Milling Aluminum - First Results

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levlandau2
Posts: 187
Joined: Tue Apr 17, 2012 1:52 am
Location: Minneapolis, MN, USA

Milling Aluminum - First Results

Post by levlandau2 » Sun Aug 26, 2012 3:29 am

I milled my first aluminum stock tonight. Overall the results were fairly good and Shapeoko seems to be promising in its potential to mill soft metals. Thanks to microwavesafe for his initial work and suggestions on how to do this.

Equipment Setup
DW600 spindle at 15-30k rpm
Acrylic side shields and plastic wrap to keep linear bearings clean
dual y-axis motors
3mm endmill from drillman1 on ebay
cutting fluid and motor oil for lubrication - manually applied with each pass
router RPM controller

The milling went fairly well. The holes and trenches being milled kept getting clogged with aluminum shavings and I had to keep them cleaned manually with a small drill bit and toothbrush. I did not use the shop-vac to suck the shavings while miling, but I'm not sure how well that would have worked since the shavings were adhering to the metal due to the cutting oil which was all over. Not sure how this can be improved upon...? I milled three plates with 0.5mm and 1mm depth per pass. Both worked but the 1mm seems problematic. It taxes the tool more and requires higher RPM which I think heats the stock and endmill much more. I have not measured this, but anecdotally, the endmill and aluminum were both warm to the touch (40-50C?) after the milling was complete.

I tried decreasing the RPM with the router RPM controller I have plugged into the spindle, but this only worked well with the 0.5mm per pass. I think the 1mm depth per pass slows the spindle RPM too much and causes the milling to slow down. I am guessing this is due to the lack of RPM measurement and control via some form of feedback. Perhaps an PID controller would fix this..? The slower RPM seemed nicer, since it produced much bigger chips and likely causes less heating of the endmill. However, I am not sure it is practical to use a lower RPM without a PID controller.


To-Do for Future Metal Milling
1) Develop automated lubrication system
2) PID RPM controller for spindle or at least RPM sensor to confirm that RPM is unstable when RPM controller is used
3) Figure out how to keep trenches milled free of shavings???

Sorry for poor quality videos. Hard to record video while cleaning shavings and lubricating the endmill.




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edwardrford
Posts: 1250
Joined: Mon Apr 09, 2012 5:40 pm
Location: Dixon, IL
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Re: Milling Aluminum - First Results

Post by edwardrford » Sun Aug 26, 2012 5:02 am

Nice work and nice writeup.

I've seen some people on youtube cutting aluminum without any sort of lubricant. The use air to clean the working area. Generally something pointing towards where the bit is cutting which can blow the shards out.

Also, I've noticed, although counterintuitive, it seems to work better to go faster than you would think you should *but* use lighter depth passes. In all of the video's I've seen, the people are moving really fast (100+ IPM), but only taking 1/16" off at a time. I've had some decent luck with my experiments following the same idea.

Regardless, great job! Are the end plates usable?

-Edward
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

Will Winder
Posts: 435
Joined: Fri Apr 20, 2012 2:40 pm
Location: Hudson, MA
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Re: Milling Aluminum - First Results

Post by Will Winder » Sun Aug 26, 2012 4:56 pm

Wow! Looks like that part came out really nice. It came out much better than my first attempt at milling aluminum.

Aside from an upgraded spindle, what other mods for your ShapeOko?

I was able to mill small holes, but the backlash killed any larger cuts I tried. I'm guessing dual y motors are required for aluminum, but maybe just the upgraded spindle? Part of my failure was probably due to the belt-on-the-outside mod which seems to create significantly more backlash if you aren't using dual-y motors.

I ended up giving up on the part I was trying to make in this picture, but salvaged some of the good holes to make a different part by hand with my stationary jigsaw.
photo.JPG
The 6 holes in the middle were milled and the two big ones made me with I had an e-stop installed.
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ShapeOko #367: Dual-Y drive, Belt on outside, 1000mm Y-Axis, DW660 Spindle, Nema-23 X/Y motors.

Primary developer on Universal Gcode Sender.

levlandau2
Posts: 187
Joined: Tue Apr 17, 2012 1:52 am
Location: Minneapolis, MN, USA

Re: Milling Aluminum - First Results

Post by levlandau2 » Sun Aug 26, 2012 9:40 pm

Will,

The upgrades I have are:
1) dual y-axis motors
2) side shields to protect rails from shavings
3) DW600 spindle
4) belts on outside

I think all of these - except belt on outside - are necessary to even try milling aluminum. I was using a dremel spindle before and it was much harder to mill anything. With the DW600 things got a lot easier when milling wood. I am guessing it would be very hard to mill aluminum with a dremel. The shields help keep the makerslide free of shavings, so I think those are essential too.


Edward,

I have experimented with 0.5mm and 1mm depth passes. It seems the 1mm is too much, since it results in an uneven depth of cut. See the image below where one side is milled all the way through, while the other still has material left on the stock. I believe this is caused by the play in the z-axis, because pushing up on the spindle causes the y-axis to move 2mm in the -y direction. In the image below, I was cutting in a counter-clockwise direction, so the z-axis moved up as it was being pulled in +y direction and milled at a lower depth. These issues did not seem so bad when I was using oil (this was dry mill run) and 0.5mm per pass. You said 1/16" works well, but that is 1.5mm, so it is even more aggressive.

This plate was milled without any lubrication. The good news is, that it was easy to clear the chips by running a shop vac by the endmill. However, both the stock and endmill became quite hot (entire stock was hot to the touch maybe 40-60C). Dry milling seems to be possible, but I am not sure what the effects on endmill life will be. Unfortunately, when lubricant is used in the manual way (where I am spraying it), chip removal becomes a lot harder since the lubricant makes the shavings stick to the stock.

