Step 14.5 — Set the four Z belts to 140 Hz over 150 mm¶
Step 5 of 36 with a helper · Chapter 14 — Calibration and tuning
(no image — see text)
Gather for this segment — steps 14.5–14.6 (~15 min)
Tools and consumables
- 2.5 mm hex key
- steel rule
- phone with a spectrum analyser app
- 4 mm ball-end hex key
- 150 mm machinist square
Already on the bench
- the four M3×16 Z idler tensioner bolts
- the four M5×40 Z joint SHCS
Parts:
- the four M3×16 Z idler tensioner bolts · already on the bench
- 2.5 mm hex key · tool
- steel rule · tool
- phone with a spectrum analyser app · tool
Do:
- Set a 150 mm span: Z bearing block top belt clip to that corner's Z idler pulley centre.
- Pluck it, read the lowest peak, adjust to ≈140 Hz. All four, then re-check after jogging down and back up.
Check
All four Z belts within a few Hz of each other at ~140 Hz, and four numbers in the tuning log.
Helper Holds the phone by each Z belt and reads the lowest peak aloud after each pluck.
What you're looking at
The four Z belts lift the gantry and are set like A and B. One odd belt shows up as scatter in PROBE_ACCURACY rather than as anything you can see. The adjuster is the Z idler tensioner bolt at the top of each upright, an M3×16.
Belt tension — six belts, each over a measured 150 mm span — the calculator needs JavaScript; the limits are in the table on this page.
Caution
Adjust at the Z idler tensioner bolt only, never the Z belt clamps on the gantry corners, on top of each front idler or A/B drive and under each Z joint: those hold both belt ends and let a belt go if loosened.
Caution
Evenness across the four matters more than hitting 140 exactly: the Voron QGL troubleshooting text points at uneven Z belts when PROBE_ACCURACY σ is high. This is the final setting; Ch 06b Step 06b.3 was the working value. (survey §4.3)
Tip
the tensioner head is under the blue slider: 2.5 mm key from below, clockwise as you look up at the head is tighter (verify on bench). The note rises.
Source: Voron docs — Secondary printer tuning § Belt tension · Ch 06b Step 06b.3