Hello there, sorry for my english. I put some image for explain my problem: how can i fix the trembling of the machine?
Please answer the questions from the sticky post. What are you using for the tubing?
IRON TUBE 25 OD
Could be anything.
Please answer the questions from the sticky, it looks like you are using a 1/4" bit so what is your cut recipe depth of cut, speed and stepe over, what spindle, rpm’s, how long is your z axis?
If you don’t wanna answer that, The only advice anyone can give is slow down or make shallower cuts.
Machine
MPCNC 25 OD printed in PLA at 30mm/s 55% infill
Conduit
25od iron
Size External CM 91x91x11 (XYZ)
Stepper Motot
NEMA 17 wantai ( 42byghw811 ) 2.5A for phase
Stepper drive
Pololu DRV8825 CLONE
Spindle:
makita RT070x SERIES
RPM: 12k (the lowest speed)
Endmill
-1 flute
-shank 1/4
-diameter of the endmill 1/8
Firmware RC7
Pc User (estlcam / repetier )
The engrave size is 2mm depth and the external cut is from a 6mmm MDF sheet
Edit
If seem i don’t want answer it isn’t correct: simple i don’t understand well US english; if you can question me as at a 4yo child should be great 
Use shallower passes. Something like .5 or 1mm per pass.
seem better now 
I suppose it was a software problem, now i will try to work better in that direction, thanks to all