running mach 3 with a usb to parallel adapter

[Neale]

Unfortunately, while what you have done on the laptop is good and probably necessary if you want to use a laptop at all, the power management and similar features are sometimes a bit more subtle than that. Particularly with the types of processor chip used in laptops, power management is critical to getting good battery life, along with things like CPU temperature management because small cases mean poorer cooling, smaller fans, etc. This means that every so often, it is possible for the CPU to temporarily suspend normal operation while it is doing various internal system management and monitoring tasks, and then carry on as if nothing had happened. We are talking about tiny fractions of a second here, and nothing that you would notice as a user if you were doing normal laptop things - browsing, word processing, watching videos, or whatever. The issue with CNC operation is that the motion control software - Mach3 in your case - has to issue a stream of pulses out of the parallel port at very precise intervals. These intervals are also down in the tiny fractions of a second level. For example, a typical pulse rate for Mach3 might be 20KHz, twenty thousand pulse per second, which means a pulse every 50 microseconds. If the CPU says every so often, "Hang on a bit, I'm busy" for, say, a couple of hundred microseconds, a normal user wouldn't notice, but you've just lost 3 or 4 pulses, and that means jerky motion on the router and loss of position - the machine is now not where Mach3 expects it to be. That's why LinuxCNC, a common alternative to Mach3, comes with a test programme to measure this kind of internal system delay (not sure if Mach3 has an equivalent - it might). You don't get this kind of thing to anything like the same extent with desktop systems, which is why Mach3 say that they do not support their product on laptops. Even desktop machines vary, and the results aren't even linked directly to CPU or clock speed as even a fast system might have poor internal system timing performance. So, what I'm saying is that while what you've done is good, and the machine won't go to sleep or whatever while you're using it, the underlying problems are beyond your or anyone's control. This is also why a USB-parallel converter doesn't help as it destroys the pulse timing in the conversion process. They might be fine for undemanding devices like printers, but not real-time use for CNC machine control.

Good news, though, is that is why people use external motion controllers like the UC100. You still use Mach3 to do the user-level machine control, but it delegates all the background pulse generation and time-critical functions to the external device which is designed and built to ensure that you get a good clean well-timed pulse train. I think when I looked at it, the UC100 spec said that it could run at up to 100KHz which is 4-5 times faster than a typical PC could manage. It's also faster than you actually need in practical circumstances, but it does mean clean, well-timed, and guaranteed pulse delivery.

Be interesting to see how it works for you.

[paulus.v]

I am controlling my CNC with Mach3 on an old IBM Thinkpad laptop (Pentium 1.8 GHz, 512 MB RAM) with a parallel port.

I made a fresh Windows XP install skipping the ACPI (Advanced Configuration and Power Interface) install by holding F5 (select standard pc) or simply F7 during install, when at the bottom of the screen is asking to press F6 if you have raid devices. This way there will be no APM/ACPI installed. APM/ACPI is responsible for reducing the parallel port clock speed to reduce power consumption, and there is no other way to disable this function.

Without the APM/ACPI the laptop runs at full power but there is no cooling problem because the cooling system relies on temerature sensors not software. There is no battery monitor, windows does not know/inform you if you are running on AC or battery or the battery level, but who cares as long as the laptop is always plugged in. The only downside, very annoying at the beginning (now I'm used to it), is that the system is not shutting down automatically. You get a message "It is now safe to turn off your computer" and need to press the power button for two seconds to cut the power.

I think the most important thing is to have a computer dedicated to control the CNC. With a fresh windows installed, any graphics enhancements disabled, and only the CNC control software installed (Mach3 or other).

This way I get excellent results even at 100 KHz with the Mach3 timer variations test software on my old IBM Thinkpad laptop.

[Neale]

That's pretty good performance, and way beyond what I get running LinuxCNC on a newly-built PC, even with its "real-time" modified kernel (which even has cpu temperature monitoring code removed). I have Mach3 demo version ready to run on a dual-boot disk on that machine although I haven't tried that one yet. That's Windows 7, though, and I'm not sure what difference that might make in practice.

[Kendrick57]

From what I read in the manual and from what has been said on this thread by using the uc100 you take the timing problem out of the equation the uc100 deals with timing all the computer does is stream locations to the uc100 and that sends them out in a timed fashion so as not to confuse the Cnc. Have I got the it just about worked out.
kendrick

[Neale]

Close enough! Mach3 sends a stream of commands to the UC100, which stores them locally and turns them into pulse streams as required. Because it holds about a second's worth of commands in its local buffer store (according to the spec on the web site) unless the PC is really busy and can't update the buffer for more than a second (which is unlikely if it's not doing anything else) nothing gets lost. Strictly speaking, the PC does not just send "location" data to the UC100 as it will also send things like spindle speed control, coolant on/off, etc, commands as well and the UC100 then generates the appropriate output signals on its parallel port. The UC100 will also send things like limit switch operation signals back to Mach3, I suspect, but for all practical purposes you don't have to worry about the details - Mach3 and the UC100 sort it out between them.

[Kendrick57]

Well it's arrived I set it up followed all the instructions still nothing works

[paulus.v]

Well it's arrived I set it up followed all the instructions still nothing works

Have you set the port number in Mach3 Ports and Pins configuration? I remember when I first tried to get Mach3 working I forgot to set the port and by default it is 0.