3/8 aluminum

[magic]

I've read through posts from the last three years but want to get a consensus on cutting 3/8 AL. I don't know if it's 6063 or not but that's what I'll probably suggest It's a Sub-Sub contracting job..

Seems like I need to make 3 passes @ .5 ips using a .25 ced Onsrud single flute - 0, at 13,000 rpm

I have a Porter cable router on my Alpha.

If all the above is correct then it will take me 6 seconds to cut one inch = 60 seconds to cut 10 inches = 72 seconds per foot = (say 85 an hour for machine time) = 1.70 per foot, not including programing....

That seems low. I don't believe the machine can cut 1/8 aluminum at .5 ips...Seems like it should be .2 ips which would make it around 6.00 per foot... I'm lost. I've never used a Single flute -0 before and that could make a difference. OR I'm bad at math.

Opinions, please

[paco]

Utility/common/3003 aluminum, when possible to cut, is very erratic. I have been able to get decent cut with 1 flute O-flute 1/4" CED but I couldn't control when the bit would clog... many parts to cut again. Stay away from low alloy and keep with T6 or better/harder. "No problem" with those.

As for step down, feed and RPM; with a 4HP HSD spindle I spin the bit at 16000 and advance at 1.2-1.7"/sec. with a step down of 0.015-0.035" depending if I'm using a 1/8", 3/16" or a 1/4" CED tool bit. Always O-flute. Straight or down cut for thin and spiral for thick. Whenever it reach 50% of the tool bit CED in term of dept of cut I calculate a 0.005" allowance. This can mean many toolpath file but it something I fell is required to keep the bit clear of re-cutting chips (way less vibration). I do a final pass slower to get the finest finish I can.

Thin AL is a bit different. When it's less than 1/16" thick, I try to use either a 3/16" or a 1/4" CED tool bit to cut in a single pass. It can mean going slower but the process is just easier.

I don't want to sound harsh but cutting AL with a porter cable wont be fun at all... though it is "feasible". Just be more conservative on the step down and the feed.

Hope this help.

[magic]

So, You would cut 3/8 with a .25 bit with 15 passes. sounds like.@ 1,25 ips because I have a router.

Lets say I just ate the extra time and ate dinner while it cut. Does 6 dollars a foot (for 3/8 thick) fit in with what a spindle CNC owner would charge?

Thank you for the advice.

[magic]

So is $6.00 a lineal foot a reasonable price to cut 3.8 AL?

[erik_f]

Why not charge by the hour just like you would with wood? What is your hourly rate?

[magic]

50 for programing 75 machining

But this is a subcontract and the other shop wants to give them a set price. I'm just wondering what others charge by the foot.

[erik_f]

You can charge what ever you like. I am inclined to think however, that you might now want to charge the same rate for wood as you do for metal since metal is not really what the bot is designed to cut, thus cutting much slower than a specialized machine. I know this doesn't help you much now, but for the future it might help to have a pay scale for wood and another for metal. If you are charging $6 a foot because it takes you 12.5 minutes to cut a foot for 3/8" aluminum (you want $75 an hour) you might want to look at what a machine shop would charge for the same job...they may be able to do what you are doing in 1/10th the time.

[mitch_prest]

you may want to do a test run and see if you can even do the job.. I am presently having a hell of a time with 1/4 aluminum. Its taking way more time than I figured.. and I have already attached one bit to the aluminum plate permanently

[erik_f]

it depends on what kind of aluminum from what I've read. Softer is actually harder to machine because of what you are running into now Mitch. I was able to machine four 2" holes with no real problems. But I stood there and sprayed lithium grease on the part every pass. It took a while. I would think at the right feeds and speeds you could get away with blowing air at the tip of the bit.

[robtown]

I've cut up to 1/2" 6063 or 6061 AL on mine PRT with a Porter Cable. Well I wouldn't say cut, it's more like shaving at 1/16" passes @ .2 ips...

I would not even consider a project cutting parts out of 3/8" AL at a set cost, unless you get a good price per part, you will take a beating in lost time from other projects, router bits and culled parts alone.

You really need to make a test run at time and materials cost. And do more than one part, do 6 on this test run. I can futz around and make anyting happen for at least a single part, it's when you gotta run 500 that you really find out how bad you stepped in it...

[Gary Campbell]

Eric...
I have cut a fair amount of aluminum on different projects. The last one was 4 drill brackets for my PRSa. 3/16" 6061 Plunge in @ .125 ips, cut @ .8ips one pass, WD40 mist, 1/4" O Flute, conventional. Sides were sent thru the sander. Cuts were untouched.

5272
Gary