View Full Version : Help with Granite Please!

Brad Ports
06-09-2010, 11:13 PM
I'm fairly new to the laser world, I am a woodworker but am having trouble getting decent results with granite. I have a ULS 30 watt, coreldraw x4 and photogav 3.0. I am attaching some pictures of what I'm getting. I have tried various power and speed settings. Any help would be welcome, getting pretty frustrated at the moment

Linda Smith Alabama
06-10-2010, 12:11 AM
I'm new at this too, but my first thought is to make sure your original photo has enough contrast, then invert it. It looks like your photos have not been inverted, that's why the eyes and shadows are white. What you see as black on your screen will be white on the granite.

Also I've been told it's very easy to overpower granite and you lose definition. I got good results on granite at 16% power (60 watt laser.)

Zsolt Paul
06-10-2010, 12:51 AM
Assuming that the file couldn't possibly look like this, it looks like too much power or the speed is too slow or both.

Dan Hintz
06-10-2010, 2:52 AM
Start with a power grid to make sure you're just able to mark the granite. Then move to Linda's suggestion of inverting the color (don't forget the background will need to be black so when you invert it turns to white and doesn't engrave). Once that is done, then you can begin to work with the contrast.

Viktor Voroncov
06-10-2010, 4:57 AM
What is your DPI setting? Looks like more than 600? Keep 150-200-300

Frank Corker
06-10-2010, 5:14 AM
Picture 1 shows too much power, too little speed, poor image.

Picture 2 shows slightly less power than picture 1 but it is a positive image and should be a negative, image is a line drawing.

Picture 3 is the better of the three, but it is still poor quality, also has had too much power and too little speed. It should be a negative image.

Below is a negative image of your picture 3 and you can see the results of what it might have looked like in positive.

I have also attached a CDR file for you to open with Corel. It contains a good quality image that has been processed through photograv for a 30w ULS laser, so that you can try it for yourself to see what the results are.

Photograv recommends 75 speed and 100 power but I would suggest you just put it through and use the handbook recommendation for Granite.

If nothing else, this exercise will give you an idea of what your image should be looking like before you go wasting more granite.

Mark Ross
06-10-2010, 8:13 AM
Search for the gold method, it brought me up to speed on granite and laser engraving pretty darn quickly. It is here on the forums somewhere.

Larry Bratton
06-10-2010, 10:24 AM
Mark, the Gold Method, as you know, requires Photoshop CSxx and he may not have it.

Here is my methodology for granite for what it is worth. (Photograv 3)
#1. Start with a good photo. Digital or scanned at 200-300dpi Size it to fit your granite tile you intend to use. You can do this when you scan it if it's not digital.
#2. Make adjustments in Corel Photopaint or Photoshop-increase brightness, unsharp mask etc.
#3. Clean up background or remove it. If you remove it, fill it with black. (Unless you want a white background)
#4. Save it.(I usually save as a Tiff file or Bmp is OK) If you save it as color, it's OK as PG is going to convert it to greyscale when you load it there.
#5. Open it in PG. Select the material, I use the generic Black Granite parameter. (In the Interactive screen, I uncheck Enhance Edges, I have usually sharpened it prior to it arriving here) Hit Final Process.
#6. Save the engraved image, it will have an ENG extension.
#7. Import into your Corel page. I have my page sized to my granite size.
#8. Place the ENG file where you want it in the page BUT, DO NOT resize it or anything, not even a little bit.
#9. I engrave granite at 100s/ 35p. My laser is a 40watt Epilog. Be sure your resolution in the driver, matches the resolution of the file. (300dpi usually). You may need to experiment with your settings to match your machine and material.
That's pretty much it, you should get a pleasing result.

Brad Ports
06-10-2010, 4:16 PM
I have tried both the Image Frank attached and the one that washed out badly on my previous post. I ran my image back through PG at 200dpi, and ran it at 25% p and 100% speed. Tell me what you think, is this the best it gets?

James Stokes
06-10-2010, 4:35 PM
No that image you need to invert. Also you are using a low quality granite.

Linda Smith Alabama
06-10-2010, 5:02 PM
The power settings look much better. You still need to invert your images. It will not look right on your computer screen, but it will engrave right.

This is the photo you just posted, but inverted.

Larry Bratton
06-10-2010, 5:04 PM
Brad, when you look at the ENG file after you have it in Corel Draw, remember, where there are black pixels that is where the laser is going to fire. You don't have to invert anything initially if your using PG. If you want the background to be the black of the granite when it engraves, change it to black in the graphic adjustment software. When PG gets it, it will invert it to white, subsequently your laser will not fire on the background and leave it natural. Those ENG files can look really weird but they work if processed correctly.

Brad Ports
06-10-2010, 5:09 PM
thanks for the responses, I can use all the help i can get. Turning out some great looking stuff on wood but this granite is kicking my backside. I'll keep trying til I get it right. Your correct, It's not the best granite, from Home Depot but until I figure this out I don't want to use the good stuff

Frank Corker
06-10-2010, 7:17 PM
Sorry Brad, that was my fault. Brain was almost in gear! The image I sent you was right for wood but wrong for granite. Import this one as it is and engrave it with the same settings you used last time.

In the attached zip file are two files to look at. I admit that they are a little rough around the edges and would need a little more work to get it just right, but having seen my mistake I have done it quickly.

The picture to look at in the zip file is how it should look before it is inverted is Image300.tif but with no hard edges (Don't engrave it, just look at it) The image should have a black background before inverting, not white.

The file you engrave is marked Image300_PFG (ENG).tif. The images you need to engrave in the future will appear similar to this.

Brad Ports
06-10-2010, 11:49 PM
Here's my latest attempts. Thanks to all of you, I think I'm starting to get there.

Dan Hintz
06-11-2010, 6:32 AM
I'd say you're already there ;)

Larry Bratton
06-11-2010, 9:28 AM
Brad..NOW your gettin it! They look great. However, be aware that you will have variations in materials as you go forward. If you find a supplier you like, stick with his material as much as possible and that will help keep your results consistent.