CNC router: suitable for FRC?

Hello!

We would like to improve our in-house fabrication capabilities, and have been torn between a DRO mill, and a CNC router.

obviously a mill would handle aluminum better, but we would like to be able to work on chassis profiles without clamping them twice (thus reducing accuracy).
A mill large enough to have that much X travel would not fit in
our workshop most likely (height limit).

This made us think about CNC routers, but none of us have any experience with them, so we thought we’d consult CD.

what do you think about using CNC routers on aluminum profiles?

What say you about this CNC router?

We appreciate your input!

  • Leav

We have a ShopBot in our shop. I have cut a few profiles in .125 6061-T6 plate when the CNC Mill was in use, but haven’t ever drilled using it. It is a
http://www.shopbottools.com/mproducts/prSstandard.htm

You have to clamp the parts down very well and take very shallow cuts on aluminum (.030 or less) or else the router will move in Z (the clamp holding the router in is not meant to take a lot of axial force). I believe it will drill holes in thin wall tubing but I haven’t tested it. Just remember it is not a mill, go slow (especially in Z) and you can make some parts.

If what you really want is a mill (and for FRC I think you want a mill) - you can find an old Bridgeport CNCs for $4000 if you look hard enough. Certainly an old manual mill and eventually convert to CNC.

-matto-

We have a manual knee mill that’s 3000 lbs w/ 30" of X travel (pretty standard), we have a CNC metal router that’s much heavier duty than the one you linked, and it’s 20x60". We have a metal router (in terms of construction) heavier duty that the one you linked, largely for wood (24"x24"). We also have a clone of hte above mill converted to CNC.

Having used all these, even our heavy duty router does not hit the precision of the manual or CNC mill WITH jumping in the vices. Rezeroing is easy.

A quality router has a great place in FRC for platework, but you’d want something much beefier than what you linked, and that’s where a CNC knee mill can be a steal (found from $3k-10k used) if your goal is to also run tubing, etc… We have a fixture on our larger router for running tubes, but it doesn’t compare in power or speed to the knee mill.

For reference, our metal router can sustain 40 ipm w/ a 3/16" cutter at .07" depth. If we’re watching the machine closely and keeping the mister and airblast going, we can do 80 ipm. It can do faster for shorter times (and if you are fine with a lot of cutter deflection), but not all day.

Be weary of numbers posted for cheap routers, and youtube videos. They are often showing hte cutting speed for brief periods of time, and in a situation where they are getting a lot of deflection int eh cutter and machine (wrecking accuracy).

We purchased this CNC this Fall. We got it up and running just a while back. We went with thehttp://www.homedepot.com/p/Bosch-2-25-HP-Plunge-and-Fixed-Base-Router-Kit-1617EVSPK/100341666# for our machine based on the recommendation of Probotix.

We are very excited to get our machine up and running. We could have done all of sheetmetal for robot last year with this machine.

We have used a CNC similar to this for the past few years that was manufactured by one of our mentors and a student over one summer. We have used it on:
aluminum tube (4x4, 1x1, 2x2), angle and plate
HDPE: 1/2" to 1.25"
Lexan: a variety of thicknesses
wood: plywood, MDF
Carbon Fiber

BTW, we use double sided tape for holder material in place when machining most of the time.

If you go with this machine, drop me a line and I will share more information if you are interested.

Another piece you might want to look into is the Precise Bits Collets.

We have a Haas TM-1P with 10 position tool changer and a Haas TL-1 on the way (it might be there already or not with the snow). On the manual side we have an old Bridgeport knee mill.

We’ve not done too much with the Haas yet at FRC but from experience it’ll handle the jobs just fine. Just realize it’s expensive, depending on the software that could be expensive, and then there’s the tools. This is not really a hobby machine it’s a professional tool.

Some CNC routers can cut aluminum quite well. I recently built this one (27" x 50" version), and using a Hitachi router and special Onsrud router bits, it cuts aluminum quite well. NOT like a mill, somewhat slower and lighter cuts, but no problems cutting.

The whole machine cost me about $3300 to build, using the generous FIRST discount with the local 80/20 distributor and some careful work on my part. The “official” cost is closer to $4000, and sources and prices are given for everything needed. You can surely buy everything you need, either from the USA for the smaller stuff, or locally for things like steel and aluminum parts. I did have to add a coolant system for cutting the aluminum. Cost under $25. A single person can assemble the machine in 10 working days, but I did it over about 3 months.

The Probotix Comet is a much lighter machine. It will cut aluminum, but even slower than the KRMx02. You also need to buy a spindle for it, which can be a non-trivial expense.

But to answer your basic question: Yes, a CNC router can be very useful for FRC. If you have time, it can rival the work on a CNC Mill, but only for softer metals like aluminum, brass, etc. Oh, and it cuts Polycarbonate really well, too!

Personally I know I’d love to get my hands on a CNC router for our FRC and FTC teams. Being able to easily do sheet metal parts would be really nice.

Although, I want to throw this idea out there; build your own.

I’ve been following this fella on youtube for a couple years, and he’s build a fantastic, high-accuracy (for a router), powerful, machine for about $2500, and with the kind of expertise that you have with FIRST teams, it could totally be pulled off. And he even has some good how-to videos if there are things you get stuck on.

And http://www.cnczone.com/ is a great resource.

You still might find that buying one is better for you, I just wanted to throw it out there.

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.

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.

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! :ahh:
We were looking to get something for under $5000.

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.

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/)](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/technologies/desktop-cnc-mill-kit-shapeoko-2

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?

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.

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. :smiley:

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.

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.