Z Steps increasing and converging infill lines!

Suddenly the printer (TAZ4) has started to print weird.

The printed layers are appart about twice the layer thickness. It is like the Z axis is moving up two times per layer.
I noticed as well that the infill lines (20% infill) are converging instead or being parallel lines.

It happens with both Slic3r and Simplify3D.

The printer was working well yesterday!

Any hint is welcome!


Perhaps your hobbed bolt is not gripping filament and pushing it through?

What temps are you printing at?
What speeds?

When the printer is not printing, are the herringbone gears turning, but the filament is not advancing?

Or is the filament squirting out but just making a mess because the z height is too high?

Perhaps a clogged nozzle?

If you raise the nozzle a few inches (3 or 4 inches is great) off the table and extrude some length of filament does it squirt out nice and straight and down towards to table? Or does it curly-cue around and goop up the nozzle?