The CLAMP Command `[MLEPC]`

The CLAMP command is available for all machine types and it has two functions. On all machines it can be used to activate and deactivate movement along specified axes. It can also be used to physically clamp and unclamp axes using auxiliary function codes. Axes can be clamped at their current location or at a specified location. The second application of the CLAMP command is to relocate the table for a punch press.

This command is most useful when programming NC machines having redundant axis capabilities (e.g., two Z axes), or to move axes to specific positions.

The following CLAMP command functions are available:

“Parametric CLAMP Format”

“Axis-Specific CLAMP Format”

“Table Clamping for Punch Presses”

“Linear Positioning with Rotary Axes”

Parametric CLAMP Format

$\textbf{CLAMP / } \big[ \textbf{ MANUAL}, \big] \begin{bmatrix}\,\begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array} \; , \end{bmatrix} \, a , b \big[ ,c \, \big]$

Specify MANUAL to suppress the output of NC control tape. This can be used to preset axes to desired locations without causing codes to appear in the tape file. GENER will continue processing in exactly the same manner whether MANUAL is coded or not.

The initial ON or OFF indicates whether the clamps are to be applied, or removed. If omitted, ON is assumed (i.e., axes are to be immobilized).

The a,b,c scalar values specify in machine coordinates the axis positions to move to either before clamping or after clamps are removed. The machine axes represented by the three scalars are dependent on the type of machine and the machining mode.

Machine

a

b

c

Horizontal lathe in turn mode

Z

X

na

Vertical lathe in turn mode

X

Z

na

Any lathe in mill mode

X

Y

Z

2 axis mill or punch press

X/U

Y/V

na

Other mills

X/U

Y/V

Z/W

Since this command either applies or removes clamps to all active linear axes its usefulness is rather limited. The most common application would be to preset the linear axes to some known position. For example the following command on a mill would cause a movement of the X axis to 15.2, the Y axis to 4 and the Z axis to 3:

CLAMP/OFF,15.2,4,3

The specified positions are in machine coordinates, not CL coordinates. Note that coding MANUAL would cause GENER to internally reset the machine position to the specified location but no motion record would be output.

Axis-Specific CLAMP Format

This command format allows one or more axes to be clamped or unclamped individually by name.

$\textbf{CLAMP / } \big[ \textbf{ MANUAL}, \big] \begin{bmatrix}\,\begin{array}{l} \textbf{ON} \\ \textbf{OFF} \\ \textbf{AUTO} \end{array} \; , \, \end{bmatrix} \;\; {\small \sim} \! \begin{pmatrix} , \begin{pmatrix}\begin{array}{l} \textbf{XAXIS} \\ \textbf{YAXIS} \\ \textbf{ZAXIS} \\ \textbf{UAXIS} \\ \textbf{VAXIS} \\ \textbf{WAXIS} \\ \textbf{QUILL} \\ \textbf{AAXIS} \\ \textbf{BAXIS} \\ \textbf{CAXIS} \\ \textbf{AAXIS},\textbf{TABLE} \\ \textbf{BAXIS},\textbf{TABLE} \\ \textbf{CAXIS},\textbf{TABLE} \\ \textbf{RAM} \big[ ,n \, \big] \\ \textbf{ALL} \end{array}\end{pmatrix} \begin{bmatrix} ,\! \begin{array}{l} \textbf{ON} \\ \textbf{OFF} \\ \textbf{AUTO} \end{array} \, \end{bmatrix} \big[ ,\mathit{value} \, \big] \end{pmatrix}$

Specify MANUAL to suppress the output of NC control tape. This can be used to preset axes to desired locations without causing codes to appear in the tape file. GENER will continue processing in exactly the same manner whether MANUAL is coded or not.

The initial ON, OFF or AUTO indicates whether the clamps are to be applied, removed, or automatically applied and removed. If omitted, ON is assumed. This initial ON, OFF or AUTO can be overridden for any specific axis by explicitly coding an ON, OFF or AUTO following the axis name.

Automatic clamping is triggered with the AUTO keyword. Automatic clamping of an axis specifies that the axis shall remain clamped by default. When motion is programmed for the axis, the clamps will be automatically removed before the motion commences and reapplied before the next move where the axis is not moving.

Automatic clamping is done differently for in cycle and out of cycle motions. When out of cycles, an axis is automatically clamped if it does not appear on a motion block. When in cycles, the axis is automatically clamped on every cycle motion. It is unclamped only for ramping motions (if needed).

The AUTO feature can be disabled by specifying the ON or OFF keyword for a given axis. The axis names are specified by one or two keywords[1].

