• Korean Journal of Computational Design and Engineering
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• v.8 no.4
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• pp.254-261
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• 2003

In mold and die shops, NC machining process mainly affects the quality of the machined surface and the manufacturing time of molds and dies. The estimation of NC machining time is a prerequisite to measure the machining productivity and to generate a process schedule, which generally includes the process sequence and the completion time of each process. It is required to take into account dynamic characteristics in the estimation, such as the ac/deceleration of NC machine controllers. Intensive observations at start and end points of NC blocks show that a minimum feedrate, a key variable in a machining time model, has a close relation to a block distance, an angle between blocks, and a command feedrate. Thus, this study addresses regression models for the minimum feedrate estimation on short and long NC blocks considering these parameters. Furthermore, machining time estimation models by the four types of feedrate behaviors are suggested based on the estimated minimum feedrate. To show the validity of the proposed machining time model, the study compares the estimated with the actual machining time in the sculptured surface machining of several mold dies.

• Korean Journal of Computational Design and Engineering
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• v.12 no.1
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• pp.1-7
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• 2007

In this paper, we present a machining time estimation algorithm for 5-axis high-speed machining. Estimation of machining time plays an important role in process planning and production scheduling of a shop. In contrast to the rapid evolution of machine tools and controllers, machining time calculation is still based on simple algorithms of tool path length divided by input feedrates of NC data, with some additional factors from experience. We propose an algorithm based on 5-axis machine behavior in order to predict machining time more exactly. For this purpose, we first investigated the operational characteristics of 5-axis machines. Then, we defined some dominant factors, including feed angle that is an independent variable for machining speed. With these factors, we have developed a machining time calculation algorithm that has a good accuracy not only in 3-axis machining, but also in 5-axis high-speed machining.

• Korean Journal of Computational Design and Engineering
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• v.6 no.4
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• pp.244-253
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• 2001

For more complete process planning, machining sequence determination is critical to attain machining economics. Although many studies have been conducted in recent years, most of them suggests the non-unique machining sequences. When the tool approach directions(TAD) are considered fur a feature, both machining time and number of setups can be reduced. Then, the unique machining sequence can be extracted from alternate(non-unique) sequences by minimizing the idle time between operations within a sequence. This study develops an algorithm to generate the best machining sequence for composite prismatic features in a vertical milling operation. The algorithm contains five steps to produce an unique sequence: a precedence relation matrix(PRM) development, tool approach direction determination, machining time calculation, alternate machining sequence generation, and finally, best machining sequence generation with idle times. As a result, the study shows that the algorithm is effective for a given composite feature and can be applicable fur other prismatic parts.

• Journal of the Korean Society for Precision Engineering
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• v.23 no.12 s.189
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• pp.38-45
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• 2006

In this work, optimal finish machining condition considering total time for mold or electrode manufacturing was investigated. First, manual finishing time according to the machining condition was analyzed for the work material. The effect of runout and phase shift of tool path on surface finish was also considered in those analyses. Secondly, optimal manual finishing processes were determined for various machining conditions. Finally, finish machining time and corresponding manual finishing time were taken into account for the estimation of the total time of manufacturing mold. Though small feed per tooth and pick feed reduced the manual finishing time, the finish machining time increased in such conditions. With a machining condition of feed per tooth of 0.2 mm and pick feed of 0.3 mm, the minimum total time of manufacturing mold was achieved in our machining condition.

• Proceedings of the Korean Operations and Management Science Society Conference
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• 2004.05a
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• pp.48-51
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• 2004

The estimation of NC machining time is of significance since it provides shop floor engineers with information for the determination of the productivity of the floor as well as process schedules. The NC machining time commonly depends on NC programs since they have various important information such as tool positions, feed rates, and other miscellaneous functions. Thus, nominal NC machining time can be easily acquired based on the programs. Actual machining time, however, cannot be simply obtained because of the dynamic characteristics of a NC machine controller such as acceleration and deceleration. Hence, this study presents a NC machine time estimation model for sculptured surfaces, considering the dynamic characteristics. The estimation model uses the distribution of NC blocks according to a factor influencing the machining time. Finally, machining time is estimated by a statistical machining time estimation model representing the relationship between the block distribution and the machining time. The parameters in the model are searched out by a genetic algorithm.

• Journal of Powder Materials
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• v.20 no.4
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• pp.297-301
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• 2013

Mirror surface machining for large area flattening in the display field has a problem such as a tool wear and a increase in machining time due to large area machining. It should be studied to decrease machining time and tool wear. In this paper, multi-tool machining method using a PCD tool and a SCD tool was applied in order to decrease machining time and tool wear. Machining characteristics (cutting force, machined surface and surface roughness) of PCD tool and SCD tool were evaluated in order to apply PCD tool to flattening machining. Based on basic experiments, the PCD/SCD multi-tool method and the SCD single-tool method were compared through surface roughness and machining time for appllying large area mold machining.

• Journal of the Korean Society for Precision Engineering
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• v.24 no.12
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• pp.42-49
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• 2007

When micro holes are machined by EDM, machining characteristics of machined holes are changed according to the machining conditions. Typical machining conditions are the kind of dielectric fluids, capacitance and ultrasonic vibrations. They influence electrode wear, machining time, radial clearance and taper angle. In this paper, machined holes whose depths are 300, 500, $1000\;{\mu}m$ are observed for each machining conditions. Using deionized water as a dielectric fluid makes electrode wear small, machining time short, radial clearance large and taper angle small. High capacitance makes electrode wear high. Ultrasonic vibrations make electrode wear large, machining time short, radial clearance small and taper angle small. From the results of experiments, the optimal machining conditions were obtained to machine highly qualified micro holes.

• Journal of the Korean Society for Precision Engineering
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• v.22 no.4
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• pp.27-36
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• 2005

Some studies have shown that unstable factors are inherent in WEDM process, causing the instability of the discharging pulse to reach about 40∼60％ in normal machining. Transient stability is an important subject in WEDM process since there is a close relationship between stability and machining performance, such as the characteristics of a machined surface, machining speed and problem of instability like wire rupture phenomenon. Among the many machining parameters affecting WEDM machining state, three specific parameters (Vr, Ip, off time ) are major controllable variables that can be applied in transient stability control. And, this research investigates the implementation and analysis of real-time micro control of the discharging stability of WEDM (Wire Electric Discharge Machining) process.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
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• 1997.10a
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• pp.183-189
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• 1997

This research is a experimental study for the machining conditions of E. D. M. They were used Cu electrode and the various amplitude of current waves for the machining by E.D.M. By the analyse the characteristics of current, voltage, roughness of surface and over cut, the next results were obtained. E.D.M. machining time become to be more longer by the increasing the tensile stress. In case of NAK 55 as the composite resin, the machining time was more faster without the relationship for the tensile stress. And if it was more increased the amplitude of Ip, it has been more faster in the machining time and more poor in the surface roughness. But it was increased Ip with 5A, it has been increased 0.3 time in over cut. So, if we want to be the precision machining, the diameter of the electrode should be more smaller than the diameter of machined hole in workpiece with E.D.M.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 1996.11a
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• pp.15-19
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• 1996

The cusp height in ball end milling, flat end milling and filleted end milling according to various surface inclination angle was calculated. The calculation result shows that, for each kind of tools, there exists certain range of inclination angle in which cusp height characteristics favorable. From machining time calculation, filleted end mill found to be superior to flat end mill in rough machining of sculptured surface.