Working man with goal - open floor - stone tile portable cnc

I am a newbie. No cnc experience. I want to be able to do custom engraving on tile and stone both in the horizontal and vertical planes. For example engraving logo on in place flooring or tile or on walls as well. It would be nice if i could engrave three dimensional objects to a minimal depth as well. The machine i would like to build would have an open floor design so it cold be customized to allow it to be affixed by suction cups to the frame to hold it to the floor or wall. I do not know if such a machine can be built in a cost effective manner given the power i anticipate for the drive motors to work in stone and given the possible weight considerations as affecting portability. Any thoughts or comments would be appreciated. This could be far harder than i thought or impossible or not that big a deal. I thought of experimenting with some of the cnc packages available for diy persons, but after spending a little time on the forums at this site, i am confident there are a lot of bright people out there that might be able to give me some guidance or end this journey. Thank you. Jim

https://grabcad.com/library/portable-cnc-milling-machine-1

As you anticipate, any machine large enough to engrave more than a few square feet at a time will be quite heavy and awkward to set up. Also, engraving in stone is a noisy and dirty process that eats up a lot of expensive diamond tooling. Have you thought of using a CNC equipped with a drag knife to cut rubber stencils instead? The stencil can be rolled out onto the floor or wall and blasted with an abrasive like silicon carbide, which would be a much faster process than CNC carving or engraving. For repeating patterns, you can simply move the stencil and blast some more.

Hey! Building the same thing right now! There isn't a lot accredited information out there on cnc machines for stones so it's a case of throwing oneself at the problem head on. I don't know if any of you have also noticed this but a lot of people here are pretty secretive and I'm still not quite sure why because a lot of the information needed to build a cnc machine is pretty straight forward. One thing I am personally stumped on are mill bits for stone because there is a wide variety of them, I'm worried I'll have to trial and error my way through different brands to find the best one. I'll happily fill you in on this part but give me a heads up if you learn anything important too!

Operation Goals:
What is your intended work area and material? I see that you want to engrave tiles and stones but not sure if you're looking for a compact 8"x8" work area solely for small art and logos or something larger like 2'x3' for vanity and kitchen sized jobs. This is typically the deciding factor for every part of your machine from motors, spindle, motion system, frame, and so forth.

Who will be using it? I am assuming you will be using this machine but if you have little minions to do your bidding, this will increase the cost and specs of your design parameters. If you're a stone fabricator already, you probably have a forklift, crane or some industrial machinery for moving stone around without snapping your backs. You can use this same device for moving your cnc machine around or get 2-4 burly men to lift it or build an expensive transport cart with a jack lift (I can throw together a rough sketch for you if you want it but I don't know the size of your machine and I'm lazy).

What is your intended budget? As Awerby pointed out and you've probably gathered, cnc machines do cost quite a bit of moola to build and run and that cost is relative to your position and goals. Without knowing too much about you, a cnc machine that can go through stone should not be cheaper than $800 if you want something really junky and a good machine can cost between $2000 to above $3000 if you're looking for something more professional grade. This is especially dependent on the size of your intended work area. If you're looking for a $15,000-20,000 cost machine on the market, building it yourself is a great way to save cost but for any machine, you make back that cost for the time you sink in designing and building it so just as a safety check, I hope this is a fun experience for yourself :)

Spindle and bit:
Your holy grail, you're probably looking for a ~1.5kw spindle for engraving but to be safe, look to your power tools and get a spindle a size stronger than what you already use, ie. I've got my hands on one of those chinese 2.2kw spindles but I'm aiming to cut through stone and metals (not gonna work perfect but more of a cheap minimum). Also keep in mind what kind of bit you want to use, chances are the largest shank any of these spindles can hold is 13mm or 1/2" and anything else you will need a custom adapter, arbor, or whatever. I'll put a link down below for a simple and budget friendly bit I just ordered to test out that you can give a spin for yourself for engraving.

https://www.amazon.com/Toolocity-FBQ...ateway&sr=8-51

If you're filthy rich, buy yourself an ATC, these are automatic tool changers and you can engrave, swap out to polishing bits, whatever, they're insane and easily double to quadruple the normal cost. I probably want to get one of these in the future but swapping bits out like a barbarian still works.

Motors:
They sell Nema 23 and Nema 34 stepper motors which you will need depending on the size of your machine. They also sell these as kits with their respective motors, drivers, power supplies, and controllers for roughly the same cost as hunting down each part individually. I do warn Nema 34's are pretty hefty so if you want to move this machine by hand, Nema 23's are normally sufficient, you just have to be a lot more careful. As for the controller, buying a nice offline controller can make things easier for minions to control or if you have an old computer on hand and can water proof it, you can run that dedicated to your machine with the controller that comes with motor kits.

Frame:
It's whatever you have on hand to hold everything together. If you don't have anything, I really recommend aluminum extrusions or aluminum in general because it is easy to design around with all its slots while being lighter than steel. It is respectfully sturdy but if you don't have a local supplier or junkyard nearby it can be above your budget. Just keep in mind that the hardware like bolts, washers, nuts, will add to your cost and clearances. You might also need a few metal plates (aluminum 7075 total overkill but sooooo strong and light) to connect things and having a solid drill press makes the task the easiest or you can always pay a machinist.

