Processing under the fire processing microscope

Medium processing: processing under the microscope

although the term "micro processing" is used in processing operations with unusually small sizes, researchers at Sandia National Laboratory (Albuquerque, New Mexico, USA) are unwilling to use the term for their small-scale milling and turning operations

for them, the prefix "micro" implies that they can produce sizes as small as 1 μ The ability of the characteristics of M. This is something they cannot do - at least not through milling and turning operations. Sandia's cutting tools are more suitable for producing a size of at least 25 μ Characteristics of M

meso machining is a term used by these researchers. Micro milling and turning tools are made by carving cemented carbide and HSS blanks with focused ion beam

the diameter of end mills made in this way may be as small as 20 μ M or so. Turning tools can be as small as 10 μ M wide. This moving beam stops automatically; This kind of tool is exactly what is needed in medium processing, because there are already suitable technologies for machine tools

the first three photos are end mills produced with focused ion beams

the other two photos are produced in the same way 18 μ The view of m-wide turning tool

here is an amazing aspect of Sandia's work. Although experimental tools must be developed, experimental machine tools are not necessary to use these tools. Researchers use these tools effectively on precision machine tools that can be purchased from commercial suppliers

the main reason for processing in research is related to nuclear weapons. Gilbert Benavides, manager of Sandia manufacturing engineering, explained the link. He said that the existing nuclear weapons have some parts that sometimes need to be replaced, and these parts are best replaced with improved versions. However, each part has a fixed size and shape, because the components around it in the assembly will not change. Therefore, the only option to add new features is to compress more features into the existing space. Medium processing can provide a way to meet this demand

there is a lot of room for imagination about what new features can be added to the engineering plastics, high reliability safety materials and low VOC environmental protection materials used in the research and development of nuclear weapons. However, this aspect is an option for Sandia's medium processing operations for additional details

ability

sandia has been skilled in milling for 20~30 μ M wide groove made of aluminum, brass and 4340 steel. Typical cut depth is 1 μ m。 One adopts 22 μ M diameter two edge carbide end mill, cutting depth 1 μ m. The processing experiment of aluminum at 18000r/min shows that this tool can process efficiently with a feed rate of up to 50mm/min. This tool can be milled for more than 6 hours (with different feed rates) without cracks

turning tools have proved to have the same durability. A representative experiment shows that a 13 μ M wide tool can cut a total of 200mm long, 4 μ M deep aluminum spiral groove (if the groove is straight without winding form)

tool

turning tool is similar to full-size turning tool. Milling cutter is not like this. When using ion beam machining tools, it is impossible to produce the grooved complex geometric structure that standard end mills generally have. In contrast, the intermediate end mill has a simple geometric cross-section, as shown in the photo in this article

does the micro tool really cut in the same way as the full-size tool? The answer seems to be yes. The light microscope was used to observe the milling process, showing the chips ejected from the vicinity of the tool. In addition, the electron microscope inspection of the milled parts, which fell by 61% year-on-year, also revealed the traces left by the tool

this sign is even more obvious in turning. Just like the full-size turning tool, sometimes it is found that the medium-sized turning tool still has clusters of chips attached to it after cutting

this photo is a miniature of a phenomenon seen in many workshops. After aluminum processing, a long chip is still attached to the tool

machine tool

the above milling test was carried out on a Boston digital machining center purchased in the 1990s. The resolution of the machine is 1 μ m， Therefore, the micro cutting tool can be positioned relative to the workpiece through "touch" mode - "consumers also hope to make packaging materials from natural materials in the same way that machinists will use when using manual milling machines. That is, the operator keeps moving from micron to micron until something that looks like chips appears (observed through a microscope) , indicating that the tool has been in contact with the part

more milling has recently been carried out on a precision machining center in willemin macodel. Medium processing turning is carried out on a diamond lathe of Moore tool, although the tool material used by Sandia is not diamond. The factory also uses Archie's wire cutting and forming machine tools to process relatively small features through EDM (in order to cover the whole range, laser processing is another field of medium processing research)

some challenges

benavides said that today, medium machining turning is more practical than medium machining milling. For milling, the inability to copy the shape of ordinary end mills is one of the constraints. On the other hand, it is difficult to display the tool in the tool holder small enough to μ M the qualified runout level of the tool

the second is the lack of diamond. Sandia's customers also need to use less than 130 μ A workpiece machined with a milling cutter of M (0.005 inch). For features such as micro external gear teeth, the factory tends to use wire cutting EDM. However, if internal gear teeth are required, intermediate milling may be required

however, the research on various machining methods continues, including milling. In order to solve the problem of tool holder and related runout in milling, Sandia is experimenting with a special spindle that rotates the tool without using a tool holder. The spindle was developed at the University of Florida with a maximum speed of 500000 R/min

medium processing technology minimum feature size and feature tolerance material removal rate

(m/s) material focused ion beam

(for making tools) 200nm

tolerance is 20nm0.5 arbitrary milling or turning 25 m (in some cases, turning is 10 m, tolerance is 2 m) 10400 aluminum, yellow copper, mild steel,

PMMA (a plastic) edm25 m, Tolerance 3 M25 million conductive materials

a more general challenge in processing is to achieve the level of expertise it requires. These cuts are not like macro processes, in which tools, parts and programs can be interchanged between different machine tools. Medium scale cutting requires the operator to understand the accumulation of micro errors under different conditions, and how to affect the accuracy of a specific machine tool through the selection of specific parameters such as speed and feed speed. Mr. Benavides said that for a skilled technician, it takes months of trying to gain this understanding. Because of this understanding, there are constraints on the scope of application of machining. He said that even among Sandia's 50 or 60 skilled technicians, only a few of them have become experts in this kind of processing. (end)