Extruder news

Hello everyone, some news on BearExxa V2 :)

Custom motor

Our custom stepper has now been validated and it is time to share some details!

In order to have a repeatable manufacturing and perfectly concentric gear, we are machining the gear directly on the motor shaft (see the 2nd and 3rd pictures). This will also reduce potential 602 pattern as this is even more precise than a press fitted gear. The gear is also hardened for a very long lifespan.

On the last picture you can also see an example of gear meshing issue that extruders based on Nema 14 with Bondtech 50T gear generally have. It is also important to note that the big Bondtech gear might move depending how well the “hobb” gear is aligned with the filament path. This means that the surface of contact can get smaller once the extruder has the filament loaded. The gear length we are using on our custom motor ensure that teeth are always fully in contact with the motor gear in every conditions and allow us to use larger and stronger bearings to support the Bondtech 50T gear.

Another advantage of our stepper is that the recommended current is matching the default Prusa current, meaning no special configuration are required in the start gcode of your slicer. It is a drop-in replacement.

Finally, the total BearExxa V2 is lighter than some Nema 14 based extruders (like the Stealthburner). And those extruders with smaller motors are generally running on CoreXY for which you have to add the weight of the gantry (and it can be heavy as it carries a rail, several carriages, idlers, screws, etc.). On Prusa i3 style motion, the bed will always be heavier than the extruder and will generate ringing in both acceleration and deceleration, so on all corners of a square for example! It is therefore clear that using a lighter stepper on the BearExxa V2 wouldn’t bring any valuable advantages.

Recent updates on “602 pattern”

MirageC has recently made a great video regarding 602 pattern, if you have not seen it then check his youtube channel! Maybe you have seen some similarities with our goal to have a perfectly centered gear on our custom motor :) . For your information, I am in contact with Bondtech and I follow the discussions closely. I unfortunately cannot share more than this at the time being.

Hotend fan

The Prusa firmware requires a third wire on the hotend fan to read the rotation and stop the print in case of problems. The E3D Revo Micro doesn’t come with such a feature and, as explained in the past, the Prusa self tests would fail. LDO has talked to Sunon and we will be able to include a 3 wires fan in our BearExxa V2 kit and ensure full compatibility with Prusa safety features! What is also good is if you are running a Revo Six on your current extruder; you will only need to add the Revo heatsink.

X end idler

A very common upgrade over the Bear X axis is to use a better idler for the belt ( https://github.com/gregsaun/bear_extruder_and_x_axis/tree/master/optional_parts/x_end_idler_tensioner_e3d ). We have decided to make it the default setup and the BearExxa V2 kit will include a better idler. For information, this idler will improve the following problems:

• Reduce potential belt wobbling due to too larger flanges
• Use teeth to reduce belt fatigue. Gates recommend to use toothed idler for diameter smaller than an equivalent 40-groove pulley
• Dual quality bearings for long lifespan

Timeline

The final revision of the extruder kit is leaving LDO factory at the moment. It includes everything for the X axis and the extruder except the fans which will need 2-3 more weeks. Once I receive the fan I will be able to start selling the kit through resellers. After all this time and your patience it is finally coming :)