Comment on Why do we still use stepper motors?
curiousPJ@lemmy.world 8 months agoSteppers have a higher precision to a servos higher speed and torque (but torque that’s not constant.)
Just trying to understand this. Then how come all CNC precision machines use a servo instead of a stepper? I mean there are some ridiculously accurate machines that can position itself over and over varying under a micron (<.001mm) but the manufacturers choose servo over stepper. Is it for the sake of holding torque that servos have to be used over steppers?
ShepherdPie@midwest.social 8 months ago
All the DIY CNC machines I’ve seen use larger stepper motors. The commercial CNC machines I’ve seen can cost $10,000 to hundreds of thousands.
curiousPJ@lemmy.world 8 months ago
It seems like the argument is that at a lower price bracket, stepper motors offer higher performance than what a equivalently priced servo+encoder+controller combo can perform.
I felt like what I’m reading in this thread wasn’t matching up with that I see out in industry… Diamond turning machines are inherently low torque, low speed, AND nanoscale operations which uses servos for driving its respective axis. See precitech -youtube and in stark comparison Roeder’s 5axis optical mold machining. Wire EDM’s were all driven by servo motors until linear motors became popular. Even those famous JingDiao test samples are made on machines driven by servos.
DreadPotato@sopuli.xyz 8 months ago
That’s actually exactly my point, steppers are objectively inferior to servos, but servos are too expensive compared performance gains for hobbyists.
Hacksaw@lemmy.ca 8 months ago
I don’t think the sentence you have is entirely accurate.
High cost servo systems (motor, encoder, and driver) are superior to high cost strippers for dynamic positioning. Even that can be tenuous for low torque low speed applications, or nanoscale applications, etc… Certainly for 3 axis table/gantry CNC systems (router, laser, 3d print) for commercial/industrial grade applications servos are superior.
If you’re aiming for a hobbyist price point steppers have better dynamic positioning performance than servos. You can build a $300-$1000 3d printer with servos, but especially at the low end, it’s not going to be good.
DreadPotato@sopuli.xyz 8 months ago
But that just highlights the statement/question in my OP, it’s just cost prohibitive to use servos as a hobbyist. You can as a hobbyist get a better system with servos, but not for a reasonable price point.
aSingularFemboyHooter@sh.itjust.works 8 months ago
Which makes them superior, which is why they are used. Cost can’t be ignored any more than the torque or speed, speccing parts that are considerably more expensive that achieve equivalent results is bad engineering unless you have a very specific application that requires it.
If it was ‘objectively inferior’ we wouldn’t use them. You build to your requirements, not by playing top trumps with competing technologies while ignoring the cost.