The CUTCOM Command [MLEPC]

The CUTCOM command is used to compensate at the machine for tool length, tool wear and fixture alignment.[1] This command is valid for all machine types, but some functions may not be available on specific machines.

The following CUTCOM command functions are available:

Length Compensation

Length compensation is used to compensate for differences between the expected and actual tool length. This capability is available for lathes and for mills having a Z axis. Length compensation can also be controlled when loading the tool.

\textbf{CUTCOM / ON},\;\textbf{LENGTH} \;\big[ , \mathit{offset} \,\big] \begin{bmatrix} ,\! \begin{array}{l} \textbf{POSX} \\ \textbf{POSY} \\ \textbf{POSZ} \\ \textbf{NEGX} \\ \textbf{NEGY} \\ \textbf{NEGZ} \\ \textbf{XYZ} \end{array} \, \end{bmatrix} \begin{bmatrix} ,\! \begin{array}{l} \textbf{NOW} \\ \textbf{NEXT} \end{array} \, \end{bmatrix} \; \big[ , \textbf{RTCP} , \mathit{type} \,\big]

\textbf{CUTCOM / OFF},\;\textbf{LENGTH} \begin{bmatrix} ,\! \begin{array}{l} \textbf{NOW} \\ \textbf{NEXT} \end{array} \, \end{bmatrix}

The LENGTH keyword is always required when controlling the application of length compensation. ON is used to enable compensation, OFF is used to disable it.

The offset value specifies the compensation switch number to use to control the amount of length compensation. If omitted, the last value specified for the current tool will be reused. If a length compensation value has yet to be defined for a tool, a default may be used, depending on QUEST settings. Not all machines support this capability.

The keywords, POSXYZ, NEGXYZ and XYZ define the direction of compensation. GENER assumes compensation is along the positive Z axis (POSZ) for all machine types except those with rotary heads, in which case GENER assumes compensation is along the tool axis (XYZ). Not all machines support the ability to define the direction of compensation.

The keywords NOW and NEXT control the deferring of length compensation. The keyword NOW causes the NC control codes to be output immediately; NEXT causes these codes to be deferred until there is a motion in the Z axis. If omitted, the default action specified in QUEST will be used.

The RTCP keyword couplet defines the tool length compensation type on machines where there are multiple length compensation types defined. If omitted, the last type specified will be used. Type 1 (the default) is the standard length compensation supported by all machines. Types 2 through 4 are defined by the post-processor developer and include various RTCP settings. The $TCLSET macro variable indicates and can change the default type.

Diameter Compensation

Diameter compensation is used to compensate for differences between the expected and actual cutting tool diameter.

\textbf{CUTCOM /} \begin{pmatrix}\begin{array}{l} \textbf{LEFT} \\ \textbf{RIGHT} \end{array}\end{pmatrix} \begin{bmatrix} ,\! \begin{array}{l} \textbf{XYPLAN} \\ \textbf{YZPLAN} \\ \textbf{ZXPLAN} \\ \textbf{XYZ} \end{array} \, \end{bmatrix} \; \big[ ,\textbf{OSETNO} ,\mathit{offset} \,\big]

\textbf{CUTCOM /} \begin{pmatrix} \begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array} \end{pmatrix}

Cutter diameter compensation can be applied to the right or left of the tool or wire in the direction of motion, generally using G41 and G42 codes. The first time diameter compensation is used, RIGHT or LEFT must be specified. Thereafter, ON can be specified to reinstate the last mode. OFF is used to disable diameter compensation, generally using a G40 code.

For machines having X, Y and Z axes, diameter compensation can be applied in different planes. If a plane is not specified then the ZXPLAN is assumed for lathes; the XYPLAN is assumed for all other machine types. The XYZ option activates 3D diameter compensation.

The offset value specifies the compensation switch number to use to control the amount of diameter compensation. If omitted, the last value specified will be reused. Not all machines support this capability.

Diameter Compensation Cornering

Some machines require that the diameter compensation outside corner interpolation strategy be explicitly defined via G codes. The following command can be used to select the required interpolation type, if required by the machine.

\textbf{CUTCOM / CORNER}, \begin{pmatrix} \begin{array}{l} \textbf{LINEAR} \\ \textbf{CIRCUL} \end{array} \end{pmatrix}

The LINEAR keyword selects straight line interpolation of outside corners. This can result in long non-cutting motions on acute angle corners

The CIRCUL keyword selects corner rounding, which joins the two edges using circular interpolation. This can result in slightly rounded instead of sharp edges at the part surface.

