running mach 3 with a usb to parallel adapter

[njhussey]

It's not the CNC machine that the software talks to, it's the BOB/controller...this then sends pulses to the machine's steppers to move the spindle to the desired positions.

The Chinese machines serve a purpose and if you accept and work within their limitations then I think that they're great as you're then a member of the CNC world....

[Kendrick57]

That is the way I look at it if I waited until I had enough money to by a realy good machine I would never have enough, I set an amount I could afford put an O.N.O on it and went looking that was what I found. It is not the best but it ticks all of my boxes.
kendrick

[Neale]

The issue, Kendrick, is that often when you don't have too much knowledge about the subject (but are willing to learn!) then it's easy to ask the wrong question. In your case, you possibly started out with the wrong question, about a USB to parallel converter. In the context of a CNC router and Mach3, this really doesn't make a lot of sense but it might not be obvious why not. If you say, "I have this Chinese router that has a BOB that needs to plug into a parallel port, and I have a laptop with Mach3 but no parallel port so how do I make the two ends meet?" then that puts it into a better context, and you are more likely to get a useful answer. The correct answer to your original question was, in effect, "You can't get there from here", but actually there are some good solutions to the actual problem.

Of course, you might get some ribbing about some aspects of what you've said. Unfortunately, to get any sense out of these forums you have to take the rough with the smooth, or at least have a skin like a rhinoceros, but you will get some really useful feedback and suggestions if you pick through what is said. Just don't insist on getting your exact question answered, because with the best will in the world, sometimes it's just not the right question! As for Chinese machines - I have no experience of them, except that I'm sure that they won't do quite all that the advertising claims. But then, what does? I'm sure that used within its capabilities, it will be able to do a good job for you. I run a home-built router built from MDF. Frankly, it's crap, but it does work and as long as I am careful about what I am trying to do, it does a useful job. Your machine is probably a lot better than mine. It's also taught me that I need something better, which is what I am building at the moment, but we all come to this game from different directions, with different needs, and, frankly, different budgets. Good luck to you, carry on asking questions, listen carefully to the answers and think about whether or not you asked the right question, and if you need to, ask why someone said or recommended what they did.

Have fun!

[Kendrick57]

Thanks for the advice you're absolutely right I started this thread from a position of just about compleat ignorance.
my knowlege has increased a lot but still has a way to go.
I expected there to be both positive and negative comments, in life I have to find the good ideas from the bad why should here be any diferent.
As for using a laptop and having problems withthe power saveing features I think I've switched them all off the laptop was switched on at 12 at 4 it was still going strong no screensaver no switch of no nothing it was still going at full power. I will still have to prove it with the Cnc but things are looking good.
will post again whe I have tried the uc100.
kendrick

[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