need to build a cnc router / mill for aluminum

[axkiker]

So I guess the title says it all. I need to build a cnc router / milling machine to mill aluminum. I dont need anything too hefty, however this will be beyond the typical aluminum sheet cutting like sign shops do.

Ill be milling out parts from aluminum bar. (probably something like 6061). the machine will probably never need to exceede a max of 1" in cutting depth. Typical surface area per part will be around 1'x1'. so nothing huge but I think a little larger than the typical router designs are built around.

Anyone on here built a machine for something like this. I have been speaking with a few people and am getting all sorts of recommendations. Some say if I can figure a way to slow the head down I will be ok. some say that I need to use an ungodly large head in the range of 7 hp.

I plan on using something like a PC router 3.25 hp. I personally think this would be plenty powerful enough. However I have no idea its only a guess. Im thinking I will need a way to provide coolent and chip removal.

I have seen a couple videos around where people have used the home built kits to mill aluminum. However they were only cutting .01 at a pass. I would really like to bump that up to at least .125. I dont have to have anything screaming fast but I cant spend 2 hrs miling a part thats only 1'x1'

I have a milling machine at home however I do not want to convert it over to a cnc. I need something dedicated to milling out these parts.

Any ideas / suggestions.

thanks

[LeeWay]

I am able to mill aluminum with my PC 2 1/4 HP router with my first router table. I have to use plenty of WD40 as it's not setup for coolant. It mills .063 aluminum in one pass. I have done some smaller brackets out of 1/2" aluminum bar. Maybe 2" square when done. Just pocketing and drilling actually on those. I was using both 1/4" carbide and 3/16". DOC on the aluminum bar is no more than .05".
I just finished up building my mill though, so I won't need to use the router for that any longer. It can just cut lexan now, which is what it was originally designed for.
I really had to keep my router blown out with compressed air though. Plastic chips are no problem for it, but aluminum isn't good to have running around in the windings. Coolant would be another unwanted by product of trying to use a router to do milling of metal. Heat should be figured in too. My little router really gets hots when I force it to cut aluminum. I/m sure a lot is coming through the end mill, but none the less, still present and hard to dissipate. The jobs I was doing lasted no more than 10 minutes tops though. This router has lasted well doing this for several years now. Just high maint.

I think you can easily build a small gantry mill to do what you want. I would use rolled ball screws. 5/8" type. Linear ways. Steel frame with a moving table rather than the gantry. 425's or 495 oz motors with either gecko 201's or preferably 203's and a 72 VDC power supply. You could buy a mini mill head and spindle and use a treadmill motor for it.

Now these aren't necessarily the cheapest things that you can get by with, but these items built into a decently accurate build will be able to mill the aluminum like you want and do it fairly well. It's a little slower on the spindle than what you might like. I am getting 3740 top speed on my X2 spindle with a tread mill motor. I will up that some when I can with a little larger pulley. I have no torque issues with it. It hasn't come even close to hinting of a stall. I don't however hog off a bunch of metal. Both my machines are fairly fast, so lighter cuts are fine.

[axkiker]

So here is what im confsed about. I have a verticle knee milling machine at home which has a 1.5 hp motor. I run it around 1000 rpms with a .5" end mill bit and can cut aluminum all day long. I have no problem cutting .250 or more per pass without any difficulty.

So why then do all the cnc mills seem to run at these crazy fast speeds. Why cant someone build a mill with a industrial 2hp motor, some type of solid spindle and mill some serious alluminum at a lower speed. A spindle would not really be that hard to make. And the motor would be attached via a belt just like a typical verticle milling machine.

Im sure there is something that im missing here because even the big industrial cnc mills run at thoes crazy speeds. So whats the deal.

[ger21]

Unless you really know what you're doing, I think you'd be better off buying another mill and converting it to CNC. Handheld routers will not hold up to milling aluminum on a regular basis. You can get away with it for limited light duty use, but they are just not designed for it. The loads are much, much higher. You didn't say what your budget is, but you can get a "real" 3HP spindle for about $2500 which would probably hold up better.

I dont need anything too hefty,

Actually, I think you do. There's a reason you don't see anyone build machines like you want to build. It's very difficult to build a machine capable of doing what you want.

[LeeWay]

If you have to make a lot of something, time is money. Most of the hobby cnc mills aren't crazy fast, but faster than 1000 RPM. To dig out that kind of metal, you really have to have a heavy machine. To make a heavy machine move at production speeds cost a lot of money.
Smaller faster mills can take lighter cuts and get the job done too, it just takes more time. Precision, speed and DOC or part run times are all connected to how much money it has in it and how fast it can make that money back. For a smaller hobby cnc, that could take some time. For a fast production machine, maybe not too long. That's just my take on it.

You could cnc that mill and run it at slower speeds. With strong enough motors, you could still hog off that kind of metal. No problem there, but if you are going to use some money to cnc it, why not throw a little more and have it run fast?