Most machines handle outside corner interpolation by automatically switching between the these two methods based on the corner angle. The CUTCOM/CORNER command has no effect on machines that automatically handle corner interpolation.

Diameter Compensation Offset

The diameter offset capability enables the user to modify the final tool path by a given amount. Thus, an offset applied by the CAM system can be removed by the post-processor. This command must be coded before diameter compensation is activated. The compensation distance cannot be changed once diameter compensation is active. The syntax is as follows:

\textbf{CUTCOM / TRANSL}, \begin{pmatrix} \begin{array}{l} \textbf{ON} \\ \textbf{OFF} \\ \textbf{AUTO} \\ \mathit{dist} \end{array}\end{pmatrix} \begin{bmatrix} ,\! \begin{array}{l} \textbf{ROUGH} \big[ ,\mathit{angle} \,\big] \\ \textbf{FINCUT} \end{array} \, \end{bmatrix}

The ON and OFF keywords enables or disables this feature. The AUTO keyword specifies that the offset value will be determined from the DIAMET couplet in the LOAD/TOOL command. If the DIAMET couplet is not used, the last cutter value is applied. You must always establish a CUTTER diameter before using the AUTO option. Each LOAD/TOOL command causes the offset value to be changed. The offset value is taken from the CUTTER command only if the DIAMET value is not used. In this case, the CUTTER command must appear before the first GOTO following a LOAD/TOOL command.

The CUTCOM/TRANSL,dist specifies that the value coded will be applied rather than using the cutter diameter. When diameter compensation is turned off, the above feature is also turned off. When diameter compensation is reestablished, so is the above feature.

The FINCUT keyword specifies that when offsetting inside corners, GENER should output a circular arc representing the curved surface. It also restricts the size of the tool that can be used in the machine to be no larger than the offset amount. This is the default. It also ensures that the finish geometry is respected.

The ROUGH keyword does not use arcs to represent inside corners, outputting instead a motion to the intersection point. This permits larger tools to be used during roughing. By default, a change in direction of 170 degrees or larger will be represented using a circular arc. This default can be changed by specifying a different angle following the ROUGH keyword.

Diameter Compensation Filleting

The CUTCOM command can also be used to insert fillets between non tangential moves while in diameter compensation. Filleting inserts tangential circular and helical moves between other CL moves while in diameter compensation. The inserted fillets (circles or helices), are always in the plane of the compensation. If the inserted fillet end points are in different planes, then the generated move is a helical interpolation, otherwise it is circular. Filleting also considers whether the corner is an inner or an outer corner.

\textbf{CUTCOM / ROUND}, \, \mathit{radius} \; {\small \sim} \! \big[ ,\mathit{angle,radius} \,\big]

\textbf{CUTCOM / ROUND } {\small \sim} \! \begin{pmatrix} , \begin{pmatrix}\begin{array}{l} \textbf{IN} \\ \textbf{OUT} \end{array}\end{pmatrix} ,\mathit{radius} \; {\small \sim} \! \big[ ,\mathit{angle,radius} \,\big] \end{pmatrix}

\textbf{CUTCOM / ROUND}, \begin{pmatrix} \begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array} \end{pmatrix}

Where: radius is the required radius of the inserted fillets and angle is the calculated angle of progression between the move vectors, projected in the plane of compensation. Multiple “angle, radius” pairs can be specified, to vary the size of the fillet based on the discontinuity angle. For example:

CUTCOM/ROUND,0,10,.5,45,.75,90,1.0,120,0

In this case, GENER will insert fillets only if the deviation angle between moves is larger or equal to 10 and less than 120. If angle is GE 10 and LT 45, then the fillet radius is 0.5. If angle is GE 45 and LT 90, then the fillet radius is 0.75. If angle is GE 90 and LE 120, then the fillet radius is 1.

The IN and OUT modifiers limit the filleting to moves that will generate inside fillets or outside fillets only. OFF will stop the occurrence of filleting. ON will restart filleting on all upcoming diameter compensation moves, using the last ROUND parameters set.

If the fillet end point goes beyond the existing move, an error message is output and no filleting is attempted.

3D Tool Compensation

3D tool compensation is used to compensate for changes in cutting tool geometry, typically when using ball or bull nosed milling tools. When 3D compensation is active, the post-processor includes the surface normal at the tool contact point in the motion data that it outputs. This additional information is used by the 3D compensation function of the machine, to account for differenced between programmed and actual tool geometry.

