Voron V2.4 Z Drive Mods — Belted Z, BelZed, and Dual Motor Options

V2.4 Mod Z-Axis Mechanical

The Voron V2.4 uses a four-corner leadscrew Z drive system with a single stepper motor driving all four Z screws through a gearbox and belt network. While this works well out of the box, many builders eventually look to modify the Z drive for better bed leveling consistency, higher Z speed, or independent bed adjustment. This guide covers the three most popular V2.4 Z drive modifications: the BelZed conversion (belt-driven Z), the full belted Z mod that replaces leadscrews entirely, and the dual independent Z motor upgrade. Each has distinct tradeoffs in complexity, cost, and performance.

Stock Z Drive System Overview

The stock V2.4 Z system uses a single NEMA 17 stepper motor mounted on the bottom rear extrusion. It drives a central worm gearbox that distributes torque to four leadscrew nuts via GT2 belts. Each Z corner has an 8mm leadscrew with a 2mm pitch (4 starts, 8mm lead). This setup provides 0.01mm Z resolution with 1/16 microstepping — adequate for FDM printing — but has several limitations:

• Single motor failure point: If the Z motor stalls or the gearbox strips, the entire bed drops. There is no redundancy.
• Mechanical backlash: The worm gearbox introduces measurable backlash that Klipper's gcode_offset can partially compensate for, but it is never truly eliminated.
• Limited Z speed: The stock gear ratio limits reliable Z hop speeds to around 10-15mm/s. Faster moves risk the motor losing steps.
• No independent corner adjustment: All four corners move together. You cannot correct a twisted gantry or tilted bed via software alone without a Z tilt adjust mod.

BelZed Conversion — Belt-Driven Leadscrew Replacement

The BelZed mod replaces the four leadscrews with a belt-and-pulley system. Instead of rotating leadscrews to lift the bed, the BelZed uses GT2 belts running from the stock gearbox to the bed corners. Each corner has a carriage that rides on linear rails, with the belt looped over a fixed pulley at the top and an idler at the bottom. When the belts move, the bed rises and falls.

BelZed Advantages

• Zero backlash: Belts have no mechanical slop when properly tensioned. Z banding from leadscrew nut play disappears entirely.
• Higher Z speed: Belt drives can reliably move at 30-50mm/s for Z hops, significantly reducing print time on models with frequent Z lifts.
• Smoother motion: No leadscrew threads means no periodic Z-banding artifacts in the 8mm wavelength range.

BelZed Disadvantages

• Requires printed parts: You need to print the BelZed carriage and idler mounts. These must be printed in ABS or better — ASA or PC is recommended for heat resistance near the bed.
• Additional hardware: Eight F695 bearings, four M5x40 shoulder bolts, GT2 belts (about 2.5m total for a 350mm build), and extra M3 hardware.
• Tensioning complexity: All four Z belts must be tensioned equally. Uneven tension causes the bed to tilt as it moves in Z.
• Lost Z resolution: Belt drives reduce effective Z resolution compared to leadscrews. With a 20-tooth pulley and 1/16 microstepping, resolution drops from 0.01mm to approximately 0.025mm — still fine for FDM but noticeable for very thin layers.

BelZed Klipper Configuration

Klipper configuration for a BelZed mod is nearly identical to stock — the Z stepper driver settings remain the same. The key changes are in the rotation_distance and max_z_velocity:

[stepper_z]
step_pin: PB4
dir_pin: !PC5
enable_pin: !PB3
microsteps: 16
rotation_distance: 40
# For 20-tooth pulley with GT2 belt: 20 * 2 = 40mm per rotation
full_steps_per_rotation: 200
endstop_pin: ^PA7
position_endstop: 0.0
position_min: -4
position_max: 250  # Change to 300 or 350 for larger builds
homing_speed: 15
second_homing_speed: 5
homing_retract_dist: 5
    

The rotation_distance of 40mm (20-tooth pulley x 2mm belt pitch) replaces the stock leadscrew value of 8mm. The max_z_velocity in the printer.cfg can be safely increased to 30mm/s, and max_z_acceleration to 100mm/s².

If you are using independent Z motors with Klipper's Z tilt adjust, change the config to use [stepper_z], [stepper_z1], [stepper_z2], and [stepper_z3] sections, each with the same rotation_distance.

