Aluminium routing - again!

[kong]

I'm having trouble yet again with routing aluminium. It's my own fault, trying to use 1/16" aluminium router cutters is asking for trouble! I think it's the feedspeed / depth of cut / spindle rpm that I can't quite get. I'm running out of patience though, as I have snapped 3 cutters today trying different things.
So if you were given the job of cutting a "computer 80mm fan grill" from 6082 aluminium, and you had a cnc router, how would you approach it? Or if not aluminium, is there a similar material that would be easier to machine this way? Thanks!

[HuFlungDung]

.03 depth of cut, use high helix endmills for aluminum
.0002 chip load per tooth * rpm (no limit on rpm, go as fast as you dare with consideration for your spindle bearings)

WD40 bath, or oil/air mist lubricator

I might also shorten a factory endmill if it is too long and flimsy.
Ramp into your depth of cut, or predrill entry holes. If you are really stuck, you could predrill the entire path with a slightly smaller drill bit (plunge roughing) and clean it up with the endmill for a finish cut.

[kong]

Cheers Hu, I have more cutters coming tuesday. i am using a water-based coolant at the mo, but it does seem to get blown away as I am only using an oil can. I guess the WD-40 may be a bit more sticky. I am using special high helix routers, single fluted, I am just inexperienced and still learning the limits of various types of cutter, but it's getting expensive!

[kong]

You the man, Hu! Yep, insufficient coolant was the problem. New cutters arrived today, so I got all messy and cut some ali. All I have at the mo is the pump oil can, so I used that to flood the piece, being careful so as not to get fluid in the motor.
The missus has cleared out the cupboard today though, and low and behold, she has tossed out a wet/dry vacuum cleaner. I'm thinking of taking out the water pump and tubing and perhaps rigging up a coolant delivery system. Any thoughts on this?

[HomeCNC]

I thought a fan grill was to protect your fingers from getting into the fan!

[HuFlungDung]

Heheh, it looks like a "child-safe shuriken" for Klingons. Good job, Kong!

[kong]

Lol, or is it to protect the fan from your fingers? Must resist the urge!
Anyhow, I ripped that vacuum cleaner apart, and it has a nice little water pump, a 1 Gallon reservoir, and transformer. There is about 6' of narrow tubing, and the flow rate is plenty fast! Here's the guts, the reservoir just slides into the top of the plastic housing, engaging a valve (the housing is upside down at the moment), then you just switch on, and pressing the white switch on the tubing releases the water. Just what i need!

[HuFlungDung]

Personally, I like an air/oil microdrop lubricator on an unenclosed machine because flood coolant can get you pretty wet if the coolant gets drawn up the cutter onto the collet and flung away. You may find you actually need a spray of coolant to get the chips out of the cut zone and this gets really messy unless your machine is built into a cabinet, and all the screws protected, etc, (which they should be anyways, I guess).

You also need a coolant collection tray and settling tank. If your machining activities are infrequent, the coolant may not keep fresh smelling all that long (considering the expense of it).

FYI, the Trico microdrop air mist unit allows you to get the chips blown out of the cut zone immediately, and uses an incredibly small amount of vegetable oil lube per hour. The chips are dry, too and no fogging or fumes (WD40 does bug my sinuses after prolonged exposure).

I know it all costs $$$ to set up

[kong]

You have made some good points, yet again! But you're right, it's all about money right now. I'm trying to turn a hobby into a business, and don't have funds for everything. You're right about the mess, it would be oh so nice for dry air lube.

[kong]

Hu, do you know anything about these? I am also looking into purchasing a vortex-type cold air gun which may be better suited to use with the router. Your opinions on this subject would be greatly appreciated. Thanks

[HuFlungDung]

Yes, Kong, I've used one of those.

You might like it. It still delivers a fair bit of coolant with the air (more than the air/oil lubricator), but not like flood coolant. The liquid mess factor is still present.

I guess I quit using mine because of always having to clean the sump because even in there, I would get some bacteria growing on top of the synthetic coolant mix. Darn those little germs If you don't use a lot of coolant, but let it sit in there for a few days, you may get this problem, too.

Also, water based coolants in tiny amounts are bad for carbides, because there is not enough being applied to really keep the cutter cool. So there is a lot of thermal cycling which can crack the tool edges. High speed steel cutters can handle this better.

I do find the Trico air/oil lubricator system is fine for carbides, and High speed tools, but it doesn't have quite enough cooling capacity for HSS, if you do heavier cuts (or drilling) in hard to cut metals, like steel.

[kong]

Cheers Hu, I think I'll leave that one as I am looking to cut down the mess. I just couldn't seem to find the info on it. I do like the look of the trico units, but the price is off-putting. I'm still looking into vortex air-coolers as they seem to be a cheaper/tidier solution, and , as you stated, the whole bacteria growth problem will not be present. I'm not exactly a busy cnc-er!