cutting 6063 speed, feed, and bit advice

[rthoma82]

I am brand new to using CNC. I successfully made my first piece out of plastic using the tutorial in the operator's manual. (that's how new) Anyway, now I've been tasked with creating tensile test dog bone samples. The ones I'm starting with are 6063 aluminum. They are already cut to the length and width, I just need to cut out the dog bone shape. I've already written my gcode and everything looks fine, my only problem is that I have no idea what speed my spindle speed should be, what the feedrate should be or even what kind of bit to use. I've tried a few things but have broken every bit so far and haven't made it more than a 1/2 inch into the first cut. Any help would awesome.
Here are the specs that I know:
Machine: Tormach 770
Material Type: Aluminum 6063
Dimensions of piece: 8 3/4" long, 3/4" wide, 1/8" thick
Feedrate: currently set at 4 (based on some online calculator I found)
Speed: currently set at 3000 (based on some online calculator I found)
Bit: 1/8" I don't know anything else about it the bit
No access to coolant, have to do this dry

not sure if you need any more info. I can try and figure out more if it's needed.

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[Jim Dawson]

The main problem is in the last sentence of your specs. ''I have to do this dry'' Some WD40 in a spray can will make a world of difference, I also use soy oil (cooking oil), apply with a brush or an oil can. If you look at the broken pieces of cutter you will see that there is aluminum welded to the cutting edges, this is due to the lack of lubrication/coolant. 6063 is gooey stuff to machine.

3000 RPM seems a bit light for a 1/8 end mill. You should be using a 2 flute end mill, this will give more chip clearance than a 4 flute. You might try to do the cuts in 2 passes, 0.063 depth of cut.

[rthoma82]

The main problem is in the last sentence of your specs. ''I have to do this dry'' Some WD40 in a spray can will make a world of difference, I also use soy oil (cooking oil), apply with a brush or an oil can. If you look at the broken pieces of cutter you will see that there is aluminum welded to the cutting edges, this is due to the lack of lubrication/coolant. 6063 is gooey stuff to machine.

3000 RPM seems a bit light for a 1/8 end mill. You should be using a 2 flute end mill, this will give more chip clearance than a 4 flute. You might try to do the cuts in 2 passes, 0.063 depth of cut.

Thanks for the quick reply. I will get a can of WD40 and try that. If 3000 rpm is too slow, what would you recommend? My first attempt I started at 5000. When that didn't work I figured slower would be better but I can bump it back up. Not to sound stupid but what is a flute? and what difference does 2 vs 4 make?

[deadlykitten]

hy / hitting proper specs is a step that requires experience, and i admit to fail it many times until starting to have a clue

sound is a key in time, sound will tell you how rigid is a fixture, or if the cutting specs are out of bounds / having a musical ear requires time

another tip is chip aspect, color, how it breaks ...

forum tips for this is like reading a book about " how to built a space ship in 24hours "

get a veteran near you, and run trials many many trials ... get bored with trials, destroy tools so to learn limits, and so on

patience & trials is the key for process stability ; kindly

[Jim Dawson]

The flutes are the cutting edges. Normally you use a 2 or 3 flute endmill on aluminum. 3 flute in the larger sizes. Using 1/8 inch you are going to want to use a 2 flute. Fewer flutes gives you more chip clearance between the flutes, needed for cutting aluminum.

5000 RPM and about 7 IPM would be in the cutting range I would try. This will give you about 160 FPM cutting speed and a tooth load of about 0.0007 with a 2 flute endmill. With a 1/8 end mill under non-ideal conditions a depth of 1/2 the diameter is normally a good place to start.

[rthoma82]

The flutes are the cutting edges. Normally you use a 2 or 3 flute endmill on aluminum. 3 flute in the larger sizes. Using 1/8 inch you are going to want to use a 2 flute. Fewer flutes gives you more chip clearance between the flutes, needed for cutting aluminum.

5000 RPM and about 7 IPM would be in the cutting range I would try. This will give you about 160 FPM cutting speed and a tooth load of about 0.0007 with a 2 flute endmill. With a 1/8 end mill under non-ideal conditions a depth of 1/2 the diameter is normally a good place to start.

Awesome. Thank you for the explanation. Still learning all the lingo too. I'm assuming IPM is the feed rate. This has been very helpful. Thank you.

[Jim Dawson]

Yes, IPM = Inches Per Minute