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1、Figure 9-12 Tool-nose radius compensation allows us toprogram the part, not the tool path. The mathematical calculations that are needed to program a part profile with angles and radii, without the aid of cutter diameter compensation, can be very involved.on a turning center. When we set the X and Z
2、 axes of the tool, we create a square point on the tool. Most of the tools we use for turning have radii. To compensate for the radii, we need to use TNR compensation, which saves us from having to mathematically calculate the cutter path (see Figure 9-12).TNR compensation also lets us use the same
3、program for a variety of tool types. With TNR compensation capabilities, the insert radius size can be ignored and the part profile can be programmed. The exact size of the cutting tool to be used is entered into the offset file, and when the offset is called, the tool path will automatically be off
4、set by the tool radius.Tool-nose radius compensation can be to the right or left of the part profile.To determine which offset you need, imagine yourself walking behind the cutting tool. Do you want the tool to the left of the programmed path or to the right (see Figure 9-13)? Figure 9-13 Tool-nose
5、compensation.Compensation direction is controlled by a G-code. When a compensation to the left is desired, a G41 is used. When a compensation to the right is needed,a G42 is used. When using these cutter compensation codes, you need to specify how much the controller is to offset. The size of the ra
6、dius is placed in the nose radius offset table, which is typically located adjacent to the tool file under the tool number being used. Tool-nose radius information can be determined from catalogs or the insert package.Other information needed to insure proper compensation is the tool nose direction
7、vector. The tool tip or imaginary tool tip of turning tools has a specificlocation or direction from the center of the tool-nose radius. The tool nose vector tells the control which direction it must compensate for individual types of tools.Standard tool-nose direction vectors are shown in Figure 14
8、. The direction vector number is usually placed in the same tool offset table as the radius value. Figure 9-14 Tool-nose radius direction vectors.To invoke compensation, the programmer will have to make a machine move (ramp on). This move allows the control to evaluate its present position and make
9、the necessary adjustment from tool-edge positioning to tool-nose radius positioning. This adjustment move must be greater than the radius value of the tool. To cancel the cutter compensation and return to cutter-edge programming, the programmer must make a linear move (ramp off) to invoke a cutter c
10、ompensation cancellation (G40).Figure 9-15 illustrates a typical part that uses tool-nose radius compensation.The program for the part follows the figure. N0001 G90 G20; N0005 G40; N0010 T0101; N0015 G92 X5.800 Z10.250; N0020 G96 S400 M03; N0025 GOO G42 Xl .30 Z.100; (Rapid position ramp on move and
11、 TNR compensation to the right) N0035 GOO X.375; (Profile of the part) N0045 G01 Z0.0 F.01; (Profile of the part) N0050 G01 X.500 Z-.0625; (Profile of the part) N0055 G01 Z-1.00; (Profile of the part) N0060 G02 Xl .00 Z-1.25 1.25 K0.0; (Profile of the part) N0065 G01 X1.25; (Profile of the part)N007
12、0 G40 G00 X2.0 Z2.0; (TNR compensation cancel and rapid positionramp off move)N0075 G28;N0080 T0100;N0085 M30; Figure 9-15 Program that utilizes tool-nose radius compensation.CANNED CYCLES FOR TURNING CENTERSCanned cycles (fixed) cycles are used to simplify the programming of repetitive turning oper
13、ations, such as rough turning, threading, and grooving. Canned cycles are sets of preprogrammed instructions that eliminate the need for many lines of programming. Programming a simple part without the use of a canned cycle can take up to four or five times the number of lines needed for a part prog
14、rammed with canned cycles. Think of the lines that are needed to produce a thread: (1) position the X and Z axes to the proper coordinates with a rapid traverse move (G00), (2) position the tool for the proper lead angle, (3) feed the tool across, (4) rapid position the tool back to the clearance pl
15、an, (5) feed the tool across. That is only two threading passes. With a canned threading cycle, a thread can be done with one line of programming. Standard canned cycles, or fixed cycles, are common to most CNC machines. See Figure 9-4 for a general list of the most commonly used canned cycles for t
16、urning centers. ROUGHING OR TURNING CYCLE (G71)The G71 automatically takes roughing passes to turn down a workpiece to a specific diameter at a specified depth of cut. The G71 cycle reads a specified number of blocks to determine the part profile and determines each pass, the depth of cut for each p
17、ass, and the number of repeat passes for the cycle. Cutting is accomplished through parallel moves of the tool in the Z axis direction. A certain procedure needs to be followed when using canned cycles. In the first procedure, the tool needs to be positioned to the rough stock boundaries.This proced
18、ure has a two-fold purpose: it tells the control how big the stock is, and it creates a Z clearance position that the tool rapids back to on each pass.The G71 uses letters to give the controller information on the part profile, the amount of stock we are going to leave for finishing, the depth of cu
19、t, and the feed rate. A G71 roughing cycle command follows. N0010 G71 P40 Q85 U.03 W.010 D750 F.012;G71 is the roughing cycle call.P40 is the block or line number that designates the start of the part profile.Q85 is the block or line number that designates the end of the part profile.U.03 tells the
20、controller that we want to leave .03 of an inch stock on the X axis of the profile for finishing.W.O1 tells the controller that we want to leave .01 of an inch stock on the Z axis of the profile for finishing.D750 tells the controller we want to take .0750 of an inch per pass per side depth of cut.
