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Cutting Aluminum

Posted: Thu Aug 21, 2014 3:31 pm
by philIam
Hi,

I am about to begin cutting aluminum. I've been cutting plexi and ABS day N night getting ready for this day! I'm looking for advice, I've read the other blog posts on aluminum but not sure if I'm getting it understood correctly. I don't want to break my bit!

The Details/Questions:

I have this bit: http://www.amazon.com/gp/product/B0006T ... UTF8&psc=1

I have the DC Quiet Spindle at full throttle

My piece is well secured

Aluminum type: 5052 @ 1/8" thickness

Planned Feedrate: 200 mm/min => 7.874
Plunge Rate: *???*
Stepdown: .0157 in/min
Lubricant:: WD-40 (how often do I spray the bit?

I'm guessing you don't want to leave tabs because there would be basically no way of getting it out. How does one do this without having your piece fly all over the place?

Thanks for anyone's help!

Re: Cutting Aluminum

Posted: Thu Aug 21, 2014 3:33 pm
by philIam
I don't have the speed controller. I have it just hooked up to my power supply VDC.

Re: Cutting Aluminum

Posted: Thu Aug 21, 2014 4:56 pm
by criznach
If your part has holes in it, use those to screw down the part that will be cut out. You can either set up a separate job for the holes, or if you don't have homing switches, it's probably safer to use the pause or feed hold feature to stop movement while you add screws. Be sure and set your safety height high enough to clear the screws.

Example:
2014-07-20 10.40.58.jpg
2014-07-20 10.40.58.jpg (333.92 KiB) Viewed 2010 times

Re: Cutting Aluminum

Posted: Thu Aug 21, 2014 5:00 pm
by philIam
Hey thanks!

I was just cutting with a feed rate of 5 inches per minute and when it was profile cutting it looked like it was CLEARLY moving too fast, like the bit couldn't move up and flew forward (on a smallscale of course).

Picture dragging a stick pushed in the groundm straight and you're holding it running the stick tries to keep up but cant and leaves this pivot after pivot markings.

Hope that's illustrative enough!

Should I go down to 2 inches perm minute?

THANKS!

Re: Cutting Aluminum

Posted: Thu Aug 21, 2014 5:39 pm
by jbrewton
I am running feed rate if 15 ipm with step down .01 on 1/2 aluminum. I however have the makita trim router. Not sure how it compares to your spindle. I use 8020 from inventables as the base with t slot clamps from rockler to hold every thing down.


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Re: Cutting Aluminum

Posted: Thu Aug 21, 2014 7:58 pm
by McMagical Eng.
The torque on the quiet cut spindle isn't huge, so you will have to go a little slower than large mill specifications. I would highly recommend using a tool calculator to figure out your feeds and speeds! These are based on tried and true methods for mechanical engineering and manufacturing... and they are free.

example: http://zero-divide.net/?page=fswizard

Good luck! I will be installing my quiet cut spindle tonight assuming the ups guy delivers tonight. Post pics when you get it all set!
Cheers.

Re: Cutting Aluminum

Posted: Thu Aug 21, 2014 9:36 pm
by criznach
5ipm isn't all that fast for aluminum. Maybe you're cutting too deep. I've been doing .15mm at 520mm/min, which is about .006" at 20.5ipm. I came up with those numbers using the same calculator that McMagical linked to above.

Cutting Aluminum

Posted: Fri Aug 22, 2014 4:45 am
by DanMc
I have basically the same spindle but I got it from China. I run 400mm/min, stepdown .01mm, and plunge 180. I always do a lead-in when plunging. For lubrication I've been using 3in1 very liberally dousing the path basically every time around, I want to try some cutting fluid next time around but the 3in1 seems to work well. This is about the max I feel comfortable with using this spindle. It's not fast, it stressful knowing that the spindle is maxed out, but it works, I've done some pretty long jobs and they always come out well. For work holding I usually try to leave just a little flashing on the bottom, either through careful programming or stopping the job at the point where I think I can just push the piece out with finger pressure, then I file/sand off the flashing. It takes a little practice to know how much material to leave. If possible, use criznach's suggestion to screw the piece down before cutting the profile, just make sure your safe height will clear the screws and/or the tool path won't pass above them.

Edit: above values were on 6061 Al with a 2 flute 1/8" end mill

Re: Cutting Aluminum

Posted: Fri Aug 22, 2014 6:40 am
by PsyKo
Hello,

Depending on the aluminium type your settings won't be the same.

2017A Aluminium is very good for milling. I use the same endmill as you do @ 600mm/min, 0.4mm/pass and something like 20k RPM on the Kress spindle.

For other softer and unknown aluminium alloys, I can't use this endmill because it heats too much, and the aluminium melts on it (reducing the cutting capabilities). I have to use a 1 tooth endmill with faster motion and lower pass to avoid heating (something like 1000mm/min and 0.1mm/pass, plunge rate 100mm/min)

Here is another topic about speed in aluminium : http://www.shapeoko.com/forum/viewtopic.php?f=6&t=1912

Re: Cutting Aluminum

Posted: Fri Aug 22, 2014 2:56 pm
by philIam
Thanks guys.

I'm running at .008 step down 5 ipm. And here's the result.

https://www.youtube.com/watch?v=5GamzFk4zbs

That sound normal? Its pretty terrifying and stressful when listening to it start a new hole.