Replacing the stock extruder gear is a cheap, quick and easy upgrade that can drastically improve print quality and reduce defects. The extruder gear’s job is to pull your filament from the spool and feed it into the hotend. The original brass gear however has large, widely spaced teeth with dull edges that can result in missed steps and cause a number of problems.
Installing a better extruder gear will provide you with finer teeth, capable of gripping the filament and passing it through without a hitch. This can drastically improve prints with small details as it offers a much more consistent flow of plastic.
*Note: Monoprice has started shipping printers with these already upgraded from the factory. If you have just purchased your printer in the last several months, it may not be necessary to replace the gear.
Purchased Parts List:5mm 40T Extruder Gear - $8.99
The following is not required but is available if necessary. The plastic lever can eventually break after repeated use, where the aluminum replacement provides a much better alternative.Micro Swiss CNC Machined Lever and Plate - $48.45
We will first need to separate the extruder assembly from the printer. Using the proper hex wrench, remove the bottom two screws in the extruder fan. When doing so, either hold the stepper motor with your free hand or push the assembly all the way to the right, supporting the motor with the frame. It will otherwise fall after the screws are removed, possibly causing damage to the wiring or motor.
Once completed, set the fan and heatsink aside, where we will only be working with the extruder assembly. In my case, I found that the gear was already upgraded at the factory, where it has fine teeth that will properly feed the extruder. Due to a severe clog however, my gear was caked in plastic and I opted to replace it anyways.
We first need to remove the screw in the upper left. Compress the spring by pushing down on the lever and carefully remove the screw holding it in place. Given the high amount of tension on the spring, not holding this can result in the pieces flying across the room.
After the lever assembly has been taken off, there is a plastic base which must be removed as well. Use the hex wrench to unscrew the screw in the top right corner that mounts it to the stepper motor. Once everything has been removed and set aside, the extruder gear will be exposed.
There is a single set screw that is holding the extruder gear in place. Using the smallest hex wrench included with the printer, loosen this with a single turn and slide the gear off of the shaft.
When placing the new gear on the motor, ensure that the hole for the set screw is aligned with the flat surface of the shaft and tighten it back into place. Make sure to leave a small gap between the motor and extruder gear so these do not rub against each other and cause friction.
With the new gear installed, you can begin reassembling everything in the reverse order, starting with the plastic base plate first. Make sure that the screws line-up with the plug as shown in the second picture below. When screwing the plastic lever back into place, leave enough slack to put the spring back before tightening it down.
As a final step before putting the extruder assembly black into the printer, I would advise sliding a piece of filament through the gear with the lever pressed. This will give you a clear view of the gear in use, where you can ensure that everything is working as expected. If everything moves like it should, you can go ahead and proceed to put everything back together.
While most upgrades and modifications having a certain level of complexity, this is one of the most simple adjustments you can make. Moving from the original extruder gear to one with increased precision, there will be a number of benefits to printing and upkeep.
Since this can change how much filament it feeds through per step, it is strongly recommended to perform an E-Step Calibration after the installation is completed. This will guarantee your printer is configured with the new gear to take full advantage of the upgrade.