BearExxa V2 development news

Hi Everyone,

I hope you are all fine and have a great summer (or winter if you have the head down compared to my country). Here are some news on the development of the new extruder.

Custom Motor

I have finished all the testing on the custom steppers and there are some good news:

• We now have enough torque with the 23mm pancake stepper!
• We now have a higher gear ratio of 3.8:1 (and we still have coprime gears for extra longevity) !
• I could see small improvement in moire, small but visible
• The motor is lighter than the previous setup with 17T gear attached to the shaft
• I could have a first estimate of the total weight of the extruder and it is lighter than lots other extruders, even lighter than some using smaller round Nema 14 steppers designed for speed! And I count the filament sensor in it!
• Our special feature seems to work fine and will reduce some variations in the production
• The smaller integrated gear allows to improve some handling and stiffness of the extruder body

On the downside we have decided to make another revision of the motor for mainly two reasons:

• We are at the very limit of temperature, it could be acceptable but not much margin. However, we have too much torque so with a refinement on the coils we can improve temperature without affecting the extruder force
• We have also found an issue in the geometry of the stepper and we must fix this before the release

I should have this new motor revision in about a month, so you still need to be patient I am very sorry. The additional good news is that we might be able to reduce the weight even more (finger crossed).

I take this opportunity to thank Jason from LDO Motors and his whole team for their help and knowledge in this custom motor development. They support all my requests (and I can have some special one :D ), they are proactive and they come with great ideas. Just a pleasure to work with LDO Motors, as always!

Kit preparation

In addition to the custom stepper we are building the BearExxa V2 kit to upgrade from stock Prusa or Bear extruder. It will include all screws/nuts/washers, the bearings, the custom stepper, the big 50T gear made by Bondtech and some other little things. It will not include the Bondtech gears you already have on your Prusa/Bear extruder nor the E3D Revo.

Nozzle fan duct

I made some extra testing with nozzle fan duct design (shroud) and tried to have a better nozzle view. I took some inspiration from the excellent work of Teookie and his Delta-P. Unfortunately, I couldn't achieve better performance than the duct I have designed for the BearExxa V2 , having a front airflow really helps according to my tests. However, I could improve the current airflow so that is a plus!

Fix and refinements

I found that some PLA doesn't unload as easily as in BearExxa V1 so I have improved the filament guide to solve this. It will helps for MMU2S/ERCF as well.

I have added a feature to reduce warping of first layer when printing the extruder and carriage with material like ABS/ASA/PC.

I have replaced the two square nuts that hold the bottom of the motor plate with hex nuts. I found that those square nuts are falling a little to easily, plus it makes a smoother body shape.

I am also testing a new way to mount the hotend fan, it makes the maintenance easier as we don't need to remove a fan mount screw when you need to access the heatsink. It also save some weight as we can remove one screw and a square nut.

I am not yet ready to have a new release with those improvements yet. I will do my best to make one before the new stepper arrive but I cannot guarantee.

That's all folks!

Happy printing :)