Posts for Tag: Aluminum

Oneshop Redding Cutting Aluminum (part two)

Over the past few days, since I did the first aluminum cut, I've been researching the most efficient ways to cut aluminum with a clean finish.

I found that the vertical cutting height should be much higher than my previous 0.2mm. This time I set it at 6mm cut depth and place it at 0.1mm optimal load; the sound wasn't quite like I would have liked, so I tweaked it a bit and got to sound a bit better.

I also found that using compressed air helps with chip removal; I already knew this, but I found with a combo of compressed air, and the silicone gets a clean-cut, and you can see what's going on.

I was able to cut down the stock to about 5mm and then start cutting out the logo design that I modeled a few weeks back. It all went very smoothly without any hitch, though I did have to be there as I didn't trust it on its own.

I started with a 1/4" 4 flute carbide bit to mill out the smaller stock, then switched over to a 1/8" 4 flute carbide bit to clear out the shallower areas and to do the final touches.

The significant difference between this cut and the previous cut operations I did the other day of the same model as I didn't understand how to set the Rest Machining option; this means the rest of the stock to cut from the previous operations.

I tried something new here as well, which was taping the underside of the stock and the board and glued the two sides together for a more secure fit. I did this primarily because I knew I wanted to cut the part out of stock, and I didn't want it loose.
I noticed that toward the end, one side of the stock was higher than the other and so I started cutting into the tape before its final pass, which was not ideal.

Since I had to be there watching and blasting it with air, it was not ideal. I've got an idea to add a few nozzles which I can attach to the air compressor so I can let it run on its own.

So the bits I got from my brother (see earlier post) were for cutting steel and titanium, which, as it happens, is not ideal for cutting aluminum. I thought it would be just using a harder bit than necessary but would work just as well, but not.


Oneshop Redding Cutting Aluminum

After acquiring the aluminum stock and endmills to cut it, I need to figure out what feeds and speeds to start cutting the material to achieve a decent outcome.

I started with a flat plain cut to remove some of the access material and give it a smooth surface to begin my next operation. I didn't realize till I started cutting that the aluminum stock is not perfect perfectly flat on top, I added an extra 0.5mm to the top of the stock to clear it off in case it was imperfect, which worked out well.

I set it at 203mm/min (8in) and 0.5mm stepdown with a 1/4" 4 flute endmill. I can probably have more of a stepdown and even increase the speed, but I'm playing it safe for now. These bits are seriously expensive, and I don't want to ruin anything in my first go.

The outcome was not a huge success; the tool edges were a bit worn just slightly enough that it left some stock when it should have cut. The chip evacuation wasn't the greatest either, so I'm going to try using compressed air and silicone wd-40 lube to give it more of a chance. Overall though the places it did cut have a very nice finish to it, something about CNC cut aluminum feels so good, such a perfectly smooth top.

The sound of the machine didn't sound like I was hoping. So for the next cut, I'm going to lower the optimal load on the bit, which should decrease the size of the chips and have a smoother finish. While cutting the aluminum heated up quite a bit and got to the point where it was too hot to touch, I think the reason why it was heating up so much is because of chip evacuation; the chips couldn't get out fast enough and so were recut and started welding with the tool. The outcome was a very rough finish and a definite color change along with it being much sharper of a surface finish.

Attempt number two, it was more successful than yesterday, I bought a can of wd-40 silicone lubricant and sprayed it periodically while it was cutting, and that did the trick, I sped it up quite a bit faster than before, and it kept up. This time the aluminum only got a little warm and all the chips consistent and small. It sounded much much better than before and had a cleaner finish. 
I tried running a few cleanup passes but didn't quite get them down right, so I ended up cutting places where I shouldn't. Very pleased with the outcome, even though it didn't look as clean as I would have liked. One thing I keep forgetting to try is compressed air that would remove the chips from getting recut, and I feel it would keep the material from overheating.

Oneshop Redding CNC Aluminum & Bits

I finally got down to it and ordered a couple of aluminum cutting bits for the Shapeoko CNC router. I bought them off of the site Bits and Bits which has a wide selection of them to choose from. I ordered a 1/8" 3 flute end mill bullnose and the same of 1/16" for smaller details. They were both about $22 each and adding shipping that bumped it up to $54.00 which is quite a lot for just two bits.

Shortly after they came in my brother gave me 14 used endmills from his shop down in Nevado CA as a late birthday gift. This was great as they were easily $20-35 a piece which I could never afford on my own. They were a bit worn from cutting titanium but a few of them where in decent shape. They ranged from a 1/2" thick to 1/16" which is going to really give me a wide range to practice with. Unfortunately, the Shapekoko can only hold up to 1/4" bits so I won't be able to use the 1/2" unless I get a new holder for it.

As for cutting material I looked a bit around online for different grades what's recommended for first cuts and found some inexpensive 6061 aluminum for $17.00 for a block 11.5"x 2.5"x 1/2".