Connecting to a CNC machine, pros and cons of USB vs PP vs Ethernet etc.

[JAZZCNC]

Both Ethernet and usb are digital so noise is likely to effect both if large enough, i have my uc300 running an inch away from my 2200w vfd and two inches from a honking great 55v toroidal transformer without issue so sounds like your noise may have been in your power supply, were you using ac filters? either that or there was something massively wrong happening in the next room.

No offense meant to you Jon but I'm doing this all the time and know all about what or not to do. The particular "next room" incident was actually a Compressor with faulty starter but the more the problem was the USB Smooth stepper had a design flaw so didn't take much to upset it. (It was one of the very first models.!! I've since tried newer versions but still had problems.!)

Regards the uc300 then fire up a Tig or Plasma cutter up near by and see how it reacts.! Vfd's and torodial supplys are nothing and it would be very bad state if they couldn't live along side one or both.
It's the things that go off around the machine that seem to affect USB/PC but what exactly I'm yet to determine and believe me I've looked and tried to put my finger on what causes it.!

End of the day I'm into building and using a CNC machine and haven't got time to chase the many things that can bring it down. What I can do is eliminate using those that don't meet the mark by testing them as I go along building machines.
First test is the Tig/Plasma test and then I work backwards from there.!!. . Very few USB devices Pass this test.!

LinuxCNC on BeagleBone Black? A back of the envelope calculation suggests that I can have my entire dedicated control computer as well as software and breakout for the cost of the Mach 3 license alone; that's a lot of difference.

Ah ah now we get to the meet of the Beef.!! . . . Linux Geek. . . Wanting to Pick a fight with Mach user's.!! . . . . Well Not happening I'm afraid been there too many times.! . . . Jog on.!

[Boyan Silyavski]

That thread made me laugh, really. How did i miss it. There is no respect for experience it seems. "Knowledge|" without experience is just a collection of facts or suggestions, from here and there.


I don't know what the hassle is about? Most expensive motion controllers have tried USB and then upgraded to Ethernet controllers. See Galil for example. Even cheap controllers have done the same. So there must be a reason for that.


What happens at low level / cheap/ controllers is that they do the same just like a follow up , after a couple of years, when parts are already cheaply available for the low end market.


Or you say people who make industrial control are stupid and don't know their business.


My blue Makita drill worth 360euro drills holes in steel and my friends green Bosch worth 50 euros drill holes in steel. My Makita can drill 10 years everyday without a glitch and the Bosch will die in month of industrial environment.


As i have pure HF plasma at home let me clear something. Glitches come from not good home grounding, the non shielded mouse and other Pc cables, not from USB or Ethernet cable if they are shielded and all electronics are in a shielded box. So basically both should work if everything to the last detail is well done.


Well Jess, now we know you . You have well presented yourself here. I am half expecting soon to hear that RP is better than ball screw and that HD alu profile gantry is stronger than steel one..

[Jon.]

Really id say its down to personal preference. I think if your using an Ethernet controller over usb because of noise its because you haven't taken the correct steps to shield the controller and that you are also happy to have your controller bombarded with noise, just because it can it doesn't mean it should. You may be correct in that ethernet has better protection against noise but that is providing the noise is entering via its ports. If your talking about noise that is infact capable of entering a grounded enclosure then there's no telling how that noise is going to enter the board, but you say it does fair better but with the correct steps either can work so again personal preference.

Bearing in mind a pc usually has multiple usb ports, but can only handle a single ethernet port so its restrained in that respect.

[m_c]

It is down to personal preference.
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However most experienced machine builders, will recommend Ethernet over USB. Over 99% of USB users never have any problems, even when questionable wiring techniques have been used, yet others, even with proper wiring techniques will have endless problems.
The fact is though, the only threads over on the Mach forum about intermittent communication issues are all about USB controllers. I personally cannot remember seeing any involving Ethernet, apart from initial setup problems.
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PCs can have more than one Ethernet port installed, it's just not a common thing to need. There are people who run Ethernet devices over a full network, but ideally you should be dedicating a computer to running a machine and connecting directly, with the same advice applying to USB.

