyzing simulation and sound signal. From machining experiments, the effect of this difference on cutting force and machining quality was verified. Lastly, we developed a minimum chip thickness and fiber fracture model in CFRP milling and analyzed the effect of fractured fibers on the machining sound. Carbon fibers located below the minimum chip thickness do not contact the tool edge and are compressed by the bottom face of the tool, and these fibers are excessively bent and broken. As these broken fibers are discharged while scratching the flank face of the tool, a loud machining sound is generated. Moreover, through the verification experiment, it was confirmed that the number of broken fibers is proportional to the loudness of the sound, and calculated number of broken fibers for one second using the fiber fracture model coincides with the high-frequency machining sound range of 7,500 Hz to 14,800 Hz.</p>