How [not] to CNC-Mill a Longboard

Hello there again!

Remember my Longboard-project? [Link here]

Well, in continuation of that project, I went to Happylab yesterday, with a roughly sketched file to CNC-mill the shape of a Longboard out of a ply of wood. I say “the shape of a Longboard” here on purpose, because the cut thing will not be useable as a longboard whatsoever. The thing ply I got is a 5mm thick 600×600 mm made from beech. That shit’s going to break quite rapidly (I guess) and it’s not the right length either, but it’s enough to experiment with it!
The goal of this project is quite the pragmatic one anyways: “Learn how to operate a CNC-Mill”. Mistakes are welcome and expected!

So, I made the plan to go there yesterday and just “quickly” get the ply cut.

Yeah. Right. Worked out perfectly. I entered and asked the guys who run the Lab if they’d help me out if I had absolutely no clue of what I was doing (which was….. quite likely), and they said “Yeah sure, but there is another guy there trying it for the first time too, I’m sure the two of you can work it out!”

And suddenly, the one hour I had planned seemed short. (regardless of the fact that planning one hour only was quite naïve)

There we were, 2 clueless guys trying to figure out how to get this huge monster started.
After said hour, I got a lot of information out of the visit, but didn’t even touch my plank of wood. Which is why I went there again the next day, with more time planned, so I fired up CUT2D, which is a program that makes it semi-intuitive to get some G-Code for the CNC-Mill.
The machine needs a couple parameters to go about it’s work, it is basically blind. Yeah, that’s a good analogy, I’ll roll with that.

Cut2D Screenshot

So the machine is basically blind, by loading up the vectors, and transforming them into Toolpaths, you tell it a pattern it should work out of the piece. Which piece though? Now you have to give it the measurements of the workpiece. How high is it? Which size? You’ll have to enter these parameters yourself.

Unlike a blind person, the machine doesn’t feel anything either, so it doesn’t know what kind of tool it has in it’s metaphorical hands, so you also specify the diameter of the drill, and if it should move along, on the outside or on the inside on one of your paths.You have to do this because the Vectors themselves have no thickness at all, zero, but the drill has (in my case, 3 mm), so the machine has to know HOW to follow the path.

There is also settings for the drilling speed, the speed at which the drill moves forward and so on.
Luckily, Happylab already created a vague database for the different material-dependant parameters, you will probably also be able to find some online.

After you created all the toolpaths, you compile them into G-Code (commands for the machine) and export them as an *.nc-file. You are done with CUT2D now, and ready to load up the file in the program that controls the CNC-Mill, in my case, this is CNC-USB 4.0 or something along those lines.

CNC2USB Screenshot

The starting point is not set yet

There you have to import your G-Code, and most importantly, set the starting point (in the physical world!) for the file. As I said already, the CND-Mill is blind, it has no clue where the drill is, and once you press start, it just executes its commands relative to where it was at that moment.
With the machine we have at Happylab, you can set the starting point manually, with a kind of remote, it is quite intuitive.

CNC "Remote"

Next thing: “Fix your f’in Material inside the Mill!”

As you might be able to imagine, you workpiece would absolutely love to move around while it is being torn apart by a drill spinning at a couple thousand rotations a minute, you’ll have to stop it from doing so by setting it up tightly in there.

Again, with our mega luxurious CNC-Mill at the Happylab, it is quite easy, the floor of it has rails where you can put (lacking the English word, I’ll just say) “fixing-things” into.

[This is where I got interrupted in writing by the CNC-machine freeing up, you’ll see why I give you that information]

hwo to fixate the workpiece

Now the data is in loaded in the program, starting point is set, workpiece is fixed, just close the doors of the damn thing and you are good to go!


[taking a deep breath…]

Ok now, this is kind of anticlimactic. So I smartassed quite a bit up there. Must sound like I know what I’m doing, eh?

Does this look like I know what I’m doing?

CNC Milling Fail

Nope. Not even close. ^^

Well, close enough for my first try. So what happened there? After I toyed around for about one and a half hours to get everything set up “properly”, three things came together that stopped me from proudly vacuuming the victorious battlefield, but rather clean up the shreds of failure: 

  1. I did not fix the workpiece tightly enough, I did it as tight as I could without bending the ply, which ties into the second thing I did wrong ->
  2. Apparently you should use ONE plate (direct translation from german: “sacrificial plate”), not a couple of them with spaces in between.
  3. I did NOT set the parameters correctly, the drill was way too fast and just tore the workpiece out of its fixation

As this happened, the owner of the place was still standing next to me since I asked him if the drill would hit the clamps with my setup.
The moment it hopped out of its fixation, I was like…. (to put it in Internet-lingo:) ROFLMAO!
I activated the emergency shutdown and laughed my ass off.

I learned something from it, and I hope you can get something out of it too ;)

Happy Making!

P.S.: I’ll try again, that’s for certain.

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