21、Notice that the decimal point was left off. No decimal point input is possible for depth of cut. When the D is commanded the controller reads from the right and decides what the depth of cut will be. Each number in each decimal position gets a value. If we wanted to take .0500 depth of cut per side,
22、 we would write it as D500. The first zero from the right has 0 tenths of a thousandths value. The next zero from the right has 0 thousandths of an inch value. The 5 in the third position from the right has 5 ten-thousandths of an inch value or 50 thousandths of an inch.F.O12 is the feed rate of the
23、 roughing passes.Next we take the example program from Figure 9-15 and convert it to a program that utilizes a roughing canned cycle (see Figure 16). We will eliminate the TNR compensation just for ease of understanding.N0001 Gg0 G20;N0005 G40;N0010 T0101;N0015 G92 X5,800 Z10.2.50;N0020 G96 S400 M03
24、;N0025 GOO Xl .30 Z.100; (Rapid position that indicates to the controllerour stock size and Z clearance point)N0030 G71 P35 Q65 U.03 W.01 D600 R010; (Canned roughing cycle call)N0035 GOO X.375; (Profile of the part)N0045 G01 Z0.0 1:.01; (Profile of the part)N0050 G01 X,500 Z-.0625; (Profile of the p
25、art)N0055 G01 Z-1.00; (Profile of the part)N0060 G02 Xl .00 Z-1.25 1.25 KO.O; (Profile of the part)N0065 G01 X1.25; (Profile of the part)N0070 GOO X2.0 Z2.0;N0075 G28;N0080 T0100;N0085 M30;Figure 9-16 Roughing cycle exampleFINISHING CYCLE (G70)The G70 command calculates the finish part profile, then
26、 executes a finish pass on the part. The finishing cycle is called with a G70, followed by a letter address P for the start line of the finish part profile and the letter address Q for the end line of the part profile. A finishing feed rate can also be included in this block. When the finish cycle i
27、s commanded, it reads the program blocks designated by the P and Q and formulates a finishing cycle. As in the roughing cycle, the tool needs to be positioned to a Z clearance plane or stock boundary prior to the calling of the G70 finishing cycle. Next we will finishthe program shown in Figure 9-15
28、.N0001 G90 G20;N0005 G40;N0010 T0101;N0015 G92 X5.800 Z10.250;N0020 G96 S400 M03;N0025 GOO X1.30 Z.100; (Rapid position that indicates to the controllerour stock size and Z clearance point)N0030 G71 P35 Q65 U,03 W.01 D600 F.010; (Canned roughing cycle call)N0035 GOO X,375; (Profile of the part)N0045
29、 G01 Z0.0 1:,01; (Profile of the part)N0050 G01 X.S00 Z-.0625; (Profile of the part)N0055 G01 Z-1.00; (Profile of the part)N0060 G02 Xl .00 Z-1,25 1.25 KO.O; (Profile of the part)N0065 G01 1.25; (Profile of the part)N0070 GOO X2.0 Z2.0;PECK DRILLING CYCLE (G74)The G74 peck drilling cycle will peck d
30、rill holes with automatic retract and incremental depth of cut. The G74 command relays to the controller the incremental depth of cut, the full depth of the hole, and the feed rate through the command variables K, Z, and E The next command shows the proper format for peck drilling. N0010 G74 X0.0 Z-
31、1 25 K.125 F.010;G74 is the peck drill cycle call.X0.0 is the center of the workpiece (X is always zero).Z-1.25 is the full depth of the drilled hole.K.125 is the depth of each peck.F.01 is the drilling feed rate.The drill must be positioned to a clearance plane in the Z axis and also to X0.0 prior
32、to the calling of the G74 peck drilling cycle. The spindle should also be reprogrammed for direct RPM input using a G97 when drilling. Examine the sample peck drilling cycle in Figure 9-17. N0001 Gg0 G20; N0005 G40; N0010 T0606; (Tool #6, .500 diameter drill) N0015 G92 X5.800 Z10.250; N0020 G97 S800
33、 M03; (RPM 800) N0025 GOO X0.0 Z.200; (Rapid position the drill to the center of the stock and .200 of an inch in front of the work face) N00B0 G74 X0.0 Z-1.25 F0.01 K.125; (Peck drilling cycle call) N0035 G28 Z1.00; (Return to home through Z1.00) N0040 T0600; N0045 M30;Figure 9-17 Peck drilling cyc
34、le.GROOVING CYCLE (G75)The grooving cycle is used to cut grooves of varying widths automatically. To use the grooving cycle, the tool must be positioned to the start of the groove prior to calling the grooving cycle. Through a series of letter addresses, the controller can be commanded to cut a groo
