Micropore forming method

Abstract

A micropore forming method includes the steps: firstly, fixing a molybdenum sheet on a worktable of machining equipment; and secondly, forming a micropore with the diameter of phi 0.38mm, the roundness of 0.01mm and the surface roughness of Ra 0.1 at a preset position of the molybdenum sheet. The micropore forming step particularly includes positioning, pre-drilling and expanding. An expanding drill with the diameter of phi 0.38mm is used for expanding on the basis of pre-drilling during expanding, cutting fluid is used for washing the expanding drill and the molybdenum sheet during expanding, the rotation speed of the expanding drill is 5000-10000 revolutions per minute, the feed speed of the expanding drill is 1-5mm / min, drilling is repeated for 8-12 times, and grease lubricant is smeared on the surface of a drill bit of the expanding drill. The micropore forming method adopts a machining mode, and the formed micropore can meet the requirement of an extremely small suction hole on machining precision.

Description

technical field [0001] The invention relates to the field of instrumentation (analytical instrument), in particular to a method for forming micropores on a molybdenum sheet of an electron microscope. Background technique [0002] The electron gun of the field emission electron microscope is a tiny high-brightness electron source, which consists of a tungsten single crystal (W (100)) coated with zirconia (ZrO) Schottky emission cathode or cold field emission cathode, suppression pole, extraction pole, focusing Its function is to provide a stable electron source for the whole system. When the surface of the tip of the cathode tungsten wire in vacuum is subjected to 10 8 When electrons with a size of V / cm are accelerated by an electric field, a considerable number of electrons will be emitted from the surface of the tungsten tip. This process is called field emission. The principle of field emission is that a high electric field causes the potential barrier of electrons to pr...

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Problems solved by technology

[0005] However, the above method has the following disadvantages: ①Using the laser cutting method to process the molybdenum thin sheet diaphragm can meet the precision requirements, but it needs to pre-configure hardware equipment such as ultraviolet lasers and computers and build corresponding workbenches and scanning galvanometer systems. The equipment investment is large, and the post-maintenance cost is also high, which leads to a substantial increase in the manufacturing cost of the molybdenum thin film diaphragm; It may cause cancer, and the ultraviolet laser is also very harmful to the eyes. Therefore, when the operator uses the above method to process the molybdenum sheet, even if the necessary safety protection measures are taken, the ultraviolet laser may cause harm to the human body.

Although grease lubricant can provide a good lubricating effect, its cleaning effect and cooling effect are far inferior to cutting fluid. If only grease lubricant is used in the drilling process, it will not be able to remove the debris in the hole in time. The adhesion of swarf particles to the cutting edge will seriously affect the cutting effect of the tool and reduce the machining accuracy; and due to the poor cooling effect of the grease lubricant, the thermal deformation of the tool will reduce its hardness, which will not only damage the service life of the tool, but also cause forming The roughness of the small hole increases, and the thermal deformation of the workpiece will make it impossible to guarantee the dimensional accuracy after cooling

Therefore, the use of grease lubricants to dry-cut micro-holes still cannot meet the precision requirements for sucking out extremely small holes

[0009] In summary, it is difficult to form a very small suction hole that meets the precision requirements by using the existing mechanical processing technology

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