mill_canned.lyx

CNC 的开放码,EMC2 V2.2.8版

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\layout Chapter

Canned Cycles
\begin_inset LatexCommand \index{Canned Cycles}

\end_inset 


\layout Standard


\begin_inset Note
collapsed false

\layout Standard

graphics need to be unsucked and mini pages replaced as it makes the graphics
 too small to read
\end_inset 


\layout Standard

Canned Cycles G81 through G89 have been implemented for milling.
 This section describes how each cycle has been implemented.
 In addition G80 and G98/G99 are considered here because their primary use
 is related to canned cycles.
\layout Standard

All canned cycles are performed with respect to the XY plane.
 With the current 3 axis interpreter, no A, B, C-axis motion is allowed
 during canned cycles.
 Inverse time feed rate is not allowed with cutter radius compensation.
 Each of the canned cycles defines a new machine motion mode.
 As a motion mode, they will stay in effect until replaced by another motion
 G word or by G80 as described below.
\layout Standard

All canned cycles use X, Y, R, and Z values in the NC code.
 These values are used to determine X, Y, R, and Z positions.
 The R (usually meaning retract) position is along the Z-axis.
 Some canned cycles use additional arguments that are listed with the specific
 cycle.
\layout Standard

In absolute distance mode, the X, Y, R, and Z values are absolute positions
 in the current coordinate system.
 In incremental distance mode, X, Y, and R values are treated as increments
 to the current position and Z as an increment from the Z-axis position
 before the move involving Z takes place.
\layout Standard

A repeat feature has been implemented.
 The L word represents the number of repeats.
 If the repeat feature is used, it is normally used in incremental distance
 mode, so that the same sequence of motions is repeated in several equally
 spaced places along a straight line.
 EMC allows L > 1 in absolute distance mode to mean "do the same cycle in
 the same place several times." Omitting the L value is equivalent to specifying
 L=1.
 
\layout Standard

When L>1 in incremental mode, the X and Y positions are determined by adding
 the given X and Y values either to the current X and Y positions (on the
 first go-around) or to the X and Y positions at the end of the previous
 go-around (on the second and successive go-arounds).
 The R and Z positions do not change during the repeats.
\layout Standard

The number of repeats of a canned cycle only works for in the block containing
 L word.
 If you want to repeat a canned cycle using the repeat feature by placing
 a new L word on each line for which you want repeats.
\layout Standard

The height of the retract move at the end of each repeat (called "clear
 Z" in the descriptions below) is determined by the setting of the retract_mode:
 either to the original Z position (if that is above the R position and
 the retract_mode is G98, OLD_Z), or otherwise to the R position.
 (See G98/G99 below)
\layout Section

Preliminary Motion 
\layout Standard

Preliminary motion may be confusing on first read.
 It should come clear as you work through the examples in G80 and G81 below.
 Preliminary motion is a set of motions that is common to all of the milling
 canned cycles.
 These motions are computed at the time the canned cycle block is encountered
 by the interpreter.
 They move the tool into the proper location for the execution of the canned
 cycle itself.
\layout Standard

These motions will be different depending on whether the canned cycle is
 to be executed using absolute distances or incremental distances.
 These motions will also be affected by the initial position of the z axis
 when the canned cycle block is encountered in a program.
\layout Standard

If the current Z position is below the R position, the Z axis is traversed
 to the R position.
 This happens only once, regardless of the value of L.
\layout Standard

In addition, for each repeat as specified by L, one or two moves are made
 before the rest of the cycle: 1.
 a straight traverse parallel to the XY-plane to the given XY-position 2.
 a straight traverse of the Z-axis only to the R position, if it is not
 already at the R position.
\layout Section

G80
\begin_inset LatexCommand \index{G80}

\end_inset 

 
\layout Standard

G80
\begin_inset LatexCommand \index{G80}

\end_inset 

 turns off all motion.
 You should think of it as the off position on a rotary switch where the
 other positions are the different possible motion modes.
 In the EMC interpreter, G80 is one of the modal codes so any other code
 will replace it.
 The result of the following lines of code is the same.
\layout Standard

