The FEDRAT Command [MLEPC]

The FEDRAT command is used to control the rate at which the tool travels. This command is valid for all machine types. The following FEDRAT command functions are available:

Feed Rate Value and Mode

General Syntax

\textbf{FEDRAT / } \big[\,\mathit{value}\,\big] \begin{bmatrix} ,\! \begin{array}{l} \textbf{IPM} \\ \textbf{IPR} \\ \textbf{MMPM} \\ \textbf{MMPR} \\ \textbf{PERMIN} \\ \textbf{PERREV} \end{array}\,\end{bmatrix} \begin{bmatrix} ,\textbf{RANGE}, \begin{pmatrix}\begin{array}{l} \mathit{gear} \\ \textbf{LOW} \\ \textbf{MEDIUM} \\ \textbf{HIGH} \end{array}\end{pmatrix}\end{bmatrix}

The feed rate value specifies the tool velocity for all subsequent motions. The value can represent either a distance to travel per minute, or a distance to travel per revolution of the tool (or part for lathes). The distance can be expressed in inches, millimeters or current CL units. Mode and units can be defined by a mode keyword (see below).

Feed rate values are modal. If a value is omitted then the most recently specified value is used.

If the machine uses feed rate tables, GENER will use the requested feed rate value to determine a feed rate number that results in the closest matching velocity.

\begin{bmatrix} ,\! \begin{array}{l} \textbf{IPM} \\ \textbf{IPR} \\ \textbf{MMPM} \\ \textbf{MMPR} \\ \textbf{PERMIN} \\ \textbf{PERREV}\end{array}\,\end{bmatrix}

The two most commonly used feed rate modes are units per minute and units per revolution. The uPM formats IPM, MMPM and PERMIN all indicate that the feed rate value is specified as a function of the distance to be traveled per minute. The uPR formats IPR, MMPR and PERREV all indicate that the feed rate value is specified as a function of the distance to be traveled per spindle revolution. When using the uPR format, the spindle must always be rotating when a move is performed. If the spindle is stopped, GENER will output a message since it is not be able to determine the tool velocity.

The measurement units of the feed rate are also specified with the mode keyword. Inch (IPM and IPR), millimeter (MMPM and MMPR) and default (PERMIN and PERREV) units are supported.

If the machine units do not match the specified units, then the value is automatically converted to the units of the machine before being applied.

Feed rate modes are modal. If the mode word is omitted then the most recently specified mode is used. If the mode selected is not available then GENER will convert the specified feed rate into a mode that is available.

On machines that support both uPM and uPR coding, the preparatory or auxiliary code for that mode will be output each time the mode word is coded. To avoid redundant feed rate mode codes, only mention the mode keyword on a FEDRAT command when it differs from the last mode specified.

\begin{bmatrix} ,\textbf{RANGE}, \begin{pmatrix}\begin{array}{l} \mathit{gear} \\ \textbf{LOW} \\ \textbf{MEDIUM} \\ \textbf{HIGH} \end{array}\end{pmatrix}\end{bmatrix}

On machines supporting it, feed rate gearing can be controlled using the HIGH, MEDIUM and LOW keywords. HIGH and LOW gears are equated to the fastest and slowest feed rate ranges respectively. MEDIUM will select the mid-range gear if there is one. Do not request a MEDIUM gear if the machine has an even number of gear ranges. If a gear cannot be specified using HIGH, MEDIUM or LOW, the “RANGE,gear” format must be used, where gear is the gear number. Gear number 1 is the LOW gear. Higher gear numbers represent higher machine gears.

If feed rates do not fall within the range of the active gear, error messages will be output and the appropriate minimum or maximum value for the gear in effect will be substituted.

For high speed positioning (i.e., RAPID), the maximum setting for the gear currently in effect will be used for the rapid feed rate.

Wire EDM Syntax

\textbf{FEDRAT / } \big[\,\mathit{value}\,\big] \begin{bmatrix} ,\! \begin{array}{l} \textbf{IPM} \\ \textbf{MMPM} \\ \textbf{PERMIN} \end{array}\,\end{bmatrix}

The above format is the only syntax valid for EDMs. The value represents a user specified estimate of the rate at which the wire is cutting through the part and is used solely for the purpose of timing calculations. No codes are output as a result of coding a FEDRAT command for an EDM.

Punch Press Syntax

\textbf{FEDRAT / } \big[\,\textbf{INCR},\big] \mathit{value}

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

The above FEDRAT command syntax is applicable to punch presses and is the only valid syntax that may be coded for these machines. The value parameter of the first format indicates the nibbling step. The nibbling step is specified as the distance per hit. If a value of 0 is given, this is equivalent to the OFF parameter.

The ON/OFF format is used to terminate or reinstate nibbling mode as follows. The FEDRAT/OFF command is used to switch to single punch mode. If FEDRAT/ON is coded, the last FEDRAT value will be reinstated.

