Granite vs Marble? Settings etc.

[Larry Bratton]

How does granite engrave opposed to marble? Are the settings about the same or different? I got in some beautiful absolutely black granite today from Lasersketch, but I don't have any settings and have never done any before. Recommendations please. Thanks

[Frank Corker]

Larry I have a 45 watt helix - I engrave at 100 speed 44 power for granite with good results

[Larry Bratton]

Thanks Frank,
Mine is a 40w, should I increase power to say..50?

[Tom Cullen]

Larry,
I find that the settings for granite can vary slightly depending on the granite it's self, by this I mean, if you get the granite online ( as you have) the flecking will be a lot less that you would find on a box purchased at a local store like Home depot. So when you engrave on granite with a lot of flecking the rule of thumb is less is more..... the power setting should be fairly low. On my system 35Watt, it's around 30 power and 60 speed ( I get my stuff at a local store) if you go higher you tend to cause a heat reaction with the embedded crystals in the granite and it really shows. So if your power and speed are correct you will only take off the outer surface and the image will look good. Not sure about the online supreme granite? I would think you could almost run that like Marble , given the flecking is very minimal. best to use a spare piece for testing and run a job a number of times on the same sheet and record the power and speed settings for each run then pick the best. I keep my for future reference.

Hope this helps

Tom

[Frank Corker]

Sorry for the delay in replying Larry - your speed recommendations and mine are the same, I'd stick with my suggestion.

[Rodne Gold]

Bear in mind ,both can be engraved 2 ways : Very high speed and low power to discolour the stone or vice versa to thermally shock it and actually make a distinct imporession on it like engraving on glass.
You can Colour fill it if you use the 2nd option but engraving it with such power often overburns the stone and you wont get a crisp white image.

[Mark Koenig]

Well I just got my laser operational on Saturday... :D

Problem is that the wife has gotten us an "audition" with a local tombstone engraver… He gave her a piece of black marble and asked for praying hands with an illuminated ring around the hands…

Found some stuff on Google but does anyone have some clip art or a Corel file that they could share??? Power setting and speeds would also be helpful… I’m new to this machine and have not had time to experiment…

I only get one chance on the marble but going to pick up some test pieces today at Lowes… Should I leave the settings the same for the marble or do they need to be adjusted from the granite...:confused:

[Frank Corker]

Hi Mark,

give this a whirl - 75watt laser recommended 100/85 speed at 300 dpi, if this doesn't work I'll eat my hat. It has all been digitised (EPS) so you can ungroup if you don't like the halo bit. I'd be interested in seeing a photo of your result if you use it. It's Corel X3

[Larry Bratton]

I am appreciative. I have been filling the marble I have been running at 30speed 100pwr (600dpi for text). I'll try these settings and do some tests.

Frank, what DPI does that apply to?

[Frank Corker]

The 300 dpi is the recommended settings to engrave (raster) at. A lot of people do engrave at 600, personally I think it's a bit too much, I do almost all of mine at 300dpi. 600 on a detailed picture quite often kills the image stone dead (pardon the pun)

[Larry Bratton]

Frank:
Oh, I raster photos at 300 but I do the text at 600. I have been doing the ones I have done in two steps. Apparently you just do the whole thing at 300dpi then? That would be quicker. I like filling the text anyway.

[Mark Koenig]

Hi Mark,

give this a whirl - 75watt laser recommended 100/85 speed at 300 dpi, if this doesn't work I'll eat my hat. It has all been digitised (EPS) so you can ungroup if you don't like the halo bit. I'd be interested in seeing a photo of your result if you use it. It's Corel X3

I accidentally set the DPI to 400, DRAT!!! The image looks good if you hold it at an angle but blurry looking strait at the picture. It was a granite plack and not marble... Are the settings that much different???

Need to order some material and do some testing...

On a better note, the wood samples turned out great!!!

Thanks Mark.

[Frank Corker]

Mark I only use granite, getting hold of a decent supplier of black marble here is like getting hold of rocking horse s**T. The settings I showed there are what is recommended by the Epilog handbook. try the settings I generally use on my machine of 44 power 100 speed and use a bit of the piece you have just finished on

[Bill Cunningham]

The quality and detail you get in marble, is much superior to granite.. Particularly on photographs..
The left is a larger flake granite, and the right is brown marble from H.D.
The granite piece is about 10 inches across, and the marble image is about 2 inches across taken with a closeup lens.. The finer detail of the marble is obvious..

[Larry Bratton]

Frank,
I did a big photo of some shrimping trawlers on a piece of granite 18" x 24" this morning. I used your setting,100speed-44pwr, recommendation and it came out beautifully. As a matter of fact I did two. I sold one of them while it was still in the machine. I'll post a photo of it when I get one done. Thanks for the advice! The photo is like 10" x 22" with some type and another small graphic, it took 26 minutes.;)

[Mark Koenig]

Frank,
I did a big photo of some shrimping trawlers on a piece of granite 18" x 24" this morning. I used your setting,100speed-44pwr, recommendation and it came out beautifully. As a matter of fact I did two. I sold one of them while it was still in the machine. I'll post a photo of it when I get one done. Thanks for the advice! The photo is like 10" x 22" with some type and another small graphic, it took 26 minutes.;)

The surface plate (flat machine shop granite inspection plate) was lapping in some out of tolerance stones. Gave me some silicon carbide lapping compound to remove the engraving… Go figure about the timing…

Going to try again tonight… What speed and power setting would that be on a 75 watt laser???

[Frank Corker]

Larry that's fantastic news. Well done mate.
Mark, just try it with 44 power and 100 speed, the worst outcome you would have that would be it might be a little too light, but I don't think you will encounter that problem but do use the engraving at 300dpi even if your graphic is 600. The time halves and the quality and results go up

[Mark Koenig]

The Silicon Carbide worked very well to remove the engraving!!!

Did some tests and realized that the piece will work better if it is polished back to it's original gloss finish...

Will you let you know what happens... I'll get it right sooner or later...

Thanks for your help...:)