CoreXZ Arm Solution

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

CoreXZ is a motion system variant of CoreXY that uses a crossed-belt configuration to control the X and Z axes instead of X and Y.

In a CoreXZ system, two motors work together to control both X and Z movement, while the Y axis remains independent and is controlled by a single motor.

How CoreXZ Works

Unlike traditional Cartesian systems where each motor directly controls one axis, CoreXZ uses both motors to contribute to movement in the X and Z directions:

Alpha motor (Motor 1): Controls both X and Z movement
Beta motor (Motor 2): Controls both X and Z movement (in a different combination)
Gamma motor (Motor 3): Controls Y movement independently

The mathematical relationship is:

Alpha position = (x_reduction × X) + (z_reduction × Z)
Beta position = (x_reduction × X) - (z_reduction × Z)
Gamma position = Y

This crossed-belt configuration allows for:

Reduced moving mass on the X axis (motors can be stationary)
Potentially higher speeds in X direction
Different dynamics compared to traditional Cartesian

When to Use CoreXZ

CoreXZ is useful for machines where:

You want to reduce the moving mass in the X direction
The Z axis doesn’t need to move as frequently or as fast as Y
You’re building a machine with a fixed gantry for X/Z and moving bed for Y
You want the benefits of a crossed-belt system but need Y to be the fast-moving axis

Common applications:

Specialized CNC routers
Custom 3D printer designs
Plotters with moving beds

Configuration

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

arm_solution corexz

[general]
arm_solution = corexz

Reduction Parameters

CoreXZ uses two reduction parameters that scale the contribution of each axis to the motor positions:

x_reduction    1.0    # Scaling factor for X axis contribution (default: 1.0)
z_reduction    3.0    # Scaling factor for Z axis contribution (default: 3.0)

These parameters allow you to adjust for different pulley sizes or gear ratios in your X and Z drive systems.

Default values:

x_reduction: 1.0 (no reduction)
z_reduction: 3.0 (3:1 reduction)

The default z_reduction of 3.0 assumes that the Z axis typically needs more torque and less speed than the X axis.

Complete Configuration Example

# CoreXZ arm solution
arm_solution                                 corexz
x_reduction                                  1.0
z_reduction                                  3.0

# Alpha (X/Z motor 1)
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 (X/Z motor 2)
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 (Y motor - independent)
gamma_step_pin                               2.2
gamma_dir_pin                                0.20
gamma_en_pin                                 0.19
gamma_steps_per_mm                           80
gamma_max_rate                               6000

[general]
arm_solution = corexz
x_reduction = 1.0
z_reduction = 3.0

[actuator]
alpha.step_pin = PG0
alpha.dir_pin = PG1
alpha.en_pin = PJ2
alpha.steps_per_mm = 80
alpha.max_rate = 12000
alpha.microsteps = 32
alpha.driver = tmc2660

beta.step_pin = PG2
beta.dir_pin = PG3
beta.en_pin = PJ3
beta.steps_per_mm = 80
beta.max_rate = 12000
beta.microsteps = 32
beta.driver = tmc2660

gamma.step_pin = PG4
gamma.dir_pin = PG5
gamma.en_pin = PJ4
gamma.steps_per_mm = 80
gamma.max_rate = 6000
gamma.microsteps = 32
gamma.driver = tmc2660

Speed Settings

It is recommended to set the alpha_max_rate and beta_max_rate to the highest speed your steppers can achieve.

These settings refer to the actuator speed (the X/Z stepper motors), which on a CoreXZ system can run faster than the requested Cartesian speed when moving in certain directions.

The motors need to be able to handle combined X and Z movements, which can require nearly the sum of both speeds.

Getting Direction Right

Movement in the X or Z direction always involves both alpha and beta motors, which can make configuring a CoreXZ solution confusing.

If you find that movement is incorrect after wiring and configuring your machine, the following solutions may help:

Problem	Possible Solution
My X and Z axes are swapped	Swap the alpha and beta motor cables, or swap the pin assignments
One of my axes goes in the wrong direction	Invert the signal of one motor by adding or removing ‘!’ from the dir_pin
Both X and Z go the wrong direction	Invert both alpha and beta dir_pins by adding or removing ‘!’
Movement is scaled incorrectly	Adjust the `x_reduction` and/or `z_reduction` parameters

Homing

If you are using homing, make sure your endstop configuration matches your CoreXZ setup:

X endstops trigger based on X position
Y endstops trigger based on Y position (independent)
Z endstops trigger based on Z position

The firmware will automatically handle the coordination of the alpha and beta motors during homing operations.

Comparison with Other Arm Solutions

Feature	CoreXZ	CoreXY	Cartesian
Crossed axes	X and Z	X and Y	None
Independent axis	Y	Z	All
Moving mass	Lower X mass	Lower X/Y mass	Higher
Complexity	Medium	Medium	Low
Common usage	Rare	Common	Very common

Troubleshooting

Problem: Movements are skewed or distorted

Solution: Check your x_reduction and z_reduction values. These should match the mechanical advantage of your drive system.

Problem: One direction moves twice as fast as expected

Solution: One of your motors may be running in the wrong direction. Check the dir_pin configuration and add or remove ‘!’ as needed.

Problem: Homing fails or moves in wrong direction

Solution: Verify your endstop configuration and ensure that X and Z endstops are correctly assigned.

Source Code

For developers or those interested in the implementation details, the CoreXZ solution is implemented in:

v1: CoreXZSolution.cpp
v2: CoreXZSolution.cpp