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

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Originally Posted by routercnc

Hi Lee,

I've been close to bringing this to your attention for a while to see if there was a way through (just in terms of giving the OP the post back I mean).

I was going to suggest seperating the thread out into "Best ways to connect to a CNC machine?" [ around post#13? ] where pros and cons of USB vs PP vs Ethernet etc. could be discussed. There are some valid discussions on that topic to be had all round I think, moderation issues aside.

Thanks

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Threads split as suggested, sorry for the delay.

.Me

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Originally Posted by JAZZCNC

Twas a Joke Hence the Jester.!!

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Yeah, I saw the jester, but I'm afraid that it didn't entirely put my mind at ease at the time. I guess I'm jaded, heard too many 'jokes' where someone's actually a bit more serious than they're letting on etc., If I actually knew you, of course, I'm sure my interpretation would have been totally different!

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Originally Posted by JAZZCNC

arguing something that wasn't relavant and pointless to the discussion.!

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From my side, if you're interested:

L.A.N. had just bought a machine with a USB controller, so whatever ethernet ones did was irrelevant; if you've just paid well over £3k for your mill, the last thing you want to see is that you need to go buy a different controller (well, except that it's jammed itself in estop again, of course.)

At this point if I'd read 'The Same can't be said for USB Controllers they've all been irratic and unpredictable...they're just not good or suitable for reliable Motion control', I think we'd have been fine. There's lots of (frankly) crap computer peripherals, so a few dozen more isn't a surprise - especially with USB peripherals where the spec often feels more a guide to how it won't be implemented.

Unfortunately, I read 'The Same can't be said for USB it's irratic and unpredictable...it's not a good or suitable connection for reliable Motion control'...I replied about USB as a connection (I've experience with it on the design side) and the rest is...well...this thread.

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Originally Posted by JAZZCNC

Now FFS lets leave it alone.!!:yahoo:

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Deal.

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Originally Posted by JAZZCNC

Nothing specialised about that tool it's just a T-slot cutter.!!!

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It's not fancy, but I think we both know what I was trying to get at there! :tongue: (Also, I'll take an undercut of twice the diameter of your largest t-slot cutter! :rolleyes:)

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Originally Posted by magicniner

I get it, Ethernet isn't suitable for something no-one here needs to do, good point(less) well made!

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I've found that it's dangerous on forums like these to assume that nobody needs to do it...and exceptionally dangerous to assume that no one wants to do it!

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Originally Posted by magicniner

I suspect there is very little TCP/IP-Free Ethernet in use outside industrial applications though.

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There's a good bit actually! Ignoring nitpicks like UDP/IP, SCTP/IP etc.,
Just off the top of my head, there's methods of attaching hard disks (like ATA over Ethernet), some thin clients etc., PPPoE does too, and that's used by almost everyone who's got VDSL2 (BT Infinity) or got Virgin Media before they moved supplying an all-in-one.

And of course, some of the industrial standards go and use, say, UDP/IP anyway!

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Originally Posted by magicniner

but neither is any other remote communication system - the motion controller deals with closed loop rigid tapping locally.
;-)

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If the communication system was explicitly designed for control purposes, you can! If you want to see a video example, the spindle encoder in the earlier rigid tapping video Dean posted is connected over CANbus. I'm sure that you can also do it over other things like Modbus/RS485 too...but I'm not going to bother finding examples.

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Originally Posted by Jess

If the communication system was explicitly designed for control purposes, you can! If you want to see a video example, the spindle encoder in the earlier rigid tapping video Dean posted is connected over CANbus. I'm sure that you can also do it over other things like Modbus/RS485 too...but I'm not going to bother finding examples.

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There you go splitting hairs again when you actually don't know the full story or have experience of the controller.!!
The only reason it's using CANbus because it's a External I/O module that connects to the Main Controller Via CANbus. Hood could have easily connected straight to the main IP-A controller, but with So much I/O to make the Chiron work he's using the I/O Module.!!. . . The Controller still does all the Work and number crunching. CANbus is just used has an easy and stable way to move I/O modules around large machines to localise I/O and keep short Signal wire runs. Other wise it would mean running long signal wires back thru machines risking EMF issues.

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Originally Posted by Jess

Yeah, I saw the jester, but I'm afraid that it didn't entirely put my mind at ease at the time. I guess I'm jaded, heard too many 'jokes' where someone's actually a bit more serious than they're letting on etc., If I actually knew you, of course, I'm sure my interpretation would have been totally different!

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Rest assured your not and never where in any Danger from me ***REMOVED***. And if you was I'm not stupid enough to post my intentions on a Forum. ***REMOVED***

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Originally Posted by JAZZCNC

There you go splitting hairs again when you actually don't know the full story or have experience of the controller.!!

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magicniner claimed that no remote communication system can do rigid tapping. CANbus is a remote communication system, and as hood demonstrates, CANbus can do rigid tapping.

I don't see what the problem is?

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Originally Posted by Jess

magicniner claimed that no remote communication system can do rigid tapping. CANbus is a remote communication system, and as hood demonstrates, CANbus can do rigid tapping.

