Bulk filament buyers get burned by one thing more than anything else: inconsistency they didn't check for. Here's the QC checklist we'd run before any large order — it's the same one we run on our own production.
1. Diameter & roundness
Measure 20+ points across several spools with a caliper or laser micrometer. Tolerance ±0.02 mm is good; ±0.05 mm is a red flag for long prints. Ask how the supplier measures — inline gauging beats spot checks.
2. Moisture content
Check the vacuum seal and desiccant on arrival. For PA/PC, a moisture analyzer reading under 0.1% is ideal. Wet filament = bubbles, stringing, weak parts — and a warranty dispute later.
3. Color ΔE
Compare spools across the lot against the master sample with a spectrophotometer or your eyes under daylight. Same color, same box: acceptable. Same color, different box: suspicious.
4. Winding quality
Tangles and cross-overs cause mid-print failures that cost more than the spool. Do a 10-meter hand feed test from a new spool.
5. Lot numbers & traceability
Every box should carry a batch code linking to production data. No batch code, no traceability, no accountability — walk away.
6. Your own test print
Before the container ships, run a temperature tower and a mechanical test part (e.g., a 3-point bend or snap test) with the exact profile you'll use in production.
VOXFIL ships batch reports with every bulk order and invites buyers to request pre-shipment samples — the checks above should be easy for any supplier worth your money.