3D Printer Not Extruding at the Start of a Print: How to Find the Cause

When the Plastic Goes Missing Tells You Most of the Story

Before you touch a single setting, pin down exactly when the plastic goes missing. According to Simplify3D, the most common pattern is a nozzle that lays down nothing for the first few seconds and then starts extruding normally. The skirt or purge line comes out broken and thin, but the part itself starts more or less fine. That is almost always a priming issue, not a hardware failure.

A second pattern is nothing on the first layer or two, then normal extrusion around the third or fourth layer as the nozzle climbs away from the bed. Simplify3D reads that as a nozzle starting too close to the surface. The third pattern is nothing at all, even several layers in, often with the extruder clicking. That points to filament stripped by the drive gear or to a nozzle that is partly or fully clogged. Also note what happened right before the print: a spool swap, a long wait with the hotend hot, or a recent bed adjustment. That context narrows things down faster than any slicer setting.

An Empty Nozzle After Heat-Up: the Priming Problem

A hot nozzle that is not printing will leak. Simplify3D calls this idle oozing: molten plastic drips from the tip while the hotend heats up, or while it cools down after the previous print. That leaves a void inside the nozzle. On the next start, the extruder has to refill that space first, so it takes a few seconds before plastic shows up again. Meanwhile, the toolhead is already drawing your part.

The fix is to prime the extruder right before the part, so the nozzle is full when real printing begins. The easiest way is a skirt, the outline traced around your model without touching it. Laying it down fills the nozzle. Simplify3D suggests adding more skirt loops if one is not enough, and every mainstream slicer has an equivalent setting. Many start G-code scripts also draw a purge line along the edge of the bed, so check that it is still there if you have edited your machine profile. You can also extrude a little filament by hand from the printer menu just before you hit print, then pull the dangling strand off with tweezers.

Nozzle Too Close to the Bed: No Room for Plastic

If the nozzle is nearly touching the build surface, the bed itself blocks the opening and the filament has nowhere to go. Simplify3D gives an easy tell: no plastic on the first layer or two, then normal extrusion around the third or fourth as the Z axis gains height. You may also see the nozzle leave a faint scuff on the plate instead of a bead of plastic.

The cure is the Z offset, which some printers and slicers call a first layer height adjustment. Simplify3D handles it through its G-code offsets. In their example, a value of 0.05 mm moves the nozzle that much farther from the bed. Raise it in small steps until plastic flows out and squishes slightly without staying round. On printers with a probe, the offset usually lives in the printer menu or the machine profile. If only one area of the bed stays dry, the problem is more likely flatness or bed leveling. To judge how much squish is right, our first layer guide shows what a good first layer looks like.

Stripped Filament at the Drive Gear

Most extruders push filament with a small toothed gear that bites into the plastic. Simplify3D notes that if you see lots of plastic shavings, or a section of filament that looks gouged out, the gear has chewed away too much material. It has nothing left to grip. This often follows one of the first two causes: a nozzle jammed against the bed or a starting clog creates back pressure, and the gear grinds instead of feeding.

Prusa's documentation separates two sounds. A loud click most likely means a clogged or deformed nozzle, while a light click usually points to the gearing. Prusa also warns that filament debris builds up in the gear's grooves over time and reduces extrusion. Compressed air, a brass brush or a plain toothpick will clear it. Snip off the damaged length, reload cleanly, and deal with whatever caused the resistance, or the grinding will be back on your next print. Our page on filament grinding covers extruder tension and cleaning in more detail.

Spotting and Clearing a Partial Clog

A partial clog lets some plastic through, just not enough to print properly. Prusa describes an early sign: filament comes out unevenly, curls up and sticks to the nozzle instead of dropping straight down. At the start of a print, that shows up as a thin skirt, gaps in the first layer and a strand wrapping around the tip. Simplify3D lists three root causes: debris trapped in the nozzle, plastic left sitting hot in the extruder too long, or weak hotend cooling that lets filament soften above the melt zone.

To fix it, Prusa says to start by fully unloading the filament. On a standard nozzle, they then describe pushing the included acupuncture needle, or a thin wire, up into the heated nozzle from below. You then run a filament load to confirm plastic comes out, and repeat the process several times. Prusa is clear that you should heat the nozzle only from the printer menu, never with an outside heat source. They also recommend gloves in case material suddenly flows. If that does not work, check our clogged nozzle guide and your manufacturer's instructions before taking anything apart.

A Troubleshooting Order That Saves You a Teardown

Simplify3D treats a clog as the cause to consider last, once the others are ruled out. So work in this order. First, load filament from the menu and watch whether it flows from the nozzle in midair, well above the bed. If it does, the extruder and nozzle are basically fine and the problem lies elsewhere. Next, start a print with a multi-loop skirt and watch the first few seconds. If the skirt fills in and the part starts cleanly, priming was the culprit.

If extrusion is missing only on the first layers, raise the nozzle slightly with the Z offset. If filament will not even flow in midair, inspect the drive gear and filament for shavings and listen for clicking. Only at that point does clearing a clog make sense. Keep in mind that a print that starts fine and then stops partway through is a different problem, often a thermal one. Likewise, under-extrusion that lasts the whole print is a broader issue than a failed start.

Sources and limits

• Simplify3D — Not Extruding at Start of Print
• Prusa Knowledge Base — Clogged nozzle (CORE One, CORE One L, XL, MK4/S, MK3.9/S)

We organize manufacturer and community documentation; we have not measured these products ourselves. The manual for your exact model takes precedence over general guidance.