Motion system:
This goes hand and hand with your frame, you will need linear rails and screws to carry everything back and forth. I didn't overthink the rails and bought SBR rails which slot into aluminum extrusions easily. Movement is more complicated.

Ball screws (recommended): expensive, thicker than lead screws, better efficiency from the motors and longer life span.

Lead screws: poor man's ball screws, perfectly serviceable if only a little limiting when looking for certain sizes

Threaded rebar: You've got a sense of humor and want to build an old school, really cheap machine, it's on the table but more of out of respect of it once being the foundation of these machines.

Timing belts: flimsy but also incredibly light, not recommended but if you are looking for very light passes on stone as soft as marble or soap stones, maybe, never tried it before.

Accessories:
Water pump or hose lead: need something to water cool the stone because it will get pretty hot if you're using an abrasive tool.

Vacuum pump and tables/pads: look these up, they are really cool and I can do them no justice here. If you want to use wood or metal ones on top of a stone, it only gets easier the heavier your machine is. I can fill you in with more information if you're looking for it later but this is a lot of information I am covering already.


Okay, that's a lot of stuff lol sorry if you knew a lot of this stuff already!

That bit looks pretty aggressive, but I would only use it in very soft stone, like soapstone, alabaster or limestone. The problem with this type of bit is that the diamonds are all on the outside, and they fall off in use, especially if confronted with a hard stone like granite. If you want more life in the tool for harder stones, you need to go to a sintered diamond/metal bit, with diamonds throughout the material so that when it wears on the outside it exposes fresh diamond.

Thanks, gotta admit I thought the bit looked like it would be too delicate but the price really makes me curious to see what it can do. I did a quick search for some softer bits and some sintered bits (thank you for pointing out the word sintered, that's a really good keyword for finding bits).

I searched up stone engraving bits and picked the softest one that came up which happened to be 180 grit. That's pretty soft I'm guessing and they look to be intended for jewlery but take this more of as inspiration rather than a recommendation.
https://www.amazon.com/SE-DT220R-Dia...gateway&sr=8-4

Searching sintered bits came up with these curious pieces, 4 different types, at their price point, they might be worth trying out once I inevitably wear out that gold one. Type D has a large gouge in it so maybe that one would be decent at eating granite.
https://www.amazon.com/Diamond-Sinte...07J1GR36Y?th=1

The only things that worry me about sintered bits is how brittle the diamond material is. If it is super brittle, couldn't it crack and chip? or at the very least the bit would require you to remeasure its diameter every time before generating g-code. Kind of some weird questions when these sintered bits are cheaper than the brazed one.

That first set of bits would be useless for cutting stone in a CNC machine. They are intended for fine shaping of fairly hard materials, but the diamond is plated on and quickly wears off. The 180 grit diamond is just as hard as the coarser diamond grit used in cutting tools, but it cuts much slower.

That 1/4" diamond sintered bit seems more promising for your purpose. With 40 grit diamond, it will cut much faster, and the sintered construction means it will last much longer. The brazed diamond bits in the "other items" area are somewhat better than plated-on diamond bits, but the coating still doesn't last too long. If you're making precision parts with this setup you probably should remeasure the tool diameter periodically, but for most things it won't matter; the diamond impregnated metal wears away very slowly. The fluting in the brazed bit helps a little by letting more coolant into the cut, but that's not essential. Yes, it can break, but it shouldn't if you take it easy with your feeds, speeds and depth of cut. If you do use these things, please write back with your impression of how well they worked, and how long they lasted.

Wish I had experience with machine stone but I don’t so all I can offer is more general ideas or points.

The first thing here is that you can build whatever you want, the trick is to get the machine to work well enough to be happy with it.

At this point I can’t see making the machine light as being a huge advantage for floors. In fact just the opposite mass would help keep the machine in place. Suction cups might work but bolting the machine to the floor would be bullet proof. If you ever watch electrician doing heavy commercial work they will often bolt their wire rack stands to the floor. It is a way to make things bomb proof while handling very heavy stuff. I’d suggest that you machine at least have the capability to be bolted down.

I would expect lots of water so making the machine out of stainless might be a good idea. At least parts of the machine.

A portable machine could suffer due to the lack of power. That is only having 110 VAC outlets available. Then again I’m not sure what the power requirements are for stone engraving. However you would likely need a vacuum pump along with possible a water pump. It might be easier to design for three phase and run everything off a generator. Otherwise you need to be real conservative with 110 power because you will likely not know what is on the circuit you plug into in a commercial building. Having the machine die mid engraving would suck.

Concrete core drills often have built in jacks to allow them to be clamped between the floor and a ceiling. This might guy be a viable alternative or supplemental fixing method.

You might have noticed a huge concern here about keeping the engraved in place. I see this as a big issue when it comes to high quality results and any movement or drift possibly resulting in disaster. I’d focus a lot of effort on making sure the machine doesn’t move.

A slightly related issue is getting the X & Y parallel with the work surface. I’m not convinced that suction cups will be good enough here.

In any event I don’t see this machine being light enough to be highly portable. Probably more like a contractors saw.

When in doubt, just copy the design of cnc machines that were made for cutting whatever you want to cut. E.g.

https://www.automationtechnologiesin...stone-machine/

Most of the commonly cut stones are as hard or harder than hard steels so you'll want something robust. When I tried drilling or cutting epoxy granite, I needed a new drill bit or end mill for every cut or hole. I now think of stone milling like the holocaust, never again!