Seems no one was stupid enough to test their CNC module on stone, so I’m going to be stupid for you.
To give some background, I already work in the stone CNC industry and have some pre-existing knowledge in this stuff, the differences being that the machines I work on are purpose-made for stone, use purpose-made stone tools, use water as a tool coolant and dust control, and are as big if not bigger than your living room. So of course, my first instinct is to come home and possibly ruin my snapmaker 2.0 for the good of the community, how bout that.
Currently I’m testing the milling of a piece of softish granite known colloquially as “fantasy brown.” it’s got a mixture of materials in it, so I’m likely extra stupid for picking something with mixed materials and hardnesses to test on, but I’ve got a ton laying around. I’m using a small diamond bit close to a flat-end mill. One may achieve better results using a more V-shaped bit, but this is only a test run and I wanted a bit with a little more chub to it for a first run. Work and plunge speeds are 150mm/m at .5mm steps, target 4mm deep. I’ll verify later but it seems a little fast as there’s a bit of chatter. I can confirm that I’ve already successfully lasered a piece of this same granite type, so I know that works. As for CNC, time and broken bits will tell.
That being said, currently it’s working. The bit is indeed making lines, though because of possibly inconsistent material thickness as granite often has, it’s not a perfect defined line. I’m also only on my first pass (.5mm deep) so perhaps on the next run there will be more success.
Both of those look pretty good. Marble is going to be a bit softer than granite, so that’s good to know. I don’t get much marble scrap from work, so unfortunately I can’t test that myself. Granite, quartz and porcelain trash are in high supply though. I’ll probably never make anything on porcelain for a number of reasons. It’s highly unlikely that I’ll ever put quartz under the CNC knife also.
The ceramic tile I’m a bit surprised about. How did the machine act while cutting it? What were your stats? The result looks pretty clean, close to what I’m looking to achieve. The tile itself looks nice.
UPDATE: Unfortunately as I was writing my OP, I was pretty nauseous yesterday, so I came upstairs to lay down and let the machine run. When I heard the noise change tone, I knew something was up, so I hobbled my way downstairs and the piece had moved. So I don’t have anything quality to show, but before that, everything looked decent. I can tell you that my piece’s thickness is inconsistent indeed as granite often is, so maybe I should shop around for what’s called a “gauge wheel” in the industry, basically a planing tool that you run across the piece to grind it to a consistent thickness. I think the SM supplies a gauge wheel, but I don’t think it’s for stone. It looks more for wood.
So I think I’ll try again, with less step depth (.2mm?), a different bit, and slower speed, perhaps 50-100mm/m, and see what happens. I’d love to keep seeing people’s tests.
Let the machine run overnight on a harder granite called “thunder white.” 50mm/m work speed, 50mm/m plunge speed, .05mm stepdown. My granite is out of level I believe, so half the job didn’t get done. The important thing is that the diamond ball end I used got worn down exactly halfway. Replaced the bit, used the same work origin, although reset the Z, and ran the job again to make sure the current target depth of 1mm was reached by a full bit, not a half bit. If the whole job doesn’t get touched this time, I’m going to reset the job for 2mm target depth.
Thus far, my guess is that the CNC can handle cutting granite, albeit very gently and slowly with gentle speeds and stepdowns. The machine just doesn’t have the RPM, dust removal, and torque to really dig out (relatively) big channels at a time like with wood, so slow and steady speeds/feeds are what you want.
Your weak point really appears to be the availability of quality bits for stone in a 1/8" shank. Either you’re going to be hard pressed to find bits that are the necessary quality for this kind of hard work, or you’re going to be replacing bits every 10 passes or so. Those bits are less than a dollar apiece, so it’s not terrible, more annoying than anything.
If you’re going to try granite like I am, I would advise dividing your passes into groups and changing the bit out every so often. Don’t expect a full job from one bit, maybe instruct your SM to cut half or a quarter of the target depth, stop, replace the bit, reset the Z, and continue.
I’m going to work on getting an estimate of how many linear inches the first bit survived on this granite, which is pretty hard.
When using the laser on granite, the surface didn’t pop? I watched masons put a thermal finish on granite with a torch. Sounded like they were making popcorn.
No popping at all. My pieces were dry and clean, and perhaps on the unpolished side it would be less likely to pop. But yeah, never had popping on anything I’ve tried.
