Инструкция по эксплуатации RepRap II "Мендель": RepRapG-Код
- 1 Introduction
- 2 RepRap G Code Fields
- 3 Individual commands
- 3.1 Checking
- 3.2 Buffered G Commands
- 3.3 Unbuffered G commands
- 3.4 Unbuffered M and T commands
This page describes the G Codes that the RepRap firmware uses and how they work.
The list of what can be done is extensible. But check this page first, and add your extension here first before you implement it.
A typical piece of GCode as sent to a RepRap machine might look like this:
N3 T0 *86 N4 G92 E0 *102 N5 G28 *13 N6 G1 F1500.0 *117 N7 G1 X2.0 Y2.0 F3000.0 *71 N8 G1 X3.0 Y3.0 *39
The meaning of all those symbols and numbers (and more) is explained below.
RepRap G Code Fields
This section explains the letter-preceded fields. The numbers in the fields are represented by nnn. Numbers can be integers, or can contain a decimal point, depending on context. For example an X coordinate can be integer (X175) or fractional (X17.62), whereas trying to select extruder number 2.76 would make no sense.
|Gnnn||Standard GCode command, such as move to a point|
|Mnnn||RepRap-defined command, such as turn on a cooling fan|
|Tnnn||Select tool nnn. In RepRap, tools are extruders|
|Snnn||Command parameter, such as the voltage to send to a motor|
|Pnnn||Command parameter, such as a time in milliseconds|
|Xnnn||An X coordinate, usually to move to|
|Ynnn||A Y coordinate, usually to move to|
|Znnn||A Z coordinate, usually to move to|
|Innn||Parameter - not currently used|
|Jnnn||Parameter - not currently used|
|Fnnn||Feedrate in mm per minute.|
|Rnnn||Parameter - not currently used|
|Qnnn||Parameter - not currently used|
|Ennn||Length of extrudate in mm. This is exactly like X, Y and Z, but for the length of filament to extrude.|
|Nnnn||Line number. Used to request repeat transmission in the case of communications errors.|
|*nnn||Checksum. Used to check for communications errors.|
N and *
Example: N123 [...G Code in here...] *71
These are the line number and the checksum. The RepRap firmware checks the checksum against a locally-computed value and, if they differ, requests a repeat transmission of the line of the given number.
You can leave both of these out - RepRap will still work, but it won't do checking. You have to have both or neither though.
The checksum, cs, for a GCode, cmd, (including its line number) is computed as follows:
int cs = 0; for(int i = 0; i < cmd.length(); i++) cs = cs ^ cmd.charAt(i); cs &= 0xff; // Defensive programming...
and the value is appended as a decimal integer to the command after the * character.
The RepRap firmware expects line numbers to increase by 1 each line, and if that doesn't happen it is flagged as an error. But you can reset the count using M110 (see below).
Buffered G Commands
The RepRap firmware stores these commands in a ring buffer internally for execution. This means that there is no (appreciable) delay while a command is acknowledged and the next transmitted. In turn, this means that sequences of line segments can be plotted without a dwell between one and the next. As soon as one of these buffered commands is received it is acknowledged and stored locally. If the local buffer is full, then the acknowledgment is delayed until space for storage in the buffer is available. This is how flow control is achieved.
Example: G0 X12
Rapid move. In this case move rapidly to X = 12 mm. In fact, the RepRap firmware uses exactly the same code for rapid as it uses for controlled moves (see G1 below), as - for the RepRap machine - this is just as efficient as not doing so. (The distinction comes from some old machine tools that used to move faster if the axes were not driven in a straight line. For them G0 allowed any movement in space to get to the destination as fast as possible.)
Example: G1 X90.6 Y13.8 E22.4
Controlled move. Go in a straight line from the current (X, Y) point to the point (90.6, 13.8), extruding material as the move happens from the current extruded length to a length of 22.4 mm.
