Hello,
I am new to machining and trying to get my brain around cutting feeds/speed/depth calculations. My interest in CNC is mostly at a hobby level and I have no formal training.
I am working with aluminum alloys and plan to build parts for inline skate racing and later on do some stuff for bicycle racing.
I am considering using a roughing tool for my first operation. The following is an example tool from Cleveland Twist Drill. I plan to use this tool to for the initial roughing of the part from 1.5" billet.
0.75” Roughing EM (http://tinyurl.com/ve7kw)
Wikipedia lists the cutting speed for aluminum as 250-350 fpm (http://tinyurl.com/yxlsd9) this is a big range and I am hoping that someone has an idea of the speeds for the 6061, 7075, and mabey Fortal alloys. I am guessing that since these are harder the will be in the 250-275 range but that is just a guess.
Most of the work of the roughing tool will be side milling. My CNC is an Acroloc with 5hp spindle motor and up to 3500 rpm range. I have a flood coolant system and I plan to purchase some coolant soon but I have not decided what kind.
For feed/speed/depth I am using an excel spread sheet with the following calculation.
RPM = SPEED / ( (TOOLSIZE/12)*PI() )
FEED = RPM * NUM_FLUTES * CHIPLOAD
DEPTH = TOOLSIZE/2
The above calculations result in rpm/feed/depth of 1324rpm, .375 deep, and a feed of 19.86. I understand that these numbers are starting points for the operation so I am looking for some ideas from people with experience.
The J&L catalog says that the Cleveland Twist Drill roughing end mill “Doubles...triples feed rates of conventional high speed tools” does this mean that I can safely run at 2xFEED (i.e. 40ipm) while keeping the rpm and depth of cut the same? 40ipm seems like it would be way to much so I am skeptical about the claim that this tool can double feeds vs. convential HSS.
Also, since I have not yet purchased coolant for my machine and am looking for a recommendation for someone working mostly with 6061 and some 7075.
Does anyone have additional ideas or thoughts about speeds/feeds/tooling/coolant for aluminum alloys?
Thanks in advance!