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Barbara Gill
12-15-2003, 10:46 AM
Does anyone have a picture of laser engraved mahogany that they could post?

Keith Outten
12-15-2003, 1:23 PM
Barbara,

I engraved some mohogany for my neice months ago, the results were excellent. I don't have the samples but I do have a few scraps from the job. Give me a couple of days and I'll see if I can get a picture to post.



Does anyone have a picture of laser engraved mahogany that they could post?

Barbara Gill
12-15-2003, 2:10 PM
Barbara,

I engraved some mohogany for my neice months ago, the results were excellent. I don't have the samples but I do have a few scraps from the job. Give me a couple of days and I'll see if I can get a picture to post.
Ok, thanks Keith.

Todd Burch
12-20-2003, 9:02 AM
Barbara, I'll have a mahogany name plaque on Monday. It is at the engravers now. I dropped it off Friday and will pick it up Monday. 6" tall x 32" wide. I prefinished it. The engraver will apply two layers of resist paper, per my request, and use two passes on his laser machine. Two passes cut deeper than one pass and I think looks a little better, especially if you will be painting or coloring the engraved area.

I asked for two layers of resist over my finished plaque because the engraved areas will be painted gold. I'll first seal the cuts with lacquer, then aerosol the gold on top of the lacquer, as it is brighter and not so dull that way. The 2 layers will help in solvent bleed through. When I pull the paper off, a little buffing with wax and I should be done.

Todd.

Todd Burch
12-23-2003, 12:54 AM
Barbara, here is the sign, finished and ready to be delivered.

Gold paint is in the engraved lettering. The engraver had some problems with it. I think his registration was slipping a little bit. Since I prefinished it, he had to make 4 passes. I watched the whole process. The problem was that on each pass, his laser was registering about 1/128" extra to the left each time he started a cutting cycle.

The first pass would burn the paper off and soften the lacquer. The second pass would burn the finish up, mostly. The third pass would remove all finish residue and start cutting wood, and the last pass cut it deeper. But, not as deep as the first attempt last week (I guess I forgot to mention that the first name plaque he screwed up by not making the text large enough).

So, after 4 passes, and it shifting left a skosh each pass, It did not end up with nice clean edges or the depth that there was in the first engraving he did. Also, the resist he used did not leave a nice crisp edge to be used as a painting mask, and the edge of the finish was a bit gummy too... :mad:

Anyway, I salvaged it, and no one will notice.

While we watched, he explained the theory of operation some, and I think that he might could have cranked up the power a little bit and slowed it down some, and he could have done it in two passes, and as a result there would have been less of a noticable "wander" and I would have had cleaner edges.

While I observed this all happening, I do not know enough about laser engraving so I kept my mouth shut. Had it been worse, yours truly would have had to make yet a third mahogany blank, and color match it, etc., and I really wasn't looking forward to doing that again. And based on what the customer is paying, this plaque will be just fine!

Scare ya? Here's is what I would suggest, and what I will do next time. I will plan on making two blanks, and cost it out that way, and have the engraver produce a sample for me to proof before he cuts the "money" piece. I think this experience is not the norm. All the samples they had in the showroom were clean and crisp. Keith, any ideas on what went wrong? (Universal Laser)

Todd.

Barbara Gill
12-23-2003, 5:27 AM
[QUOTE=Todd Burch]Barbara, here is the sign, finished and ready to be delivered.

Thanks for the picture and the story Todd. I will be interested in hearing what Kieth and other laser owners have to say about the trouble.

Keith Outten
12-23-2003, 8:46 AM
Todd,

Obviously I can't expand on the technique that your engraver uses with his machine but I normally use only one pass when using a masking material. Lasers will lose their power over a period of time and the tube needs to be replaced to bring it back to full power. Possibly your engraver is in the final stages before purchasing a new or rebuilt tube.
The shifting problem sounds like a belt that is stretching.

I prefer to use only one pass as it seems to be less disturbing on the masking material as it is only burned one time and the edges seem to hold up better. When paint is applied the edges are pristine, at least for me so far.

I use this same technique on leather, using a very high power setting and slow speed the engraved area is deep enough to hold paint and leaves a nice edge. Most of the time acrylics and Corian are done the same way with adjustments in the power setting to allow for the depth required.

If a very deep engraving is required then I can see the need for multiple passes, the depth you can attain in raster engraving mode is much less than in vector cutting mode. I haven't tried it yet but it is possible to vector cut the text outline first then raster engrave the remaining areas. This would clean cut the mask and leave the edges undisturbed when the raster engraving is done. It would also leave a very deep cut for the paint to settle into around the edges.

