板材送进夹钳装置设计(工作原理+任务书+说明书+CAD图纸+英文参考文献)
英文原文CHAPTER III
COST STUDY OF HIGH-SPEED CUTTING UNDER DRY AND WET CONDITIONS
FOR MACHINING PROCESSES OPTIMIZATION
3.1 Introduction
The aim of this study is to optimize the machining processes by investigating the relationship between the high speed machining (HSM) and the tool life for the cutting conditions under testing. Furthermore, studying the effect of cutting fluid on the selected wear criterion, and relationship between different wear criteria and machining cost for the cutting inserts under HSM.
This investigation showed that wear rate is proportional to cutting speed supported with similar observations [12,18,19]. Studying the correlation between high wear rates at high cutting speed and machining costs, provides better understanding on the performance of this policy and the benefit of its adoption. Currently, little or no data have been published relating the life -cycle costs, tool performance, work piece surface roughness and work piece dimensional accuracy when using solid and indexable cutters [10]. However, studies have found that tool costs in metal cutting machines are a third of the cost of producing parts. Therefore reducing product cost is the first objective of a tool management system[16]. The benefits of adopting this research guideline will help determine the optimal machining cost and tool replacement policy based on different wear criterion values. Additionally this study provides insight in process control and helps the managers in the early process planning steps to associate factors such as preventive maintenance, levels of inventory, and machining cost.
3.2 Experimental Study
The study developed a guideline of choosing the right cutting tool, cutting speed, and selecting the appropriate wear criteria of the cutting tool inserts for the work material under study. In this study variable wear criteria ranging from 0.lmm to 0.6mm (tool life limit) were taken into consideration. This experiment was conducted in accordance with the International Standard Organization ISO 3685 1993 [46].
The test was done on a (Clausing1300) variable spindle speed machine with a maximum power of 7.5Hp (see Figure 3-1). The tool wear measurements were performed using an optical microscope with a magnification of up to 300 times, and a Scanning Electron Microscope (SEM). The rotational speed of the work piece was measured before every cut by a (HT-5100) handheld digital Tachometer to insure that the work piece was accurately running at the exact cutting speed. On the other hand, the work piece material was replaced when the length/diameter ratio reaches 10, based on ISO 3685 1993 [46], to ensure work piece stability and safety. Two precut were carried out with 1.2 mm depth, to clean up the thin layer of rust, and to ensure work piece straightness.
Figure 3-1 The tuning machine used during the test.
3.2.1 Workpiece and Cutting Inserts
In this study, hot rolled ASTM 4140 steel was selected as the workpiece material. The work piece properties are listed as follows:
Description: Hot rolled alloy steel bars, SAE 4140H (UNS H4140)
Dimensions: 15 cm Diameter x 62.25 cm length
Heat Treatment:
Vacuum degassed/processed, Cal-Al treated, annealed and special straightened, conforming to ASTM A322 and A304
Chemical compositions:
The composition of the work piece material is listed in Table 3.1 according to the ASTM standards. The experiment was carried out in accordance with the international standard organization ISO3685-93 [46], the experiment was stopped and the work piece was changed when the length /diameter ratio reached 10 to meet the requirements of ISO3685 [46]. The hardness of each bar was checked across the diameter, and the average hardness measurement was 29HRC. The types of tested cutting tool inserts are listed on Table 3.1 according to the ISO designation. Three types of cutting inserts were used in the experiment as illustrated in Table 3-2; and the coating properties are also listed in Table3-3. The configuration of the investigated three cutting inserts was the same as listed in Table 3.4. The general cutting insert assembled geometry is shown in Figure3-2. The inserts were mounted rigidly on a tool holder are depicted in Figure3-3 with an ISO designation of SVJBR 2525 M16. 953
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