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View Full Version : Can Lasercut vary glass tube power whilst raster engraving to give relief effect?



john banks
11-08-2011, 4:50 PM
As title, can Lasercut based machines vary the power pixel by pixel from bitmap colour information to raster engrave with variable intensity to give a relief/variable burn effect in say laser ply like an Epilog can?

I understand the glass tubes have a minimal effective power, and I read that their power is varied by an analog voltage rather than PWM like the RF tubes. However, PWM at a high enough frequency and a low pass filter can effectively be a digital to analog converter, so what is there a practical difference?

Rich Harman
11-08-2011, 4:52 PM
I don't think so. However if I remember correctly, Rodne suggested that it may be possible. It would like to know too.

John Dahl
11-08-2011, 5:27 PM
My version of Lasercut 5.3 can do that by mapping a greyscale bitmap for a 3d effect.

Rich Harman
11-08-2011, 5:37 PM
Hi John, can you explain how it's done? Shenhui supplies LaserWorks with their lasers, I've heard it is the same but I don't know for sure.

John Dahl
11-08-2011, 6:23 PM
I've got a Chinese laser, via Connecticut. It's a Jamieson LG-640. I started to answer your how to question, and realized that the 3d option (greyscale mapping) isn't built into the lasercut package, but in another application that came from Jamieson, called EZphoto. It's a plug in for Corel X4 that sets up the bitmaps for the LaserCut corel plugin. So, I guess I was wrong. LaserCut doesn't do this on its own. Sorry.

john banks
11-08-2011, 7:08 PM
Do you get a varying depth of engrave/relief in your lasered material for different colours in your bitmap or does the software just process it to 1 bit depth bitmap and use dithering/half toning to get the greyscales so the engrave look good even though the final surface is fairly flat?

john banks
11-08-2011, 7:45 PM
Does RetinaEngrave do this?

John Dahl
11-08-2011, 7:58 PM
You need to start with a greyscale image, like Gantry sells. The software maps the power to the greyscale (not color) such that the white is engraved the least, and black the most. It works much like the ULS or Epilog software.

john banks
11-09-2011, 4:50 AM
Sounds great. I wonder if they do it with a higher density of "on" pulses for the black areas rather than varying the power of the laser. If the results look good I doubt it matters though?

john banks
02-13-2012, 8:08 AM
RDCAM 5 does indeed do this. I tried it this morning.

If you select "output direct" then it will map grayscales to power dynamically. Use the minimum and maximum power to select the range, I used 10 to 60% and played with both to prove that it respects these boundaries by engraving solid squares and watching the ammeter. Even with a solid black it does not run my tube above the maximum power.

On its own this technique doesn't give enough contrast to the engraving if you use a grayscale photo, but it may be able to enhance a halftone effect or give more depth.

Interested in how other users get on with this.

Rodne Gold
02-13-2012, 9:18 AM
It can only be used for 3d engraving as it doesnt dither the image to 1/2 tones. Try fill a circle with a radius fill in Corel , black in centre , white at edges - should engrave as a dish.

Khalid Nazim
02-13-2012, 10:16 AM
I am assuming that you are talking about a bitmap image. So I can create a circle in Corel with a gradient fill going from black in the center and white at the edges, export it as a bitmap, import in RDCAM. What do I do in the RDCAM bitmap settings to engrave it like a dish?

Rodne Gold
02-13-2012, 11:19 AM
Do what John Banks said....

Chuck Stone
02-13-2012, 11:33 AM
I am assuming that you are talking about a bitmap image. So I can create a circle in Corel with a gradient fill going from black in the center and white at the edges, export it as a bitmap, import in RDCAM. What do I do in the RDCAM bitmap settings to engrave it like a dish?

You would be using the grayscale image, not a bitmap.

Rich Harman
02-13-2012, 12:34 PM
The "Output Direct" option will not be available on older versions of LaserCut.

Bitmaps can be greyscale, or any number of colors.

john banks
02-13-2012, 1:57 PM
Yes Khalid, it can be grayscale or RGB (didn't try CMYK) bitmap. When Laserworks imports images I find it shows them as grayscale. In the layer parameters choose scan and then output direct and select your min and max power values, speed etc. If you select min and max the same then it appears that anything that is not white will raster engrave with this power so you need a gap between min and max. Black will raster engrave at the max power. It appears that grays are interpolated in between. Presumably an RGB value of 0x010101 will be minimum power. I find my tube will engrave well at speed at 10% (at lower frequency of on/off it will vector at 5%), so there is potentially a situation where you could have a step in power between 0% at RGB 0x000000 and 10% at RGB 0x010101 but at 400mm/s speed even on paper or cardboard the gray is faint.

But engraved photos without halftones or certainly a massive increase in contrast look like they have poor contrast. I haven't tried combining the methods, but it may be more useful for a 3d engrave as Rodney says as I find on wood that varying the power affects the depth more than the color.

I quite like the halftone effect on wood, even the simple version in Laserworks with a boost to 1000 DPI then a low enough "Net graphic" frequency (say 20-25 lines per inch) works quite well. I don't have photoshop or photograv, but will play with Corel Photopaint and see how it compares using ideas from the Gold method, and also play more with the settings in Laserworks.

On another note whilst playing with bitmaps I found that adjusting the backlash to 0.2mm/s at 600mm/s and 0.3mm/s at 800mm/s works well, but 400mm/s is much higher quality as it seems that there is either a randomness to the backlash at higher speeds, or perhaps the timing synchronisation with turning the laser on (or its response) can occasionally be inaccurate so if you have a sharp vertical line such as on a large font then you get a situation where there is a "splattered" look if you try to go too fast where the laser is coming up to power, giving a feathered edge, but not one that has a consistency you can adjust with backlash. I did have to loosen my X belt a little as the stepper was skipping steps. On images it is OK at 800mm/s, just for text and precision I'll slow it down I think. I might have a play with some of the accel stuff to see if that can help. Where do you guys find the engraving quality limit on these machines?

Also tried 1200mm/s and it works nearly as well as 800mm/s, but jobs unless they are wide can easily take a little longer due to the accel/decel times.

Chuck Stone
02-13-2012, 2:44 PM
Bitmaps can be greyscale, or any number of colors.

Sorry.. I meant bitmap in the way it is normally used here.. as in 1 bit per pixel.
(that's the way I originally learned back in the stone age and it stuck!)

john banks
02-14-2012, 8:01 AM
Tried Dee's 3d heart engraving and it works well at 200mm/s, 0% min power (otherwise you don't see the white), 30% max power and 2 passes, any faster the precision is lost, any more powerful and the cherry or tulip wood is overpowered. It does give an engraving about 1mm deep though, but will be too slow to be commercially viable to design or produce except for small items or quick bits done with contour function perhaps.