N1000 G90 G81 X1 Y1 Z1.5 R2.8 (absolute distance canned cycle)
\newline 
N1001 G80 (turn off canned cycle motion)
\newline 
N1002 G0 X0 Y0 Z0 (turn on rapid traverse and move to coordinate home)
\layout Standard

produces the same final position and machine state as 
\layout Standard

N1000 G90 G81 X1 Y1 Z1.5 R2.8 (absolute distance canned cycle) 
\newline 
N1001 G0 X0 Y0 Z0 (turn on rapid traverse and move to coordinate home)
\layout Standard

The advantage of the first set is that, the G80 line clearly turns off the
 G81 canned cycle.
 With the first set of blocks, the programmer must turn motion back on with
 G0, as is done in the next line, or any other motion mode G word.
 
\layout Standard

Example 1 - Use of a canned cycle as a modal motion code 
\layout Standard

If a canned cycle is not turned off with G80 or another motion word, the
 canned cycle will attempt to repeat itself using the next block of code
 that contains an X, Y, or Z word.
 The following file drills (G81) a set of eight holes as shown.
 (note the z position change after the first four holes.) 
\layout Standard


\begin_inset Minipage
position 0
inner_position 0
height "0pt"
width "60col%"
collapsed false

\layout Standard
\align left 
N100 G90 G0 X0 Y0 Z0 (coordinate home) 
\newline 
N110 G1 X0 G4 P0.1 
\newline 
N120 G81 X1 Y0 Z0 R1 (canned drill cycle) 
\newline 
N130 X2 
\newline 
N140 X3 
\newline 
N150 X4 
\newline 
N160 Y1 Z0.5 
\newline 
N170 X3 
\newline 
N180 X2 
\newline 
N190 X1 
\newline 
N200 G80 (turn off canned cycle) 
\newline 
N210 G0 X0 (rapid home moves) 
\newline 
N220 Y0 
\newline 
N220 Z0 
\newline 
N220 M2 (program end)
\end_inset 


\hfill 

\begin_inset Minipage
position 0
inner_position 0
height "0pt"
width "50col%"
collapsed false

\layout Standard
\added_space_top 0.3cm \added_space_bottom 0.3cm 

\begin_inset Graphics
	filename G81mult.png
	width 2.5in

\end_inset 


\end_inset 


\layout Standard

The use of G80 in line n200 is optional because the G0 on the next line
 will turn off the G81 cycle.
 But using the G80.
 as example 1 shows, will provide for an easily readable canned cycle.
 Without it, it is not so obvious that all of the blocks between N120 and
 N200 belong to the canned cycle.
\layout Standard

If you use G80 and do not set another modal motion code soon after, you
 may get one of the following error messages.
\layout Quote


\family typewriter 
\size footnotesize 
Cannot use axis commands with G80
\newline 
Coordinate setting given with G80
\layout Standard

These should serve as a reminder that you need to write in a new motion
 word.
\layout Section

G81
\begin_inset LatexCommand \index{G81}

\end_inset 


\layout Standard

The G81 cycle is intended for drilling.
\layout Standard

0.
 Preliminary motion, as described above.
\layout Standard

1.
 Move the Z-axis only at the current feed rate to the Z position.
\layout Standard

2.
 Retract the Z-axis at traverse rate to clear Z.
 This cycle was used in the description of G80 above but is explained in
 detail here.
\layout Standard

Example 2 - Absolute Position G81
\layout Standard

Suppose the current position is (1, 2, 3) and the following line of NC code
 is interpreted.
\layout Standard

G90 G81 G98 X4 Y5 Z1.5 R2.8
\layout Standard

This calls for absolute distance mode (G90) and OLD_Z retract mode (G98)
 and calls for the G81 drilling cycle to be performed once.
 The X value and X position are 4.
 The Y value and Y position are 5.
 The Z value and Z position are 1.5.
 The R value and clear Z are 2.8.
 OLD_Z is 3.
 