Conclusion: Aluminum milling is possible with said upgrades above, but not ideal or automated.


Improvements Needed:
1) Firm up z-axis. (with double makerslide?)
2) Figure out how to clean chips while lubricating endmill - don't know how to do this, not too excited about having smelly and toxic coolant in my basement....
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bobt
Posts: 132
Joined: Tue Apr 17, 2012 7:08 pm

Re: Milling Aluminum - First Results

Post by bobt » Mon Aug 27, 2012 1:21 am

For coolant and coolant systems look here:

http://www.littlemachineshop.com/produc ... 2122081959

They have all things for small hobbyist machines.
Also they have environmentally/nose friendly coolants there.


Bob Teeter
"What Box???" ShapeOko #397

roberlin
Posts: 59
Joined: Tue Apr 10, 2012 12:12 pm
Location: Baton Rouge, Louisiana

Re: Milling Aluminum - First Results

Post by roberlin » Mon Aug 27, 2012 2:24 am

I made my first attempts at aluminum this weekend also.

Started with a 1/16th inch endmill at 300mm/min taking off .2mm per pass.
Broke the mill after a few minutes (my first snapped mill!)

Next, I backed off to a 1/8 inch endmill, 200mm/min, .2mm per pass and it worked beautifully.
I'm not using any lube, and nothing seemed to get hot at all. It may be that the shallow passes helped with this.
I'm running double makerslide on the gantry, a la I.C., and dual y axis motors.

At least with the parameters I'm using, the dw660 doesn't seem to be necessary-- I'm using a proxxon (cranked up to full speed which is a nominal 20k rpm) which is about 1/6 the power of a dw660.

I should say that all of this is with 1/16th inch stock, which is the thickest I had around. But I'm hoping everything will hold up with the at least 1/8th...

levlandau2
Posts: 187
Joined: Tue Apr 17, 2012 1:52 am
Location: Minneapolis, MN, USA

Re: Milling Aluminum - First Results

Post by levlandau2 » Mon Aug 27, 2012 6:25 pm

roberlin,

Can you provide any measurements or feedback on the double makerslide on x-axis??? Does this upgrade firm up the z-axis and spindle to the point where it does not wobble? I have enough wobble in the spindle right now that it creates 2mm error in the y-dimension.

When the spindle pushes into the aluminum, the bit moves in the y-dimension as opposed to the z.

Does your setup have any spindle wobble??

As for the heating, the 0.2mm per pass is quite gentle, and I am guessing this is why you did not have heating. I was doing 1mm, which heated things up quite a bit (dry milling).

edwardrford
Posts: 1250
Joined: Mon Apr 09, 2012 5:40 pm
Location: Dixon, IL
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Re: Milling Aluminum - First Results

Post by edwardrford » Mon Aug 27, 2012 7:13 pm

levlandau2 wrote:...

Edward,
...
You said 1/16" works well, but that is 1.5mm, so it is even more aggressive.
....
what the hell was I talking about? I want to say that I meant to type 1/64" because that would have made way more sense, but for some reason I was thinking that I used 1/16" depth passes...which clearly I couldn't have been. Oh well, disregard my statement... I'll try to figure out what I was doing and post back.

-Edward
Shapeoko 1 #0 - a couple of upgrades.
Shapeoko 2 #0 - a couple of upgrades.
Shapeoko 3 #2 - Stock

roberlin
Posts: 59
Joined: Tue Apr 10, 2012 12:12 pm
Location: Baton Rouge, Louisiana

Re: Milling Aluminum - First Results

Post by roberlin » Tue Aug 28, 2012 2:32 am

levlandau2 wrote:roberlin,

Can you provide any measurements or feedback on the double makerslide on x-axis??? Does this upgrade firm up the z-axis and spindle to the point where it does not wobble? I have enough wobble in the spindle right now that it creates 2mm error in the y-dimension.

When the spindle pushes into the aluminum, the bit moves in the y-dimension as opposed to the z.

Does your setup have any spindle wobble??

As for the heating, the 0.2mm per pass is quite gentle, and I am guessing this is why you did not have heating. I was doing 1mm, which heated things up quite a bit (dry milling).
The double makerslide seems to have stiffened up the z-axis a lot. I don't have serious measurements, but putting a ruler next to the end of the mill and pressing on the top of the spindle, I would guess it's less than a quarter of a millimeter of movement.

2mm sounds like a lot. It might be worth trying microwavesafe's twisted x-axis mod as a partial solution.

jrsteensen
Posts: 118
Joined: Mon Jun 11, 2012 9:29 pm

Re: Milling Aluminum - First Results

Post by jrsteensen » Tue Sep 04, 2012 3:52 pm

bobt wrote:For coolant and coolant systems look here:

http://www.littlemachineshop.com/produc ... 2122081959

They have all things for small hobbyist machines.
Also they have environmentally/nose friendly coolants there.


Bob Teeter
On my little cooling system I designed, I went way cheaper. I grabbed the nozzle from there, but used surgical tubing, down to a 5 gallon bucket with an aquarium pump in it. I was planning on lining the area below my table in plastic, with a common sink drain (WELL filtered - chips in recycled coolant is BAD!) as a return to the bucket. Total cost was about 80 bucks as designed. When it gets too contaminated, swap the coolant, otherwise just top off as necessary. A flood system is MESSY though - make sure you build an enclosure around the bot.

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