Low RPM Spindle

[kolias]

Forgot to ask the question here...

What spindle do you use to cut Aluminum on your CNC?

(preferably 110VAC or DC)

[jsheerin]

I use a PC890 router run at its lowest speed (~10k rpm). It's not amazing but works okay. I'm planning on using a mini-mill (X2 size) milling head with a dc motor in the (hopefully) near future. I plan to also use this as a drilling head. In theory you could use a higher speed spindle (maybe one of the Chinese spindles) to cut metal, but you'd need to move it fast to take full advantage of it and your machine would need to be rigid.

[kolias]

I thought that even 10K RPM is high to cut aluminum. What I read is that 2K-3K is the ideal RPM to work in Aluminum.

I have a VS Bosch Colt with an RPM range of 16K-30K. I wouldn’t even try to do anything in Aluminum at 16K RPM.

[jsheerin]

No, look at the spec's on the some real milling machines. Some go as high as 40k rpm. 10k rpm is typical. That's not to say it will work in your application. Those machines are much stiffer and can likely move faster while cutting than yours can if you have a typical router. If you can move faster you can get the chip load up into a more reasonable range so the cutting tool works properly.

If you haven't tried your spindle, how do you know it won't work? I'm not saying it will, but trying it won't kill it. I've accidentally cut steel with mine (went through the side of a bolt in some aluminum) and it was fine. Take very light cuts, like 0.01" depth of cut with a 1 flute or 2 flute 1/4" tool maybe starting around 15ipm. I run 10k rpm with a 2 flute end mill which would be equivalent to running 20k rpm with a 1 flute. This will be a super small chip load for your cutter which isn't that great, but it works for the typical routers people are building here.

[jjacstcy]

10k seems a bit slow to me. I haven't finished my machine yet to determine its capabilities. However, I cut .250 aluminum plate at work with a 5hp spindle running at 32000 rpm's with a feed rate of 70ipm. The average starting rpm is 18000 using a 1/4 single flute bit with a feed rate of 40ipm. I can cut 8 4'x'8x1/4" sheets full of 6" letters before I need to change the bit.

[lancut]

Use Super-PID to control your router speed. I cut aluminum @5000 rpm with my Milwaukee router controlled by Super-PID.

www.SuperPID.com - Super-PID Closed-loop Router Speed Controller

I have no financial gain out of this. Just an very happy customer.

[kolias]

Now that is good news for me, never thought about it but certainly I will give it a try

Regarding the Supper-PID I’m aware of it and I may consider it in the near future

Thank you all for the info

[louieatienza]

Originally Posted by jsheerin No, look at the spec's on the some real milling machines. Some go as high as 40k rpm. 10k rpm is typical. That's not to say it will work in your application. Those machines are much stiffer and can likely move faster while cutting than yours can if you have a typical router. If you can move faster you can get the chip load up into a more reasonable range so the cutting tool works properly. If you haven't tried your spindle, how do you know it won't work? I'm not saying it will, but trying it won't kill it. I've accidentally cut steel with mine (went through the side of a bolt in some aluminum) and it was fine. Take very light cuts, like 0.01" depth of cut with a 1 flute or 2 flute 1/4" tool maybe starting around 15ipm. I run 10k rpm with a 2 flute end mill which would be equivalent to running 20k rpm with a 1 flute. This will be a super small chip load for your cutter which isn't that great, but it works for the typical routers people are building here.

It wouldn't be hard to test. I believe for the Amana spiral O flute they recommend 120ipm at 18000rpm for 1/4" at 1/4" depth. I never attempted this. But what I did do was make 6 pockets about 3/8" wide and about 3 inches long. I set my feedrate at 100ipm but changed the depth on all 6 slots by .015", cutting each with one pass. I thought I would gall up the bit and break it. To my surprise it cut through all of them. I did get some edge burring at .090" pass, and I still have some backlash issues (new couplers sent with the wrong bore!) but .075" gave me a clean edge. just an anecdotal example to demonstrate how you could test cuts.

[kolias]

I dont even cut wood at 100ipm LOL but I’m glad to hear that

It looks like that my Colt will do the job

[louieatienza]

Originally Posted by kolias I dont even cut wood at 100ipm LOL but I’m glad to hear that It looks like that my Colt will do the job

Heck, I used a Sears Craftsman trim router on my first machine! Granted, these aren't ideal conditions for cutting, but for occasional stuff, it's good to know it can be done.

[lancut]

You can cut almost anything with high rpm's provided sufficient federate. My preference is to slowdown the rpm so I can use high speed cutting tools vs the lot more expensive carbide tools. That why I was suggesting the S-PID in early post, it provides all the torque while cutting @ low rpm. It can control anything as long as it have brushes and powered by AC current. Hope this helps.

[kolias]

I like the super-PID but I find it kind of expensive for now.