\layout Standard

The following moves take place.
 
\layout Standard

1.
 a traverse parallel to the XY plane to (4,5,3) 
\layout Standard

2.
 a traverse parallel to the Z-axis to (4,5,2.8).
 
\layout Standard

3.
 a feed parallel to the Z-axis to (4,5,1.5) 
\layout Standard

4.
 a traverse parallel to the Z-axis to (4,5,3)
\layout Standard
\added_space_top 0.3cm \added_space_bottom 0.3cm \align center 

\begin_inset Graphics
	filename G81ex1.png

\end_inset 


\layout Standard

Example 2 - Absolute Position G81
\layout Standard

Suppose the current position is (1, 2, 3) and the following line of NC code
 is interpreted.
 
\layout Standard

G91 G81 G98 X4 Y5 Z-0.6 R1.8 L3 
\layout Standard

This calls for incremental distance mode (G91) and OLD_Z retract mode (G98).
 It also calls for the G81 drilling cycle to be repeated three times.
 The X value is 4, the Y value is 5, the Z value is -0.6 and the R value
 is 1.8.
 The initial X position is 5 (=1+4), the initial Y position is 7 (=2+5),
 the clear Z position is 4.8 (=1.8+3), and the Z position is 4.2 (=4.8-0.6).
 OLD_Z is 3.
\layout Standard

The first preliminary move is a traverse along the Z axis to (1,2,4.8), since
 OLD_Z < clear Z.
\layout Standard

The first repeat consists of 3 moves.
\layout Standard

1.
 a traverse parallel to the XY-plane to (5,7,4.8)
\layout Standard

2.
 a feed parallel to the Z-axis to (5,7, 4.2)
\layout Standard

3.
 a traverse parallel to the Z-axis to (5,7,4.8) The second repeat consists
 of 3 moves.
 The X position is reset to 9 (=5+4) and the Y position to 12 (=7+5).
\layout Standard

1.
 a traverse parallel to the XY-plane to (9,12,4.8)
\layout Standard

2.
 a feed parallel to the Z-axis to (9,12, 4.2)
\layout Standard

3.
 a traverse parallel to the Z-axis to (9,12,4.8) The third repeat consists
 of 3 moves.
 The X position is reset to 13 (=9+4) and the Y position to 17 (=12+5).
\layout Standard

1.
 a traverse parallel to the XY-plane to (13,17,4.8)
\layout Standard

2.
 a feed parallel to the Z-axis to (13,17, 4.2)
\layout Standard

3.
 a traverse parallel to the Z-axis to (13,17,4.8)
\layout Standard
\added_space_top 0.3cm \added_space_bottom 0.3cm \align center 

\begin_inset Graphics
	filename G81ex2.png

\end_inset 


\layout Standard

Example 3 - Relative Position G81
\layout Standard

Now suppose that you execute the first g81 block of code but from (0, 0,
 0) rather than from (1, 2, 3).
 
\layout Standard

G90 G81 G98 X4 Y5 Z1.5 R2.8 Since OLD_Z is below the R value, it adds nothing
 for the motion but since the initial value of Z is less than the value
 specified in R, there will be an initial Z move during the preliminary
 moves.
 
\layout Standard
\added_space_top 0.3cm \added_space_bottom 0.3cm \align center 

\begin_inset Graphics
	filename G81.png

\end_inset 


\layout Standard

Example 4 - Absolute G81 R > Z
\layout Standard

This is a plot of the path of motion for the second g81 block of code.
\layout Standard

G91 G81 G98 X4 Y5 Z-0.6 R1.8 L3 
\layout Standard

Since this plot starts with (0, 0, 0), the interpreter adds the initial
 Z 0 and R 1.8 and rapids to that location.
 After that initial z move, the repeat feature works the same as it did
 in example 3 with the final z depth being 0.6 below the R value.
\layout Standard
\added_space_top 0.3cm \added_space_bottom 0.3cm \align center 