My mill with a spindle speed of 3740 is not really fast. Pretty slow actually. I run rapids of 200 IPM on both X and Y and 120 IPM on Z. I don't cut with it that fast though, but when it gets done doing one process, it doesn't waste time getting to the next one.

[axkiker]

ok so maybe my thinking is a little off. maybe I really do need something alot larger or should I say heavier duty than what I realize.

So with that said do you all think its possible to build one capable of the work I need to do. As far as the frame etc goes I dont see building that a problem. I can build that as heavy or light as it needs to be. I assume that ill have to upgrade to larger size stepper motors in order to swing the extra weight but that should not be a big deal. My main concern is the motor and spindle. It looks like ill need something in the 3- 5 hp range.

Now I thought about purchasing one of the high frequency spindles out there. However I honestly dont see the need. I think one could be fabbed up from scratch then ran via a pully and motor setup. Much like a knee mill.

In the scheme of things this would not be that large of a machine. Most of the big cnc outfits out there are made to cut solid blocks of aluminum into complex parts. This is not nearly that complex. I just need something which will take flat aluminum bar or plate and do alot of pocket work with a follow up cutout.

Once again this is all off the top of my head. So im sure im off on many of my ideas. what do you all think. sounds like a good project.

[BobF]

You could use a high frequency "motor". My lathe has a variable speed drive. This is simply a 3 phase motor running with a variable frequency inverter drive. The electronics take a 220 volt single phase input and output 220 volt 3 phase at variable frequency. The frequency control gives you variable speed within a range. You can buy a drive and a motor in 2 HP range for about $500. This is a motor designed stationary installation and it wieghs about 45 pounds. You could use belt drive to run a spindle. If you have a moving gantry style machine it would need to be pretty beefy to hold the motor, and need some stout motors to move all the wieght. You might want to consider a moving table design. This type of motor runs at 1750 rpm in normal operation (connected directly to AC). With the variable frequency drive the drive would output 0.5 to 360 hertz. You would have a speed range of 200 or so to 3000+ rpm. If you used a router as a spindle the variable speed routers run a low speed of 8-10000 rpm up to 22-24000 rpm. This will be the big difference. Most mills designed for metal run spindles at the lower speeds of the motor example above. The biggest challenge of the spindle design is the side loads imposed by cutting and the accuracy needed for some cutting jobs. Here is drive designed for the motor example above and at the bottom of the page is a suitable motor.
http://www.driveswarehouse.com/Drive...0-015NFU2.html
A similar motor runs my lathe. It has a 2 step pulley system for the belt drive to the spindle. Changing the belt step gives you a choice of higher torque and lower speed limits, or higher speeds and less torque. This is a wood lathe, but I have cut aluminum on it with wood cutting gouges. I can't do high precision work, but I can cut aluminum with some care.

[axkiker]

so im curious why no one has made their own spindle and attached a motor via belt etc. Seems to be a pretty easy task if you have some machining equipment. I hear alot of people talk about the router being the weak link due to bearing and power. Well why not eliminate it by making a spindle of your own. Am I missing something here.

Also since a router seems to not be large enough has anyone tried running multiple motors. Ex: multiple treadmill motors runing a spindle via a belt.

any thoughts

[EL34]

When I was looking at potential designs for a new router a few months ago, I looked at a lot of web sites of home made machines.

I saw lots of pics of home made spindles with one and even two motors. Some had multiple pulleys so you could change speed.

Crusing the web gave me a ton of cool ideas. Takes a bunch of time, but it was worth it.

[Gads]

your thoughts sound ok motor belt etc. I converted a small clausing knee mill
and run a 1/2hp 1750rpm. you don't need rpm you need torque and rigidness.
the drawbacks i have found with my system have all been due too machine
rigidness and play, backlash, wear, etc.

I put a 2h/p 3750 on my mill and it was too much for the machine to handle
not the cnc. I think my motors are 400oz. or so 2 to 1 ratio. i believe i have
made it go 50ipm but leadscrew and bearings cant take that speed for long.

running short on time hope this helps, any questions just send me a message

[axkiker]

hey thanks for all the help. ill do a search for home made spindles and see what I come up with. I have a friend of mine who is an aircraft mechanic checking to see what type of bearings they use. I figure if I can use thoes they sure as heck should hold up.

thanks

[LeeWay]

The proper bearings for a home made spindle that is built for high speed aren't cheap. This coupled with the precision needed to build the spindles and the cost of a big enough motor and controller with the desired qualities are what puts most guys off on attempting to build their own. It can be done. Some guys have and are doing these. Just do a search for spindle designs on here and several should pop up.
The end result though is that you really can't make these much cheaper than you can buy them for unless you have a full blown machine shop already. Then perhaps slightly cheaper.
There is however, always that next great design or building technique that is waiting to be found or exposed. Give it some thought and research. Come up with something that we can make ourselves.