CNC router: suitable for FRC?

[Mulcahy]

We have a shopbot. It gets used as much as any machine in our shop - including the drill press and cnc mill. You can cut aluminium with a single flute cutter. The end product is not as finished as it is on the mill, but the ability to rapid prototype is priceless. We also make a lot of mock-ups using MDF and Lexan to check the fit of parts before they are sent out for final machining by our awesome sponsors. I would highly recommend getting one.

[Leav]

Hey everyone!

thanks for the replies!

just to clarify: when I said "aluminum profiles" I actually menu "aluminum tubing, mainly rectangular".

from your answers I gather that it's possible but maybe not the best idea.

does no one make CNC routers intended to cut aluminum?

[techhelpbb]

Originally Posted by Leav

Hey everyone!

thanks for the replies!

just to clarify: when I said "aluminum profiles" I actually menu "aluminum tubing, mainly rectangular".

from your answers I gather that it's possible but maybe not the best idea.

does no one make CNC routers intended to cut aluminum?

If you take a look at my post you'll see that the Haas TM-1P can machine just about anything an average Bridgeport can which includes aluminum. It's more than fast, powerful and rigid enough, it's got coolant and with the proper tools it'll do a great professional job.

Gantry routers will do aluminum but there are limits in speed, power and rigidity. I've cut plenty of aluminum on gantry routers just know: your machine, keep the number of flutes down as low as possible, use smaller diameter end mills, and mind the suitable feed rates (you'll mind the feed rates anyway on most CNC machines). If you must use a general purpose shop router as the spindle consider getting a SuperPID for it.

Will these cheaper machines be a 100% replacement for something like the Haas TM-1P: absolutely not. Will they do some work: sure just don't get too crazy. Keep in mind the forces involved and respect them.

[Leav]

Originally Posted by techhelpbb

If you take a look at my post you'll see that the Haas TM-1P can machine just about anything an average Bridgeport can which includes aluminum. It's more than fast, powerful and rigid enough, it's got coolant and with the proper tools it'll do a great professional job.

Sorry I didn't get a chance to click the link when I wrote my post, I was on my phone.
Now that I've clicked, I must say I was taken aback by the price!
We were looking to get something for under $5000.

Originally Posted by techhelpbb

Gantry routers will do aluminum but there are limits in speed, power and rigidity. I've cut plenty of aluminum on gantry routers just know: your machine, keep the number of flutes down as low as possible, use smaller diameter end mills, and mind the suitable feed rates (you'll mind the feed rates anyway on most CNC machines). If you must use a general purpose shop router as the spindle consider getting a SuperPID for it.

Will these cheaper machines be a 100% replacement for something like the Haas TM-1P: absolutely not. Will they do some work: sure just don't get too crazy. Keep in mind the forces involved and respect them.

I think that's an important thing to take from this: If we're willing to keep feed rates down, It would probably be ok to use a gantry router.

This is good news as far as I'm concerned, since the gantry router form factor is better suited to our shop (the ceiling is pretty low, about 3m/9feet at most).

Thanks everyone! i'll be back when we compile a list of optional machines and i'll ask for your opinion again.

[RandomStyuff]

Don't know if this question fits here or in another thread but it felt very related. A few weeks ago I saw the Shapeoko 2 CNC router (http://www.shapeoko.com/) which felt to me really inexpensive relative to the option of a CNC mill. I assume nobody would have experience with the new version but does anyone know based on the old version if it would be something that fits for FRC uses?

Would it be possible to use such equipment for things like making gearbox plates or a drive system frame (in terms of accuracy). I understand that routers take longer than mills, but I expect being able to do slow is better than not being able to do at all .

I've found it including some more details and price here: https://www.inventables.com/technolo...kit-shapeoko-2

[DonRotolo]

Originally Posted by Leav

I think that's an important thing to take from this: If we're willing to keep feed rates down, It would probably be ok to use a gantry router..

Emphasis mine. No, you need to calculate the correct feed rate based on the tool (router bit) manufacturer's specification, and take a smaller depth cut. Taking too small of a 'bite' (from a low feed rate) is just as bad as taking too big of a bite (from a high feed rate). Look up the term "chip load".

But yes, if you are willing to keep the pass depth down to maybe 0.125 or less, cutting aluminum (including profile) is not a problem.

