Dimension adds Adrian's extruder distance E value so firmware does not have to calculate it on it's own and can set the extruder speed in relation to the distance that needs to be extruded. Some printers don't support this. Extruder distance is described at:
and in Erik de Bruijn's conversion script page at:
Nophead wrote an excellent article on how to set the filament parameters:
The default 'Activate Dimension' checkbox is off. When it is on, the functions described below will work, when it is off, the functions will not be called.
Extrusion Distance Format Choice
Default is 'Absolute Extrusion Distance' because in Adrian's description the distance is absolute. In future, because the relative distances are smaller than the cumulative absolute distances, hopefully the firmware will be able to use relative distance.
Absolute Extrusion Distance
When selected, the extrusion distance output will be the total extrusion distance to that gcode line.
Relative Extrusion Distance
When selected, the extrusion distance output will be the extrusion distance from the last gcode line.
Extruder Retraction Speed
Default is 13.3 mm/s.
Defines the extruder retraction feed rate. A high value will allow the retraction operation to complete before much material oozes out. If your extruder can handle it, this value should be much larger than your feed rate.
As an example, I have a feed rate of 48 mm/s and a 'Extruder Retraction Speed' of 150 mm/s.
Default is 2.8 millimeters.
Defines the filament diameter.
Filament Packing Density
Default is 0.85. This is for ABS.
Defines the effective filament packing density.
The default value is so low for ABS because ABS is relatively soft and with a pinch wheel extruder the teeth of the pinch dig in farther, so it sees a smaller effective diameter. With a hard plastic like PLA the teeth of the pinch wheel don't dig in as far, so it sees a larger effective diameter, so feeds faster, so for PLA the value should be around 0.97. This is with Wade's hobbed bolt. The effect is less significant with larger pinch wheels.
Overall, you'll have to find the optimal filament packing density by experiment.
Retract Within Island
Default is off.
When selected, retraction will work even when the next thread is within the same island. If it is not selected, retraction will only work when crossing a boundary.
Default is zero.
Defines the amount the extruder retracts (sucks back) the extruded filament whenever an extruder stop is commanded. Using this seems to help prevent stringing. e.g. If set to 10 the extruder reverses the distance required to pull back 10mm of filament. In fact this does not actually happen but if you set this distance by trial and error you can get to a point where there is very little ooze from the extruder when it stops which is not normally the case.
Restart Extra Distance
Default is zero.
Defines the restart extra distance when the thread restarts. The restart distance will be the retraction distance plus the restart extra distance.
If this is greater than zero when the extruder starts this distance is added to the retract value giving extra filament. It can be a negative value in which case it is subtracted from the retraction distance. On some Repstrap machines a negative value can stop the build up of plastic that can occur at the start of perimeters.