[CATastrophe]

Hello
I been thinking about building a cnc for my business,which is monument business.

the main engraving will be on soft marbles and if it can just make small touch engraving on black granite its great.
1)please let know what spindle rpm is recommended for engraving on marbles-should it be slow rpm or fast?
2)do u think a 2.2kv spindle is strong or we need a stronger one?
3)what typ of rails and motors recomended?do u think a round rails with step motors is ok?or i need gear rails?with servo motor?
4)what bits i need to engrave on marbles?and where is a good place to buy?shoud it be tungsten carbide blades or hss or vidia blades for marbles?
5)should we use water when we engrave on marbles?
6)whats the speed recommended for engraving stone and down rate?
7)any recomended structure is welcome

thanks in advance

CATastrophe

[RustyCH]

I think, You will facing a lot of troubles of the Dust/sand from the marble machining. In my experience, its deadly for all precision equipment, if you put sand in it, therefore take a lot of care for protecting the sliders, ball bearing etc. from dust and marble slurry.
I guess, fore stone machining, diamond tools are the right try, like for engraving glass etc. You even can try different tools with a Dremel by hand to see, if it will work. Normally, the hard particles in stone will grind all tools away in short time.

[josephmartins]

Hi CAT,

I just happened to read the title of your post this morning when I received my CNCZone Weekly Newsletter.

If I understand you correctly, you wish to use CNC to draw images on granite - not the three dimensional carvings created with a sandblaster, but the artwork usually created by barely scratching the granite's surface with a handheld engraving tool. Am I correct?

I ask because I used to [hand] engrave artwork on granite at a monument business in Massachusetts in the early 90s. Back then there was a competitor that used some sort of laser engraving (dot matrix style).

I am curious if anyone has developed a way to accomplish the same thing using CNC - so I'll keep an eye on this thread. However, I think you'll find that nothing can really take the place of hand-drawn engravings or hand-sandblasted carvings on granite. You can see the dramatic difference in the finished pieces.

If a $19.99 tool engraver with a carbide tip can do it, I would imagine just about any CNC hardware would suffice. Rusty mentioned dust. The process doesn't generate a lot of dust [relative to, say, sandblasting], but I can just see even the smallest amount wreaking havoc with expensive hardware if you do not have some sort of vacuum near the bit. If you have your heart set on creating the artwork with a machine, I'd suggest looking into the laser engravers as well. They were designed to etch on any surface.

[jimbarb30]

You can try carbide but i think diamond will be
best, use a high RPM and continous water flow.
Also your machine needs be able to handle
grit and water.

[ianrobertson]

A friend tried this ten years ago. He had a shallow aluminum pan to hold the stone submerged and used air turbine with diamond burrs. He gave up. It would probably work with the Z loaded with a weight as too much depth would (and did) cause a problem.

[AdamM]

Hi Cat how are things?


You are going to want to contact Granquartz or Diamant Boart.

They are going to tell you that you will use an electroplated mill for marble and a Sinterized or widia mill for granite.

http://www.dbstone.com/catalogs.cfm

go there for the Stone fabrication and processing tools catalog, you will be interested in pages 69-71.

you will have to talk with granquartz to get there catalog, they sell ADI tools.

You can go here to take a look though.

http://www.aditools.com/prod/Pietra/...olpit_gran.htm

http://www.aditools.com/prod/Pietra/...colpit_mar.htm



Both companies will give you recommended feeds, speeds, doc's etc.

You are going to need water, and you really need to listen to what is happening. You ears will tell you alot, machining marble and granite isnt a science, its an art.

If you need more info send me a pm.