35、ve of varying width and depth.The next example shows the proper format for the grooving cycle. NO010 G7S X.750 Z-.S0 FO.125 DO 1.125 K.125;G75 is the grooving cycle call.X.750 is the diameter at the bottom of the groove.Z-.50 is the end position of the groove.F0.125 is the incremental retract of the
36、 grooving tool.I is the depth of cut on the X axis.K is the depth of cut on the Z axis.The controller looks at the position of the tool prior to the calling of the grooving cycle and uses that information to establish the groove width and depth positions. The programmer, when positioning the groovin
37、g tool, will have to take into consideration which corner of the tool is the leading edge. She/he may have to make adjustments for the width of the tool. Note that the last feed rate that was active prior to the grooving cycle will be the grooving feed rate. It is not possible to express a feed rate
38、 within a grooving cycle. Take a look at a sample grooving cycle in Figure 9-18.Figure 9-18 This figure shows a part that would be appropriate for a G75 grooving cycle. N0001 G90 G20; N0005 G40; N0010 T0505; (Tool #5, .125 wide grooving tool) N0015 G92 X5.800 Z10.250; N0020 G96 S200 M03; N0025 GOO X
39、l .250 Z-1.125; (Rapid position that indicates to the controller our stock diameter at the groove location and the Z position of the start of the groove) N0030 G75 X.750 Z-1.375 F0.125 1.125 K.125; (Grooving cycle call) N0035 G28 X2.00 (Return to home through X2.00) N0040 T0500; N0045 M30;The groovi
40、ng cycle is primarily used to cut a groove that is wider than the tool. If the groove is the same width as the tool it may be just as easy to program the groove in linear blocks.THREAD-CUTTING CYCLE (G76)The G76 thread-cutting cycle can cut multi-pass threads with one block of information. By using
41、several letter address parameters, the control will automatically calculate the correct number of cut passes, depth of cut for each pass, and the starting point for each pass. To use the G76 thread-cutting canned cycle, the following commands need to be programmed: N00010 G76 X.712 Z-1.125 10.0 K.07
42、6 D0.012 E0147 A60;X.712 is the minor diameter of the thread.Z-1.125 is the absolute Z position of the end of the thread.10.0 is the radial difference between the thread starting point and the thread ending point. The I is used for cutting tapered threads. For cutting straight threads a zero should
43、be programmed.K.076 is the thread height expressed as a radius value (i.e., major diameter minor diameter divided by 2).D0.012 is the depth of cut for the first pass (in a radius value). Note: Every pass after the first pass will be decreasing in depth.F is the thread lead (i.e., 1 divided by the nu
44、mber of threads per inch). Note: The F can sometimes be substituted with E.A is the included angle of the thread.Prior to calling the G76 thread-cutting cycle, the tool must be positioned to the major diameter of the thread. The tool should also be positioned in front of the thread Z axis start posi
45、tion by a distance of at least double the thread lead. This insures that the proper lead will be cut throughout the length of the thread. The spindle should be running in direct RPM (G97), not constant surface footage control. Consider the sample G76 thread-cutting cycle in Figure 9-19. N0001 G90 G2
46、0; N000S G40; N0010 T0505; (Tool/45, 60-degree threading tool) N0015 G92 X5.800 Z10.250; N0020 G97 5300 M03; (Direct RPM input)N0030 GOO Z.200; (Z axis rapid position in front of the thread start point).N0040 GOO ;(1.00; (X axis rapid position to major thread diameter)NO050 G76 X.897 Z-t .25 K.051 D
47、120 F. 0833 A60; (Threading cycle)N0060 G28; (Return home)N0070 T0500;NO080 M30;Figure 9-19 This part would be appropriatefor a G76 thread-cutting cycle.Now that we have an understanding of canned cycles and how they are used,we need to put our knowledge to work. After the chapter questions there are some part prints. Use the part prints and the tool table shown in Figure 9-20 to program these parts. The programs should include canned cycles and tool-nose radius compensation where appropriate.Part #1 Written by: Kellv Curran Machine: Mazak Q10N Date 07/03/95 Sheet 1 of 1