Sometimes my tool will appear to run off in a random direction. The actual tool path on screen shows that the tool left the programed path. This happens even when no one touches the controls and is a program I have run a dozen or more times. It just seems to happen at random intervals. Its almost like a software bug. It happens rare enough that it hasn't been a major issue but it just ruined a good drill and part that was 1/2 way done. Now I'm irritated. I have a home modified mini mill converted with Automation Technologies electronics, a UC100 motion controller, and Mach4 software. Any ideas?

Hi,
the fact that its random and happens on tried an trued Gcode files suggests electrical noise to me.

The UC100 is a great little controller but is subject to electrical interference. This is a recurring issue with USB connected
controllers.

In the first instance use a short, short as possible USB lead of the best quality you can find. Install ferrite  split rings, one at each end and one
in the middle.

You should run your spindle through a GOOD line filter at a minimum and a line reactor a best.

Additionally it sometimes helps to draw AC supply for your spindle from a different AC circuit then the AC supply for the PC, controller power supplies etc.
This type of electrical noise is called 'conducted noise' an is often overlooked by CNCers. Line reactors are the best remedy for spindle induced
conducted noise.

Craig

what do you mean "tool left the programed path" do you mean that you see on screen exactly what real happened?("tool run off in a random direction")
or you see on screen that every thing is ok?(in that case craig full corect its look like some electric issue)

Hi Guys
I have seen this as well, when I was trying different development versions to find one that has G76 working for my lathe I had one version I tried (4360 I think, but none could be found from the ones I tried that G76 worked) where Mach 4 seemed to draw it's own tool path and then proceeded to follow it. I had a simple series of longitudinal cuts, I was watching the progress on the screen when a random angled line appeared part way through the job on the tool path display and then Mach followed that path - like it wasn't out of control but it miss interpreted the Gcode and was following what it though it should. I don't think it's a noise issue because Mach followed some random path it drew itself on the tool path.
Steve   

Hi.
I am having the same issues. The machine is doing something different than drawn on the screen according to the gcode. But when it is moving wrong ist shows this wrong movement on the screen. As if it knows what it is doing - but not what the gcode says…
It already ruined quite a few pieces and I am about to switch hardware if it doens't get fixed…
Most of the time it happens when its spiraling down. In this case the Z height is wrong and X/Y is slightly off.
When I stop, reload the code and restart its fine again… any ideas?!
Fabian

It could be you are loosing steps, is the Z depth shallow?

No I am using servos. The thing is. It shows the wrong toolpath on the screen. And shows also wrong X,Y and Z values.
Sometimes it also makes just a straight line until it hits soft limits...

Some code and pictures would help us

So here ist the part of the code.

The whole code is attached. The part with the issue starts at line 5790

It should do a 20° zig-zag, go down to Z-19.5 and cut the circle (green marking)
Instead it did go stright down do Z-19.5 an run of to top left (red marking) I hit stop and moved out manualy after that.

(Nr. 5: Teil 1)
G00 X-5.9419 Y-158.3946 Z4.0000
G00 Z0.5000
G01 Z-19.5000 F1000 S18000
G01 X-5.8770 Y-157.8966 F1800
G02 X-113.5301 Y-109.8941 I5.6858 J157.4670
G02 X-136.8240 Y-79.0688 I113.8117 J110.2184
G01 X-137.2211 Y-79.3806
G00 Z-17.5000
G01 X-136.8240 Y-79.0688
G02 X-140.6545 Y-72.0465 I135.2650 J78.3402
G01 X-141.0555 Y-72.3604
G01 Z-19.5000 F1000
G01 X-140.6545 Y-72.0465 F1800
G02 X-156.6145 Y21.0256 I140.8045 J72.0496
G02 X-138.6026 Y75.9061 I155.8834 J-20.7651
G01 X-138.9949 Y76.2309
G00 Z-17.5000
G01 X-138.6026 Y75.9061
G02 X-134.5787 Y82.8194 I137.1220 J-75.1850
G01 X-134.9671 Y83.1420
G01 Z-19.5000 F1000
G01 X-134.5787 Y82.8194 F1800
G02 X-38.5199 Y153.2543 I134.6813 J-82.9580
G02 X-4.4203 Y157.9347 I38.3996 J-153.2082
G01 X-4.2411 Y158.4397
G00 Z-17.5000
G01 X-4.4203 Y157.9347
G02 X3.5788 Y157.9554 I4.4135 J-159.8570
G01 X3.7580 Y158.4515
G01 Z-19.5000 F1000
G01 X3.5788 Y157.9554 F1800
G02 X114.0372 Y109.3483 I-3.4151 J-157.5713
G02 X135.8361 Y80.7192 I-114.2914 J-109.6381
G01 X136.2295 Y81.0358
G00 Z-17.5000
G01 X135.8361 Y80.7192
G02 X139.7518 Y73.7440 I-134.3065 J-79.9818
G01 X140.1490 Y74.0627
G01 Z-19.5000 F1000
G01 X139.7518 Y73.7440 F1800
G02 X156.7024 Y-20.2502 I-139.8884 J-73.7525
G02 X139.6954 Y-73.8605 I-156.1338 J20.0281
G01 X140.1704 Y-74.0318
G00 Z-17.5000
G01 X139.6954 Y-73.8605
G02 X135.7743 Y-80.8327 I-138.2406 J73.1583
G01 X136.2530 Y-81.0061
G01 Z-19.5000 F1000
G01 X135.7743 Y-80.8327 F1800
G02 X39.6657 Y-152.9711 I-135.9091 J80.9778
G02 X2.1216 Y-157.9902 I-39.5732 J153.0882
G01 X2.0657 Y-158.4911
G00 Z-17.5000
G01 X2.1216 Y-157.9902
G02 X-5.8770 Y-157.8966 I-2.1306 J159.7596
G01 X-5.9419 Y-158.3946
G00 Z4.0000

Forgot the screenshot