3D Printing from the Command Line with CuraEngine

A guide to slicing STL files using CuraEngine CLI, based on real-world troubleshooting.

Finding CuraEngine

CuraEngine is bundled inside the Cura application:

# macOS
/Applications/UltiMaker\ Cura.app/Contents/Resources/CuraEngine

# Linux (typical locations)
/usr/share/cura/CuraEngine
# or
/opt/cura/CuraEngine

# Windows
C:\Program Files\Ultimaker Cura\CuraEngine.exe

Basic Command Structure

CuraEngine slice \
  -d <definition_search_paths> \
  -j <machine_definition.json> \
  -e0 -j <extruder_definition.json> \
  -s <setting>=<value> \
  -l <input.stl> \
  -o <output.gcode>

Required Settings (CuraEngine 5.x)

CuraEngine 5.x has many undocumented required settings. Without these, you'll get errors like:

[error] Trying to retrieve setting with no value given: roofing_layer_count

Here's a working minimal set:

CURA_ENGINE="/Applications/UltiMaker Cura.app/Contents/Resources/CuraEngine"
DEFS_PATH="/Applications/UltiMaker Cura.app/Contents/Resources/share/cura/resources/definitions"
EXTRUDER_DEFS="/Applications/UltiMaker Cura.app/Contents/Resources/share/cura/resources/extruders"

"$CURA_ENGINE" slice \
  -d "$DEFS_PATH:$EXTRUDER_DEFS" \
  -j "$DEFS_PATH/fdmprinter.def.json" \
  -e0 -j "$DEFS_PATH/fdmextruder.def.json" \
  -s center_object=true \
  -s mesh_position_x=60 \
  -s mesh_position_y=60 \
  -s layer_height=0.2 \
  -s infill_sparse_density=20 \
  -s support_enable=true \
  -s support_type=buildplate \
  -s adhesion_type=brim \
  -s material_print_temperature=200 \
  -s material_bed_temperature=60 \
  -s roofing_layer_count=1 \
  -s flooring_layer_count=1 \
  -s top_layers=4 \
  -s bottom_layers=4 \
  -s wall_line_count=2 \
  -s machine_width=220 \
  -s machine_depth=220 \
  -s machine_height=250 \
  -s material_diameter=1.75 \
  -s support_z_seam_away_from_model=1 \
  -s support_z_seam_min_distance=1.0 \
  -s lightning_infill_support_angle=40 \
  -s scarf_joint_seam_end_height_ratio=0 \
  -s reset_flow_duration=2.0 \
  -l model.stl \
  -o output.gcode

Centering Models on the Build Plate

Problem: By default, models may be placed at their original coordinates, often far outside the build area.

Solution: Use these settings together:

-s center_object=true \
-s machine_center_is_zero=false \
-s mesh_position_x=60 \
-s mesh_position_y=60

The mesh_position_x/y values offset the centered model. For a 220x220 bed:

Models get centered around (50, 50) by default
Adding 60mm offset moves them to ~(110, 110) = true center

Adjust based on your bed size: offset = (bed_size / 2) - 50

Common Settings Reference

Setting	Description	Example
`layer_height`	Layer height in mm	`0.2`
`infill_sparse_density`	Infill percentage	`20` (20%)
`support_enable`	Enable supports	`true`
`support_type`	Support placement	`buildplate` or `everywhere`
`adhesion_type`	Bed adhesion type	`brim`, `raft`, `skirt`, `none`
`material_print_temperature`	Nozzle temp °C	`200`
`material_bed_temperature`	Bed temp °C	`60`
`material_diameter`	Filament diameter mm	`1.75`
`wall_line_count`	Number of perimeters	`2`
`top_layers`	Solid top layers	`4`
`bottom_layers`	Solid bottom layers	`4`

Batch Slicing Script

#!/bin/bash
# slice_all.sh - Batch slice STL files

CURA_ENGINE="/Applications/UltiMaker Cura.app/Contents/Resources/CuraEngine"
DEFS_PATH="/Applications/UltiMaker Cura.app/Contents/Resources/share/cura/resources/definitions"
EXTRUDER_DEFS="/Applications/UltiMaker Cura.app/Contents/Resources/share/cura/resources/extruders"

STL_DIR="${1:-.}"
OUT_DIR="${2:-./gcode}"

mkdir -p "$OUT_DIR"

for stl in "$STL_DIR"/*.stl; do
  filename=$(basename "$stl" .stl)
  echo "Slicing: $filename"
  
  "$CURA_ENGINE" slice \
    -d "$DEFS_PATH:$EXTRUDER_DEFS" \
    -j "$DEFS_PATH/fdmprinter.def.json" \
    -e0 -j "$DEFS_PATH/fdmextruder.def.json" \
    -s center_object=true \
    -s mesh_position_x=60 \
    -s mesh_position_y=60 \
    -s layer_height=0.2 \
    -s infill_sparse_density=20 \
    -s support_enable=true \
    -s support_type=buildplate \
    -s adhesion_type=brim \
    -s material_print_temperature=200 \
    -s material_bed_temperature=60 \
    -s roofing_layer_count=1 \
    -s flooring_layer_count=1 \
    -s top_layers=4 \
    -s bottom_layers=4 \
    -s wall_line_count=2 \
    -s machine_width=220 \
    -s machine_depth=220 \
    -s machine_height=250 \
    -s material_diameter=1.75 \
    -s support_z_seam_away_from_model=1 \
    -s support_z_seam_min_distance=1.0 \
    -s lightning_infill_support_angle=40 \
    -s scarf_joint_seam_end_height_ratio=0 \
    -s reset_flow_duration=2.0 \
    -l "$stl" \
    -o "$OUT_DIR/$filename.gcode" 2>&1 | grep -E "(Print time|error)"
    
  if [ -f "$OUT_DIR/$filename.gcode" ]; then
    echo "✓ Created: $filename.gcode"
  else
    echo "✗ Failed: $filename"
  fi
done

echo "Done! G-code files in: $OUT_DIR"

Usage:

chmod +x slice_all.sh
./slice_all.sh /path/to/stl/files /path/to/output

Troubleshooting

"Trying to retrieve setting with no value given"

Add the missing setting with a sensible default. Common culprits:

roofing_layer_count=1
flooring_layer_count=1
support_z_seam_away_from_model=1
reset_flow_duration=2.0
lightning_infill_support_angle=40
scarf_joint_seam_end_height_ratio=0

Model coordinates outside build area

Check your G-code for coordinates beyond your bed size:

grep "^G[01].*X.*Y" output.gcode | head -20

If coordinates are wrong, ensure you have:

-s center_object=true
-s mesh_position_x=60  # Adjust for your bed
-s mesh_position_y=60

G-code file is tiny/incomplete

The slicer crashed mid-process. Check stderr for the specific missing setting and add it.

Alternative: Using Printer-Specific Definitions

Instead of fdmprinter.def.json, you can use a specific printer definition:

ls "$DEFS_PATH" | grep -i ender  # Find your printer
# creality_ender3.def.json, etc.

Note: Printer definitions inherit from base definitions and may still require the same additional settings.

Resources

CuraEngine GitHub
Cura Settings Documentation
Print3r - Alternative CLI wrapper for multiple slicers

JacobFV/cura-cli-guide.md

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