Ok, I've got an FTC team (First Robotics, see link for more info,

General CNC CNC Routers
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Ok, I’ve got an FTC team (First Robotics, see link for more info, we have 7th to 9th graders) and we’re putting together a proposal to get a CNC setup. This will be invaluable for us because, as a community team, we don’t have easy access to a machine shop like most schools. We’re pretty much limited to hand tools, drill press, and a chop saw with a metal blade for cutting aluminum stock (most parts are aluminum for weight/strength). We (well, I but they use it) have a 3D Filament printer which we use a lot.

An initial comment up front. We’re not against kits as they provide a great learning exercise during assembly and calibrating. They’ll be doing design in either Inventor or PTC Creo. If you have a recommendation other than the OX, I’d love to hear that too. I know the Inventables machine get’s shout outs on occasion so pros/cons would be good. For size, most of our parts are pretty small (less than 6 inches) as we have a maximum robot size of 18 inches (cube). We do cut side panels that large so 500x500mm build area would be great. I don’t think we would need much larger typically.

So, as I’ve been looking, I think that the openbuilds machines make a lot of sense and the OX seems to be the most robust of the ones I’ve seen. The option of a Build-It-Forward means we might save a bit up front, plus be able to help others (including other teams) also achive CNC ability (most teams use pre-drilled parts like those from http://www.tetrixrobotics.com/ or https://www.servocity.com/html/channel___brackets.html).

So, in putting together a proposal, I need to make sure I include everything. I was thinking of getting the kit from SMW3D as that seems highly recommended. We’d go for the rugged options (heavy wheels, upgraded spindle, etc). I don’t know if we should plan for an even larger spindle as most cutting would be in aluminum plate, but probably no more than 1/4" thick. I’m not sure what thickness we would need for the build-it-forward. Plus, we might need thicker as we move to more involved designs with recesses and motor mounts.

In addition to the machine, what supplies would be needed/recommended? Again, it’s much easier to include in the original budget than ask for more later. Endmills (what types and how many), extra sensors/controllers/etc. Software? I know there are free versions out there but does it make sense to use a reasonable cost commercial option? While more expensive, reducing some complexity might help kids who don’t have time/experience to overcome multiple failures getting things working. We’re not trying to be crazy frugal, just get the best bang for the buck. Once I get together a good proposal, I can shop it around to potential sponsors.

Thanks!!!
http://www.firstinspires.org/robotics/ftc

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Oh, added comment. Is the 400W spindle only 1/8" bits? If so, does it make sense to get a bigger one to support at least 1/4" shank mills? I would expect they would last a lot longer and provide much better cuts (my experience it more on a Bridgeport).

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And why the advantage of a GT3 belt over GT2? Just strength and stretch resistance? Cost is a pretty big bump.

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Hey Jerry.
1/4" thick aluminum is about it for the OX.

You can run up to a 6.35mm collet in an ER-11, though note you will only use such a large endmil in soft woods, there’s not enough arse on a 400w.

You can use a bigger spindle such as the porta-cable. This is not Al friendly as RPM cannot be fine tuned.

Inventables makes a great kit, nice plug and play solutions available.

Tool chain: draft in your Creo, (loved this program at one time), use CamBam or other solution for CAM software, then if you get TinyG or GRBL use Chilipeppr to dump Gcode. That’s all softwares needed. CamBam is not free but like it considerably.

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I thought the OX was capable of much more depth of cut. I know the per-pass removal might be shallow (how shallow??), but the depth of cut should be limited by z-travel and bit-length (which is why I was asking about 1/4" shank cutters). I thought the OX was on the larger size when looking for spindle capabilities??

I may have to do some more research. We would need a machine that can do effective milling (I see people posting about fly cutters though). What’s the barrier here?

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The depth of your final machining starts to be tool deflection. Even guys running through 2" wood will start to notice the tool side loading and deflecting. On a commercial machine the gantry is overly grid so the tool will break. On a hobby based machine the tool deflection can resonate through the gantry and assimilate to chatter. So yes you are correct it can do deeper cuts but beyond 1/2" aluminum your going to test the machine and your abilities.

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Ok, so is there a good comparison between the various machines for rigidity of the spindle assembly? Looking at the OX (or perhaps other C-build machines), they seem like they would be pretty tight. I do understand the resonance issue (we run into that with 3D printers). How does the OX compare with the X-Carve from inventables. The OX seems much more massive (but that doesn’t always lead to more stiffness).

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Jerry, hadn’t used the new X-carve. I can’t speak for them. Perhaps one of the guys over on the Shapeoko group has used both and can give some feedback.

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I’m glad to see another FIRST team around here. My family is neck deep in FRC (High School).

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My kids would love to be involved in FRC. Unfortunately, our high school doesn’t participate in it. Due to the size and scope, I think it’s out of the range of an unheated quarter-garage shop … even with a benchtop CNC :slight_smile:

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@Jim_Fancher keep waiting on Tripp to tell me he’s ready to use parts around here to build a bot. Really would love to put a robot kit out there, not sure of all the regulations but sure would be fun to kit something out.

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@Brandon_Satterfield A chassis might be as far as you could take a kit, but that would be a big help for some teams. Plan on going to the Regional competition in Houston with us. We’ll show you more than you ever wanted to know about FIRST. :o)

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I’m not sure if a pre-cut chassis would be allowed under the FTC rules. Purchased custom machining is somewhat restricted. Teams would have to come up with their own design. That’s why a cnc makes so much sense.