Test 5

Flow (extrusion multiplier)

Seven hexagonal pads in a row, each one step taller than the one before. The top of every pad is printed with a slightly different amount of plastic, from 91 % to 109 %. Look at the tops with a low light, pick the smoothest one with no gaps and no ridges, then print the fine file for that pad: seven more pads, 1 % apart. The best one gives your new extrusion multiplier.

About 8 g of filament and about 30 minutes per print, with no changes to your profiles.

PrusaSlicer has no flow setting per object, so the file sends a flow factor (M221) at the layer where each pad's top begins: the four top layers of pad 1 print at 91 %, those of pad 2 at 94 %, and so on. The pads below and above share those layers, but only their hidden insides. The file also fixes the speed of the pads at 60 mm/s, so every top is printed the same way, and puts everything back to 100 % at the end.

Open the file with File › Open project. Never with Import, never as a ZIP: an import keeps the shape but drops the flow factors, and every pad would print the same.

What you need

To print

The coarse file, then one fine file
PrusaSlicer 2.9 (2.7 is the minimum that opens the project)
Your own printer, print and filament profiles, already working
The first layer, the temperature and the pressure advance already set
The filament to test, dry: about 8 g per print
A bed at least 180 mm wide

To read it

A lamp you can move, or a phone torch
A fingernail
The selector on this page

Before printing

Step 1 What it is for, and when to run it

The coarse flow test printed: seven hexagonal pads in a staircase on a thin strip with the numbers 1 to 7 — The coarse print in PETG: from pad 1 (91 %) to pad 7 (109 %). The top lines run the same way on every pad; the low rim on pad 7 is where the file puts flow and speed back to 100 %.

It finds the extrusion multiplier of a filament: how much plastic PrusaSlicer asks for, so that solid layers are full without being overfilled.
Run it after pressure advance, once per filament (and per nozzle). The result goes into Filament Settings › Filament › Extrusion multiplier.

Too little plastic leaves gaps between the top lines and weak walls; too much makes ridges, rough tops, blobs and parts that come out slightly too big.
Read it on top surfaces, not by measuring a wall with a caliper: a wall wobbles a little, so it always measures too thick, and 0.02 mm already means 5 %. That is why this test reads tops, as Ellis' guide recommends.
It comes after pressure advance: PA changes how the line starts and ends, which shows on the tops.
BeginnerThe multiplier is a correction on top of the filament diameter. Most filaments land between 0.92 and 1.05.

Step 2 Which file

File	Pads	When
`flow_coarse_91-109.3mf`	91, 94, 97, 100, 103, 106, 109 %	First: finds the zone
`flow_fine_<from>-<to>.3mf`	7 pads, 1 % apart, centred on one coarse pad	Second: the one for your best coarse pad (the selector names it)

There are seven fine files, one for each coarse pad: 88-94, 91-97, 94-100, 97-103, 100-106, 103-109, 106-112. Print only the one the selector gives you.

Download on Printables All HexCalibr tests on Printables

The fine file covers ±3 % around the coarse pad you chose. The coarse step is 3 %, so the right value is always within that range.
Every file is 150 × 30 mm and about 8 mm tall: it fits any bed from 180 mm.
ExpertOn an IDEX or multi-tool printer, assign the object to the tool you calibrate (right-click › Change extruder). The multiplier belongs to the filament profile of that tool.

Step 3 Before you start

Write down the extrusion multiplier in your filament profile (Filament Settings › Filament). You need it at the end.
Nothing else to change: layer height, speed and flow are set by the file for the pads only.

The layer height is forced to 0.2 mm (half the nozzle): the file must know where each pad's top begins.
The pads print at 60 mm/s, every line, as Ellis' guide recommends for this test. The slicer sees a slow print and never slows the small top pads down; a speed factor (M220) brings them to 60 mm/s.
The narrow raised strip at the back of pad 7 is not a pad: its last layers put the flow and the speed back to 100 % and show the end message.
If you cancel the print, send M221 S100 and M220 S100 from the console before the next print.

Print and read

Step 4 Open, slice and print

File › Open project, then Slice now. In the preview the pads rise one step each, from 1 on the left to 7 on the right.
Print the coarse file. Do not touch speed or flow while it prints.

Step 5 Read the tops

Pads 1, 4 and 7 of the same coarse print side by side under the same raking light: deep dark grooves between the lines on pad 1, an even top with faint lines on pad 4, raised, separate lines on pad 7 — Pads 1 (91 %), 4 (100 %) and 7 (109 %), same photo, same light. Pad 1: dark grooves between the lines. Pad 4: the lines close up into an even top. Pad 7: too much plastic, so each line stands up as a ridge.

Hold a light low, raking across the top lines, and look at the middle of each pad.
Too little: gaps or dark grooves between the lines; you may see the infill through them.
Right: lines joined with no gaps, a flat, even top; the lines are still faintly visible, and you can still feel them with a fingernail.
Too much: ridges (lines standing higher than their neighbours), a rough top that catches your fingernail, plastic piled up at the edges.
If two pads look alike, run a fingernail across the lines of both: keep the one where it glides evenly, without dropping into grooves or catching on a raised line.
If they still feel equally good, take the higher one: a little too much is better than a little too little.

Common misreadingThe edges always look fuller: the perimeters and the turnarounds of the top lines add plastic there. Judge the middle.
Common misreadingA glossy, perfectly smooth top can be too much: look for the faint lines, and for ridges under a fingernail.
Common misreadingYou can feel lines on every pad, even the best one: that is the shape of each printed line, not a flow error. The multiplier only makes the lines even; for a truly smooth top, turn on ironing (Print Settings › Infill › Ironing, expert mode) on the parts that need it.
Common misreadingGaps only on one side of each line, or rough patches that move from pad to pad: wet filament or a worn nozzle, not the multiplier.
Pad 1 is the lowest and pad 7 the highest, but every top is the same: four layers over sparse infill, with the lines running the same way on every pad. The height does not change the reading.

Step 6 Choose the fine file, then the new value

Tick the best pad of the coarse print: the selector names the fine file to print.
Print it, read it the same way, tick its best pad and type the extrusion multiplier your profile has now: the selector gives the new value.

1. Coarse print: tick the best pad

Pad	Flow	Best
1	91 %
2	94 %
3	97 %
4	100 %
5	103 %
6	106 %
7	109 %

Pad	Flow	Best
1	–
2	–
3	–
4	–
5	–
6	–
7	–

New multiplier = the multiplier now × the best pad's percent ÷ 100. Example: 0.98 now, best pad 96 % → 0.98 × 0.96 = 0.94.

Step 7 Save the value

Close-up of pad 4 of the check print flow_fine_97-103 after saving the new multiplier: the top lines are joined into a flat, even surface, still faintly visible, with no gaps and no raised lines — The check print `flow_fine_97-103` after saving the new value (PETG, 0.85 → 0.88): pad 4 (100 %) is the best one. Lines joined, no grooves, none standing up; you still see and feel them.

Type the new value into Filament Settings › Filament › Extrusion multiplier and save the filament preset (the disk icon).
Print the fine file flow_fine_97-103 once more if you want to check it: pad 4 (100 %) should now look best.

The value belongs to this filament on this nozzle. A new spool of the same filament usually keeps it; a different brand or colour can differ by a few percent.
If you later change the nozzle or the hotend, run it again.