Cross Hatch?

[Chuck Stone]

Chuck

I would try a couple of different things. One change the dpi settings with each pass. Two, try de-focusing the machine by about 1/16" to see if you can get a softer image. Three, check your mode settings in your driver. See if you have a relief mode and try that.

If you have the option to manually adjust the half-toning algorithms experiment with that a bit.

As a last resort convert the image to a bitmap and engrave it. There you can use any of several conversion methods to prepare your artwork.

One more thing--you can insert a subtle fill as background using the post script fill tool. We used to do that when making patterns for spin casting. This will take some practice but it will work.

Well .. I varied the dpi from 500 to 1000, changed the PPI from Auto to 1000,
changed the focus 1/16" and then 1/8", changed the halftone from Error
Diffusion to Dithering (2x2 matrix, dot pattern) but so far the best I could
do is scrape off the lines with a tiny chisel.

I'm not sure about the post script fill tool, but I could easily insert a
background. This is 100% raster image done in Photoshop and I'm sure
I could find that option somewhere.. I'll look.

Perhaps I could render clouds of 99% black on a 100% black background?

[Chuck Stone]

Just an update..

Changing the DPI, PPI (wouldn't affect raster anyway) and doing a polish
pass don't seem to make a difference. Still looks like I'm running the laser
through a screen. Changing the dithering options changed the output, but
not affecting the cross hatch in any meaningful way.
I'm doing several passes, and the lines are always in the same position,
both horizontal and vertical

.. just wish I knew what was going on 'under the hood'

[Scott Shepherd]

Did you try making the background 80% gray yet?

Also, it could be a bearing issue. I just had a job and banding was off the chart. I changed my bearings and all was good again. Don't overlook it being a mechanical issue.

[Mike Null]

Changing the dpi setting in your machine will definitely change the raster result.

I agree with Steve--it could well be bearings.

When your machine is off can you move the carriage around freely? If so you may be able to feel bearing wear.

[Niklas Bjornestal]

Do you use any "scaling" (in the advanced settings tab when printing). I had some trouble with banding when engraving anodized aluminium and mirrors that went away when i changed the scaling to 0.

[Chuck Stone]

I'm not going to overlook anything, believe me! I appreciate the input so
I can try out things I haven't thought of.

The scaling is off, and I did an 80% with no change. (now that I think
of it, might have been 90%) Also filled in one area with a pattern but that
didn't make a difference.

I can move the head and rail freely, but that doesn't mean the bearings
aren't a problem .. I just have nothing to compare it to. I suppose I should
just take them out and clean/inspect just because. I know the previous
owner wasn't up on the mechanical stuff, and I haven't used it enough to
really dig into it myself beyond routine maintenance. I know the bearings
and bushings wear over time, and some materials throw off particles that
can become lodged in tight places .. especially with those places have
some sort of lubricant in them.

But the pattern is so regular.. and repeatable.

I think the next time I run it, I'll offset the position with a few sheets of
paper just to even it out a little.

Fortunately, these are masters for a silicone mold. So I can fill in the
background with vaseline and mineral spirits before I pour. It won't get
rid of it completely, but should help to minimize it when I pour the positive.

Thanks for the ideas, people .. still working on it!

[Roy Brewer]

...where I should look?

Chuck,

Sorry if I missed this question in this long thread, but you do have color management turned OFF(or Simulate OFF in X5), right?

[Doug Griffith]

I'm not sure about the post script fill tool, but I could easily insert a
background. This is 100% raster image done in Photoshop and I'm sure
I could find that option somewhere.. I'll look.

In PS I would try:

filter:noise:add noise:gausian
or
filter pixelate:mezzotint:fine
or
filter:sketch:halftone pattern:note paper then levels

[Andrea Weissenseel]

Chuck, in the manual (pg 62) are samples for selecting the dithering. There are sample pictures included - I would try using "Bayer" with a 2x2 raster and "Enhanced Dithering" checked. There is also a Tipp of making a polishing run when engraving 3D, with a complete black mask 100% Pwr 100% Speed

[Rodne Gold]

That cros hatch thing seems to be an issue with 3d engraving on the GCC machines , we have had that and I have tried all sorts of strategies to remove it with no luck whatsoever. I do a lot of masters for casting and never use 3d for em , the results are too unpredicatable. If I want a 3d effect , I might assign 3-5 colours to various elements and engrave with 3-5 different depths , this actually works better than true 3d
The best results you will get using 3d are with substrates like MDF where the croshatch type moire pattern tends to dissapear , the harder the substrate like acrylic or corian , the worse it becomes.
IMHO 3d engraving is a waste of time. If I want to do true 3d masters , I use artcam and a cnc rotary machine (my Tekcel and sometimes my Roland) and the results are far superior to the lasers output and are much more controllable.
Check that you have the latest firmware and drivers for your machine , they might have improved 3d in them,,not sure tho,

[Mike Null]

We did our masters in acrylic using CorelDraw with a patterned background and various shades of gray. These were run on an old Epilog.

Never tried to do 3d art for masters.

[Chuck Stone]

Thanks for more ideas.. I'll be trying these this morning/afternoon.
(these things take about 4 hours!)

Roy.. no color management issue, running straight out of Photoshop because
1. I know it better, and
2. I'm not sure how to work with layers in Corel yet. I haven't spent
much time in Corel since version 3!

Doug.. I haven't done those particular things, but have added some
texture, which didn't change anything. Adding noise seems counter-intuitive,
but it's worth a shot. Are we hoping to keep the software busy with the
background so it doesn't add it's own?

Andrea.. the polishing run didn't change much, it seems to put down a
lighter version on top of the heavier one, cross hatch included. I didn't
try the Bayer yet, but used the enhanced dithering and a couple of the
other options and 2x2 (can't remember which ones right now)

Rodney .. I'm not actually using the 3D settings, although I have. (same
results) I'm running it in Black and White mode, and I've assigned 16 levels
of power/speed combinations. I'm getting an OK 3D effect with a heavily
modified grayscale image run in RGB mode (haven't tried others only because
most of the tools I use in Photoshop are only available in RGB mode)
I do have the latest drivers/firmware, but no .. they don't seem to have
done anything in the 3D portion of the software that I can tell.
Since my work is strictly hobby, ArtCam or a CNC machine would be hard
to justify .. as would the cost of having someone else do it for me.
Besides, I'm a stubborn old Yankee I'll learn to make it work, or I'll
learn to love it the way it is.

I'm coming to think that no matter what is in the file, this is just something
the driver is doing in the background .. on it's own. It seems to be too
regular and repeatable to be random. I'll be digging into the bearings this
morning and see what I find, and have a few suggestions here that I can
incorporate, too.

While it isn't true 3D, I've done some nice things with it in the limited way
I've been using it..

[Mike Null]

Chuck

If you are running in the b/w mode do you have the option to set it for Jarvis or Stucki within your software?

[Chuck Stone]

Chuck

If you are running in the b/w mode do you have the option to set it for Jarvis or Stucki within your software?

I do .. so far I think I've only used the Floyd Steinberg though..

I just don't see what there would be to dither in solid colors, though.

[Niklas Bjornestal]

Rodney .. I'm not actually using the 3D settings, although I have. (same
results) I'm running it in Black and White mode, and I've assigned 16 levels
of power/speed combinations.

You shouldnt use Black and White mode, you should use Manual Color Fill. If you use Black and White mode it convert the colors to greyscale and dithers them.