\begin_inset Graphics
	filename G81a.png

\end_inset 


\layout Standard

Example 5 - Relative position R > Z
\layout Section

G82
\begin_inset LatexCommand \index{G82}

\end_inset 


\layout Standard

The G82 cycle is intended for drilling.
\layout Standard

0.
 Preliminary motion, as described above.
\layout Standard

1.
 Move the Z-axis only at the current feed rate to the Z position.
\layout Standard

2.
 Dwell for the given number of seconds.
\layout Standard

3.
 Retract the Z-axis at traverse rate to clear Z.
 The motion of a G82 canned cycle looks just like g81 with the addition
 of a dwell at the bottom of the Z move.
 The length of the dwell is specified by a p# word in the g82 block.
\layout Standard

G90 G82 G98 X4 Y5 Z1.5 R2.8 P2
\layout Standard

Would be equivalent to example 2 above with a dwell added at the bottom
 of the hole.
\layout Section

G83
\begin_inset LatexCommand \index{G83}

\end_inset 


\layout Standard

The G83 cycle is intended for deep drilling or milling with chip breaking.
 The dwell in this cycle causes any long stringers (which are common when
 drilling in aluminum) to be cut off.
 This cycle takes a Q value which represents a "delta" increment along the
 Z-axis.
 Machinists often refer to this as peck drilling.
 
\layout Standard

0.
 Preliminary motion, as described above.
 
\layout Standard

1.
 Move the Z-axis only at the current feed rate downward by delta or to the
 Z position, whichever is less deep.
 
\layout Standard

2.
 Dwell for 0.25 second.
 
\layout Standard

3.
 Retract at traverse rate to clear Z 
\layout Standard

4.
 Repeat steps 1 - 3 until the Z position is reached.
 
\layout Standard

5.
 Retract the Z-axis at traverse rate to clear Z.
\layout Standard

NIST lists the elements of the command as G83 X- Y- Z- A- B- C- R- L- Q-
 
\layout Standard

I find this command very handy for many of my deep drilling projects.
 I have not tried to use the L for a repeat so can't say much about that
 feature.
 A typical g83 line that I would write might look like G83 X0.285 Y0.00 Z-0.500
 R0.2 L1 Q0.05.
 EMC moves to position X0.285 Y0.00 at the z height before the block.
 It then pecks its way down to Z-0.500.
 Each peck pulls the drill tip up to R0.2 after moving Q0.05.
\layout Section

G84
\begin_inset LatexCommand \index{G84}

\end_inset 


\layout Standard

The G84 cycle is intended for right-hand tapping.
\layout Standard

0.
 Preliminary motion, as described above.
\layout Standard

1.
 Start speed-feed synchronization.
\layout Standard

2.
 Move the Z-axis only at the current feed rate to the Z position.
\layout Standard

3.
 Stop the spindle.
\layout Standard

4.
 Start the spindle counterclockwise.
\layout Standard

5.
 Retract the Z-axis at the current feed rate to clear Z.
\layout Standard

6.
 If speed-feed synch was not on before the cycle started, stop it.
\layout Standard

7.
 Stop the spindle.
\layout Standard

8.
 Start the spindle clockwise.
\layout Section

G85
\begin_inset LatexCommand \index{G85}

\end_inset 


\layout Standard

The G85 cycle is intended for boring or reaming.
 
\layout Standard

0.
 Preliminary motion, as described above.
 
\layout Standard

1.
 Move the Z-axis only at the current feed rate to the Z position.
 
\layout Standard

2.
 Retract the Z-axis at the current feed rate to clear Z.
 This motion is very similar to g81 except that the tool is retracted from
 the hole at feed rate rather than rapid.
\layout Section

G86
\begin_inset LatexCommand \index{G86}

\end_inset 


\layout Standard

The G86 cycle is intended for boring.
 
\layout Standard

0.
 Preliminary motion, as described above.
 
\layout Standard

1.
 Move the Z-axis only at the current feed rate to the Z position.
 
\layout Standard

2.