[subnoize]

Hello!

I apologize if I missed the topic where this was explained! I did search, maybe I'm not wording it correctly.

So, I've got a Grizzly version of the X3. I used CNCFusion's conversion kit and electronics from Probotix. It is basically me teaching myself how to do this so I'm mostly ignorant at this point.

I have this problem where the cut will be going nicely but then as the Z axis is being adjusted up it suddenly makes a mistake or stalls or slips (I can't hear the mechanical sounds which would be a huge clue as to what the real problem is) but the LinuxCNC has the end mill's actual Z position wrong and now plunges the end mill deep into the piece being milled.

If I hit the big red button, back the Z out and re-home it and run again it rarely happens again and never in the same place if it does. Its almost like a nervous twitch.

I don't know if this is related but if I set the jog to half speed sometimes the Z axis stalls on up movement. At full speed jog it move very rapidly and never stalls. At half speed it has a lot of vibration.

So, anyone have any ideas or maybe some places to start?

I have micro-stepping set to 2 and the Z axis max travel speed is 30 ips.

thanks,

snz

[109jb]

What you are describing is is losing steps. This can be caused by a number of things.

1- First thing to check is if the gibs on the Z-axis are too tight and if the ways are properly lubricated. If the ways are too tight the axis will bind and can lose steps.

2- If you are running the voltage and current below what the stepper can handle then you could be giving away torque.

3- If you have acceleration set too high it could stall because it has to ramp up to speed. Lower the acceleration in the setting of the control software for this one.

4- Motor could simply be undersize for the task.

The part you describe where it vibrates at 1/2 speed and stalls there easier than at full speed sounds like you are experiencing mid-band resonance. One simple thing that appears to be able to help this is to add a mechanical damper which is basically a flywheel. here are some youtube examples that demonstrate.

Stepper Motor Damper Test. - YouTube

Penny Damper - YouTube

[109jb]

Oh yeah. Higher tech drivers can compensate and combat mid-band resonance.

[subnoize]

Ah, yes! All good places to look but I'm finding out it might be something more basic!

I'm sitting there using all sorts of bad words and complaining about my Z axis when my youngest (14 years old) says, "you know when you run the CNC it makes the lights in my room flicker." It hit me like a ton of bricks! Being a single dad I moved into this rental property in haste and have hated it ever since. Beside none of the plugs being suitably grounded the power isn't consistent. It flickers. I don't know if its from the house wiring or the connection to the house but I have noted the flux on the history of my alarm system. It basically pings me every time the power goes out and even a brown out is something it reports.

So, on a hunch I fired up the X3 and started running test patterns and the first completed with no issues. The second got 2/3rds of the way thought and wham! A serious enough brown out that the computer halted and the mill stopped and the fault light came on.

I may have power quality issues. I've been rather worried about power outages anyways because what I intend to cut is actually very expensive and cannot tolerate defects.my plan eventually was to run two CyberPower AVR 1500VA. One would be for the computer and the second for the mill. With the sine wave conditioned Automated Voltage Regulator I could probably run for a good 13 to 18 hours without bad power spikes or dips. Max power outage would be 10 minutes for the mill and 15 minutes for the computer and drivers so they would smooth out small problems.

Your ideas are still valid and you might be right about the vibration. I also think the acceleration is the problem since I can get the Z index to stall going down as well. Thanks for the help! I will be calling the guys over at Probotix come Monday morning about the vibration.



Snz