FRC & different types of CNC

Technical Manufacturing
#1

There are plenty of threads on CNC, but none are quite on target for a question I have:

How would you compare the applicability of different types of CNC machines to FRC? Our team is excited to be moving into a new larger space (though we are remote learning right now), and there will be some investment in metal manufacturing machines the team will share with Career & Tech Ed classes in a new dedicated metal fab shop. There is an interest in exposing students to a variety of methods, and currently under consideration are a 4x4 CNC router, a desktop (or at least small footprint) waterjet, and a CNC plasma cutter. For plywood, an existing laser cutter will be available, and possibly an existing wood-only router as well.

Our lead mech mentor has suggested a CNC Mill (e.g. CNCMasters Supra line) will add more versatility than the other (mostly 2-axis) machines. He also provided his own readout on the options in terms of capability, safety, maintenance, waste/messiness, etc. We do have manual mills and lathes already (a large & small machine of each).

I know the Omio X8 is a recommended small router, but I think something a bit larger & made-in-USA would more likely be purchased (the school’s 4x8 router used for wood only is Shop Sabre brand I think).

As far as types of CNC machines useful for FRC. If we have a CNC router, do we really need a CNC plasma cutter? Or would it be better to go for the CNC mill (I suspect the latter). Are there applications best suited to the plasma?

Also, on the topic of coming up the learning curve with CNC, despite the potential to get a CNC mill, it seems like 2-axis sheet cutting is likely a good place to start, and then as students master that, move on to more complex things (i.e. on a CNC mill or router). Am I thinking about that right?

The other factor I’ll mention is time. Our team is reasonably well-resourced, except we get a below average amount of meeting/shop time vs. other teams. During a normal season, we’ll meet 2 or 3 times a week starting in January. During the school year before that, we’ll only meet weekly or even just every other week (so training up new students before Jan is challenging). Shop at the school is completely inaccessible during summer, and most take summer off, except a few of the more enthusiastic students and mentors will try to do a project/class or two. The school system has said that, within a couple years or so, it will introduce one or more robotics classes during the school day, and I believe this will be a game changer for us. For now though, time is incredibly precious, and we need to keep things as simple as we can. So again, from that perspective, 2-axis sheet cutting CNC seems like a logical skillset to add first.

Thanks,
Chris

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#2

I would say our most useful (most used) “big” tools are, in order:
Omio CNC router,
Lathe with DRO,
Mill with DRO
Bandsaw
Drill press

We also do some 3-D printing.
We have occasionally water-jetted, but I don’t think we’ve plasma-cut.
The mills we have access to are 2- & 3-axis CNC, but we don’t really do full-blown CAM on them, usually just manually entering a hole pattern or something like that on a small part (bigger/more complex things get done on the Omio).

The size of the Omio fits our needs. And it does good work on 2-D sheets and some 3-D stuff frame tubes, and the like. I don’t know what we would choose if we needed larger. It seems like a solid starting point to me for most teams.

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#3

There are a lot of good threads on the subject on CD. Spectrum’s “First 10 k$” is a good place to start: Spectrum's FIRST $10000 - Google Drive

Assuming you have the basics covered (band saw or chop saw, drill press, a small manual lathe) I would personally prioritize a CNC router, as you get the most bang for the buck. You can make accurate 2D parts from almost any material (mostly aluminum), and that’s good enough to build almost the whole robot. They can also be had for less than 5 k$, although there’s definitely a large range of price and quality out there. I don’t think you need anything bigger than a 2’ x 3’ bed for FRC, and that size fits great through doors and into a small shop.

My second priority would be a CNC laser cutter (~100W CO2, 2’ x 3’). This gets the most use in our shop because it’s crazy fast, uses cheap materials, and takes zero CAM work. I can teach a student how to use it in half an hour, and they can crank out MDF/plywood prototypes, and Delrin/HDPE/Polycarb final parts all season. Just make sure you have a way to exhaust it outside.