Todd, for the type of sign shown in your photo I would have also suggested using gold acrylic for the text. Engrave the sign first then cut and insert the gold acrylic inlay on top of the plaque. This makes a really nice looking sign and no mask or paint is required. Of course paint is less expensive, but gold acrylic would be much cheaper than four passes with the laser.

Aaron Koehl
12-23-2003, 9:34 AM
Todd,

It does sound like he's having some machine problems--and probably ought to consult Universal about it.

As far as the first failure and the mask--that sounds a little like inexperience coming into play. Of course, in general this is due to the fact that laser manufacturers provide poor documentation, and much of what engravers learn is from trial and failure. Keith and I have honed our techniques over the past few years, with large success--having a workshop and knowledge of these engineering materials behind the engraver, combined with mastery of the software used is paramount to quality engraving.

Every material engraves differently, even among the same types. For instance, finished and lacquered wood obviously engraves differently from unfinished. As far as the speed and power are concerned--that all depends on the wattage of the laser, with some catches, of course. Slowing the speed and increasing the power will indeed burn harder, but will also increase the smoke damage. Multiple, faster passes decrease the smoke damage considerably (especially with photographs). Indeed, with large text and a lacquered piece, burning hard will get a more pristine engraving. Unfortunately, burning too hard will eat (burn) away at the mask, as the heat propagates through the wood differently than the surface of the mask, which will char and melt around the edges. Using a good mask with good masking technique can prevent this.

If there is a coat of lacquer on the wood, the smoke 'damage' will wipe right off--especially around big text as in this job. The addition of an air nozzle on the laser head and powerful dust collection also helps reduce any damage due to smoke residue.

As far as the graphic design and placement--I always prefer to preview and measure what gets sent to the laser. Often, for 'high risk' jobs (where we're engraving on user-provided materials), we will engrave right on a mask at a real low power and high speed, just enough to mark the mask and check the placement, without committing to engraving the material.

Keith and I have engraved several leather photo albums with varying textures, and always get a crisp paint line. Using a wood roller to flatten the mask onto the piece really makes a difference here. (really!)

I hope you have better luck next time--the picture looks good, but of course we can't really be critical without seeing the piece up close! I think a vector cut inlay would look excellent in that piece, of course, it's more expensive than the paint- but then again wouldn't scratch off if mishandled.

Regards,

_Aaron_

Todd Burch
12-23-2003, 9:37 AM
Keith, thanks for the info.

The first pass he made was as a vector image. Then, he noticed the shifting and converted the image to raster.

The info you offered about 1 pass with the mask is wonderful. I will definitely give instruction for that next time.

I had to match their existing signs, so gold paint was the only option in this case. Would the gold acrylic be inlaid before or after finishing, and how thick? Is gold acrylic transparent/translucent enough to put a light behind it to illuminate it from the back? Would the gold acrylic be proud of the surface?

Do you prefinish wood like I did in this case?

Finally, you used the term "very deep engraving is required"? How deep is "very deep" on Mahogany?

They charged $35 for doing the engraving for the first plaque (2 passes), and redid the second plaque (4 passes) for free.

Thanks Keith, Todd.

Aaron Koehl
12-23-2003, 9:51 AM
Keith, thanks for the info.

The first pass he made was as a vector image. Then, he noticed the shifting and converted the image to raster.

Vector graphics always engrave with a more pristine edge over raster images. Of course, this isn't to be confused with the vector (perimeter) cutting mode of the laser, which can't be used for solid fills. I try to use vector images whenever possible, or very high-res edited raster images.

The info you offered about 1 pass with the mask is wonderful. I will defitately give instruction for that next time.

I had to match their existing signs, so gold paint was the only option in this case. Would the gold acrylic be inlaid before or after finishing, and how thick? Is gold acrylic transparent/translucent enough to put a light behind it to illuminate it from the back?

I would say to inlay acrylic after finishing, but Keith would know better in this regard.

The gold mirrored acrylic is opaque, but there are many translucent acrylics out there that take illumination beautifully. Vector cutting the acrylic will also free up the design for script and more ornate designs--when using a mask/paint, text has to be pretty plain and thick as it is tough to paint thin lines in the mask (even with aerosol). This is especially true of text, as any imperfection in text characters are easily discernable with the eye.

Do you prefinish wood like I did in this case?

Prefinished and lacquered woods are great for engraving, as they do allow you to burn deeper and get a 'prettier' burn, as the smoke residue wipes easily off of finished materials. The raw woods aren't so lucky, and require different engraving technique.

Finally, you used the term "very deep engraving is required"? How deep is "very deep" on Mahogany?

Very deep is between 1/32" and a 1/16".

They charged $35 for doing the engraving for the first plaque (2 passes), and redid the second plaque (4 passes) for free.

It's good that they offered to help you out. This piece looked to be 10 in. by 3 (in that neighborhood), with the text itself and preparation being pretty plain. That's in the ballpark.

