# GCode Macros

Variable Substitutions and Expressions in GCode Macros
FDM (3D Printing) variable substitutions
All Modes "pre" and "post" (header/footer)
• {top} = offset in mm of bed top Y axis
• {left} = offset in mm of bed left X axis
• {right} = offset in mm of bed right X axis
• {bottom} = offset in mm of bed bottom Y axis
All Modes "post" (footer)
• {time} = job run time (printing/milling) in seconds (fractional)
• {print-time} = alias for {time} ... deprecated after 2.8
• {print_time} = alias for {time} ... 2.9 and beyond
3D printing / FDM mode only
"feature" macro only (as of 3.4)
• {feature} = feature region of the print (brims, infill, etc)
• {minx|miny|maxx|maxy} = position in mm of extents of the print area
"pre", "post", and other macros
• {temp} = hot end temperature
• {bed_temp} = bed temperature
• {fan_speed} = active cooling fan speed (usually 0-255)
• {material} = length in mm of material (filament) used
• {layers} = total # of layers
• {layer} = current layer number
• {height} = current layer height in mm
• {range(from,to)} = evaluated using {layer} and {layers}
• {pos_x} = last output X position
• {pos_y} = last output Y position
• {pos_z} = last output Z position
• {progress} = 0-100% state of print output
• {tool} | {nozzle} = current tool in use
• {tool_count} = number of tools used in print
• {tool_used_n} = whether tool # n is used in print
• {z_max} = max build height in mm
• {z} = current z position
• {e} = amount of filament extruded
Logical Code Flow (IF / ELIF / ELSE / END)
;; IF { layer >= 10 && layer <= 20 }
;; ..... inside 10-20 layer={layer}
;; ELIF { layer >= 15 && layer <= 25 }
;; ..... inside 15-25 layer={layer}
;; ELSE
;; ..... did not match previous tests layer={layer}
;; END
PREAMBLE control (v3.4+) allows for intro comment and config list to be re-positioned after the header or disabled. This was introduced to allow GCode output to work with Ultimaker.
`;; PREAMBLE OFF`
`;; PREAMBLE END`
Axis Remapping (v3.5+) allows for over-riding the default axis names. Useful for swapping axes and changing output for specific firmware targets. The format of the map is a JSON object.
`;; AXISMAP {"X":"Y", "Y":"Z", "E":"E1"}`

Comments Rewrite (v3.8+) converts `;` comments into `()` parenthesis format
`;; COMMENT_REWRITE_PARENS`
Minimize the size of GCode output (v3.8+)
`;; COMPACT-OUTPUT`
Set decimal precision (n = integer) (v3.8+)
`;; DECIMALS = n`
CAM variable substitutions
• {tool} = CAM tool #
• {tool_name} = CAM tool name
• {time} = dwell time in seconds
• {time_ms} = dwell time in milliseconds
• {time_sec} = dwell time in seconds
• {speed} = spindle speed
• {spindle}, {rpm} = spindle speed (v2.7+)
Axis Scaling (v3.7+) allows for a factor to be applied to X,Y,Z coordinates. Useful for some machines like the Roland MDX-40A that uses an unusual coordinate space. Default axis scale is `1`
`;; SCALE { "X":100, "Y":100, "Z":100 }`
CAM & FDM : simple algebraic expression support
• Text inside `{}` is evaluated algebraically with access to JS classes and methods
• `{Math.min(layer/layers, 0.5) + 1}`
• `{token+n} {token-n}`