I don't see what the problem is?

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Problem is CANbus isn't doing the ridgid tapping the Controller is doing it. CANbus is just shifting data which it does best.!!

I think the Valid point Magicininer was making is that it's not the Communication protocol that does the work on any machine usually it's the main Controller it's self.! . Just Like it's the Encoder module working in conjunction with the Main controller on the Cslabs devise. CANbus just lets them talk to each other, albeit very fast.
Also in this case it's actually the main controller that is doing the coordinated movement between spindle and Axis by controling the Servos (Hood's spindle is Servo driven) which is connected to Control software via Ethernet.
The Encoder module is just reading the High resolution encoders which require high data rates which CANbus is very good at.! The controller deals with these internally and send the relavent signals needed for movement to what ever does the moving or turning.!!

Would you pair put the handbags down! :)

In terms of Mach3, Ethernet is the more reliable communication method for external motion controllers.
The reason for this, is Mach3 can't handle any errors or glitches in the communication method.
Ethernet handles errors and glitches at a hardware level, it's also an isolated system, so is much more tolerant of external noise, and should a packet fail to reach it's destination, the hardware (ok, it's technically the embedded code in the Ethernet controller if you want to split hairs) will handle the problem and resend it until it reaches it's destination.
USB doesn't have that, so any packet of data that gets corrupted, has to be detected and handled by software. I'm sure if the plugins could be designed to do this, they would, however it's one of the things that Mach3 was never designed to handle, as it was originally written to talk directly to the parallel port.
I think it would be fair to say external motion control, was simply patched onto the Mach3 core.

One key point to remember, is once you involve Ethernet or USB, you are no longer running realtime. All you're essentially doing is running a faster version of ye olde RS232, in that you send commands to a controller, and the controller (hopefully) tells you it's been done.


However, USB can be used reliably. I run several KFlops, and they are far more stable than my USS ever was with Mach3. My lathe still occasionally locks up Mach3 (my manual lathe is the sole trigger for this!), but no where near as often as the USS ever did.
I am in the process of moving to KMotionCNC, as it can handle communication problems far more gracefully (and it has less issues, but that's for another topic!), and will happily resume once things are back to normal.

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Originally Posted by Jess

magicniner claimed that no remote communication system can do rigid tapping. CANbus is a remote communication system, and as hood demonstrates, CANbus can do rigid tapping.

I don't see what the problem is?

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In the original context of this thread, which was to do with computer to machine controller interfaces, magicniner's claim is correct.
In the case of CS-Labs they use it for inter-module communication, which is where it excels.

CANbus is a very resilient system, and can be very fast, however nobody uses it as a communication method between a computer and CNC machine. You could use it for realtime operation if you designed a suitable internal slot card that the computer could access directly and control in realtime, but you're then into a very glorified parallel port like system.

Im with jess on this one, usb is far more reliable.

I run both my machines with uc300's from a laptop. it never looses connection, has an excellent 100khz buffer and has been left on for over a week in the past with no issues.

I also have a wired network with multiple routers tried over the years and they all failed from time to time. I know not the same but doesn't give me much faith.

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Originally Posted by m_c

Would you pair put the handbags down! :)

However, USB can be used reliably. I run several KFlops, and they are far more stable than my USS ever was with Mach3.

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No my Hand bag is always read for Action.!!. . Lol

Now Come on M_C we both know you are talking about a very High quality product when using Granite's Kflop controller it's not your average USB Mach3 controller.
The point I was making in first place is that USB isn't stable as Ethernet when used with Mach3 which we know thru experience is true. We Have Both pulled our hair out with USS(USB Smooth Stepper for those we are wondering.!!) and I've done much the same with every other run of the Mill USB controller for Mach3.
Ethernet on the Other hand is another ball Game. Classic example is the Pokeys 56/7E and now 57ECNC which do Motion control they are cheap and work great they never Miss a beat. The 56U on the other hand was a pain when used for motion control with Mach3, mainly I think because it relied on USB for 5v but still it couldn't be trusted.!

USB driven card Isn't ok for Motion control unless your prepared to spend on quality devices like Granite's Kflop etc so to me it's not for the average DIY user and best avoided.! And now with Ethernet devices coming more available at sensible money what the point.!

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Originally Posted by Jon.

II run both my machines with uc300's from a laptop. it never looses connection, has an excellent 100khz buffer and has been left on for over a week in the past with no issues.

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See this is the point.!! . . . . I've used the uc300 and it was fine. Untill you turned some high frequency device on near by then it would freakout. (In the USS case next Room.!!)
Yes it can be said it's the Cards fault not USB protocol but this doesn't happen with Ethernet driven devices I've used. They handle EMF and such crazyness much better in my experience.
I'm not into communication and all that goes with it. But I am into CNC and all that goes with that and I know thru experience that Ethernet is better than USB when it comes to running a CNC machine using Mach3..!! . . . Which is what started this whole Hang bag stuff in first place.!
It's just some people have to twwist words and things around to suit there own Ego's!!