RepRap does subtle things with feedrates. Thus:
G1 F1500 G1 X90.6 Y13.8 E22.4
Will set a feedrate of 1500 mm/minute, then do the move described above at that feedrate. But
G1 F1500 G1 X90.6 Y13.8 E22.4 F3000
Will set a feedrate of 1500 mm/minute, then do the move described above accelerating to a feedrate of 3000 mm/minute as it does so. The extrusion will accelerate along with the X, Y movement so everything stays synchronized.
RepRap thus treats feedrate as simply another variable (like X, Y, Z, and E) to be linearly interpolated. This gives complete control over accelerations and decelerations in a way that ensures that everything moves together and the right volume of material is extruded at all points.
The first example shows how to get a constant-speed movement. The second how to accelerate or decelerate. Thus
G1 F1500 G1 X90.6 Y13.8 E22.4 F3000 G1 X80 Y20 E36 F1500
Will do the first movement accelerating as before, and the second decelerating from 3000 mm/minute back to 1500 mm/minute.
To reverse the extruder by a given amount (for example to reduce its internal pressure while it does an in-air movement so that it doesn't dribble) simply use G1 to send an E value that is less than the currently extruded length.
Move to the origin. This causes the RepRap machine to move back to its X, Y and Z zero endstops. It does so accelerating, so as to get there fast. But when it arrives it backs off by 1 mm in each direction slowly, then moves back slowly to the stop. This ensures more accurate positioning.
If you add coordinates, then just the axes with coordinates specified will be zeroed. Thus
G28 X0 Y72.3
will zero the X and Y axes, but not Z. The actual coordinate values are ignored.
Unbuffered G commands
The following commands are not buffered. When one is received it is stored, but it is not acknowledged to the host until the buffer is exhausted and then the command has been executed. Thus the host will pause at one of these commands until it has been done. Short pauses between these commands and any that might follow them do not affect the performance of the machine.
Example: G4 P200
Dwell, or delay. In this case sit still doing nothing for 200 milliseconds. During delays the state of the machine (for example the temperatures of its extruders) will still be preserved and controlled.
Units from now on are in inches.
Units from now on are in millimeters. (This is the RepRap default.)
All coordinates from now on are absolute relative to the origin of the machine. (This is the RepRap default.)
All coordinates from now on are relative to the last position.
Example: G92 X10 E90
Set the current position to the values specified. This would set the machine's X coordinate to 10, and the extrude coordinate to 90.
Unbuffered M and T commands
Example: M104 S190
Set the temperature of the current extruder to 190oC and return control to the host immediately (i.e. before that temperature has been reached by the extruder). See also M109.
Request the temperature of the current extruder in degrees Celsius. The temperature is returned to the host computer.
Turn on the cooling fan (if any).
Turn off the cooling fan (if any).
Example: M109 S190
Set the temperature of the current extruder to 190oC and wait for it to reach that value before sending an acknowledgment to the host. In fact the RepRap firmware waits a while after the temperature has been reached for the extruder to stabilise - typically about 40 seconds. This can be changed by a parameter in the firmware configuration file when the firmware is compiled. See also M104.
Example: N123 M110
Set the current line number to 123. Thus the expected next line after this command will be 124.
Example: M111 S6
Set the level of debugging information transmitted back to the host to level 6. The level is the OR of three bits:
#define DEBUG_ECHO (1<<0) #define DEBUG_INFO (1<<1) #define DEBUG_ERRORS (1<<2)
Thus 6 means send information and errors, but don't echo commands. (This is the RepRap default.)
Reserved for Immediate Stop. Not yet implemented.
Set the PWM for the currently-selected extruder. On its own this command sets RepRap to use the on-board potentiometer on the extruder controller board to set the PWM for the currently-selected extruder's stepper power. With an S field:
it causes the PWM to be set to the S value (70% in this instance). M113 S0 turns the extruder off, until an M113 command other than M113 S0 is sent.
This causes the RepRap machine to report its current X, Y, Z and E coordinates to the host.
Example: M126 P500
Open the extruder's valve (if it has one) and wait 500 milliseconds for it to do so.
Example: M127 P400
Close the extruder's valve (if it has one) and wait 400 milliseconds for it to do so.
Select extruder number 1 to build with. Extruder numbering starts at 0.