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Add a washer to the screw, to avoid damaging the printed part.
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Insert the screw through the hole on the opposite side to the hexagonal cavity.
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Thread the hex nut onto the screw and tighten the screw.
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When the nut is fully seated, remove the screw being careful not to dislodge the nut.
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The printed parts for the extruder include a PTFE tube cutter tool that matches the specifications required for the Bear extruder. The part name is ptfe_cutter_50mm_60deg.stl
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Follow this guide to prepare the PTFE tube Trim PTFE Tube.
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Clean up strings from your printed parts with tweezers and a hot air gun (be careful).
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Carefully check the inside of the holes in the X ends, where the smooth rods will be inserted.
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Remove any elephant foot with a deburring tool.
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Check all bridges. If a bridge is falling in its center: heat tweezers with a lighter and press on the area with the poor bridging, to flatten it.
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Make sure the filament path through the extruder body is clean, round, and clear from obstructions.
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Try to insert the belt from your original Prusa in the Bear x_carriage. Use a slotted screwdriver to make sure the belt goes fully inside. If you have trouble inserting the belt, it might be due to the following issues:
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Your prints are over-extruded. When you print functional parts you MUST calibrate your extrusion multiplier. This is not optional, every spool is different and will melt differently. Check our calibration guide: Extrusion multiplier and filament diameter
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You are not using a genuine Gates 2GT belt or your belt profile is not corresponding to 2GT.
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You are using a different filament than plain PETG and the shrinkage coefficient is different. In this case, you can compensate for shrinkage within your slicer.
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1. Unload the filament and allow the hotend to cool. Turn off the printer and remove the power plug.
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2. Protect the printing surface and use a tray to catch small components that might fall during the disassembly.
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3. Remove the M3x40 screw securing the Rambo/Einsy cover and disconnect all the plugs, from the board that make up the extruder cable bundle.
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4. Cut the zip ties and remove the screws clamping the extruder cable to the Rambo/EINSY box and remove the 3mm nylon filament. Completely unwind the spiral/fabric wrap from the cables.
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5. Cut the zip ties securing the extruder cables on the cable guide and remove the cable wrapping. Untangle the wires.
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6. Unscrew and remove the cable guide.
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7. Disconnect the X motor from the Rambo/Einsy. MK2.5(S) only: remove the X end stop cable from the Rambo/Einsy.
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1. Cut the zip ties holding the extruder assembly to the linear bearings.
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2. Remove the timing belt. Replace if worn or damaged.
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3. Carefully remove the extruder from the X axis. Make sure you are not damaging any wires.
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4. Tear down the entire extruder by reversing the assembly instructions provided by Prusa.
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5. All the printed parts will be replaced. Most of the electrical parts and fasteners can be reused.
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6. Check all wires and connectors for possible damage especially where wires may have been bend or clamped too tightly.
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1. Remove the screws holding the z-tops in place.
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2. Pull the z-tops off the smooth rods. Try to avoid pulling the rods out of the z-motor mounts. If a rod does come loose, avoid rotating it within the linear bearings.
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3. MK2.5(S) only: Remove the two M2x12 screws securing the x-end limit switch.
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4. Remove the three screws holding the x-end motor.
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5. Pull the rods out of the x-end-motor and idler mounts taking care not to bend or twist the rods.
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6. Remove the screws, securing the trapezoidal nuts to each x-end and spin those nuts to the top of the lead screws and remove them. They will be reused.
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7. Lift the x-ends off the z-axis rods by lifting both the motor and idler mounts evenly.
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Congratulations you have finished this step and are ready to start with the assembly :-)
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Got to the next chapter: 2. X axis
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