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  1. #1
    After a PC crash I am looking into using one PC to drive 2 machines at the same time. Has anyone any experience/advice on using one PC to drive two machines?
    I intend to use Denford VR Milling to drive one machine via USB and Mach 3 to drive the second machine via a PCI parallel/serial port to drive the second machine.

  2. #2
    Two machines from one PC with each machine running at different times will work, if you try to run Mach3 simultaneously with any other software you are likely to have problems with a conflict for resources.
    You think that's too expensive? You're not a Model Engineer are you? :D

  3. #3
    Cheers.
    I was hoping to run them both at once. It will take me a week or so to get everything set up as I will need a mouse,keyboard and monitor next to each machine but as the new PC is a lot faster then the old two put together I will give it a go and report the results

  4. #4
    Quote Originally Posted by ngwagwa View Post
    Cheers.
    I was hoping to run them both at once. It will take me a week or so to get everything set up as I will need a mouse,keyboard and monitor next to each machine
    Get a KVM switch. That's what I'd do if I were you.

    Quote Originally Posted by ngwagwa View Post
    but as the new PC is a lot faster then the old two put together I will give it a go and report the results
    It may work but only if you are not using parallel port but some controllers.

  5. #5
    A KVM switch is no use as I have one monitor/keyboard/mouse next to one machine and another set next to the other. There are enough USB ports to connect 2 mice and keyboards just need to get a VGA splitter for the monitors.

    I will be using the Parallel and Serial port for the Mach3 machine (these ports are on a PCI card) and a USB port for the Denford machine.

    I got the Mach 3 sde of it up and running today and it is only using 2% of CPU and 40% of the memory. Tomorrow I will look at the Denford side of things.

  6. #6
    Quote Originally Posted by ngwagwa View Post
    I got the Mach 3 sde of it up and running today and it is only using 2% of CPU and 40% of the memory. Tomorrow I will look at the Denford side of things.
    One of the things to watch out for is the speed of each machine; I would anticipate that both will work, but they'd both slow down a bit as the USB and Parallel communications each need to perform CPU interrupts (literally what it says on the can - a message comes in, and it forces the CPU to stop what its doing and handle this right now), which might not play well together.

    The other issue I see is that with a system running off the parallel port, if there is no command buffer, it relies upon the real-time element to work correctly. Imagine if you're half way through a diagonal move which requires synchronised movement of X and Y, but your PC has to deal with something else halfway between sending these signals - you might get a not so diagonal line - but this is purely speculation! I'm looking forward to hearing about your results :)

  7. #7
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 12 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,247. Received thanks 236 times, giving thanks to others 5 times.
    Andy has put his finger on it - the issue is not that Mach3 uses significant cpu power, but that it needs to be able to issue step signals in real time with as little delay as possible. Any other activity can cause small delays, which translates into uneven signals sent to the drivers, which means rough running. That's why laptops, for example, aren't supported by Mach3 via the parallel port - the cpu has a habit of putting user jobs on hold while it does some internal housekeeping which wrecks the steady pulse stream needed. If you really need to run two things at once, best thing would be to add a motion controller on the Mach3 side and scrap the parallel port. These buffer moves so that slight cpu delays aren't significant. However, I'm a little concerned that you also talk about Mach3 using the serial port. That's not usual, so I wonder if there is some other complication in your setup.

  8. #8
    Regarding synchronised Xand Y movement the G01 command tells the machine to move straight to the stated x,y & z so there won't be any issues there.

    The Mach 3 uses the serial port to control the VFD as this was the easiest way to do it with existing boards in the unit.

  9. #9
    Quote Originally Posted by ngwagwa View Post
    Regarding synchronised Xand Y movement the G01 command tells the machine to move straight to the stated x,y & z so there won't be any issues there.
    Mach3 is responsible for converting that single gcode command into the pulses for the steppers. It's the output of those pulses which I'm suggesting might be affected, not the interpretation of the gcode.

    Think about that Gcode command - the number of pulses on X, Y and Z to reach the desired location depends on where the machine currently is. G01 also implies that the movement is linearly interpolated (i.e. it has to move in a diagonal line, not two sides of the triangle.) The synchronization and output of those pulses in a timely manner on each axis is very important.

    Sent from my SM-G950F using Tapatalk

  10. #10
    Neale's Avatar
    Lives in Plymouth, United Kingdom. Last Activity: 12 Hours Ago Has been a member for 6-7 years. Has a total post count of 1,247. Received thanks 236 times, giving thanks to others 5 times.
    ...and to put some numbers on that, at 750mm/min, Mach3 will be driving that parallel port at, maybe, 2000 pulses per second. 10 msec delay while the cpu is doing something for the other job means that 20 pulses will be delayed or maybe even lost. At best that means rough running as the steppers are continually changing speed due to varying pulse rates and at worst missed steps and lost accuracy.

    You originally asked for people with experience to respond. I suspect that you might have trouble finding anyone who runs like this because it's such a potentially dangerous way to go. You are even recommended to avoid things like internet browsing while running Mach3 for these reasons. Use a motion controller like a UC100 and you might be in with a chance as the device unloads a lot of the time-critical pulse generation from the PC.

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