Cutting problem, Random Cuts

[Scott13]

I don't think I'm having problems with my g-code or v-carve but I thought someone may be able to help me on this site. I use v-carve pro and mach 3 on my table. About 90% of the time simple designs come out fine, but lately I get cuts in wrong areas. For example; I attempted to cut the letter B out of wood, had it clamped tight so no chance of material movement, and 1st pass went past my stop point then dropped to make the second pass. This resulted in the first pass cutting further into my piece than my second pass. Also, I just attempted to cut a clock. At almost 90% complete my router dropped for a second pass and cut off where it was supposed to by about an inch. I reset the machine and computer and attempted this g-code again. This time it cut the clock wrong in the exact same place AND an additional wrong spot. I don't think its a problem with v-carve since most the time the problem isn't repeatable but in this instance part of it was exactly repeatable. I'm at a loss and I'm not great at reading g-code or calibrating mach 3. Does anyone have any ideas on what this could be. I'm stuck only being able to cut simple designs due to the longer the machine runs on a file I understand I give it more time to make a mistake. It seems to happen on a few simple designs but on nearly all longer more complex designs. I have pictures in jpeg format but was unable to get them to upload.

[TReischl]

A machine cutting somewhere it is not supposed to is usually an indication of lost steps OR a loose mechanical connection in your drive systems. A typical problem is a coupler having come a bit loose. One I ran into was a stepper motor had managed to get a bit loose in the mount so it could turn a bit, plus it could move back and forth.

So, check that you do not have a problem mechanically.

Another problem is when the Z retracts and it hits the switch or bottoms out.

Then there is the really nasty problem of electrical noise. . . can drive ya right up the wall. More than likely it is mechanical.

Here is what I always remember when I run into a problem like you are having:

Vectric software is used by thousands of people everyday, they write lots of programs everyday. . . it is highly doubtful the software has suddenly decided to go buggy all by itself. And, if you are using Mach, you are using an extremely popular program also run by thousands everyday.

[martin54]

What operating system are you running, what have you got installed on the computer other than mach3? Have you turned off everything you can in windows like auto scan & update, sleep mode/hibernation, screen savers, power down of monitor/hard drives etc etc etc etc

If this is only happening on a longer run then it could well be something to do with windows & background applications it is running.

If at all possible your control computer should never be connected to the internet & be stripped of everything it doesn't really need in order to run mach3, best not to have a lot of other software on there either if possible just mach3. Try not to leave anything plugged into usb sockets while cutting either.

[Scott13]

Thanks you guys. I've checked the steppers and couldn't find anything mechanical lose but I'm going to keep checking everything I can think of. As far as the computer goes, I'm using Windows xp, no other programs installed, and it's not hooked up to the Internet. I do however load my Vcarve files on a jump drive and load them into Mach 3. I usually leave the jump drive hooked up throughout the cutting process. Could leaving it in the usb really be causing an issue like this? I agree hat the problem sounds mechanical in nature, however I am stumped as to why the probelem was repeated in the same exact spot of code along with other issues. I'm still at a loss

[martin54]

yes leaving a usb stick plugged in can cause problems if windows decides it wants to scan the usb port while mach3 is running, had that problem myself & was told never to leave stuff plugged in by someone on cnczone.
Mach3 does not like anything else going on while it is running so you have to turn off or disable as much of the windows automatic checking as possible. Do you have anti virus software installed, if so remove it, turn off auto updates & any other security within windows. Turn off screen savers & set monitor, hard drive & computer to never turn off.

found this post not read it but may help

http://www.machsupport.com/forum/index. ... 346.0;wap2

I am not saying for one minute it is not mechanical but if short jobs machine ok & longer jobs cause problems it may well have something to do with something windows is doing after a period of time sitting idle. A program running on its own is counted as inactive time.

If you think it is mechanical then try machining on a different part of your table, that way if it is something like binding at a certain point on a shaft then moving the job may show this, slow down speed & feed settings as well which will help eliminate problems caused by acceleration & de-acceleration issues.
with the power on try to move each axis by hand, you shouldn't be able to if motors are working properly.

[highpockets]

Here's something I just ran into. Running a Win10 computer with nothing running in the background, a pretty clean computer. CNC started acting up by running over on cuts and sometimes plunging down into the work piece. In general doing so very strange moves. Turned out to be a failing hard drive. Windows was taking up so much time trying to read the hard disk that Mach3 couldn't keep track of the machine commands.