For my CNC I use PETG. I haven't had any problems with filament I use and I use some of the cheapest stuff out there. The thing I learned with PETG is to cool it as fast as you can while printing. Before I started cooling it fast the prints were not as strong, now I have prints that I couldn't break unless I really abuse them and they don't chip off or crack , they bend and twist first. Also , play with the temps, my current filament works best 216C , higher it doesn't cool fast enough and lower the layers don't bond well. Print something like a long rectangle with a few layers and 20% infill and try to break it, alter temps till it bends but not breaks is how I do it. Even a few degrees can make a difference, 210C didn't work and neither did 220C, 215C was close, 216C was just right. I use a bed temp of 70C and print on glass + hairspray (aquanet) . I sometimes break the glass removing a print it adheres so well, cheap $1 picture frame glass from dollar stores laid on top of 3/8 inch glass bed.