[Edit] You do not need a plasma cutter IMO! The router can do anything you would do with a plasma. It’ll be slower, but way easier to maintain (same goes for Waterjet). We’re fortunate that there are a number of laser and waterjet cutting companies in the area that can cut parts quickly for us if we can’t or don’t want to wait for the router.

I hope that helps.

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#4

CNC Plasma Cutters aren’t particularly common in FRC, but could certainly be used. The big advantage of plasma cutters over Routers/Gantry mills is their ability to cut steel and other hard metals. However, FRC teams generally aren’t using large sections of steel, so this is somewhat wasted. You can still cut aluminum on a plasma cutter though, so you can definitely get mileage out of the machine in an FRC setting.

The one feature that CNC routers/gantry mills have over plasma cutters is that they can perform some operations than plasma cutters cannot. Plasma cutters are purely 2D machines that always deliver thru cuts, while routers are capable of 2.5D machining , meaning they can cut to specific depths and vary cutting profiles based on different Z axis dimensions.

If you’re trying to cut something like a latticed belly pan, that’s something that can certainly be done on a larger CNC router, but will take time (and be whiny). It could be pumped out (relatively) quickly by a plasma cutter. However, if you want to cut bearing holes into 2x1 tubing or cut pockets into a material, you’re going to need a mill or router to accomplish those tasks as opposed to a plasma cutter.

I don’t think I would ever purchase a CNC plasma cutter over a CNC router specifically for FRC purposes, but if I was in a shop that had a plasma cutter I could definitely find ways to use it. It depends on if the shop will ultimately want to be able to cut steel or other materials for purposes other than FRC.

There’s also an outside chance you could purchase or create a combo machine, given that both CNC router and CNC plasma cutters are gantry machines, just with different tooling. It would take substantial foresight into the operations and switching of the machines, however (clearing flammable cast off material before using the plasma, ensuring the plasma heat doesn’t warp the flat table required for CNC milling, etc).

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#5

What is your design philosophy for building a robot? What materials, mechanisms, and methods are employed already? Are you looking to change your design philosophy with a new machine?

This will heavily dictate what you want/need. Now, you said you want to expose students/the team to different technologies, so If I may…

I am not terribly experienced* compared to many people, however, I suspect you will find little difference between finished parts. Frankly a lot of the learning is getting the CAM paths up and running for such-and-such-machine-type, the rest of the process is mostly watching paint dry.

Brass Tacks for FRC exclusive usage: I would avoid the plasma, as that is prohibitive to plastics. Waterjet is cool, but sometimes the abrasive medium can be a pain with parts that interact, this won’t be a problem often, but just a point to consider. Laser is awesome for rapid prototyping with 1/4" plywood and can be stupid accurate, but you really need to vent the machine and might have some material limitations (I am not very well versed with laser tbh). So it comes down to the mill vs router IMO. You just need to consider what the primary function of the machine will be. Based on the degree of other manufacturing capabilities I would go for the router, especially if you are commonly cutting .050-.125 inch Aluminum sheet and plastics, and have a finger brake.

*I do professionally work with large CNC routers (think >8ftx12ft), and have worked with water and lasered parts, but i haven’t run those machines.

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#6

Heh, mostly! More precisely: Long periods of abject boredom punctuated with moments of sheer terror – like when you got the speeds wrong and instead of cutting the aluminum you are melting it and you are just about to weld your tool to your work piece!

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#7

I put the emphasis on mostly for a reason :wink:. I would be remiss if i didn’t own up to throwing a 500lb gantry with a 7.5HP spindle through some plastic north of 720 inches per minute… cutter survived.

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#8

@chrisrin I have a lot of experience in this area. Your total budget is going to have a big impact on which direction you should go with this. Please send me a private message and I’d be happy to offer a few suggestions.

