Why not brushless motors in direct drive extruders?

[Catalin_RO]

@zapta Quite interesting. Those might be suitable for axis 4 and 5 in a prosumer CNC...

[zapta]

This video has a teardown of such an actuator. Plenty of poles and a planetary gear for torque, and a smart builtin controller.

https://www.youtube.com/watch?v=Mhxz2Bj2RXA&t=615s

It's not light and not cheap but interesting.

[rjenkinsgb]

@zapta said in Why not brushless motors in direct drive extruders?:

Skyentific on youtube often deal with low speed, high torque motors for his robotic actuators.

Those are clones or descendants of the MIT "Cheetah" robot actuators.

They were originally a modified open-loop motor for a large drone, with a hall position sensor and epicyclic gearbox included, to allow them to function as fully commutated BLDCs.

And, they specifically have the ability to be back-driven to accept the weight and shock loading in a robot limb application to emulate biological muscle & limb elasticity, without a high-ratio gearbox that would be damaged by such loading.

The originals are clearly visible in this clip:
https://www.youtube.com/watch?v=xkfXW6XMXao

James Bruton came up with a lower cost DIY version, using generic drone motors with belt reduction rather than the custom epicyclic gearing:
https://youtu.be/Id11PWxnd4M?list=PLuzW8n0FM__UQutfHUF7jf4jbZwmWM1L6&t=196

[Pertti]

Thanks for everybody showing interest around this topic. Looks like reducing weight increases costs as usual.

[Pertti]

Ha-haa, here it is,found in Hollow shaft extruder thread:
https://www.youtube.com/watch?v=f0SuaIMxAs0

[o_lampe]

@Pertti Now you can enjoy your "told you so..." moment. Only 18 month later
ODrive was a starting point, but simpleFOC took the edge off cost-wise. (and it's open source)
Too bad, there are only a few driverboards available. Most of them are DIY projects, which we have to order from jlcpcb.

[Pertti]

@o_lampe I like this group because of this habit of sharing and commenting innovations.

[CNCModeller]

@Pertti @o_lampe I've bought the shields from here in the past and they seem to be good quality. It only takes a couple of weeks to arrive in the UK

SimpleFOC Shield v2.0.4 FOC BLDC servo stepper motor controller brushless motor driver board develop card

https://a.aliexpress.com/_mPDYIZC

[o_lampe]

@CNCModeller These are the official boards, but there are a few designs from forum members. Some are all_in_one boards with STM32 MCU, motor driver and magnetic or optical sensor. None of them are for sale, only by JLCPCB-order.

[CNCModeller]

@o_lampe yeah I have a few different ones, including ones I've got from JLC but for anyone wanting to just have a go they're perfectly usable.

[o_lampe]

@CNCModeller I'm currently playing around with used hoverboard motors and controllers.
There is a github group that has hacked the controller board and offers firmware with FOC, too.
Can't compare them yet with simpleFOC, but in one point they are ahead of them which is interesting for my wind-turbine project. (regen-braking)