3D tool compensation can be activated and deactivated as follows:

\textbf{CUTCOM / NORMAL}, \begin{pmatrix} \begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array} \end{pmatrix}

3D tool compensation requires that the CAM system generate an additional triplet of motion data defining the surface normal vector at the tool contact point. The generation of this additional surface normal information is CAM system dependent. However generated though, GENER requires that a MULTAX/ROLL (or MULTAX/3) command be present in the CL file before activating 3D compensation. If the CAM system generates more than 3 triplets of data (e.g., MUTLAX/4) then a MULTAX/OPTION command can be used to identify the meaning of the various triplets of data in subsequent GOTO commands (see “The MULTAX Command”).

Fixture Compensation

Fixture compensation is used to compensate for differences between the expected and actual fixture location on machines. Depending on the type of fixture compensation supported by the machine (if any), one of two possible formats can be used.

Per-Axis Fixture Compensation

The first method of controlling fixture compensation is by applying or removing it from one or more linear axes. The keywords XCOORD, YCOORD and ZCOORD indicate which axes are to be affected. At least one axis must be programmed.

\textbf{CUTCOM / ON} \;{\small \sim} \! \begin{pmatrix} , \begin{pmatrix}\begin{array}{l} \textbf{XCOORD} \\ \textbf{YCOORD} \\ \textbf{ZCOORD} \end{array}\end{pmatrix} \big[ ,\mathit{offset} \,\big] \end{pmatrix}

\textbf{CUTCOM / OFF} \;{\small \sim} \! \begin{pmatrix} \!,\! \begin{array}{l} \textbf{XCOORD} \\ \textbf{YCOORD} \\ \textbf{ZCOORD} \end{array}\end{pmatrix}

The offset value specifies the compensation switch number to use to control the amount of fixture compensation. If omitted, the last value specified will be reused. Modern machines generally do not use this format.

All-Axes Fixture Compensation

The second method of controlling fixture compensation is by applying or removing the offset from all linear axes simultaneously. Commonly called work coordinate systems, this can be controlled by the keyword ADJUST and an offset number.

\textbf{CUTCOM / ON},\;\textbf{ADJUST},\mathit{offset} \begin{bmatrix} ,\! \begin{array}{l} \textbf{MAIN} \\ \textbf{EXPAND} \\ \textbf{AUTO} \end{array} \, \end{bmatrix} \begin{bmatrix} ,\, \begin{array}{l} \textbf{NOW} \\ \textbf{NEXT} \end{array} \, \end{bmatrix}

\textbf{CUTCOM / OFF},\;\textbf{ADJUST} \begin{bmatrix} ,\! \begin{array}{l}\textbf{NOW} \\ \textbf{NEXT} \end{array} \, \end{bmatrix}

If (G) or (M) codes are used to identify the work coordinate system, code the numbers 1 through the number of available systems. GENER will make the proper adjustments to output the corresponding code, typically a G54 series of codes. Do not program the actual (G) or (M) code on the command.

The keywords NOW and NEXT control the deferring of fixture compensation. The keyword NOW causes the NC control codes to be output immediately; NEXT causes these codes to be deferred until there is a motion. If omitted, the default action specified in QUEST will be used.

To remove fixture compensation, code the OFF parameter alone with the ADJUST keyword.

Some machines support an extended range (or bank) of fixture compensation codes. These can be used by specifying the EXPAND option. Specify MAIN to use the “normal” range. AUTO can be specified to let the post-processor automatically choose the range based on the number of offsets available in the normal range. If the range choice is omitted, the QUEST defined default range will be used. This default can be changed by using the following command:

\textbf{CUTCOM / ADJUST} \begin{bmatrix} ,\! \begin{array}{l} \textbf{MAIN} \\ \textbf{EXPAND} \\ \textbf{AUTO} \end{array} \, \end{bmatrix}

The MAIN, EXPAND or AUTO choices are modal and will be used if a range choice is not explicitly specified on a CUTCOM/ON,ADJUST command.

Rotary Table Dynamic Fixture Compensation

Rotary table dynamic fixture compensation compensates for the position of the workpiece on a rotary table, but it does so for positioning rotary motions only. This form of fixture compensation cannot be used for continuous rotary motions.

\textbf{CUTCOM / TABLE}, \begin{pmatrix} \begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array} \end{pmatrix}

ON enables dynamic rotary table compensation. OFF disables it. The $DYNFIX macro variable indicates and can change the activation status.