Cartesian Arm Solution

Version Support: This arm solution is supported in both Smoothieware v1 ✅ and v2 ✅

The Cartesian arm solution is the most common type of machine configuration used in 3D printers and CNC machines.

In a Cartesian machine, each actuator (motor and linear rail) directly corresponds to an axis in Cartesian space:

Alpha actuator controls the X axis
Beta actuator controls the Y axis
Gamma actuator controls the Z axis

This is the simplest arm solution, as there is a direct 1:1 relationship between the motors and the movement in space - no mathematical conversion is needed.

Why Cartesian?

Cartesian is the default and most straightforward arm solution for several reasons:

Simple to understand: Direct motor-to-axis mapping makes troubleshooting easy
Easy to calibrate: Steps-per-mm calculation is straightforward for each axis
Predictable behavior: What you command is exactly what moves
Wide support: Almost all CAM software and G-code assumes Cartesian by default
Proven reliability: Decades of industrial and hobbyist use

Configuration

To configure your machine to use the Cartesian arm solution, add this to your configuration file:

V1 Configuration:

arm_solution cartesian

V2 Configuration:

[motion control]
arm_solution = cartesian

This is the default setting in Smoothieware, so if you don’t specify an arm solution, Cartesian will be used automatically.

Complete Configuration Example

Here’s a typical Cartesian configuration:

V1 Configuration:

# Cartesian arm solution (can be omitted as it's the default)
arm_solution                                 cartesian

# Alpha (X axis)
alpha_step_pin                               2.0
alpha_dir_pin                                0.5
alpha_en_pin                                 0.4
alpha_steps_per_mm                           80
alpha_max_rate                               12000

# Beta (Y axis)
beta_step_pin                                2.1
beta_dir_pin                                 0.11
beta_en_pin                                  0.10
beta_steps_per_mm                            80
beta_max_rate                                12000

# Gamma (Z axis)
gamma_step_pin                               2.2
gamma_dir_pin                                0.20
gamma_en_pin                                 0.19
gamma_steps_per_mm                           400
gamma_max_rate                               300

V2 Configuration:

[motion control]
arm_solution = cartesian

[alpha]
step_pin = 2.0
dir_pin = 0.5
en_pin = 0.4
steps_per_mm = 80
max_rate = 12000

[beta]
step_pin = 2.1
dir_pin = 0.11
en_pin = 0.10
steps_per_mm = 80
max_rate = 12000

[gamma]
step_pin = 2.2
dir_pin = 0.20
en_pin = 0.19
steps_per_mm = 400
max_rate = 300

Common Cartesian Machines

Cartesian configurations are used in:

Most desktop 3D printers - Prusa i3, Creality Ender, Ultimaker, MakerBot, etc.
CNC routers and mills - ShopBot, X-Carve, Shapeoko, industrial mills
Laser cutters - Most CO2 and diode laser cutters
Pick and place machines - SMT assembly machines
Vinyl cutters - Cricut, Silhouette, Roland cutters
Plasma cutters - CNC plasma tables

Advantages and Disadvantages

Advantages ✅

Simplicity: Easiest to understand and troubleshoot
Direct control: Each motor controls exactly one axis
Easy calibration: Straightforward steps-per-mm calculation
Large build volume: Can be scaled easily in any direction
Well documented: Extensive community knowledge and resources
Predictable costs: Standard linear rails and components
Universal G-code: Works with all standard G-code without modification

Disadvantages ❌

Moving mass: Often requires moving the bed (Z) or entire gantry (X/Y)
Speed limitations: Limited by the mass being moved
Workspace shape: Rectangular workspace may not be optimal for all applications
Mechanical complexity: Requires precise alignment of perpendicular axes
Belt stretch: Long X or Y belts can stretch under acceleration

Comparison with Other Arm Solutions

Feature	Cartesian	Linear Delta	CoreXY	SCARA
Setup complexity	Low	Medium	Medium	High
Calibration difficulty	Easy	Medium	Medium	Hard
Build volume shape	Rectangular	Cylindrical	Rectangular	Semicircular
Speed potential	Medium	High	High	High
Z-axis speed	Low	High	Low	Medium
Moving mass	High	Low	Medium	Low
Mechanical precision needed	Medium	High	High	Very high

Troubleshooting

Problem: One axis moves in the wrong direction

Solution: Invert the direction pin for that axis by adding or removing ‘!’ from the dir_pin configuration:

# Change this:
alpha_dir_pin    0.5

# To this:
alpha_dir_pin    0.5!

Problem: Movements are the wrong distance

Solution: Calibrate your steps_per_mm for each axis. Measure actual movement and adjust:

new_steps_per_mm = current_steps_per_mm × (commanded_distance / actual_distance)

Problem: Axes are not perpendicular

Solution: This is a mechanical issue. Check that your frame is square using a carpenter’s square or by measuring diagonals.