Help me convince my school admin to let us use our CNC router!

Is the CNC router being used for “fine woodworking”? I asked a former coworker if the CNC router he had from his old cabinet making shop could be used to cut aluminum for our robots. He said it could cut the aluminum but he would not since there would always be some aluminum dust and it would colour the wood that is cut afterward. I’m not sure how true this is though.

The machine is owned by the school, not the team. We have the budget to purchase an omio, but we’re pursuing this option first.

The router is in the wood shop, but not connected to any sort of ventilation system as far as I know. We would connect to our own vacuum system regardless.

To be honest, the CNC router isn’t being used for much of anything at all right now… We use it to cut lexan, and it’s been used once or twice to make random art projects.

Thank you to everyone who has submitted photos and videos, and I will definitely reach out to ShopBot (and I’m kinda embarrassed I didn’t think of that…)

Just because a tool can do something doesn’t mean it should.
And by that I mean I would avoid cross-contamination at all cost. It’s generally a bad idea to machine both metals and woods on the same tabletop equipment, because the metal shavings can get embedded in the wood grain of future parts, and sawdust can ignite given the right combination of circumstances (namely the heat that can be generated from machining improperly lubricated metal).

If the school DOES plan to use it for woodworking, this will probably be a hard sell (and an inadvisable one at that).

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You’re saying you should cut multiple materials (wood and metal) on a single machine? Spending Shopbot money for a wood-only CNC seems like a huge waste of money to me…

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I think it all comes down to the care and maintenance for the machine, as well as learning how to properly use it. My school uses their ShopBot to cut wood, polycarbonate, and metal. But we clean up thoroughly after we are done. Keeping your workstation clean is essential, and will help to avoid hazardous conditions such as sawdust igniting. Another factor is how well you know your machine. If you don’t know how to properly lubricate the metal, or use the wrong bit, then you shouldn’t be using the machine in the first place. If everyone took the time to sit down and understand the process that goes into using the machine, the chances for dangerous conditions and mistakes is far less.

If you take care to avoid mixing wood dust and hot metal shavings, and you don’t care about the finish on the wood products, then you shouldn’t have a problem. So for a team making plywood prototypes you should be fine using the same machines as long as you take care to vacuum well between materials. If on the other hand you’re running a wood shop where you care about the finish of the wood and have a dedicated ventilation system that’s full of sawdust, you probably don’t want to be cutting metal on those tools.

In my high school we had a wood shop with many of the same tools in our shop, but we weren’t allowed to use them for the same reasons listed above.

Were I used to work, they would just change over hoses and tooling, and clean the work area when swapping between woods, plastics, and metals. I would assume finish is mostly impacted by tooling and spotless-ness of the work area.

Does anyone have non anecdotal evidence of running wood and metal on a router and then having poor edge quality when going back to wood?

This sounds like it’s 100% not a thing. Your machine isn’t covered in aluminum powder that’s just waiting to get all over wood when you switch from cutting metal to wood.

If you vacuum/blow your chips off and swap bits (which you should be doing anyways - aluminum bits are not the right geometry for cutting wood), I fail to see how you would see any evidence on the finished wood part that aluminum is present.

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The part that may concern a wood worker more would be imperfect cleaning and ending up with aluminum chips in their wood or the possibility of cutting fluids that are used for cooling on the aluminum getting into the wood prior to finishing, especially if an MDF or similar sacrificial piece is used.

Edit:
All that said, Whinston Moy (https://www.youtube.com/channel/UCxdCeHBUOlcCWr6RM8acEog) has a low powered hobby style CNC and switches materials regularly and doesn’t seem to have issues. His Videos may be a good reference for how to switch between materials and how to present safety.

Bryce, you said you’ve already done some plastics - in your shoes I’d adjust my teams design language to mostly polycarbonate and nylon (whichever I could get cheaper), rather than go to war with the administration over this.

Get them used to the team doing a lot more work on it first, then maybe circle back and start working on permission for metal again?.. Emphasis on investing in new tooling and other supplies for metal work vs plastic, explaining all the ways the team is preparing to “do it right” after establishing de facto shop bot ownership over two or three seasons of extensive plastic and wood?..

Of course, I say with access to a full shop where we’re voluntarily moving to plastic design language and minimum weight rather than tool-limited to plastic design…

(Which reminds me, let’s chat at Kickoff - if you have a couple Al parts we can look into running them on our tools)

The concern was not the quality of the cut. It was the possibility of a customer complaint about fine metal particles embedded in the wood. This should not be a concern if the school is not using the router for “fine woodworking”.

While polycarbonate is definitely great for something’s, it’s hard to use it for everything. Gearbox plates, drivetrain rails, gussets, arm mounts, etc etc etc, I simply wouldn’t trust with polycarbonate.

I’ve done all of those except for drivetrain rails, and IIRC 6814 uses Kitbot for drive.

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Teams have used polycarb for all of those things in the past. One I remember seeing in 2012 was almost entirely polycarb:

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@Cory we cut aluminum and wood on ours, and it’s completely a non-issue. Change tools, and vacuum after each. But, we don’t do “fine” woodworking.


There’s also Delrin, Nylon, and other plastics that teams have successfully made gearboxes and other drive components out of before.

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Okaaaaay, 1678’s 2014 intake was designed to be super floppy, I was talking about rigid arms. But yes ur right, I completely forgot about nylon and delrin plates. (Although I personally don’t think I would ever do non metal gussets for drivetrain and etc like some people here have)

To be clear*, the gearbox pictured is made from polycarbonate on most of its sides. AndyMark also had a polycarbonate plate on older versions of the toughbox, before moving to their currently cast nylon housing.

But 1678’s intake is only one example (here’s more), and was only “super floppy” in one dimension. It may be perfectly acceptable or even desirable to be compliant in a particular dimension, depending on your design priorities and resources (tailor your design to the resources you have). There are also options for rigid polycarbonate that is perfectly capable of working in the right applications. Not to mention it can be very easy to integrate polycarbonate plates with existing aluminum COTS stock options to further expand the possible designs even if you’re only cutting polycarb on a router.

There’s plenty of design space to use the tools that are available.

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Our 2014 robot would like a word (entire claw is waterjet polycarb). When you start looking at things in terms of what you can make you can do some pretty neat stuff.

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