tailieunhanh - Metal Machining Episode 12

Tham khảo tài liệu 'metal machining episode 12', kỹ thuật - công nghệ, cơ khí - chế tạo máy phục vụ nhu cầu học tập, nghiên cứu và làm việc hiệu quả | Model-based systems for simulation and control 323 and side views of the stock to be removed by a two-flute square end mill 16 mm in diameter rotating with a spindle speed of 350 rev min. When the feed rate was set at 100 mm min in a trial cut the dimensional error varied with large amplitude as shown in Figure b . Then using an equation similar to equation the feed was adjusted as follows critical fa error f siml wherefa error is the feed adjusted for the limit of dimensional error critical and sjml is the error simulated under the trial conditions. Figures c d and e show the adjusted feed rate measured error and simulated and measured cutting forces. The dimensional error is almost constant over the workpiece as expected. The simulated and measured cutting forces show good agreement Figure shows the principle of a second use of the machining scenario to diagnose faults in an operation. A fault may be excessive tool wear tool breakage chatter vibration tangling of chips incorrect workpiece positioning incorrect tool geometry workpiece geometry incorrectly pre-machined incorrect tool preset among others. In any case it will cause the measured force variation with time to differ from the expected one. If a measured wave form differs from the expected one by more than a set amount a fault hypothesis library is activated. It holds information on how different types of fault may be expected to change an expected pattern. A fault simulation routine modifies the expected pattern accordingly. This is compared with the measured pattern and a fault diagnosis is produced from the best match between measured and simulated alternatives. Fig. Diagnosis procedure for faulty machining states Takata 1993 324 Process selection improvement and control Fig. Diagnosis of machining a different workpiece Takata 1993 To demonstrate the system s abilities the workpiece shown in Figure was prepared and machined instead of the intended workpiece .