Ch 07Checkpoint
Checkpoint 07¶
Checkpoint · Chapter 07 — A/B belts and tensioning
- Both belts routed to match p.126 (A) and p.127 (B); each belt stays in one plane, neither crosses the other.
- No half-twist anywhere; belt teeth face away from the extrusion at the X carriage; each belt's toothed face stays on the same side all the way round.
- Teeth meshed on both toothed motor pulleys — each pulley indexes when the belt is nudged, no slip — and on the two XY-joint toothed idlers (A at the right joint, B at the left); smooth back on every plain stack.
- Belt not riding on any printed part at any of the fourteen contacts at six locations, checked at both ends of X travel and both ends of Y travel (p.142).
- Equal length of belt protruding from the X carriage on both belts, after moving the gantry and returning (p.141).
- Carriage bolts and all four M3×8 belt clamps fully tightened; nothing slips under a hard pull.
- Both belts read within a few Hz of each other at ~110 Hz over a 150 mm span, re-checked after moving the gantry — provisional; Ch 14 Step 14.4 sets the final value.
- Gantry moves through the full XY envelope by hand with even resistance, no ticking, no notchiness.
- Probe insulated (front + sides only), fitted, lead uncut with its factory connector, tip 6 mm below the plastic, cable in its channel.
- No hall-effect magnet fitted (p.145 skipped).
- Turn the A motor pulley by hand: the carriage moves diagonally. Turn both pulleys the same way: it moves in a straight line. That is CoreXY.
Common mistakes¶
- Tensioning to final now. Ch 06b releases A/B tension completely as its first move, and it cannot run until the printer is alive (Ch 13); the final value is Ch 14 Step 14.4 — cold, door open, just before the 14.6 soak. Set ~110 Hz, confirm A ≈ B, move on. Chasing the last 5 Hz here is time you will spend again.
- Cutting the second belt to a tape measure instead of against the first. Any length error becomes a permanent tension imbalance you will try to fix with the tensioners, which cannot fix it. Fold-cut both together, or remove the routed first belt and cut the second against it (Step 07.8).
- Wrapping the wrong element of a rear drive unit. Each drive unit holds the motor pulley for its own belt and an idler stack for the other belt. Putting the A belt on the B motor pulley looks plausible and locks the two axes together. The p.126 top-left and p.127 top-right insets show which is which.
- A half-twist in a long run. It shows up as a belt that runs fine at one end of travel and rubs at the other. Sight down each straight run and confirm the teeth face the same way at both ends.
- "Fixing" the teeth-on turn at an XY joint with a half-twist. Each belt meets one toothed idler at the XY joints — A at the right joint (Step 07.16), B at the left (Step 07.17) — and wraps it teeth-on by design. A twist put in to get the smooth back there walks the belt off a flange at the far end of travel.
- Reading a harmonic on the phone. Spectrum apps show peaks at 2× and 3× the fundamental; 220 Hz reads as "too tight" and sends you loosening a correctly tensioned belt. Take the lowest peak, and take three plucks.
- Forcing a belt round a bearing stack. You will damage the flange or unseat a bearing. At a front idler, pull the M3×40 SHCS, thread the belt, refit and redo Step 07.5 (Step 07.15, p.134). A drive unit or XY joint has no such screw — find what is fouling instead.
Next¶
Ch 08 — Toolhead: Stealthburner, Clockwork 2 and the Nitehawk-SB V2, where all five Rev D+ deviations land.
Good stopping point · ~30 min since the last one
inductive probe insulated, fitted, set to height and its cable routed; endstop magnet correctly skipped; A/B cable cover on. Gantry is a working XY system. Do not tension further and do not square the gantry.