Specifier

Description

XAXIS

Primary X axis

YAXIS

Primary Y axis

ZAXIS

Primary Z axis

UAXIS

Secondary X axis

VAXIS

Secondary Y axis

WAXIS

Secondary Z axis

AAXIS

Only A axis or head A axis

BAXIS

Only B axis or head B axis

CAXIS

Only C axis or head C axis

AAXIS,TABLE

Table A axis

BAXIS,TABLE

Table B axis

CAXIS,TABLE

Table C axis

RAM [,1]

Primary attachable head/nutating axis

RAM,2

Secondary attachable head/nutating axis

The ALL keyword can be used to select all axes that have physical clamp/unclamp capability codes defined in the CLAMP section of the questionnaire.

The scalar value in the second CLAMP command format specifies in machine coordinates the axis position to move to either before clamping or after clamps are removed.

When clamping rotary axes, the angle specified is the exact angle to which the axis will be clamped. For example, if a C-axis is wrapped around to 730 degrees and a CLAMP/CAXIS,ON,0 is coded, the C-axis will not move 10 degrees to 720. Rather, it will wrap all the way back to 0 (zero) degrees.

There are two main uses of the CLAMP command. One is to define a new position in machine coordinates and optionally output the codes to move to that position. The other use is to switch control back and forth between two similar axes on a machine (e.g., Z and W axes).

The following commands cause a rapid motion in only the Z and X axes of the machine. All of the other axes remain unchanged.

RAPID
CLAMP/OFF,XAXIS,16,ZAXIS,10

When using the CLAMP command to switch control between similar axes, it is important to understand that the following two commands are not equivalent.

CLAMP/ZAXIS,ON
CLAMP/WAXIS,OFF

When GENER is told to clamp an axis ON, it physically clamps the axis, outputting an (M) code if one is available. The only way to unclamp the axis is to code another CLAMP command, this time specifying OFF.

When GENER is told to clamp an axis OFF, it removes physical clamps using an (M) code if it was physically clamped on the machine. If a parallel axis exists on the machine, output to that axis will be inhibited, but it will not be physically clamped.

Switching control between X,Y,Z type linear axes may always be done by coding CLAMP/OFF commands with the name of the axis to be used next. GENER will insure that the appropriate NC control tape is created to switch control back and forth. This method is not recommended for rotary axes. For switching control between rotaries, first code the appropriate CLAMP/ON commands for axes to be deactivated. Next, code CLAMP/OFF commands for the ones you want to activate. At most two (2) rotaries may be active at any one time.

In the following example, the initial machining state has both the Z and W axes unclamped and the Z axis selected for output.

CLAMP/WAXIS,OFF

Subsequent Z movement will be done using the W axis.

CLAMP/ZAXIS,OFF

Subsequent Z movement will be done using the Z axis.

CLAMP/WAXIS,OFF

Subsequent Z movement will be done using the W axis.

CLAMP/ZAXIS,ON

The Z axis is immobilized.

Subsequent Z movement will be done using the W axis.

CLAMP/WAXIS,ON

The W axis is immobilized.

Any attempt to move a Z or W axis will now cause an error.

CLAMP/ZAXIS,ON

The Z axis is already immobilized!

Table Clamping for Punch Presses

$\textbf{CLAMP / TABLE } \; {\small \sim} \! \begin{pmatrix} , \begin{pmatrix}\begin{array}{l} \textbf{XAXIS} \\ \textbf{YAXIS} \end{array}\end{pmatrix} \, ,\mathit{value} \end{pmatrix}$

With this format the parameter TABLE is required in addition to XAXIS,value and/or YAXIS,value. For punch presses, axis values are specified as delta amounts and not as absolute values.

Two types of table repositioning are supported by GENER. The machine may support a single (G) or (M) code that causes the entire table repositioning sequence to occur. Axis shift values are output with the code to indicate the new clamp position. Alternatively, repositioning may have to be done in steps. In this case a repositioning start code is output to begin the repositioning sequence. A motion to the delta amount specified on the CLAMP command is then output. Finally, the repositioning end code is output.

On some machines, the machine axes readouts are reset automatically. Other machines depend on GENER to adjust for the new clamp positions.

Linear Positioning with Rotary Axes

Clamping can also be used to force a machine to perform linear moves using a table rotary axis. This is known as “Polar” positioning.

Note

The use of the CLAMP command to enable Polar positioning and Polar interpolation has been deprecated in favor of the MODE/POLAR command (see “Polar Interpolation” and “Polar Emulation”).

In order for Polar positioning to work, there can be only two linear axes active. They must be perpendicular and one of them must be parallel to the table rotary axis that is to be used. For example, a Y axis may be clamped on a mill. Full X,Y,Z capability is maintained by using the X axis and the C rotary table for XY positioning and the Z axis for Z positioning.

Full LINTOL capability is available and will be needed to cut straight lines in the plane of the rotary axis. If LINTOL is not used, all feed moves will be curved because of the motion of the C axis.

Tool vectors that are not parallel to the rotary axis can be supported using the SETANG and ATANGL options on the LOAD/TOOL (or TOOLNO) commands. In order that they be supported, the tool vectors must be possible at the desired rotary axis destination. If they are not, a fatal error will occur saying that the desired tool vector cannot be reached.