Datum

Bay 4 · Line 1, 2 and 3

Measured

Everyone publishes a tolerance. We publish the measurement.

A tolerance is a promise about a spool you have not been sent. This page is about the one you were.

The extrusion line in Bay 4: the die, the cooling bath and the winder, lit low.

  1. 01

    Dry, blend, dose

    Resin is dried for four hours before it goes anywhere near a screw. Masterbatch is dosed gravimetrically at between 1.5 and 4% depending on the pigment. A wet pellet makes a bubbled strand and there is no fixing it downstream.

  2. 02

    Extrude at 1.9 mm

    The die is cut larger than the finished strand because the polymer is still going to be pulled. Melt temperature is held to ±1.5 °C: the single biggest cause of diameter drift on any line is the barrel wandering.

  3. 03

    Bath and draw

    Straight down into water. The strand sets in the first 400 mm and the puller downstream decides the final diameter — speed up and it thins, slow down and it thickens. That is the control loop.

  4. 04

    Gauge on two axes

    A twin-axis laser micrometer reads the strand 500 times a second on two axes 90° apart. The line runs at 12 m/min, so that is a reading every 0.4 mm. One axis gives diameter; the difference between the two gives ovality. The stored trace keeps one record every 8 mm — 41,875 of them on a 1 kg spool — because nobody needs six years of 500 Hz.

  5. 05

    Wind, weigh, seal

    Traverse winding, no crossovers that can trap a lower layer and jam you at 3 a.m. Weighed to the gram, dried again, vacuum sealed with desiccant and a dated humidity card.

  6. 06

    Keep the trace

    The whole series is stored against the batch number for six years. Quote the number on the flange and we will send you the file for your spool, not a representative one.

Batch 24-A-0912 · PLA · Sodium · wound 11 August · operator RH

One kilogram, first metre to last.

420 of the 41,875 records kept for this spool, evenly spaced along its length. The shaded band is the ±0.02 mm limit. The slow rise and fall is the barrel breathing against the room; the fine ripple is the puller.

0 48 96 144 191 239 287 335 1.770 1.750 1.730 mm metres wound
Nominal
1.750 mm
Limits
±0.020 mm
Measured range
1.739 – 1.756 mm
Mean
1.7489 mm
Std. deviation
0.0030 mm
Outside limits
0 of 420 plotted

Ovality

Round matters more than thick.

An extruder meters by volume, and it assumes the strand is a circle. A filament that measures 1.75 mm on one axis and 1.71 mm on the other is inside almost everybody's diameter tolerance and will still under-extrude on every wall it prints, because the volume is not what the slicer thinks it is.

That is why the gauge reads two axes. We hold the difference between them to 0.015 mm, and it is on the certificate.

41,875
records kept per 1 kg spool
±1.5
°C melt stability
0.02
% moisture at sealing
41
tonnes a year, three lines