Engaving Black Marbel

[janko cervencik]

I have Pinnacle M-25W laser engraver.I'm trying engrave picture on black marbel and looks bad!!!???:(I have a settings DPI200, PPI-Auto, Sp-100,PWR-60 Vector function-All Raster, Error Diffusion,Diffusion type-Jarvis and Raster contrast-0.
Can enybody help me please.
Thanks Jan

[Kevin Huffman]

Hey Janko,

Can you do me a favor and email that picture to kevin.huffman@signwarehouse.com? Or post it here on this forum. If I had the picture I could engrave it here and tell you what kind of settings I found to work best.

One thing you can try is inverting the image in the software or using the invert feature in the driver.
Marble is a very different material, it is one of the only materials I know of that turns white when you engrave it, all others turn black or darker when you engrave them.

[Shaddy Dedmore]

Could be lots of things. What marble are you using, Lasersketch? They recommend using less power than normal, and only 300dpi max.
What program are you using to format the photo (photoshop, painshop pro...). Are you using PhotoGrav?

Here's what I would do to get adequate results on my Epilog Laser (so it may be different).

Open my photo software (Paint Shop Pro in my case). Sharpen it up a couple times, change to grey scale. Crop to what looks good. Then resize (sometimes called resample) to what I will be using. I'd use 300dpi and whatever size fits. Then I'd reduce my colors to 2, and choose Floyd or Stucki dithering, whichever looks best.

(if you have photo grav, just make it greyscale and size/crop it, then use PG)

THEN I'd import into corel and place where I want it. Don't resize after you get it in corel because the dots have already been set in the other program.

When you etch, and if you use too low a power, you can always re-run it for a deeper cut. So it's good to start too low.

Lasers basically burn little holes in your material. With wood, the holes edges are sloped due to smoldering and 'cause it's soft (the upper part of the hole is wider than the deeper part). (and glass makes little micro fractures so the holes can't be very close together or they just all blend together, but that might be what you want). Marble is harder, so the holes have sharper edges and can thereby be closer together (higher resolution/DPI). if you put the holes too close together though, they start to overlap (depending on the slope of the hole), which causes you to lose detail. SO... increasing your DPI doesn't always mean you'll get better detail, you might end up losing detail.
But the marble from different places, or even different batches from the same place can vary. I THINK Lasersketch marble is softer than what I get from my local place. I can only use 300 dpi so far on the batch I have, but I can go all the way to 1200 using my local marble (only 12x12, not edge polished).

I know you said you were using 200, I just thought I'd through that out there. I'm in a talky mood again.

Could you post a pic of your orig, and your result like Kevin Suggested?

thanks
Shaddy

[George M. Perzel]

Hi Janko;
Just offhand- your dpi settings are way too high- I don't recommend anything above 600 and my best results have always been with 300. Are you using Photograv?
George M. Perzel

[Rodne Gold]

I thought he was using 200 DPI which isnt high at all?
He doesnt say why the pic is bad either.
Is their banding , is it not white etc.

The laser actually leeches colour out the marble and needs very low power to do so , overpowering will burn the marble and create a brown or off white effect.

As an aside
The 1/2 tone method one uses is also vital , something that generates a lot of small cells is not that useful.
Bear in mind a laser can only engrave one colour and shades of grey depend on cells of of these one colour spots with various overlaps and spacings
Regardless of DPI . its the cells that can be engraved that count.
High DPI will alow the laser to engrave more spots per inch , but this is in reality irrelevant as the LPI (cells per inch) counts more in terms of resolution and representation. For example , 600 dpi will allow 600 dots per inch (in one direction only , top to bottom, left to right is a function of PPI) to be engraved. but if a cell consists of a 6x 6 block , only 100 cells per inch can be engraved. If the spot size is too big , even these cells can be totally undefined. For example if you want to be able to ACTUALLY engrave 600 dots per inch , the spot size HAS to be less than 1/600th of an inch ie 0.0017" for you to be able to "see" discrete spots.
A single greyscale pixel in the image will be engraved as a cell and the laser , even at the highest DPI will NOT hold more than a 100-150 LPI count. One can either represent a single pixel as a cell or a group of pixels as a cell
IE when using a pic , the pixel count counts. Ideally one should have about 100 pixels per inch of engraved output (or even less) , any more is in reality , useless as the program will have to group these and represent them as a single 1/2 tone cell and sort of guestimate a value of the shade of grey.
Using a high DPI photo and a "fine" 1/2 tone method will make a mess , the 1/2 tone method you use depends on spot size ,dpi ., ppi . materials etc but generally the coarser it is (within reason) the better , fine settings and too much power tend to overburn the material and dont allow proper spacing and you lose the greyscale effect.
Thus DPI , PPI , 1/2 toning etc are all interdependant. Using Corel or the lasers own driver is not an ideal solution , results are variable and often one doesnt have the time to fiddle etc. Often what you see on screen is way too fine for the material or is not what one actually gets
Thus we find by far the easiest way to do photos is to use photograv which 99% of the time works very acceptably.