[Lee Roberts]

Really id say its down to personal preference. I think if your using an Ethernet controller over usb because of noise its because you haven't taken the correct steps to shield the controller and that you are also happy to have your controller bombarded with noise, just because it can it doesn't mean it should. You may be correct in that ethernet has better protection against noise but that is providing the noise is entering via its ports. If your talking about noise that is infact capable of entering a grounded enclosure then there's no telling how that noise is going to enter the board, but you say it does fair better but with the correct steps either can work so again personal preference.

My thoughts are the same, +1 for this post.

If people stoped for a second and actually read what was being said, then...never mind... I guess we are all limited in some ways to our own experiences, a level of understanding for things and struggle with other things.

.Me

[JAZZCNC]

Really id say its down to personal preference. I think if your using an Ethernet controller over usb because of noise its because you haven't taken the correct steps to shield the controller and that you are also happy to have your controller bombarded with noise, just because it can it doesn't mean it should. You may be correct in that ethernet has better protection against noise but that is providing the noise is entering via its ports. If your talking about noise that is infact capable of entering a grounded enclosure then there's no telling how that noise is going to enter the board, but you say it does fair better but with the correct steps either can work so again personal preference.

Bearing in mind a pc usually has multiple usb ports, but can only handle a single ethernet port so its restrained in that respect.

This is the situation Jon from my point of view has someone who Builds machines for others compared to someone like your self who just uses a Machine in a DIY capacity or maybe even Small business venture.
Last Machine I Built went to Scotland which is a 500mile 10hr round trip. I can't afford for to be running up and down the country chasing ghost problems.

It's a FACT whether you agree or not that USB gives more trouble than Ethernet. Just becuase it's working for you without issue doesn't mean it will or does for others. I know this to be true thru experience dealing with Chasing USB ghost's.
I pride my self on the Quality of my Control box's in comparison to many other builders, (and believe me I've been inside a fair few so called Top rated machines costing Several £1000 more than what I build that I wouldn't even turn on.!!) I use correct filtering and ground techniques inside Industrial Steel cabinets along with shielded cables using differential signaling. So I know it's nothing to do with My end but still USB throws Ghost problems and Lockups that cannot easily be explained.

This I can't and Don't want happening on any machine I put my Name on. This is the reason why EVERY component I use when building a Machine gets tested on my own personal machine and for several Months at a time not just a few hours. Could say I torcher them to death or Glory.! . . . NO USB device as passed the Tig/Plasma test.!! . . . . Yes there well maybe some of the Higher end devices that will pass but why should I bother when I've found Ethernet is consistantly more stable on just about every device that uses it. The Cslabs Controllers I use these days are Bullet proof and Never fail or throw wobblys for unexplained reasons.

AND just to prove that USB freaks out when Ethernet doesn't Purelogics PLCM-E3 and Pokey's 57CNC both come with USB and Ethernet connections. The USB on the PLCM couldn't even handle the Mig test before crazyness happened. Ethernet it didn't flinch and when Tig was used it didn't seem to affect it either unless I went right up next to the Controller.!! . . . Pokey's I'm still torchering.!!

[FatFreddie]

I suspect that the underlying UDP ethernet protocol is nearly as error prone as the USB protocol, however, the TCP/IP layer which sits above it and does the error correction is (as has been pointed out) extremely robust so the end result is much better.

I can see both sides of the argument but theory is worth nothing if it doesn't work in practise...

For what it's worth, I've got a 3D printer which is extremely noise sensitive on the USB connection (to the point I now download the print to a memory card and print from that) and a USB CNC controller which I haven't had a problem with but there are dire warnings on the website about using a good quality cable - see https://www.youtube.com/watch?v=NUu9xwDfJ9k

[Jon.]

I good example of usb technology would be an external hard drive ... and in my experience these never loose connection. So what is being compared here is not the technology but the boards themselves as proven everywhere, usb is extremely stable... o hang on my ethernet card needs resetting. damn thing screws up all the time. :P

[Neale]

I suspect that the underlying UDP ethernet protocol is nearly as error prone as the USB protocol, however, the TCP/IP layer which sits above it and does the error correction is (as has been pointed out) extremely robust so the end result is much better.

