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CNC Technology

ELECTROCHEMICAL MACHINING AND ELECTROCHEMICAL DEBURRING

Electrochemical machining (ECM) is essentially a reverse metal-plating process (Figure M-112). The process takes place in a conducting fluid or electrolyte pumped under pressure between electrode and workpiece. As workpiece material is deplated, it is flushed away by the flow of electrolyte. Workpiece material is removed from the electrolyte by a filtration system. Advantages and …

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ELECTROLYTIC GRINDING

In the process of electrolytic grinding (ELG), an abrasive wheel much like a standard grinding wheel is used. The abrasive wheel bond is metal, thus making it a conducting Wheel-cathode medium. The abrasive grains in the grinding wheel are nonconducting and aid in removing oxides from the workpiece while helping maintain the gap between wheel and work. ELG,like ECM, is a deplating …

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CUTTING TOOLS IN HIGH-SPEED MACHINING

Metal removal rates are faster today than ever before. What was considered high-speed machining a few years ago is now regarded as conventional. Two major factors in high-speed machining are sfpm (surface feet per minute) for the machine tool and ipt (inches per tooth) or inches per revolution for the cutting tool.For heavy metal removal, …

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TOOL COATINGS

Tool coatings are applied by the use of chemical vapor deposition (CVD) or physical vapor deposition (PVD). Each coating process has distinct advantages in the proper application.Tool coatings are useful because of their high hardness and low coefficient of friction. Coatings improve tool performance whether the substrate is HSS or carbide.CVD coatings are produced in a high-temperature ( ) process. …

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TOOL MATERIALS

To select the most appropriate tool for a machining operation, an understanding of tool materials is critical. The following outline provides a generic look at tool materials. Each tool manufacturer has a complete description and application guidelines for their specific grades. Always follow these recommendations. HSS HSS steels, used mostly for drills and reamers, can be used on …

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OPERATING THE CNC MACHINE TOOL

Manual Data Input Manual data input, or MDI, as its name implies, is the mode in which program data may initially be entered using the CNC’s keyboard. MDI mode also allows for editing or deletingn existing program data. A complete block or complete program may be entered and run in MDI mode. However, once the data are …

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SINGLE-POINT THREADING

One of the considerations in threading is the lead-in and ending of a thread (Figure M-69). When the threading operation begins, the spindle is rotating at the correct spindle speed, but the tool is not moving. Distance A, or at least part of it, is traveled while the feed rate is accelerating from zero to a …

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TURNING CENTER PROGRAMMING

Turning center or lathe programming follows much the same techniques as those used for machining center programming. A part drawing must be studied to determine the sequence of machining operations and the cutting tools required. The programmer must be familiar with the material being machined to select appropriate feeds and speeds. Once again, as in milling, programming should be …

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GENERAL PROGRAMMING TECHNIQUE

There are no hard-and-fast rules for CNC programming. Ten different machinist programmers will probably come up with 10 variations in developing a program for the same part. Your experience in manual machining will provide the basis for developing a CNC program, and like all things, your programs, at least early on, will go through …

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INCREMENTAL POSITIONING DIMENSIONS—G91 MODE

In incremental mode, each programmed motion is independently measured from the previous point (Figure M-35). For example, the drawing shows a four-hole pattern with each feature dimensioned relative to the other features. If the part were to be drilled starting from the setup point indicated, each tool positioning move would be an increment equal to the drawing dimensions. Positioning from the …

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