Retraction is used at the places in a print where the printer has to do a travel move between two printed parts. Without retraction, extruded material will hang between the parts. By using retraction, “stringing” (thin threads of plastic in between the printed parts) is prevented, resulting in a much cleaner model. Exercise caution when using flexible materials or models that require a lot of retractions as it may lead to grinding of the filament.
Retract at layer change
This setting forces the printer to retract the filament before it starts printing the next layer.
This is the distance in millimeters that the material is retracted from the nozzle. A long retraction creates more stress on the material, takes time and minimizes oozing. A short retraction has an increased chance of oozing, but keeps the material secure and print time shorter.
Retraction speed: retract and prime
This refers to the speed, in millimeters per second, at which the material is retracted and primed. A high-speed retraction minimizes oozing, but can cause material grinding. A low-speed retraction has an increased chance of oozing, but will protect the material.
Retraction extra prime amount
This is the extra amount of material that is extruded after a retraction to compensate for oozed material after a travel move. This setting can be useful, especially with flexible filaments as these require extra pressure to print properly. By increasing the retraction extra prime amount, more pressure is added which helps compensate for the material.
Retraction minimum travel
This setting determines the minimum distance the print head must travel before a retraction move is initiated. With retraction-intensive models, you could increase the value, which decreases the number of retractions and reduces the possibility of grinding. However, the value must not be set too high as this might lead to stringing and cause ugly “blobs” to form on the print.
This close up of a tiny fence shows retractions (in purple) on the left model. The right model is not allowed to retract (in blue) the short distance between the railing bars due to a minimum travel restriction that is greater than the actual distance
Maximum retraction count
The maximum retraction count sets the maximum number of retractions on a certain length of filament (see minimum extrusion distance window). All retractions above this value will be ignored. The benefit of maximizing the amount of retractions is that it decreases the possibility of grinding. However, for models with a lot of holes (e.g. a voronoi print), this can lead to stringing if the value is too low.
Cross section of the feeder
Minimum extrusion distance window
This is the length of filament over which the maximum retraction count is enforced. This value protects the number of retractions on the same piece of filament.
For example: If you set the maximum retraction count to 25 and the minimum extrusion distance window to 1.0 mm, it will do a maximum of 25 retractions per 1.0 mm extruded filament.
Combing will reduce the chance of defects on outer surfaces of the print by recalculating all nozzle travel moves to stay within the perimeter of the print. This results in greater travel distances, but with a reduced need for material retraction.
If combing is disabled, the material will retract and the print head will move in a straight line to the next point.
Combing disabled (left) has retracted travel moves that move outside the print’s boundaries. Combing enabled (right) has unretracted travel moves within the print’s boundaries.
Avoid printed parts
By enabling this setting, the print head will avoid printed parts when traveling. When the shortest route from one point to another in the print is obstructed, the print head will move around it. This decreases the possibility of coming into contact with parts of the model that have already been printed, in turn reducing the chance of surface defects or material mixing. To use this setting, you must first enable combing.
The travel moves in both images start and end at the exact same location. Avoid printed parts is disabled for the model on the left, and enabled for the model on the right.
This setting defines the distance (in mm) between the nozzle and the print when avoid already printed parts is enabled. A greater avoid distance means a reduced chance of contact with the printed model, however a large avoid distance will significantly affect the length of the travel moves, impacting the print time, and chance of oozing.
Layer start X-Y
This setting defines the position closest to these coordinates to start the next layer. The setting is normally set to the far-right corner because that is where the Ultimaker 3's switching bay is located.
Note: This is a different setting than the Z-seam. The z-seam alignment setting only adjusts the start position of the outer wall, where this setting normally starts at the infill.
Z-hop when retracted
With this setting, the build plate will move down by the set value when a retraction is performed, allowing the print head to travel over the print without the nozzle touching it. This prevents the nozzle from hitting the object or leaving “blobs” or scratches on the print surface. Please note that for prints with lots of retractions/travel moves, this can increase the print time.
Z-hop only over printed parts
The 'Travel' category includes the option 'Avoid printed parts'. When this is enabled, the nozzle will avoid these parts when possible in order to reduce scratching the model’s surface. When there is no way to avoid the part, the printer will perform a Z-hop when traveling over the part.
This setting specifies the height (in mm) at which all Z-hop moves are performed during the print.
Z-hop after extruder switch
This feature will trigger a Z-hop when the nozzle moves to the switch bay, reducing the chance that oozed material will come in to contact with the printed model.
Continue reading about Cooling settings.