1、毕 业 设 计（论 文）外 文 参 考 资 料 及 译 文译文题目： 微孔的加工方法 学生姓名： 学 号： 专 业： 所在学院： 指导教师： 职 称： 20xx年 2月 27日说明：要求学生结合毕业设计（论文）课题参阅一篇以上的外文资料，并翻译至少一万印刷符（或译出3千汉字）以上的译文。译文原则上要求打印（如手写，一律用400字方格稿纸书写），连同学校提供的统一封面及英文原文装订，于毕业设计（论文）工作开始后2周内完成，作为成绩考核的一部分。外文原文Options for micro-holemakingAs in the macroscale-machining world, holemak
2、ing is one of the most if not the mostfrequently performed operations for micromachining. Many options exist for how those holes are created. Each has its advantages and limitations, depending on the required hole diameter and depth, workpiece material and equipment requirements. This article covers
3、 holemaking with through-coolant drills and those without coolant holes, plunge milling, microdrilling using sinker EDMs and laser drilling. Helpful Holes Getting coolant to the drill tip while the tool is cutting helps reduce the amount of heat at the tool/workpiece interface and evacuate chips reg
4、ardless of hole diameter. But through-coolant capability is especially helpful when deep-hole microdrilling because the tools are delicate and prone to failure when experiencing recutting of chips, chip packing and too much exposure to carbides worst enemyheat.When applying flood coolant, the drill
5、itself blocks access to the cutting action. “Somewhere about 3 to 5 diameters deep, the coolant has trouble getting down to the tip,” said Jeff Davis, vice president of engineering for Harvey Tool Co., Rowley, Mass. “It becomes wise to use a coolant-fed drill at that point.” In addition, flood coola
6、nt can cause more harm than good when microholemaking. “The pressure from the flood coolant can sometimes snap fragile drills as they enter the part,” Davis said. The toolmaker offers a line of through-coolant drills with diameters from 0.039 to 0.125 that are able to produce holes up to 12 diameter
7、s deep, as well as microdrills without coolant holes from 0.002 to 0.020. Having through-coolant capacity isnt enough, though. Coolant needs to flow at a rate that enables it to clear the chips out of the hole. Davis recommends, at a minimum, 600 to 800 psi of coolant pressure. “It works much better
8、 if you have higher pressure than that,” he added. To prevent those tiny coolant holes from becoming clogged with debris, Davis also recommends a 5m or finer coolant filter. Another recommendation is to machine a pilot, or guide, hole to prevent the tool from wandering on top of the workpiece and ai
9、d in producing a straight hole. When applying a pilot drill, its important to select one with an included angle on its point thats equal to or larger than the included angle on the through-coolant drill that follows. The pilot drills diameter should also be slightly larger. For example, if the pilot
10、 drill has a 120 included angle and a smaller diameter than a through-coolant drill with a 140 included angle, “then youre catching the coolant-fed drills corners and knocking those corners off,” Davis said, which damages the drill. Although not mandatory, pecking is a good practice when microdrilli
11、ng deep holes. Davis suggests a pecking cycle that is 30 to 50 percent of the diameter per peck depth, depending on the workpiece material. This clears the chips, preventing them from packing in the flute valleys.Lubricious ChillTo further aid chip evacuation, Davis recommends applying an oil-based
12、metalworking fluid instead of a waterbased coolant because oil provides greater lubricity. But if a shop prefers using coolant, the fluid should include EP (extreme pressure) additives to increase lubricity and minimize foaming. “If youve got a lot of foam,” Davis noted, “the chips arent being pulle
13、d out the way they are supposed to be.” He added that another way to enhance a tools slipperiness while extending its life is with a coating, such as titanium aluminum nitride. TiAlN has a high hardness and is an effective coating for reducing heats impact when drilling difficult-to-machine material
14、s, like stainless steel. David Burton, general manager of Performance Micro Tool, Janesville, Wis., disagrees with the idea of coating microtools on the smaller end of the spectrum. “Coatings on tools below 0.020 typically have a negative effect on every machining aspect, from the quality of the ini
15、tial cut to tool life,” he said. Thats because coatings are not thin enough and negatively alter the rake and relief angles when applied to tiny tools. However, work continues on the development of thinner coatings, and Burton indicated that Performance Micro Tool, which produces microendmills and microrouters and resells microdrills, is working on a project with others to create a submicron-thickness coating. “Were probably 6 months to 1 year from testing it in the mar
