I am building a AlfaMendel 3D printer (edited : The original question named it to be Prusa Mendel I2). I printed the extruder drive using PLA material from the STL available in the package but I'm not able to insert the hobbed drive as well as the filament in it. The dimensions of hobbed drive is correct.
Is the problem related to shrinking of print material while printing the extruder drive or something else.
I have included few pics of the extruder drive and hobbed drive.
This image shows the maximum possible insertion of hobbed drive in the extruder drive.
Also note, quote:
Parts included in Github repository have the wrong dimensions for the nut traps! Download the correct version from [Thingiverse Greg's Hinged Accesible Extruder]
Are you sure you have the correct parts for the original Prusa Mendel i2? Maybe you have a different version? The original extruder mount uses an M8 hobbed bolt, not an MK8 hobbed extruder gear. The first is 8 mm in diameter, the latter is 9 mm in diameter.
Edit: After you updated your post to hint to the correct printer, it appears that my answer still holds. You did use the incorrect extruder gear. The 9 mm gear doesn't fit in the extruder part as it requires an 8 mm diameter extruder gear.
It might be difficult to find a 8 mm hobbed gear with a 3 mm shaft diameter, they are usually 5 mm (as in the stepper shaft diameter) or 8 mm (as in the diameter of 8 mm bolts that are frequently used for extruder setups). You could redesign the part (load STL in a 3D CAD program and make the changes). By the way, PLA should not shrink so much. As can be seen in the photo's, it looks like your current printer does not print very accurately, that may also contribute.