MuellerNick, furious tap dancing and name calling doesn't change any reality.
1. Smoothstepper moved the unreliable part (pulse generation) of Mach3 to hardware and did so cheaply. Could it have initially chosen a more noise resistant interface than USB? Sure. But so what? Lots of folks on Mach and LinuxCNC are sending 5V TTL around to do all sorts of things because that's what the breakout boards offer. Could this be done better? Sure, but so what?
In fact, the Mesa FPGA boards so beloved of the LinuxCNC crowd are, drumroll please, 5V TTL! And guess what, a lot of the encoders to be used with servos are also 5V TTL. Hmmm, what were they thinking?
2. Why don't you explain which part of that LinuxCNC thread I didn't understand? All I've said is that Linux is not Real Time either, so we are basically arguing a matter of degree. The thread concurs and quantifies the degree to which it is not reliably Real Time. There's threads all over Linuxcnc.org that connect jitter to the max step rate that Mach users think in.
In the end, both Mach3 and LinuxCNC have the same problem in that the underlying OS is not really Real Time if you look closely enough. It is a matter of degree with LinuxCNC starting with a little advantage. Both need the same fix to eliminate this problem, outboard hardware, so why keep waving your hands about it?
Here's Andy Pugh himself saying essentially just that:
http://www.linuxcnc.org/index.php/e...nuxcnc-questions/10613-centroid-cnc4?start=36
He suggests an external step generator such as Pico or Mesa if there is too much jitter. Gee, sounds just like a conversation about Smoothstepper.
3. "This simply means that the contol and the user knows exactly where the axis are. No matter how big the threshold, no matter what backlash, no matter how many steps lost, no matter wether one axis stalled due to overload. LinuxCNC uses this while in rapid. It doesn't matter if the axis is 1 mm behind, the control will catch up. It also allows different laging behind. Less when going slow, more when going fast. And an exact stop is just that. An exact stop!"
My Mach3 servo-based system does all that. It will catch up just like that system you mention. The lag changes based on prevailing conditions, it catches up, and that all happens regardless of backlash, axis stalling, sticktion, and even phases of the moon. Did you not understand how servos work under Mach3? None of the things you've mentioned are the reasons to carry the loop back to the control. You still fail to provide a concrete example of what you're getting for your theoretical advantage beyond the three things I have already mentioned in my first post.
4. "They do have a feedback that is read from the machine. They are not guessing like Mach does." And again you fail to provide any example of why this matters? Sounds good, but it is hand waving otherwise.
5. "Btw: Do you know the OS of the Haas controls? Linux!" And Siemens, Cincinnati, and many others have used Windows. So what? Oh golly, here is an announcement that Centroid is going to stop supporting Linux and will exclusively be on Windows 7:
http://www.elrodmachine.com/Centroidcnc.htm
Centroid, BTW, is one of the most popular retrofit control systems around.
6. "That's being repeated over and over again. Once more, that was true some years ago. A dumb machine that Mach could handle is as easy to setup with LinuxCNC as with Mach." Nope. Linux desktop market share not only has not gained, it has fallen off due to this issue. It never has taken off except in cases where it is totally embedded like a Tivo box or where it is being used by the Geeks. If you're already a Linux Geek, more power to you. If you're just an ordinary bloke, it's a problem. Or, go back and read the Centroid release where they say the same thing.
7. "I don't know of a single commercial machine that uses Mach. With commercial, I mean being sold and NOT directed at the hobbyist like Tormach. But I know a few machines running in production and with LinuxCNC. I also do know retrofitters that use LinuxCNC."
Oh do come along. This is your biggest fabrication yet. Because a couple guys have retrofitted LinuxCNC to some old machine you're going to declare that Tormach is not a commercial machine? Or that bunches of CNC Routers and Plasma Tables are also not commercial machines? Pick and place machines too and the list goes on. Even though their owners are running shops and making products that are their livelihoods that's not commercial? What in the world is "commercial" if making your living with it doesn't count?
Are all the machines using MachMotion just hobby machines?
http://machmotion.com/
8. "Haha! A used controller for $900 that works and fits exactly that machine. Good luck! And "just add Yaskawa drives". Why should I throw out 3 servos and three servo amps just to either buy Yaskawas (you forgot the amps) or rip out any axis drive and replace it with a stepper?
You switched to retrofit! And whenever someone makes a retrofit with Mach, the first thing is to open the cabinet and throw out everything in there. You won't get it running with Mach. Then, they rip out the servos and replace them with steppers. That makes no sense to anybody who has some brains."
Okay Nick, you apparently never met anyone doing much retrofitting. I meet them all the time and talk to them in great detail about it through CNCCookbook. And where did I say anyone was switching to steppers? As for the Yaskawas, frequently the reason you can find the controls so cheap is they're parted out separately or the drives and servos are burnt out.
9. "Try LinuxCNC, don't listen to the sheeple!" And still more name calling without any facts. Not very professional or engineer-like, but it's fun for you, I'm sure. Facts are usually more persuasive, if less entertaining.
Sincerely,
BW