If the punch press is currently in single punch mode and a FEDRAT value is coded, the mode will be switched to nibbling and the nibble increment will be output to the nibble increment register (if it is supported). If nibbling is not supported on the machine, GENER will simulate nibble mode by outputting the number of punches (at the specified nibble increment) required to make the requested move. The INCR parameter is optional and should be coded for purposes of upward compatibility.

If the punch press has a contouring attachment, then the FEDRAT command is identical to a 2 axis mill while the punch press is in contouring mode.

Inverse Time Selection

\textbf{FEDRAT / INVERS}, \begin{pmatrix} \begin{array}{l} \textbf{AUTO} \\ \textbf{ON} \\ \textbf{OFF} \end{array}\,\end{pmatrix}

A feed rate mode called 1/t (inverse time) is typically available on machines having rotary axes. In this mode, instead of outputting the feed rate as a function of the distance to be traveled, GENER first calculates the amount of time it will take the machine to complete the required move at the given feed rate. It then outputs the inverse of this value. 1/t is recommended for feed motions involving rotary axes.

ON causes subsequent motions to be output using 1/t feed rate coding. OFF reverts back to either uPM or uPR mode, depending on which was last specified. The AUTO option causes GENER to temporarily change to 1/t mode if necessary for a rotary axis move and then revert back on the next non-rotary motion.

Set High Feed Threshold

\textbf{FEDRAT / RAPID} \begin{bmatrix} ,\! \begin{array}{l} \textbf{MAXIPM} \\ \textbf{MXMMPM} \\ \textbf{MXPERM} \end{array} \end{bmatrix} ,\mathit{feed}

Path planning optimizations by default look for RAPID motions to delimit the start and end of cutting passes. Use this command to set a feed rate threshold that defines a feed positioning motion. Path planning will treat feed motions as positioning ones, if the interpolation rate exceeds or matches the specified feed value. The maximum feed threshold can be specified in inches per minute (MAXIPM), millimeters per minute (MXMMPM) or CL units per minute (MXPERM, the default).

\textbf{FEDRAT / RAPID}, \begin{pmatrix}\begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array}\end{pmatrix}

ON reinstates the last specified feed as the threshold to include both RAPID and high feed motions as part of the positioning sequence. OFF (the default) only recognizes RAPID motions as positioning.

Feed Rate Limiting

\textbf{FEDRAT /} \begin{pmatrix} \begin{array}{l} \textbf{MAXIPM} \\ \textbf{MXMMPM} \\ \textbf{MXPERM} \\ \textbf{MAXDPM} \end{array} \end{pmatrix} , \begin{pmatrix} \begin{array}{l} \mathit{value} \\ \textbf{ON} \\ \textbf{OFF} \end{array} \end{pmatrix}

This command adjusts the maximum linear and rotary interpolation rates. GENER will limit the velocity of the tool to the specified value, given in inches per minute (MAXIPM), millimeters per minute (MXMMPM) or current CL units per minute (MXPERM). GENER can also limit the velocity of individual rotary axes to the specified value, given in degrees per minute (MAXDPM). OFF resets the maximum feed to the actual machine axes maximums. ON reapplies an earlier specified feed limitation.

Feed Rate Coverage Control

\textbf{FEDRAT / LENGTH}, \mathit{length} \; \big[,\mathit{offset}\,\big]

\textbf{FEDRAT / LENGTH}, \begin{pmatrix}\begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array}\end{pmatrix}

By default, GENER computes feed rates both at the tool tip and at a QUEST defined distance up along the tool axis. The distance traversed (for the purpose of feed rate calculations) is the larger of the two. Coding length changes the default length to the specified value, measured in part units. Coding the optional offset adjusts the tip location up (positive) or down (negative) by the specified amount. The default length is defined in the questionnaire; the default offset is always zero.

Feed Scaling

\textbf{FEDRAT / SCALE} \; {\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] \end{array}\end{pmatrix} ,\mathit{value} \end{pmatrix}

\textbf{FEDRAT / SCALE}, \begin{pmatrix}\begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array}\end{pmatrix}

This command is used to apply a scale factor to individual axes for feed rate computation purposes. Specify an axis name keyword followed by a non-zero positive scale factor for each machine axis that requires special feed rate scaling. GENER will use the scaled delta axis value for subsequent feed rate calculations. See here for a table correlating axes name keywords with machine axes. OFF removes any feed rate scaling in effect. ON reapplies previously specified feed rate scaling factors.

Feed Adjustment

This command is used to control whether GENER adjusts feed rates to respect the physical limitations of the machine. The default setting is controlled in QUEST.

\textbf{FEDRAT / ADJUST}, \begin{pmatrix}\begin{array}{l} \textbf{ON} \\ \textbf{OFF} \end{array}\end{pmatrix}

ON enables feed adjustments. While enabled, the programmed feed value will be adjusted if necessary on a block by block basis to take into account the maximum feed velocity of all axes that are moving as well as the minimum block processing time (if one is defined).

OFF disables feed adjustments. The feed value output will be as programmed in the CLDATA, while respecting the controller feed register limitations.