_Aaron_

Todd Burch
12-23-2003, 10:04 AM
Aaron, thanks for your reply too. I think you are right about both a machine problem and about the inexperience. The first plaque was done by "M" and the second by "G". I looked for "M" on my second trip over there and "M" had just been laid off (3 days before Christmas...) so "G", the CEO, did the engraving. (But what do I know - "G" could have done it the first time too... but the technique used was certainly different the second time).

They have 4 laser engraving machine. 2 are huge, stone engraving machines, 4' wide and as long as the material needs to be. The other two are roll around, 18" x 36" and 24" x 36". I think the machine they used for my project was 100 watt, while the small roll around was 80 (or 50?) watt. He mentioned it, but it escapes me.

The first plaque did have a LOT of smoke damage on the resist. The second had ZERO smoke damage on the resist. They did like you mentioned and did a high-speed, low power pass just on the resist to show me where it would cut. It was not centered so they moved it about 3/16". I asked if the resist would still work optimally as a paint mask, seeing how it was burned some. He was not sure, so they replaced the resist mask before proceeding with the actual cutting. There wasn't a big difference in the speed between the alignment pass (just on the mask) and the actual 4 passes he made for cutting - it went very fast, perhaps about 10-12 minutes per pass.

He did not have an air nozzle on the head, but did have a small Penn State blower unit sucking all the smoke outside, which seemed to be working OK.

He did not "roller" the resist down. There were variances in the "color", so some areas were not down as much as others. I would say it adhered good (it was dark, not light) around 70% of the area.

So, let me know when you get a bigger laser bed! I would have rather you guys done this job!

The client, when they saw the first plaque, went goo-goo over it (the deeper engraving, the crisp edges, and my wood work - which the latter is the only common thing between the two plaques now...but hopefully I'll woo them with the finish job...) and asked if logos could be handled. So, I think they'll order a whole new sign board, but I don't need these kind of hassles on the next job.

I'll post a close up after while. Thanks Aaron. Todd.

Todd Burch
12-23-2003, 10:08 AM
The plaque itself was 6" high x 32" wide. The letters are 1" tall. On the first plaque, the engraving was just over 1/32" deep. On the second plaque, it might be 1/64" deep.

Todd.

Todd Burch
12-23-2003, 11:01 AM
OK, here are several pictures.

First, these are 3 signs. The "Suite" sign is the one the client loaned me to use as a model. The "raw" sign, in the middle, is the first plaque the engraver cut with the wrong size letters. Notice the gold paint where I was experimenting with a color match for the gold paint. The bottom sign is the one that gets delivered today.

<img src="http://www.burchwoodusa.com/miscpix/commercial/sign_all3.jpg">

Notice the "Suite" sign, on the top right, the wavy wood.

Next is a closer shot of the "Suite" sign, showing the current quality of their signage.

<img src="http://www.burchwoodusa.com/miscpix/commercial/sign_Suite.jpg">
Finally, a close up. Crapola.

<img src="http://www.burchwoodusa.com/miscpix/commercial/sign_Suite_close.jpg">

This is the engravers first engraving on the "raw" sign. Note the crisp walls. I was very pleased with this one.

<img src="http://www.burchwoodusa.com/miscpix/commercial/sign_walls_1.jpg">

Now, here is the final engraving. Yuk. I'll address the sloppy paint in a second...

<img src="http://www.burchwoodusa.com/miscpix/commercial/sign_walls_2.jpg">

Sloppy paint - best I could do. I mentioned earlier that the machine was shifting over each pass. In this final image, here are the results.

<img src="http://www.burchwoodusa.com/miscpix/commercial/sign_T.jpg">

At both "A"s in the picture above, this overspray is how much the machine drifted on the final pass and where it burned away the resist. I was able to scrape away some of it, but in some places I just left it.

The section along "B" is where 1) the resist was burned away and 2) the finish got gummy. I did the best here I could in cleaning it up. Noone will be looking at it this close.

Finally, at "C", you will see a deviation in the cutting along the right vertical wall of the "T". Again, this is where he adjusted the engraving mid-way between a pass. Not a crisp wall at all, but the gold paint hides it.

The finish between their sign and mine, while a close color match, certainly does not have the same depth. Their sign is very muddy which is characteristic of a gel stain. What's the point of using Mahogany when you are going to finish it that way?

I'll report later how they accepted it. Todd.

Brad Schafer
12-23-2003, 5:30 PM
okay, i gotta ask ... what exactly is a "PC"?

signed,

dopey

Todd Burch
12-23-2003, 5:51 PM
Professional Corporation. I didn't know either!

Chris Padilla
01-29-2004, 12:40 PM
okay, i gotta ask ... what exactly is a "PC"?

signed,

dopey

Politically Correct??? :p