Problem- X2 CNC mill too much vibration and not cutting properly.

[alexccmeister]

Hi all,

My first X2 cnc is up and running. But as expected, I have run into my first problem. The pictures I think will tell you alot about what problem I am having milling aluminium.

Its not exactly circular as there is a slight backlash in the y axis. My feedrate is 200 (I am working in metric so not sure what this figure represent). Depth of cut initially was 1mm (think this is too much). So I adjusted it to 0.5mm DOC instead. Still too much? Diameter of hole is 46mm (suppose to be) and I varied my RPM for trial from around 2000 to 4000. Too fast?

How do I get a smooth surface?

Also, When milling, the mill just vibrates too much. Can't pinpoint where the vibration is coming from. I suspect its the Z column as this is the weakness of X2. For those who owned a cnc X2, how do you manage to mill good looking and accurate parts? Thanks in advance for your help.

Alex

[The Blight]

The weakest point is the gibs and the dovetail ways. The column is not that weak. It's not an easy task to adjust the gibs, but you can get some fairly good resaults without doing much to the mill. First of all, you should try moving the table/head back and forth and check where it binds. When you have found the high spot, you can either adjust the gibs so that they run fine there, and loose everywhere else. Or you can lap or scrape the ways to remove those high spots. This takes time, and it might not be easy if you don't have a level piece of steel or granite to mark the ways with. I have taken 2mm cuts with the mill at over 200mm/min with this mill (10mm mill) without hearing much complaining. Thats after I had lapped the ways on it though.

Took a look at your picture.. wow.. are you using any coolant? is the endmill new and sharp? Looks like your using a dull cutter on soft aluminum with no coolant. If thats the case, then ignore the first part of this post (unless you want to improve the mill).

[alexccmeister]

Hi TB,

You may be right about the dull tool. No I am not using coolant. Will try with a new cutter and see what happen. BTW, is 200mm/min feedrate too slow for cutting aluminium? I read on another tread about cutting aluminium that the poster use feedrate of 200ipm. That works out roughly 5080mm/min FR. I have tuned my motor to have a velocity of 3800mm/min. Not sure if I am doing this right. But then again the FR is controlled in the Gcode is it not?

Thanks.

Alex

[alexccmeister]

Is it good to pour concrete into the dovetail column to make it more rigid and more mass?

I am definitely adding a plate at the back of the mill to keep the column permanently vertical.

Alex

[gun_mike]

Cutting aluminum at 200ipm sounds like a production type machine. Good cutting results in the correct speed (spindle RPM) and the correct feed rate. It's also based on the diameter of the cutter, the number of teeth, and in some cases the rake angles on the cutter itself. I had similar problems with my first cnc machine. I was using dull endmills, little to no coolant, and incorrect spindle speed and feed rates.
It never hurts to add a squirt of oil or a shot of WD-40 to your cutter every once and a while during a program.
Heres a handy little calculator for determining the correct speed/feed for Aluminum
http://www.jonathansaada.com/speeds_feeds_alum.php

Heres another one for various other materials
http://www.jonathansaada.com/speeds_feeds.php

Hope this helps,
mike