There are gaps or cracks in my prints. 
If you notice gaps or separating layers in your prints it’s possible that your print just isn’t getting enough plastic – this is called under extrusion and it can have several different causes.


First you should make sure it’s not an issue with the file your printing.

1      In MakerBot Print, navigate to File > Insert Example Prints and select the 20 mm Calibration Box example file.

2      When the model appears on your build plate, click Print Settings. In the sub menu, if you see any settings other than Support enabled right-click on the custom setting and select Reset All to Default Value.

3      Print the model and examine the printed box.


If your calibration box has a flat, solid roof, your MakerBot Replicator Z18 is not having under extrusion problems. The issues you’re seeing on your own prints may be due to your 3D model files or the slicer settings you’re using.


If your calibration box has gaps and cracks or appears brittle, the under extrusion you’re seeing is unrelated to your file and the next thing to look at is how the filamne tis loaded and routed. You should check the following:

•The filament spool - you should be using a large spool of MakerBot PLA filament, the MakerBot logo should be facing up and the filament should unwind in a clockwise direction. Make sure there are no tangles and that the spool is spinning freely.

•The temperature in the room – the MakerBot Replicator Z18 operates best between 15-24°C (60-75.2°F).

•The Smart Extruder+/Smart Extruder – confirm you are using an extruder optimised for the MakerBot Replicator Z18, rather than for a different MakerBot 3D Printer.


If this haven’t resolved the problem you should check the routing at the top of the MakerBot Replicator Z18.

•If you observe bends and kinks in the filament guide tube, you will need a new guide tube.

•If you have a Smart Extruder with an extruder guard and it is causing wear on the filament guide tube, you will need a guide tube and a filament swivel guide to replace the extruder guard.

•If the metal arm that supports the guide tube in the top compartment is damaged, or doesn’t move freely, you will need to replace it.

•Sometimes loading a spool of filament from the bottom drawer will give you too much resistance to the extruder pulling the filament in. You can choose to route the filament from the left side of the printer and use a spool holder to mount the filament.


If this hasn’t resolved your problem the next step is to determine whether the problem is coming from your Smart Extruder+/Smart Extruder or some other aspect of the filament routing system.


NOTE: If you are using a MakerBot Filament Case, switch to loading through the filament drawer while you go through this process.


1. Use a tool to unlock the lid of the MakerBot Replicator Z18.
2. Use the control panel to select Filament > Unload Filament.
3. Open the filament drawer and remove the spool. Unspool about three and a half feet of filament and cut the length free from the spool.
4. On the control panel dial, select Filament > Load Filament to begin the loading process. When the extruder is fully heated, load the length of filament you just cut. Feed the filament directly into the loading tube on the top of the extruder. Do not feed it through the filament guide tube. Do not route it under the extruder guard if you are using an older Smart Extruder that has one.
5. Wait until you see plastic emerging from the extruder nozzle before pressing the control panel dial to finish the filament load process. When youre done, make sure to replace and relock the lid of the MakerBot Replicator Z18.
6. Print the 20 mm Calibration Box example file with standard settings, as you did at the beginning of this process.
7. Examine the second printed box.


If there are gaps or cracks in your print it sounds like there’s something wrong with your Smart Extruder+/Smart Extruder.


If the box has a flat, solid roof, the under extrusion you were seeing before isn’t related to the Smart Extruder+/Smart Extruder. Let’s try to fix it by experimenting with some of the slicer settings available in MakerBot Print.


Raising the temperature of your extruder from 215°C to 230°C will help the plastic coming out of your extruder to cohere better. Be careful though, raising the extruder temperature can also introduce thin strings of plastic between different sections of your print, weaken bridges and overhangs and make it more difficult to remove rafts and supports. Printing at higher temperatures regularly could also decrease the lifespan of your Smart Extruder+ or Smart Extruder.


To raise the temperature of your extruder on a specific print, click the Print Settings button in MakerBot Print. From the Print Settings sub-menu, select Add a Custom Settings, select Extruder and checkmark Extruder Temperature, then select Done. On the Print Settings menu, change the Extruder Temperature to 230. Then re-slice your model with the new settings.


If this didn’t resolve the problem, you should stick with your new temperature settings and also try adding some extra shells. Shells are the perimeters printed on each layer of your object, additional shells make the outside of your object thicker and stronger and can make up for weakness caused by under extrusion.


To add extra shells to a print, click the Print Settings button in MakerBot Print. From the Print Settings sub-menu, select Add a Custom Settings, select Shells and checkmark Number of Shells, and select Done. Back on the print settings menu, increase the number of shells to 3. Then resliced your model with the new settings.


If this doesn’t resolve your issue, we recommend continuing to experiment with the temperature, speed and shell settings, but if you're not seeing any improvement, please open a case with MakerBot Support.