[kurth]

Hi,
Have you thought about using a laser? We are buying a 120 watt laser from ULS that we will mainly be using to cut acrylic and composites but during the sales pitch they showed us some balls that they had engraved and it would probably be tons faster than milling.
Kurth

[CATastrophe]

i have just post the message this morning and i am really suprised and thanksfull for your post reply!!!

for engraving on black granite we allready use laser machine which makes soft carvings (drawings ,portraits...)
since its a very thin engraving which just takeout the wax cover i am wondering if a cnc can also engrave bmp photo like the laser machines.

but our main use for the cnc will be carvings on soft marbles and not granite-from other threads i saw -carving in black granite 3d shapes is impossible.

if my cnc will be able to carv on soft marble ,that will make me very happy.

i have seen some machines that carv direcly on stones leters without water and they use vidia bits.

i will surf on the website Adam sent me and get some information on the best bits we can use for soft marbles.

i wonder if there are 3d blades for marble carvings.


anyone got photo of diamond bits ??how long will it live for?
anyone got the best spindle settings for marbles?whats the correct rpm??slow or fast for soft marbles?down rate....

thanks again for all

best regards

CAT

[rdpzycho]

hi, my first post here.

for the rails, linear rails are the easiest to build for me and my personal preference for looks. if there will we lots of dusts you may use bellows to protect everything that moves, especially if you're going to use ballscrews.

if you are going to use stepper motors you must use large ones. rule of thumb requires a step motor with twice the amount of torque you actually need to be precise in open loop. servos are good but they are quite more expensive.

do you need to engrave deep on the stone?

[b25hf4u]

Used to operate a full size purpose built CNC stone cutter.
My recommendation is to make sure you use bellows on all screws, e use to have a rack pinion on protected tracks. belts would work fine also.

For the sliding part use Flat linear bearing, they will be the best and last the longest, and as long as they have plenty of grease and a good wiper they will lasts for a long time.

Go to Granquartz for tools, they are great and very helpful or Braxton-Bragg.

I am assuming you will wet cutting, wet cutting will extend your tool life greatly, some tools we used had been around for 2 to 3 years due to great care and plenty of water.

Feedrates : plunge around 1 IPM, travel in material can go from 20 to 1 ipm depending on material removal. Marbles usually like slower feedrates to reduce chipping. RPM is dictated by your bits, usually up to 30k rpm, we would use a standard router occasionally, otherwise spindle ran at 15000

Granite and materials do fine in water processing,allow 24 hours to air dry before sealing.

[trailgrind]

I used to work in the stone industry, it isn't impossible to carve black granite but it will wear everything out more quickly and will take more time to carve. Using a CNC you would probably have to program multiple passes to get your desired dept. We used to regularly do profiles on black granite. In addition your diamond bit life can be almost indefinite with "retipping" services where you send your bit to a company and they put new diamond on (either electroplated for marble or sintered for granite). You can actually buy the equipment to do this but it is quite expensive. I agree with others about the water, you want to use lots of it for a couple of reasons.
1 reduce dust that you are inhaling, and reduce your chances of developing silicosis (in coalminers it is called black lung and basically turns your lungs to scar tissue that doesn't work for breathing).
2 provide lubrication to the bit cutting or polishing the stone. I had to alter my polishing grinder to better spray the water or i couldn't get a mirror finish on the stone.
3 cool the bit and stone
Hope this helps and isn't too redundant

[mosiac71]

...as thats what we run at work but we only run benchtops not engraving but the feature is in the cad software to import jpeg, bmp etc. and transfer to surface, you then choose depth of machining and accuracy of shapes and away you go. Its amazing how fast it works it out. But maching side can take an age as the more accurate you go the longer it takes to machine.
The other interesting thing is generally the shallower you cut the better the result as you have smoother transitions in Z.
Hope that helps

[ViperTX]

Are you really speaking about engraving marbles? It just brought to mind Jennifer Garner's recent movie.....Kingdom......marbles seem to play a big part in the movie....

What do you do with engraved marbles.....?

[Litografa]

Here is short video about hammer type stone engraver - may be this information will be interested.
http://www.litografa.lt/index.php?grafik_3k_en