View Full Version : Voodoo jogging problem..

25-05-2010, 02:06 PM

This is a weird one, although it would be nice if someone said 'that's a common problem, here is the fix'..!

When I jog my machine X+, it moves at about 1800 (Mach 3), but when I jog X-, it goes at 4000.. Now, if I jog at X- (4000), then jog the Y axis, the Y axis moves at full speed...

BUT..! If I jog X+ (1800), then try to jog the Y axis, it moves at half speed...

Really cant work out what is going on but this problem has made for some interesting parts cut on my cnc router, weird arcs, wrong size sections etc.. I have a feeling this might be electronic rather than mach, just dont understand why it would do this..

Any ideas guys?


John S
25-05-2010, 04:32 PM
You havn't got sticky keys enabled on the computer have you ?

25-05-2010, 04:42 PM
Hi John..

Oooh.. If only life was so simple...! Fraid not John..
Just to make life even more interesting, the X axis voodoo has now reversed itself, X+ now does 4000, X- does 1800.. I did not change anything, just fired it all up again..


John S
25-05-2010, 07:08 PM
Laptop or desktop ?

26-05-2010, 09:12 AM
How strange.. It did not post my reply last night..

Laptop John.. pretty basic one, P3 600Mhz with 384Mb ram.. Am running the basic 3 axis screen from Mach website (75% less processor usage) and have had everything running fine a few days ago.. But this weird problem cropped up when I was cutting some mdf mounts for my router.. The circle cutout was not exactly circular and dimensions came out very strange.. When I jogged it I noticed the different speeds I was getting at different directions of the same axis..

Just fired it all up and the problem persists.. Have a fast dual core desktop pc in my house, but it is a bit of a brute, especially the huge monitor.. Will haul it all into the workshop and hook it up if you think that is my problem..


John S
26-05-2010, 12:24 PM
Below are the specifications for running Mach3 stably. Mach3 Minimum Requirements:

32-bit version of Windows 2000, Windows XP, Windows Vista, or Windows 7 Operating System
1Ghz CPU
Non-integrated Video Card with 32MB RAM
Basic Computer Skills (ability to copy/rename files, browse directories, etc)
Desktop PC (if using the Mach3 Parallel Port Driver - laptops are not supported because the power saving features of the chipsets disrupt the pulse stream, PCMCIA and USB parallel adaptors will *not* work.)

26-05-2010, 01:00 PM
Hi John..

You are right I am sure.. Friend reckoned I could get away with using the laptop as he had shown me posts from other forums where others had used low power laptops, I did reconfigure Windows 2000 into PC mode, which disables the power saving features.. Sigh, looks like I got to haul my big pc into the workshop.. Should tell me if that was the problem anyhow..

Will let you know how I get on John.. Thanks..


26-05-2010, 02:30 PM
On some but not all laptops, configuring windows power saving to PC mode doesn't cure all the ills. Some of them are buried deep in the BIOS and you can't get rid of them at all.

Also - Windows isn't and never will be, a real time operating system. Anything which could interfere with the speed at which the stepper pulses are generated could be the source. And, unfortuately, something that works on one machine, might be death on the next machine.

I would be suspicious of AVG as well. Don't get me wrong, AVG is good and not a particular CPU hog, but anything other than Mach itself, should be treated with suspicion. Even a screen saver could get in the way.

26-05-2010, 02:55 PM
Especially with a low-end CPU and limited memory you are doing a lot of swapping to a slow disc. That will play havoc with any timings as soon as more than one app is running....

To run realtime apps successfully in Windows you need a fast CPU and lots of memory to minimise swapping. You need to harden Windows by removing all drivers you don't actually need - audio, graphics, modems, networks, CDs. You can create different hardware profiles that enable or disable specific hardware and load of apps. So you can have an 'on network' profile with network, cd, AVG and a 'CNC profle' with all these turned off. You disable all power management, although sometimes older machines don't let you.

Better still use the embedded version of Windows which doesnt swap and runs in memory - Most apps will run OK in it as long as they have been written well.

Then again, why mess around, you can pick up a good Pentium4/Windows XP desktop on ebay for 50 or so...

26-05-2010, 06:49 PM
All good advice...

If I wait a couple of weeks I can have my friends PC, dual core with 2Gb ram.. Just did not want to wait...
Going to move this PC into the workshop now and got to try and get online in there too if I want to read any more posts.. !