tailieunhanh - COMPUTER NUMERICAL CONTROL PROGRAMMING BASICS phần 4

Xoắn ốc, parabol, và nội suy khối được sử dụng bởi các ngành công nghiệp sản xuất các bộ phận có hình dạng phức tạp, chẳng hạn như các bộ phận hàng không vũ trụ và chết cho các cơ quan xe hơi. tuyến tính nội suy Nội suy tuyến tính bao gồm của bất kỳ điểm chương trình liên kết với nhau bởi các đường thẳng, cho dù các điểm gần nhau hoặc cách xa nhau (Hình 11). | TOOL CHANGE POSITION ZERO FOR MOVE ZERO FOR MOVE TO HOLE 2 TO HOLE 3 Fig. 21 In incremental programming all dimensions are taken from the previous point. Kelmar Associates In incremental positioning the work coordinates change because each location is the zero point for the move to the next location Fig. 21. On some parts it may be desirable to change from absolute to incremental or vice versa at certain points in the job. Inserting the G90 absolute or the G91 incremental command into the program at the point where the change is to be made can do this. R Plane or Gage Height The word-address letter R refers to a partial retraction point in the Z axis to which the end of the cutter retracts above the work surface to allow safe table movement in the X Y axes. It is often called the rapid-traverse distance gage height retract or work plane. The R distance is a specific height or distance above the work surface and is generally .100 in. above the highest surface of the workpiece Fig. 22 which is also known as gage height. Some manufacturers build a gage height distance of .100 in. into the MCU machine control unit and whenever the feed motion in the Z axis is called for .100 in. will automatically be added to the depth programmed. When setting up cutting tools the operator generally places a .100 in. thick gage on top of the highest surface of the workpiece. Each tool is lowered until it just touches the gage surface and then its 27 length is recorded on the tool list. Once the gage height has been set it is not generally necessary to add the .100 in. to any future depth dimensions since most MCUs do this automatically. Fig. 22 Using a .100 in. gage block to set the gage height or R0 on the work surface. Kelmar Associates Cutter Diameter Compensation Cutter diameter compensation CDC changes a milling cutter s programmed centerline path to compensate for small differences in cutter diameter. On most MCUs it is effective for most cuts made using either linear or circular