Full Belted Z Replacement

A more radical approach than BelZed is replacing the entire stock Z drive — worm gearbox, leadscrews, and motor — with a fully independent belted system. This typically uses four NEMA 17 motors (one per corner), each driving a GT2 belt loop. The motors are controlled independently by Klipper, allowing full Z tilt adjustment. This is the same approach used on Trident and V2.4 builds that run CanBus on all axes.

Hardware Requirements

• 4x NEMA 17 stepper motors (0.9-degree recommended for higher Z resolution)
• 4x GT2 20-tooth pulleys
• ~3m GT2-6mm belt
• 4x F695 or 625 bearings for idlers
• 4x stepper motor drivers (TMC2209 or TMC5160)
• A controller board or expansion board with 4 free stepper driver slots

Klipper Z Tilt Adjust Configuration

With independent Z motors, you enable Klipper's powerful z_tilt system. This automatically adjusts each Z motor to level the bed after probing:

[z_tilt]
z_positions:
  -175, -129   # Front-left corner
  175, -129    # Front-right corner
  -175, 129    # Back-left corner
  175, 129     # Back-right corner
# Coordinates depend on your build size and probe location
points:
  0, 0
  200, 0
  0, 200
  200, 200
speed: 100
horizontal_move_z: 5
retries: 3
retry_tolerance: 0.01
    

Run Z_TILT_ADJUST before every print via your PRINT_START macro. The gantry levels automatically within 0.01mm flatness across all four corners. This eliminates the need for manual bed leveling entirely.

Quad Gantry Leveling (QGL) vs. Z Tilt

QGL on the stock V2.4 controls the A and B steppers (Z belts) to level the gantry. With independent Z motors, Z tilt adjust replaces QGL's role. You should not run both. Disable QGL in your print start routine and substitute Z_TILT_ADJUST instead. QGL is designed for the stock single-motor Z system; it will fight with independent Z control and cause erratic behavior.

Dual Independent Z Motor Upgrade

A middle-ground modification is keeping the stock leadscrews and gearbox but adding a second Z motor. This provides redundancy without abandoning the stock architecture. Two motors drive the gearbox in parallel through a belt loop. If one motor fails, the other can still move the bed.

Configure this with Klipper using [stepper_z] and [stepper_z1] sections. Both use the same rotation_distance (8mm for stock leadscrews), but the second motor is slaved to the first. Full Z tilt adjust is not possible with only two motors driving a shared gearbox, but you gain safety redundancy and can distribute the load across two drivers, reducing thermal stress on each.

Performance Comparison

Choosing the Right Mod for Your Build

If you are printing primarily functional parts and ABS, the stock Z system is perfectly adequate. Upgrade to BelZed if you are chasing surface finish and want to eliminate Z-banding. Go for the full belted conversion if you print at high speeds (300mm/s+) and need frequent Z hops. The dual motor upgrade makes sense for reliability-focused builds running 24/7 production where a single motor failure would be costly.

Whichever path you choose, ensure your linear rails on all four Z corners are well lubricated and smooth. The best Z drive mod in the world cannot compensate for sticky or binding Z rails. Use Super Lube 21110 synthetic grease or equivalent — lithium grease is not recommended as it thickens in cold environments and can cause Z binding on the first layer after printer cooldown.

Z Endstop Considerations

All Z drive mods require rethinking your Z endstop strategy. The stock V2.4 uses a microswitch endstop triggered by the gantry at Z=0. With a belted mod, the bed position relative to the gantry changes. You have two options:

• Bed-mounted endstop: Mount a microswitch or optical endstop on the frame that triggers from the bed carriage. This measures the bed position directly, independent of belt stretch or wear.
• Probe-based homing: Use a probe (Klicky, Euclid, TAP, or Beacon) to home Z by probing the bed surface. This is the most accurate method and eliminates the endstop entirely from Z homing.

Probe-based homing is strongly recommended with any Z drive mod. Add [probe] and [safe_z_home] sections to your Klipper config:

[safe_z_home]
home_xy_position: 175, 175
speed: 100
z_hop: 10
z_hop_speed: 20
    

The home_xy_position should be the center of your build plate. This moves the toolhead to center, then probes down to find Z=0, avoiding any bed tilt issues when homing at a corner.