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Why did my flexi fuse?

Pick what went wrong. Almost all of these come down to one setting, and it is usually not the one people reach for first.

The joints will not move at all Over-extrusion, nine times out of ten.
  1. 1 Drop your flow rate to 96% and reprint one segment to test. This is the single most common cause and the easiest to check.
  2. 2 Turn on elephant foot compensation at 0.15mm. Squashed first layers weld the bottom of each joint together before the rest of the print even starts.
  3. 3 Raise your Z-offset by 0.02mm. Too close to the bed does the same thing as over-extrusion.
  4. 4 Drop the nozzle 5 to 10°C. Hotter plastic spreads wider than the slicer thinks it will.
  5. 5 Check the clearance against your nozzle in the table below. A 0.6mm nozzle cannot print a joint drawn for a 0.4mm one.
They move, but they are gritty and stiff Usually nothing wrong. Flexis need breaking in.
  1. 1 Work each joint back and forth twenty or thirty times. Most loosen right up and stay loose.
  2. 2 If it stays gritty, you have strings inside the joint. Dry your filament and raise retraction a little.
  3. 3 Still stiff after that, go down 1 to 2% on flow.
A joint snapped when I flexed it Printed too small, or too few walls.
  1. 1 Check the scale. Below about 60% the links get thinner than two extrusion widths and there is nothing holding them. Use the file we ship at that scale instead of shrinking the full-size one.
  2. 2 Raise walls to 3 perimeters. Joints are thin, so almost all of their strength is wall rather than infill.
  3. 3 Dry your filament. PLA that has sat out for months goes brittle and snaps rather than bends.
  4. 4 Raise the nozzle 5°C for better layer adhesion. Joints fail between layers, not across them.
The thin end fused but the body is fine Cooling, not clearance.
  1. 1 Raise minimum layer time to 8 seconds. Small layers at the tail finish before the plastic has set, so the next layer lands in something still molten.
  2. 2 Turn the fan to 100% for those layers.
  3. 3 Print a second copy alongside it. Two models give each layer twice as long to cool and often fixes this on its own.
The bottom layer is squashed and wider than the rest Z-offset or bed temperature.
  1. 1 Turn on elephant foot compensation at 0.1 to 0.2mm.
  2. 2 Raise Z-offset by 0.02 to 0.04mm.
  3. 3 Drop the bed 5°C after the first layer. A hot bed keeps the lowest few layers soft enough to spread under the weight above them.
It came off the bed partway through A dirty bed, almost always.
  1. 1 Wash the plate with dish soap and warm water, then wipe with isopropyl. Fingerprint grease beats every adhesion setting you can change.
  2. 2 Slow the first layer to 20mm/s.
  3. 3 Add a brim. Flexis have a small footprint for their height, so they lever themselves off more easily than solid prints.
  4. 4 Keep draughts off it. An open window behind the printer will lift a corner.

Joint clearance by nozzle

A print-in-place joint needs a gap your slicer will refuse to bridge, so the minimum scales with your nozzle rather than with the model. Print a 0.4mm model on a 0.6mm nozzle and it welds itself shut.

Nozzle Clearance Notes
0.2mm 0.15mm Slow, but the finest joints you can get.
0.4mm 0.25mm What almost everything ships tuned for.
0.6mm 0.35mm Faster. Expect chunkier joints.
0.8mm 0.45mm Fine for big prints, poor for small ones.

And by material

Filament Adjust by Why
PLA Baseline What we design and test against.
PETG Add 0.05mm Oozes more and sticks to itself, so joints fuse at clearances PLA survives.
ABS or ASA Add 0.05mm Shrinks as it cools, which tightens joints after the fact.
TPU Not advised Flexible filament in a print-in-place joint mostly welds itself shut.

These are starting points from our own printers, not laws of physics. Every machine is a bit different, which is why we publish the exact settings we used on each model's page.

Still stuck?

Send us a photo of the print. We will tell you what went wrong, whether or not it was one of ours.

[email protected]

Test it on one of ours

A model we have already printed on three machines is a better way to tell a bad file from a bad setting.