I’ve been toying with some ideas around brushless servo motors instead of stepper motors for a while. I have all of the designs to get exact position control perfect, including smoothing out the torque ripple (I do not care to share these at this time).
My question is, if I was capable of offering a brushless motor packaged inside a NEMA17 package with all of the drivers, rotation sensors, and processor inside that would simply wire to a stepstick-based adapter board on your RAMPS/etc board, would anyone buy them? We’ve been using stepper motors for a while now, and people have expressed interest in servo motors, but brushless motors like this have, up until now, been too expensive to implement except in the most expensive of designs.
David
Servos are great. My only beef with them vs steppers would be the price and cycle life. I would love to see some nema’s with built in rotary encoders to act similar to servos.
If you can get the price to be reasonable and the performance to be good, then yes, you would probably find significant interest.
A typical stepper+driver setup can be had for ~$15-25, depending on the strength and degree accuracy in the motor and the specific driver you pick. If you can create a drop-in replacement for around the same price it’d sell like crazy, there’d be the possibility of a price premium for the ability to be closed loop, but I wouldn’t count too heavily on that.
The greater the price premium the more would have to be offered in terms of torque/weight vs a stepper, or possibly total torque (but that would be of more interest to CNC builders rather than 3d printer builders).
Similar lower cost concepts (lower relative to the cost of existing servo options) already exist, both to close the loop on steppers and to turn brushed DC motors into servos, but none of them are integrated into a standard stepper shell they’re all bolt on solutions. They also have significant price premiums over the standard stepper+driver setup which keeps them more niche and less attractive to tinker with.
You will also probably find far greater acceptance and assistance from the community if your project and product are open source. The hobbyist 3D printing community was built by open source enthusiasts and the power users and people whose voices tend to be trusted are all far happier with open source than closed source (and especially patented) things. They’re usually viewed with suspicion at least or hostility depending on the company’s behavior.
@Eric_Davies I was referring to brushless D.C. Motors, not steeper motors. I understand that they are rather similar, but the brushless motors have some speed and smoothness advantages.
That kickstarter is for Steppers with encoders, this design is an actual servo.
This is the brushed DC version I know of existing (as a bolt on solution): https://www.crowdsupply.com/citrus-cnc/tarocco
And this is the open source documentation of it: https://hackaday.io/project/9433-brushed-dc-servo-drive
There was clearly interest in it, and very recently, but between the non-drop-in nature of it and the price premium it isn’t yet a runaway success. Those are the two biggest barriers I would see you facing, very effectively overcoming either one would lead to much greater success I would expect. As would an open source design.
Actually, the wembi uses brushed motors, not stepper motors. From the kickstarter page: "WEMBI essentially allows to emulate a stepper motor with a brushed motor ", so your brushless motors would be potentially be an improvement on that. However, you can look at the number of their backers to gauge the interest level at their price point.
Thanks for all the feedback guys. I will do some more research, put together a few more prototypes, and see what I can put together. Any further ideas are greatly appreciated.
The Wembi is in the same type of devices that I’m going for, but at a lower price point, an easier to use form factor (NEMA17 direct drop-in), and with BLDC motors. Like I said in my original post, the idea is to use a torque ripple compensation algorithm that will smooth out the motor really well.
I’ll keep you all posted as this progresses.