Except, longer tools will be needed to cut the entire thickness, and these are less rigid than short tools. For example, I use a 3/16" diameter cutter with a cutting length of only 3/8". I cannot cut anything deeper than 3/8". But this tool is very rigid and doesn't deflect much at the proper feed speed (60 IPM, 12000 RPM, 3/32" pass depth (=1/2D)). A tool with a cutting length of, say, 1.25" will be less rigid, but it will cut 1" box stock without trouble - but maybe only at 40 IPM, 8000 RPM, and perhaps only 0.06" depth. (The tool bit can cut at 1D pass depth, but the machine cannot supply that kind of force)

[DavisDad]

Originally Posted by DonRotolo

Emphasis mine. No, you need to calculate the correct feed rate based on the tool (router bit) manufacturer's specification, and take a smaller depth cut. Taking too small of a 'bite' (from a low feed rate) is just as bad as taking too big of a bite (from a high feed rate). Look up the term "chip load".

But yes, if you are willing to keep the pass depth down to maybe 0.125 or less, cutting aluminum (including profile) is not a problem.

Except, longer tools will be needed to cut the entire thickness, and these are less rigid than short tools. For example, I use a 3/16" diameter cutter with a cutting length of only 3/8". I cannot cut anything deeper than 3/8". But this tool is very rigid and doesn't deflect much at the proper feed speed (60 IPM, 12000 RPM, 3/32" pass depth (=1/2D)). A tool with a cutting length of, say, 1.25" will be less rigid, but it will cut 1" box stock without trouble - but maybe only at 40 IPM, 8000 RPM, and perhaps only 0.06" depth. (The tool bit can cut at 1D pass depth, but the machine cannot supply that kind of force)

Thanks for the detailed info DonRotolo. Really helpful! Am working on lightening cutouts. What about a miniature chop saw between 1/2 diam drill holes?

[DonRotolo]

Originally Posted by DavisDad

Am working on lightening cutouts. What about a miniature chop saw between 1/2 diam drill holes?

I don't understand the question.

[DavisDad]

Originally Posted by DonRotolo

I don't understand the question.

I'm interested in a non CNC method for making these lightening cut-outs (1/4" Al):
'



By drilling 1/2" holes and cutting between with something like this:



Your thoughts appreciated.

[DonRotolo]

Ah. OK.

Um, no. I don't think you can control a chop saw carefully enough to do it.

Traditional method would be to drill holes, and then use a jigsaw or scroll saw to cut out the openings.

Less common method would be to use a wood router, hand-held, with a 1/4" or larger aluminum-cutting bit, using a plywood or MDF template, and a bearing or collar, to cut out the 'triangles' after drilling access holes. Note that this is more dangerous than average, gotta be super careful and slow (about 1" per second). And hearing/eye/skin protection is mandatory. (We did this with 3/16" aluminum some years ago, nobody died...)

Of course, you can also do it with a coping saw. Assign it to a freshman.

[Akash Rastogi]

Originally Posted by DonRotolo

Traditional method would be to drill holes, and then use a jigsaw or scroll saw to cut out the openings.

Print your CAD drawing scaled 1:1, tape it to wood, cut out wood part using bandsaw + scroll saw, proceed to use wood template on metal part + scroll saw. You can just tape the paper to your metal, but I like having the wooden part as well.

[DavisDad]

Originally Posted by DonRotolo

Ah. OK.

Um, no. I don't think you can control a chop saw carefully enough to do it...

What if the piece were clamped fast in a jig that controlled the depth of the plunge cut; there would be a stop to control cut length/depth?

[techhelpbb]

Originally Posted by DavisDad

What if the piece were clamped fast in a jig that controlled the depth of the plunge cut; there would be a stop to control cut length/depth?

The blade is round. Unless you can plunge to the diameter of the blade you'll get a pocket with an arc ramp at either end you'll have to cut anyway. The other suggestions like a scroll saw are just as good and I bet you will end up there anyway. No sense in adding risk by increasing the surface area between the blade and work and that circular saw is likely to screach.

[DavisDad]

thanks y'all for the feedback.

I've been cutting Al plate, bar, and rod w/ a 10" carpentry chop saw with excellent results. The carbide tip blade cuts fine through 4" rectangular bar. Some cuts start as plunge cut and I've had no problems.

My thinking is that it'd be quicker and cleaner to make the cut below and use a jig saw to remove "ramp". I need 8 each of these and could set jig for each angle/depth and get it done faster than scrolling each cut-out.