Hi outback machinist,
I've got (2) Mazak QT15's, and yes, even in good condition, the Parker hydraulic pumps are a bit loud. I have a QT20N with a Nachi pump, and it is much quieter than the Parkers.
One thing i've learned over the years is that most shops do not change the hydraulic oil in the machines often enough. Mazak says every 6 months...I think this is a bit too soon. I try to change the fluid every 12 to 18 months.
People think because the system has a replaceable filter that the fluid will last forever. Hydraulic fluid is in constant contact with the air at the top of the fluid inside the tank, and the fluid will absorb some moisture over time. Plus, tiny metal wear particles can find their way into the oil.
I guess my point is if the previous owners of the machine didn't change the hydraulic oil (some shops NEVER change the oil), your pump may have some wear issues, causing a little more noise.
One thing you can do is drop the main system pressure just below the green arrow on the main system guage. Sometimes Mazak has the main pressure set slightly above the arrow, but this is inefficient and unecessary.
One more thing, the electric fan mounted above the hydraulic unit can get pretty noisy as it gets older. You may want to get a new, quiet, fan for the old one. I've replaced mine with much quiter fans. Also, the electric fans on the rear of the machine for cooling the electrical cabinet can get noisy with age.
Otherwise, the Mazak QT15 is the most common cnc lathe ever built, and is a rugged workhorse of the cnc machine shop world. I wished Mazak still made this machine...instead of the Nexus (i.e. Cheapus) series.
Good luck,
Greg Hale
Onwer
CNC Tool Corp.
Abingdon, VA