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#9

Thanks all. I think my intuition from past reading seems pretty close to valid based on responses… A laser cutter (already have) for plywood prototypes + a 3x2 or larger CNC router for metal and plastics seem to be top priorities. A CNC mill will enable some more things, but with more learning curve, so maybe master the router first. The little 12x18 desktop waterjet they’re considering looks easy to use… maybe almost as easy as the laser cutter & easier than the router, so it could end up being used a lot by a time-constrained team like ours, though maintenance will be higher that the laser. Plasma also has uses, but probably lowest priority of the machines for FRC.

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#10

I teach Engineering and Robotics, mentor FRC and have a workshop with all of the tools you are considering. The advise above and your summary fit with my experience. For FRC, we use the laser cutter, 4x4 router and manual mill extensively. I have procedures to simplify the CNC mill and we are considering moving our tube operations to the CNC mill, to take advantage of the ATC.

One comment is that our 4x4 CNC router gets significantly more use than our Omio router. It has our tube jig and becomes the default for sheet materials. For FRC, rather than investing in a water jet I would invest in a larger CNC router, fixturing and an enclosure. I would only add the waterjet at a size that could cut a belly pan.

We use our plasma cutter extensively in class (steel), but never for FRC. We have considered it to do a lightening pattern on a belly pan, but never invested the time.

  • Edit: if the waterjet workflow is as easy as a laser cutter and you have a solution for the waste, this would be interesting, but it is still a second choice to a router do to size and sheet material limitations.
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#11

There is a very good chance that you can use that Shop Sabre for metal. I don’t see why you wouldn’t be able to. We have a Laguna Swift 4x4, which is decently similar, and it cuts metal all day long. It’s all in the setup

Unless the shop teacher is strictly against metal on the router, I’d go for that

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#12

Once we convinced our tech teachers to let us use their 4x8 “wood only” CnC for polycarbonate, they realized that, with a little adjustment to cutting speeds, it works like a champ. Being able to CnC 1/4" polycarbonate in-house is unbelievably useful for robot design and manufacturing.

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#13

Good point. We have one on our omio—building yourself a tube jig is well worth your time.

#14

This may depend on the type of work they are using their CNC router for.

A former coworker ran a cabinet making business as a side hustle and had a large CNC router. When I asked if he could cut some aluminum pieces, he said he would not because it would be extremely difficult to get the metal dust out of the machine. Some of the metal dust would transfer to the wood that is cut afterwards and ruin the finish.

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#15

My team uses an X-Carve that the school bought and we can only use it for polycarb. We made the entire 2020 robot out of polycarb plates, the only aluminum was on the frame and a couple pieces to support the shooter.

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#16

I just grabbed a SnapMaker on the cheap for personal use–it hasn’t arrived yet. My intent is to try to see what I can do with gingerbread and pie crust with the router, but it’ll probably see some use with making our robots prettier. For actual parts, we’ve got the 4’x8’ machine, so there’s no reason to go crazy trying to accommodate something smaller.

How do you like the X-Carve?

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#17

CNCd gingerbread sounds like a fantastic plan. The X-Carve is a mixed bag for us. Our team did not have to pay for it but that also meant that we had no say in the purchase. It mostly cuts wood for classes but during the season we use it the most. Its really big which was nice for a couple of the parts we made for 2020. Its not the stiffest machine so we have to cut pretty slow or the parts come out wrong. We also cannot cut aluminum. We really only use the X-Carve because its the only router we have access to, and its better then nothing. We would rather have an Omio (and are considering buying one) but the X-Carve has been great to get us into the realm of CNC plates.

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#18

Cool, thanks.

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#19

Just want to call this out, but if the “small desktop waterjet” is the Waser, there have been multiple people here who have mentioned issues with that machine holding the (fairly loose) tolerances required for FRC work. I don’t personally have any experience with it, but I’ve seen that around and would feel remiss to not put it out there (to be corrected if anyone with firsthand experience wants to chime in).

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#20

You can always DIY your waterjet cutter: Waterjet cutter built with a cheap pressure washer - YouTube :wink:

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