<p>On the reprap wiki it says using Znnn it sets a new axis position.  But then it says &quot;No physical motion will occur&quot;. What would the line <code>G92 E0</code> be used for?</p>

The
```
G92
```
command is used to set the start position (origin) of one of more axes (including the current extruder) to any arbitrary value. The command
```
G92 E0
```
is often used to perform retraction and nozzle priming. For example, the following commands are often used in start-gcode sequences (prologues) to prime the current extruder by extruding a small amount of filament:
```
```
G92 E0     ; Reset the extruder's origin
G1 F200 E3 ; Extrude 3 millimetres of filament
G92 E0     ; Reset the extruder's origin
```
```
RepRap Wiki: G92: Set Position