Noises coming from the Z axis

[lewc]

Hi All,

I work as a woodwork teacher and we recently picked up an AR8 for our workshop. I was a complete CNC newbie until the last 12months and it's been fun to learn how to use.  I was playing around today with a cutting board (surfacing, juice groove and cutting out the shape) and how to clamp it down, when the Z-axis started making some strange grinding noises. 

I had paused the profile cut to add some more clamping pressure on the board. While it was still in the paused place, in a 4mm channel, I started the profile cut again. The spindle returned to home but caught on the timber and made its way back to the home position and continued the cut but the tool path was off. What I should have done, was HOME the spindle and then start the cut. Lesson learned.

However, the Z-axis makes a noise. I contacted the company that supplied it and he walked me through a few things to check - still made some noise. Due the situation at the moment, it's unlikely he can get out to inspect it.

Has anyone experienced this type of noise before? I'm concerned that I've knocked something out of alignment or bent something.

I've taken a few videos to try and pick up on the sound. 1 is straight after it all happened, 2 is after I had a look at the belt and a few other things and 3 is after resetting my origin points and trying a new cut - which went as normal. Sorry about the long post, I hope it made sense, just trying to learn as much as I can.

[stevem]

Try some WD40 on the ball screw. It kinda sounds like it's dry. Just because it's a new machine doesn't mean there was enough lube on the screws.

[cletus]

Is it my aged eyes or is the z-axis screw wobbling?

[stevem]

It does look like the ball screw is wobbling!

[Mezalick]

Apr 2, 2020 8:32:10 GMT -5 stevem said:

Try some WD40 on the ball screw. It kinda sounds like it's dry. Just because it's a new machine doesn't mean there was enough lube on the screws.

I would strongly suggest NOT to use WD40..

It will leave a residue that will build up over time causing more problems.



3 in 1 would be a perfect lubricant to use.



Michael

[lewc]

Apr 4, 2020 15:53:25 GMT -5 cletus said:

Is it my aged eyes or is the z-axis screw wobbling?

Thanks for the replies. I've got some 3-1 oil that I can try to see how it goes.

When I was first checking it out, it kind of seemed like the ball screw was wobbling a bit but I was't sure. It's a little reassuring (or maybe not) that someone else might have noticed it. 

Would the moving spindle have enough force to bend it or move it from where it's meant be?

[stevem]

My mistake! I meant to say 3-1 oil not WD40. If the Z ball screw is bent, it was like that when it was built. I don't see how a short piece of 1/2" steel could be bent while running the machine.

[johnb]

New or not, a daily wipe down of all the screws with 3-in-1 oil is recommended procedure in my AR-16 Elite manual. If that doesn't cure it, the next thing to check would be grease. It's always possible they didn't load that bearing with grease at the factory. Find and follow the instructions for that process.

[Bob]

Have you checked the coupler connecting the Z axis screw and the stepper motor? If it's slipping it could cause noises similar to what you hear. Check that set screws are seated on the flat portions of the axis and on the stepper motor shaft.

[Bob]

And, on an unrelated issue...Be sure to check the coolant level in the reservoir. The tubes going into the spindle look a little empty when it's not running. The tubes on my machine don't appear to drain out like the ones on your machine.

[wtphdrew]

You need to grease the ball screw, it needs to be greased about every 500 machine hours, I'm running most of my machines about 18 hours a day, while it's a pain the first few times, it just becomes normal after a while and I just grease it monthly, sometimes more often. I actually wrote a CNC routine to run the axis back and forth while I'm greasing.