Full Version: Need Help With Banding Problem
From: logojohn [#8]
21 Jan 2007
To: Awardsguy [#1] 21 Jan 2007
If your driver has a photo mode you can use a medium shade of grey instead of solid black so it leaves a more smooth frosted look. The dithered dots leave less chance of banding You could convert to a bitmap and dither it with coreldraw or photograv if your driver can't do it.
Reduce the dpi to 300-400 instead of 600 at the laser driver settings.
For very large areas I sometimes create 2 vector hatch fill lines at 90 degree angles with a very tiny space in between. But it is still rastered and not vector lasered. Since you are rastering thin lines very close to each other you do not get the unwanted patterns. Its like the bottom left in this image but the lines are close enough that the space is not visible to the naked eye and you can apply a pen thickness to close it up. I even did one image that was over 12 inches by 17 inches on glass using that method and it looked perfectly smooth with no chipping.
xhatch example
Sometimes it also helps to just reduce the speed and power proportionally especially with older lasers.
former native Iowan (angel)
EDITED: 21 Jan 2007 by LOGOJOHN
From: Awardsguy [#9]
21 Jan 2007
To: logojohn [#8] 21 Jan 2007
From: Harvey only (HARVEY-ONLY) [#10]
21 Jan 2007
To: Awardsguy [#5] 22 Jan 2007
EDITED: 21 Jan 2007 by HARVEY-ONLY
From: Awardsguy [#11]
22 Jan 2007
To: Harvey only (HARVEY-ONLY) [#10] 22 Jan 2007
From: laserman (MIKEMAC) [#12]
22 Jan 2007
To: Awardsguy [#11] 22 Jan 2007
Gary,
Right now what I would do is to use the Texture option in the driver. In the advanced tab ENABLE Image Enhancements and then put a check mark into the texture box.
The files will be larger but this should cure your striping problem in order to get this job done.
If this works then do the job and then we will address a couple of things to check that should correct the problem.
From: Harvey only (HARVEY-ONLY) [#13]
22 Jan 2007
To: Awardsguy [#11] 22 Jan 2007
That is indeed a strange one. Every explanation I try to think of is negated by that. It may be that what is at the top and bottom are more prone to showing that problem.
Some general rules of (my) thumb that I had to use with Corel 9 and to prevent problems.
Be sure that the width and height, pixel wise). of the image are both divisible by 4, 'long word' in computerese. If not, changing the size of the width of the image by one pixel width, (as a decimal in the width box on the toolbar), usually solves the line down the middle problem.
Be sure that the image is an even multiple of the engraving DPI, or an even fraction like 1/2, 1/4, 1/8. This is after you have resized it. Do this by re-sampling it to the size you have made it and the proper resolution. This prevents misinterpretation in the driver. This usually solves any possible software glitch. If you still get it it will probably be a mechanical problem.
From: Awardsguy [#14]
22 Jan 2007
To: laserman (MIKEMAC) [#12] 22 Jan 2007
I did check the texture box early on to see if that would help. It did a little. I have been putting the laser .070 out of focus and it's worked pretty well for getting rid of the vertical banding. There is faint horizontal banding, but it isn't too bad. It's allowing me to get the job done, however I do need to figure this out. My wife says that I'm prpbably the only one who will notice it.
I just had to engrave one twice because of some paper that I used for placement came loose and interfered with the laser. After the second lasering the vertical bands are very prominent.
Any advice is appreciated.
I'm going to try Harvey's suggestions and see what happens.
Also, I normally use the HPDFO lens. I switched to the standard lens that came with the unit and that seems to have helped some. (edit)
EDITED: 22 Jan 2007 by AWARDSGUY
From: laserman (MIKEMAC) [#15]
22 Jan 2007
To: Awardsguy [#14] 22 Jan 2007
Gary,
you should use the standard lens and run the focus 0.030 to 0.040 out. The Hpdfo is made to stay in focus with very little tolerance. by running the Hpdfo Len's you are basically defeating the purpose of the lens.
I would check the X belt tension once the dust settles. This may be all that it is.
Have you tried to move the graphic into another area of the table?
Try running the graphic in question at 18 power 33 speed just as a test.
EDITED: 22 Jan 2007 by MIKEMAC
From: Awardsguy [#16]
22 Jan 2007
To: laserman (MIKEMAC) [#15] 22 Jan 2007
Well, after trying several of the suggestions, I finally have acceptable (for me, and I'm picky) engraving. I owe you and Logojohn and Harvey and Carl a drink. If you're going to be in Vegas, I'll buy. It was a combination of several things that worked. I tried so many that I'm not sure what I did. I just saved the settings and I'm going with it. Thank you all very much for the help!
I hate the learning curve.
From: Dave Jones (DAVERJ) [#17]
22 Jan 2007
To: Awardsguy [#16] 22 Jan 2007
I don't know if I missed this in your posts or not, but is the image you are engraving a vector image or raster (or combination)?
If it's a raster or combination, maybe do a test engrave using a simple vector image with a solid rectangle and see if it has any bands.
From: Awardsguy [#18]
22 Jan 2007
To: Dave Jones (DAVERJ) [#17] 22 Jan 2007
From: Harvey only (HARVEY-ONLY) [#19]
22 Jan 2007
To: Awardsguy [#18] 28 Jan 2007
The answer appears.
The dithering in the filled rectangles is conflicting with the DPI of the laser. Convert those to bitmap at an even multiple of the laser's DPI and it is solved.
From: Awardsguy [#20]
28 Jan 2007
To: Harvey only (HARVEY-ONLY) [#19] 28 Jan 2007
Thanks Harvey, I will give that a try.
As you know I had a problem getting to the EE site. I thought I'd try another computer. Haven't had time to try the fix from Computer Associates on the other 2 and I'm a little gun-shy about using my work computers until I've done all of the diagnostics.
I appreciate your help with everything.