Thinking about building a CNC router table for home use? Maybe you can benefit from my experiences. But know this: my machine is odd, odd in several ways.
The X and Z motors are housed in a box made of Plexiglas (of all things). The plexi box provides rigidity and doubles as a cooling tower. The breeze comes from a discarded computer fan.
The dust is kept out with a ready-made floor vent filter from Home Depot.
The cables are held out of the way with a Plexiglas scissors contraption. (Sorry about the cluttered background)
Of all the materials available why would anyone use Plexiglas to build a CNC machine? It’s stiff, lightweight, and it exposes things I want to keep an eye on. It’s fairly cheap and easy to work. (I buy it wholesale for about $100 for a 4 x 8 sheet). You can buy a shatter-proof polycarbonate version for a few dollars more than the more common acrylic type. Ironically, the cheaper stuff’s clearer and resists scratching better than the “bullet-proof” variety.
MDF is far better for many projects, especially temporary versions. But it’s so damned dusty. So I minimize the use of it. In a fraction of the time it would take me to build something form aluminum or steel I can make up a plexi version. If they pan out I can convert to metal later.
This picture was shot before I added the scissors or the filter. In fact, I’ve added and taken away so many things that the once nice clear case looks quite ratty. I need to just go ahead and make a new one.
Almost all CNC routers are driven mechanically with lead screws. When the screws turn they move the gantry or the trolley or the spindle. Good screws are expensive. So rather than lead screws I used off-the-shelf racks and pinions (R&P) in all three axes (ax-eez). I didn’t know when I was building my machine that the most popular hobbyist CNC router on the market, the ShopBot, uses R&P.
No, I did it because it seemed easier and cheaper. Probably an even greater factor was availability. Racks and pinions can be ordered (new) from McMaster-Carr.com fairly cheaply. If cost is no object lead screws are probably better. I say “better” because it’s easier to design in a lower gear ratio. And that’s a good thing.
And while R&P is no stranger to the CNC world- the motor pinions are usually not interfaced directly with the racks. Usually a gear-reduction of some kind is designed in. The consequence of this direct-drive is higher gearing which is not a good thing. It just so happens that I got away with it– probably the result of my motor selection which was also pure luck.
(If I lost you talking about direct drive- I’m simply saying that my motor has a gear (actually a pinion) on the end of the shaft. That pinion is held directly against the teeth of the rack. So the only way to alter the gear ratio is to change the diameter of the pinion. And I already have the smallest pinion available so I cannot gear my system down. It would be better if I could.)
Every thing I did differently was done to make it easier for me, quite often cheaper. But I’m tickled! It hauls ass and does smooth precise work. If you copy my machine, and you intend to use it as a wood router, you’ll be very satisfied.
I wanted to have something that was capable of doing some real work. I wanted it to have enough power to haul around a full-sized router, cut real wood. I wanted to be able to use quarter inch bits and cut at least 1/4″ deep into hardwood or plexi or other plastics.So, should I get this motor or that motor? It was a pure crap shoot. I absolutely did not know. I got lucky. That’s all it was. I could’ve just as easily ordered the wrong stuff.
But this thing does great. Plenty of torque, certainly adequate for it’s intended purpose.
But- successful as my machine is- I’m still no good for advice if you’re going to build something much bigger or much smaller. I wouldn’t know which motors or electronics to recommend. Over time I hope to learn how to make those decisions.