[George M. Perzel]

Correction- thought DPI was 1200- just can't see as well as yesterday.
George

[janko cervencik]

I have Pinnacle M-25W laser engraver.I'm trying engrave picture on black marbel and looks bad!!!???:(I have a settings DPI200, PPI-Auto, Sp-100,PWR-60 Vector function-All Raster, Error Diffusion,Diffusion type-Jarvis and Raster contrast-0.
Can enybody help me please.
Thanks Jan
I have a picture, which I scan in my scaner.The picture on the marble looks terrible..:( What I do wrong?The scaner is no good?I scan the picture 300 dpi. I have use speed 45 and pwr 25, then my DPI=300.I'm using Marbel from Laser Bits.I'm using Paint Shop Pro8.

[Kevin Huffman]

Can you do me a favor and send me that Corel Draw file you are working with? I can open it here and see what I would change about it.

I don't think you have a bad scanner.

You are going to have to change the file to grayscale, color mode will be black and white. DPI will start at 200.

Let me take a look at that picture and I will be able to to help you better.

[Laura Zaruba]

Have you read our past posts on marble (try doing a search) ? I know I had a lot of trouble at first. Here is info I posted awhile back (I use Lasersketch parameters, PhotoGrav, PhotoShop & Corel 11):

They told me to load the parameter, then open the photo. I always select "Interactive Process" and the first thing you should select is the "Simulation On" tab. Set your speed, power, resolution and lens size FIRST. Otherwise you'll make all your adjustments for the wrong settings. After that is set I start at the beginning with "Adjust Gray" and work my way through.

After I process the photo, I usually save the engraved image and take a look at it in Photoshop since most could use some quick clean up work. After that's done, I save the image, open it in Corel and engrave.

I use an Epilog Mini 35 watt and for marble I scan photos at 600 dpi, open in Photoshop, reduce the image to the size to be engraved and reduce the resolution to 200-300. I use that same resolution in Photograv & Corel. Lasersketch suggested a power of 45 and speed of 45-50. However, my salesrep was suggesting other settings today so I'm still playing around with everything.

[mike wallis]

Hi Jan,
the marble in the photo you posted looks to have alot of speckles in it. From my experience this creates light and dark spots when engraving. This could contribute to one of the problems your having along with some possible photo issues.
Mike

[Michael Wells]

Jan, Just a quick note to offer a shot in the dark.....I have had results almost identical to that when I tried to use the Black marble setting on a piece of absolute black granite. Some companies have tried to sell the granite for the black marble before. I ran into this a couple of times and they are a little difficult to tell the difference occasionally. The biggest difference is in the hardness ratings of the material, so they cannot be lased at the same settings. Try a much lower power and speed setting and see if it improves the result. If it does, you may have recieved some Granite. You can also work up from the lower settings without moving the piece to achieve the optimal settings.

The visual differences are sometimes slight, but you can always tell by the existance of granite flecking which should be mostly absent in the marble.
Hope that helps, but keep us advised...
Michael

[George M. Perzel]

Hi Janko;
Somewhere I may have missed it, but are you using Photograv?
George M. Perzel

[Kevin Huffman]

Hey George,

I don't think he does. Janko keeps saying Corel Draw. I am still waiting on that image so I can take a look at it.

[Kevin Huffman]

Hey Janko,
Here is what a came up with.
I want to attached 3 images to this post. But the file sizes are to large. The only one it will let me save is the Begin file. The one you sent me.
So here is how I did it, I imported the Begin image into Corel Draw, size it to the size I wanted. Resampled it at 300 DPI and then Inverted it.
Then I went File/Print. Clicked Properties.
On the Option Tab
Mode = Black and white
DPI = 500 (any lower made it worse)
PPI = Auto

Black Pen
Power = 40
Speed = 100

Raster Tab
Error Diffusion, Floyd.

Sent to the laser and had it engrave. The picture came out awsome, as I was carrying it to our publishing department to get picutres taken, I was approached by many people wanting me to engrave them the same image. I told them it was customers file and I would have to get he permission.

[janko cervencik]

Hello Kevin.

Of course you have a permission use my pic...:)
I want to Thank you all of you for Help..:)
I'm sure I'm going have a lot more questions later on...:)
I wish you Happy Hollidays
Janko :)