My first engravings, and a question

[Mike vonBuelow]

Ok, so I found some dragon clipart and just want to make sure I understood the basic operation. I tested 3 speed & power settings, but since I was using scrap wood, I'm sure my results aren't totally reliable. But I was happy to finally laser something.

Feeling confident, I went ahead and tried out a 2nd project. I noticed, however, that there is some grid lines that appeared - is there any way to get rid of them? I tried using tweezers to scrape the engraved area with some success, but I accidentally knicked off a piece of lettering (see the "h" in "whatever" on the left side).

Higher DPI perhaps? Maybe the wood I'm using isn't meant for engraving per say... maybe it needs a mask and paint...

Yes I'm a NEWB!

[Dee Gallo]

Hi Mike,

This thread has been discussing the same thing: http://www.sawmillcreek.org/showthread.php?t=149883

There are several suggestions offered for fixing it, maybe one will work for you? Let us know if you solve the problem, we'd all like to know!

cheers, dee

[Larry Bratton]

Mike,
It would be very helpful to you and the forum if you would post the type of equipment you are using. It's difficult to give a good answer if we don't know what kind of laser it is, wattage etc. Edit your signature to include that info.
The wood you have engraved in these photos looks like unfinished pine. If it is, pine is not a real good wood for engraving. Maple, alder, walnut etc, preferably with a finish on it works well.

[Mike vonBuelow]

Signature not showing up for whatever reason...

Pinnacle 25W Mercury.... IIRC, I was at 90% speed and 100% power
Corel

[James Terry]

Those darn 25 watt Mercurys. Rotate your stock (http://www.sawmillcreek.org/showpost.php?p=1435534&postcount=12) 90degrees so that the grain lines are with the travel of the laser head. When crossing against the grain, you will get the little square pattern. So yeah, you will need to rotate a LOT of your work.


http://www.webglider.com/laser/2008/DSC07104.JPG

http://www.webglider.com/laser/2008/DSC07106.JPG

[Frank Corker]

Looks like a grain issue to me. In between the hard pieces the softer stuff will crumble. That said, even with acrylic you will get the crosshatching look and you need to have me dots per inch, where they overlap a little to even out the look.

[Chuck Stone]

Those darn 25 watt Mercurys. Rotate your stock (http://www.sawmillcreek.org/showpost.php?p=1435534&postcount=12) 90degrees so that the grain lines are with the travel of the laser head. When crossing against the grain, you will get the little square pattern. So yeah, you will need to rotate a LOT of your work.


This makes sense in my head, but I have a similar machine and it still
does this on plastics, which don't have any grain. (not trying to hijack
the thread, just mentioning it because it might still be another issue)

I was able to change mine (somewhat) but not get rid of it. I pulled apart
the head assembly and cleaned everything again (don't use acetone on the
clear plastic spacers! :eek: ) and realized that there the screw behind the
mirror wasn't actually touching it.. it wasn't long enough. Perhaps it was
a replacement screw? I put a spacer behind the mirror to tighten it up.
The cross hatching changed but didn't go away. I also don't know which
item changed it. :o

[Mike vonBuelow]

Thanks all - 2nd attempt tonight.

[Rodne Gold]

Ridging is a fact of life with all lasers when hogging out large areas..never been able to get a nice clean surface myself. the deeper you go , the worse it gets - especially with plastics
Even my CnC router and my engravers leaves "milling marks"
You can minimise ridging by using a polishing pass or trying to either raise or lower DPI , using a shade of grey rather than a solid black when engraving , making sure all Y axis components and belts etc are to spec , using a lot of air assist , using a mask and sandblasting after, taping material down so its epansion and movement is minimal , trying various PPI values , using less speed , rotating with the grain , lasering slightly out of focus and so on. Real bad when doing masters cos even something as negligable as a fingerprint can be transferred to the mould. Often the best strategy is using a postscript or patterned fill instead of solid and making it a "feature" rather than a bug.
The pattern on your circular engraving looks more like a halftone effect or moire than just plain ridging.

[Richard Rumancik]

Mike - what kind of file are you sending to the laser for the project in the right photo? Is it a vector file with color fills, a vector file with black fills, a grayscale bitmap or b/w bitmap? Finally, are you using Black & White Mode or Manual Color Fill mode in the driver?

[Mike vonBuelow]

Richard, et al.,

Here's the screenshots of my settings (using Adobe AI 10 this time) along with a screenshot of the file I was trying to print. I used the trace tool in greyscale using 16 colors.

[Mike vonBuelow]

In addition to the screenshots above, I re-oriented my wood with no luck - although it may be a tad less pronounced.

Here's some screenshots:

[Mike vonBuelow]

and one more of the main landing gear closeup

[Dan Hintz]

That is some of the worst dithering I have ever seen this side of a 20 cent newspaper print. You have issues with settings... fix those, and I have a feeling a lot of your ridge issues will magically disappear.

[Mike vonBuelow]

...and another question that comes to mind - would inverting the image help ?

I concur it's a settings issue. I guess I'm going to spend the $100 for the 30-day tech support from SW.

[Bill Cunningham]

It looks like your engraving directly from a greyscale image, using only the basic halftone supplied by the driver.. This usually won't work for wood, glass, or granite. What you need is photograv, the Gold method( technique is on the creek someplace, use the search function) or your own dithering method, and engraving from a binary file (Black/white line art), and not a 8 bit gray scale or 24 bit colour image.

[Mike vonBuelow]

Gold Method is HERE (http://www.sawmillcreek.org/showthread.php?t=93559)

[Gwendolyn Lee]

...and another question that comes to mind - would inverting the image help ?


I don't know that inverting it would help - to me, it looks like an issue with the graphic itself. I think your resolution may be too high (and this does not indicate the resolution you are sending it to the laser on). I've found, once in the laser driver, 500dpi is be too high, esp if you are working at 100% dither - 250 or 333 (depending on the wood) tend to work nicely, maybe 50% dither.

Also, if you're engraving at 100% dither and 500 dpi (where every-other-pixel is black/white on a 500 dpi image), your laser pulse may be overlapping - a "1000 dpi laser" will not physically let you print every-other-pixel, esp not on wood when it chars. The laser beam itself may be slightly larger than .001, like, say, .0015. Compound this with the grain, and the gradient will be indistinguishable.

[Niklas Bjornestal]

Try changing to error diffusion in the raster settings, that will give much better result.