Z-Hop and Travel Moves on Carbon Fiber Nylon: Stop Scars, Blobs, and Nozzle Drag

You pull a carbon fiber nylon bracket off the plate and there's a rough scar down one wall and two little blobs fused on top of the part. Structurally it's fine. Cosmetically it's a sanding pass on every single part, and you know the drag didn't happen on a printed layer — it happened while the nozzle was flying across the print. That's a travel move problem, and the answer isn't cranking Z-hop to the max.

What Z-Hop Actually Costs You

Z-hop lifts the nozzle during travel so it clears geometry instead of plowing through it. The price is that every lift drags a bead of melt out of the nozzle. Carbon fiber nylon sits in the hotend at 275–290°C as a stiff, ooze-prone melt, so the hop smears a thin strand onto the next wall or drops a blob at the landing point. Too little hop and the nozzle keeps kissing the top layer. Too much and you get hairy towers.

Numbers That Work on a 0.6mm Setup

On a 0.6mm hardened steel nozzle I run Z-hop at 0.3mm. Below 0.2mm the nozzle still touches high spots; above 0.6mm you're just making longer strings. Set it to hop on retract only, not on every travel, and use a spiral/helix hop if your slicer has it — the nozzle comes down in an arc instead of dropping straight onto the part and leaving a divot.

Let retraction do the real work: 0.4–0.8mm on direct drive, plus a 1–2mm wipe on retract so the nozzle leaves the wall dry. Travel at 150–250 mm/s so ooze has less time to fall. Turn on travel-inside-part or avoid-crossing-walls if you have it, so moves cross infill instead of the visible outer skin.

When Z-Hop Makes It Worse

Tall, thin parts hate it. Every hop is a hard Z reversal, and on a wobbling tower that's extra ringing and occasionally a knocked-over print. If your drag marks are only on the first layer, that's Z-offset, not Z-hop. And if you're fighting strings across open air, Z-hop is a band-aid: drop nozzle temp 5–10°C and check retraction first.

Check the Spool Before You Blame the Slicer

Wet CF nylon foams at the nozzle. That foam drools, and then Z-hop paints the drool onto your part — I've watched a tech chase a Z-hop setting for an afternoon when the spool was the whole problem. Dry at 80°C for 6–8 hours and feed from a dry box. Diameter consistency matters just as much: a spool that swings a few hundredths changes your extrusion width, your ooze changes with it, and a hop distance that was dialed in on one spool scars the next.

The Setup I Run

For predictable ooze I keep the material consistent. TINMORRY PA6-CF holds its diameter spool to spool, so the hop height I set on Monday still looks right on Friday's batch. For finicky geometry IEMAI PA12-CF comes out of the bag dry enough that I get fewer nozzle pops feeding blobs into the travel path. Both are printed with the settings posted on their pages, not a guess from a spec sheet.

Affiliate disclosure: some links are affiliate links — you pay the same price, we earn a small commission that keeps our testing free.