I can see both sides of the argument but theory is worth nothing if it doesn't work in practise...

For what it's worth, I've got a 3D printer which is extremely noise sensitive on the USB connection (to the point I now download the print to a memory card and print from that) and a USB CNC controller which I haven't had a problem with but there are dire warnings on the website about using a good quality cable - see https://www.youtube.com/watch?v=NUu9xwDfJ9k

Looking at a USB cable, it appears to use ground, power, and data in and data out. So, single-ended connections. Typical Ethernet connections use twisted-pair and, presumably, differential signalling. That suggests that Ethernet, at a hardware level, should be intrinsically more noise-resistant (although my own 3D printer has run for many, many hours over USB without any problem, although that is in a domestic environment without machine tools and EMI generators nearby). I think FatFreddie has it right with reference to TCP, though. A typical USB connection will be using an application-specific protocol that assumes a reliable connection (I know my 3D printer does this as I've looked at the code) so any data corruption or loss will be catastrophic, where the TCP protocol gives a highly reliable connection; any packet loss or corruption short of losing the whole connection will be detected and corrected by resending packets. Ethernet-connected motion controllers appear to use IP as they need network addresses and I presume they also use TCP over this - why shouldn't they? So, an error-correcting protocol over a more noise-resistant hardware connection gives so much more safety margin than a simple protocol over less-protected hardware. Be interesting to see the Ethernet-level error counts in a noisy environment, though.
What you are losing, of course, is any claim to a real-time protocol, but as the network connection is being used to transfer, typically, high-level movement instructions which can be easily buffered, by buffering a couple of seconds'worth of data you can still withstand a short loss of communication during a noise burst, the TCP stuff does its job and makes sure the data gets there eventually, and the pulse generator bit of the motion controller chunters away happily working from buffered data.
Conclusion - theorist meets practical experience, shakes hands, and goes off for a pint...
Personally, I like learning from experience, and preferably someone else's experience 'cos that costs me less! But trying to relate that back to theory might give a bit more insight sometimes and lead to a better understanding and maybe a way to move forward. Cathedral builders used experience to create magnificent buildings but theory and better understanding of materials gives us skyscrapers. If that is an advance...

[Lee Roberts]

Looking at a USB cable, it appears to use ground, power, and data in and data out. So, single-ended connections. Typical Ethernet connections use twisted-pair and, presumably, differential signalling. That suggests that Ethernet, at a hardware level, should be intrinsically more noise-resistant (although my own 3D printer has run for many, many hours over USB without any problem, although that is in a domestic environment without machine tools and EMI generators nearby). I think FatFreddie has it right with reference to TCP, though. A typical USB connection will be using an application-specific protocol that assumes a reliable connection (I know my 3D printer does this as I've looked at the code) so any data corruption or loss will be catastrophic, where the TCP protocol gives a highly reliable connection; any packet loss or corruption short of losing the whole connection will be detected and corrected by resending packets. Ethernet-connected motion controllers appear to use IP as they need network addresses and I presume they also use TCP over this - why shouldn't they? So, an error-correcting protocol over a more noise-resistant hardware connection gives so much more safety margin than a simple protocol over less-protected hardware. Be interesting to see the Ethernet-level error counts in a noisy environment, though.
What you are losing, of course, is any claim to a real-time protocol, but as the network connection is being used to transfer, typically, high-level movement instructions which can be easily buffered, by buffering a couple of seconds'worth of data you can still withstand a short loss of communication during a noise burst, the TCP stuff does its job and makes sure the data gets there eventually, and the pulse generator bit of the motion controller chunters away happily working from buffered data.
Conclusion - theorist meets practical experience, shakes hands, and goes off for a pint...
Personally, I like learning from experience, and preferably someone else's experience 'cos that costs me less! But trying to relate that back to theory might give a bit more insight sometimes and lead to a better understanding and maybe a way to move forward. Cathedral builders used experience to create magnificent buildings but theory and better understanding of materials gives us skyscrapers. If that is an advance...

Really well said Neale.