3D printing · Slicer settings · 5 min read
Stronger prints with wider lines: the extrusion width checklist
When a part breaks, the usual fix is more walls or more infill. CNC Kitchen tested a setting most people never touch, extrusion width, and found that wider lines bond layers better and can make a part stronger without adding print time.
Video: Extrusion Width - The magic parameter for strong 3D prints? by CNC Kitchen (14 min, 2019). All credit for the testing goes to Stefan; go subscribe.
Shimko3D take
This is the cheapest strength upgrade I know of for brackets, hooks and clips: change one number, not the model. The video is from 2019, but the reason it works (the nozzle pressing a fatter line into the layer below) hasn't changed. Alexandre Chappel uses the same trick for speed in our fundamentals guide.
The checklist
- Find the right setting. Extrusion width is how wide each line is. In OrcaSlicer and Bambu Studio it's called line width. It is not the flow ratio or extrusion multiplier, which only changes how much plastic comes out. ▶ 2:17
- Know why wider can be stronger. A line wider than the nozzle gets pushed down and out under pressure, so it fuses harder with the layer below. Weak layer bonds are where most FDM parts break. ▶ 2:17
- Change one thing at a time. The test kept nozzle, filament, temperature, fan and layer height fixed and only changed line width, from 90% to 250% of a 0.4 mm nozzle. Do the same when you test, or you won't know what helped. ▶ 3:08
- Up to about 140% you won't see a difference. Benchys looked basically the same from 90% to 140%. Rough overhangs and missing thin walls started around 160% and got bad by 250%. ▶ 4:39
- Layer strength peaked around 150%. In the pull test, layer adhesion rose up to about 150% line width, then dropped, possibly because the rougher surface starts cracks sooner. ▶ 6:31
- Compare at the same wall thickness. Two walls at 200% and four walls at 100% give about the same wall. Testing those pairs shows whether the gain comes from the wider line itself, not just from more plastic. ▶ 8:36
- For load-bearing parts, try fewer, wider walls. In the hook test, two walls at 200% held more weight than four walls at 100% and printed faster, because there are fewer lines to lay down. ▶ 10:34
- Test it on your own part. Print the part you actually need twice, once at your normal line width and once at about 150%, with nothing else changed. Break or load both and keep whichever wins.
Before you trust it
- The numbers come from one printer (a Prusa i3 MK2S), one PLA and three samples per setting. Trust the direction; treat the exact percentages and weights as approximate.
- A wider line at the same speed pushes more plastic per second. If your hotend can't melt it fast enough you get under-extrusion, so slow down or check your max volumetric speed.
- OrcaSlicer lets you set line width per feature. Keeping the outer wall near normal and widening inner walls and infill should keep the outside looking clean (my suggestion, not something the video tested).
Try it on your next print
Got a bracket or hook that keeps snapping? Print it at your normal line width and at 150%, and see which one gives up first. Got a result? Send it to me; I'll feature the best ones.
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