Like you I have only used two of these in non-CNC rolls, conveyor drives. But there is nothing wrong with them. I would not hesitate to use them on a CNC application. I found them easy to setup using the provided setup software.
The only better units would be the SureServo2 line, higher encoder resolution. I have used these in a CNC application with good success, the spindle/C-axis on my lathe.
Thanks for the suggestion, I didn't even look at the SureServos because I didn't realize they had been revamped. I missed the "2" in the name. SureServo has been kicking around a long time and last time I looked at them there were warnings about impending discontinuation. So I just avoided them.
I am about to do some analysis, which, if I'm not careful, might sound like I'm taking a dump all over your attempt to be helpful. So before I start I want to plainly state that's not what this is. I understand that you made the recommendation not just because encoder resolution is higher, but because it is something you've actually used on a CNC machine and can vouch for. I do appreciate that. I am just trying to make sense of the proliferation of these ultra-uber-ungodly-high resolution encoders that have been getting put on servos in recent years. It seems not that long ago, 512PPR was normal, 1024PPR was high/normal, 2048 PPR was "high precision," and 4096PPR was "F. you money."
- Encoder resolution on my existing motors is 2,000PPR
- Encoders on the LS servos are 131,072 ppr
- pretty sure they're magnetic
- pretty sure they're serial
- That's a 65x improvement over what I have (theoretically)
- SureServo 2 encoders are 16,777,216 ppr
- pretty sure they're magnetic.
- Can't tell if they're serial but that seems to be the new popular thing, so they probably are (even though there's like 30 pins in the encoder plug).
- That's an 8,388X improvement over what I have and a 128X improvement over LS (theoretically)
That seems like a decisive win for SureServo2, but....
- I am not convinced that magnetic encoders are as accurate as their resolution implies.*
- But assuming that they are, if they are serial, then I am not convinced that they can communicate their position to the drive fast enough to matter, unless you're only going like 10 RPM. If it's running 3krpm and serial packet #77 reports a position of 89,587 and serial packet #78 reports 97,998, then it has effectively the same resolution as my 2000ppr optical encoders.
- But assuming I'm wrong about that too, I have had no issues related to the 2000ppr encoders on my existing motors. The ballscrews are 5mm pitch (5.08 TPI) so that's 10,160 pulses per inch, for 0.000,098" resolution. I Can't imagine myself ever needing the machine tuned well enough that the comparatively "low resolution" of the existing encoders would be the limiting factor. So 65X improvement or 8,388X improvement, I don't think I will notice.
- Just for fun, linear resolution (if it's to be trusted) would be
- LS: 0.000,001,502"
- SS2: 0.000,000,012"
- WOW. I would have no way to verify accuracy at that level. Would anyone? IS there any earthly technology able to measure 12 billionths?
(*) I think they are just an analog magnetic displacement sensor and the "PPR" comes from the input resolution of the ADC that the sensor is connected to. I could connect the potentiometer out of an old tape deck to the 32 bit input of a AD7177 chip and call it a 4,294,967,296ppr single-turn encoder. I'll give them credit for using something better than an old tape deck pot, but still, it "technically could be anything." Hypothetically SureServo2 and LS could use the same sensor, but sureServo2 has a higher resolution ADC. Hypothetically, that analog sensor could be less accurate than my 2000ppr optical encoders. Again, unless I'm wrong. I am actually talking out of my butt. I don't know how they actually work, just making educated guesses. And I know nothing about the serial protocol they use.
