Mysterious lines appearing

[Ed L Miller]

Howdy all,

Last month I noticed some vertical marks mysteriously showing up after running a text engraving job.

Machine and Software Specs:
Universl Vl-200 @ 30Watts
CorelDraw 12

I start out drawing a rectangle and then type some text, I then center the text vertically and horizontally in the rectangle. I make sure I don't have any guidelines or anything else set for printing.

I then send the job to the printer and hit Start.

As soon as the job is done engraving, I notice that there are two perfectly space vertical lines that were engraved onto the top of the item; typically a wooden box top.

The lines are exactly the height of the text and usually spaced half the width of the text on both sides. Similar to the drawing shown below.

| Hello world! |

The veritcal pipes are the unwanted laser marks that are showing up on the top of the box. They are usually engraved with less power as the text too.

I just did a wooden box top with three lines of text and these annoying lines appeared on every line. :(

I can't see anything on the CorelDraw screen that would cause this. It doesn't happen everytime either.

Has anyone else ever experienced this problem?

BTW- I once had a similar problem with faint horizontal lines engraving across my text as well. It hasn't happened for over a year though.

Any ideas?

Thanks!

Regards,
Ed
No Splinters

[James Jaragosky]

I do not know what the solution to your problem is.
but I would like to point out that I believe that that the link to your site in your sig, is in violation of terms of use of this site. you might want to change that.

[Scott Challoner]

Although I have a LaserPro, it is also 30 watts and has a Synrad tube. If you have a Synrad tube, it may be the same fix. The lines occur when the head stops to change directions and there is a little bit of laser energy still leaking out. There is typically a trickle pulse applied to the tube so it is never completely off while running. I had to change the frequency of the trickle pulse. This is a setting in the machine that is very easy to change. In my case, it would leave these lines only when I was using LaserLights material. Some materials seem more succeptable than others to these marks. I would call your tech support and ask them if this is a viable fix.

[Richard Rumancik]

I think Scott is on the right track. The ULS has a tickle circuit like the Synrad. I found these words in the ULS OEM manual. You should contact them before opening up and changing the setting.

If you laser a graphic with a laser bleed problem, the little lines will tend to follow the shape of the graphic ie. be equal distances left and right and follow the shape.

Many CO2 lasers have this problem. They pre-energize the laser to a threshold just below lasing for fast response, but if it is a bit too high, it fires when it should not.

(GCC calls this "laser leakage" or "bleeding", in one place it was translated as "laser incontinence".)


(From a ULS OEM manual)
5.7 Laser Tickle
It is a common practice with CO2 lasers to provide some means of stimulating the mixture when the laser is off in order to improve its response. ULS lasers have a built in, low duty cycle, secondary modulation signal called a tickle signal to accomplish this effect. This signal is pre-tuned at the factory for optimal performance of the laser and normally does not require adjustment. However, as a laser ages the pulse width and or frequency of this signal may need to be increased. This should only be done with authorization of the ULS service department. If the tickle signal needs adjusting it can be changed using the dipswitches according to figure 11 below. If the tickle must be modified it will be necessary to remove the dipswitch cover near the connector on the laser, see figure 1 for the location of the dipswitch cover.
Warning: An improperly set tickle signal can cause the laser to
produce a continuous beam.

Found at

www.testra.com/laser/ULS%20laser%20integration%20manual%20June%202002.p df (http://www.testra.com/laser/ULS%20laser%20integration%20manual%20June%202002.p df)

[Richard Rumancik]

Ed - One thing I noticed after posting - the GCC info I have shows the lines being little horizontal lines not vertical like you saw. I can't actually remember the appearance of the lines when I has a tickle problem. This is a little puzzling, but check out with ULS and see if they think it is a tickle issue.

[Mike Mackenzie]

Ed,

If you pm me your e-mail address I will send you the instructions on how to correct this issue.

[sunil jain]

I also face problem sometime while engraving graphic.
Horizontal line in right side along with photo is engraved.
Is it a cause due to machine or graphic.

[Bob Davis]

It seems obvious but... Did You delete the rectangle before engraving? If not the machine may be picking up and rastering the outline, even if it's quite narrow.

[Richard Rumancik]

Sunil - Here is a picture of what GCC says an image will look like if the tickle is at the wrong setting ("over-agitated" laser tube). I can't say if it will look identical for every laser tube manufacturer.

Ed says he is getting short vertical lines but Mike Mackenzie has not actually confirmed it is a bleed/laser tickle problem.

[Ed L Miller]

It looks like the C02 bleed/tickle adjustment has solved my problem. Thanks for all the info and MiKe for sending me some good instructions.

Sunil: the problem I was experiencing with horizontal lines was a perfectly straight line going across the graphic image or text. Initially I thought it was the graphic, but then when the text did the same thing; there went that theory. It hasn't happened for a long time. When I first hit the problem my machine was only about a year old; therfore, I'm not sure if it was the laser bleed or something else. It hasn't happened for a couple years now; however, it destroyed about $50 worth of products along the way (mainly tiles). :(

I never saw the type of fuzz around a graphic like Richards pic shows. I think I would have totally freaked out on that one.

Thanks again for all your help...now back to getting my CNC mill engraving. :)

Regards,
Ed

[Rags Alan Ragland]

ED
I had the same problem with my Epilog and found that the drive belt had a nick in it that would slow down the lens head just enough to cause the lines.
Replaced the belt and the problem went away.
Rags




Epilog 36EXT/75W Sand blaster cabinet and Chroma-crystal unit
corelX3

[sunil jain]

Bob, Richard :

lines are some time eliminated when the graphics is converted into grey scale. there is no rectangular border in graphic.

To all in form : Hello and thank you,

I face another problem:

When i mirror image horizontally and vertically the design and then engrave. Some part of the designs are left unengraved. I have to convert the vector design into bmp's then it is done. Kindly help.

[Richard Rumancik]

lines are some time eliminated when the graphics is converted into grey scale.

When i mirror image horizontally and vertically the design and then engrave. Some part of the designs are left unengraved. I have to convert the vector design into bmp's then it is done.

Problem 1: not sure if this is a tickle problem or not. If you convert to grey scale the laser will convert it back to b/w during processing. Could be something else going on but I don't know offhand what it is.

Problem 2: If I understand this, you are trying to raster-engrave filled vector shapes, but when you mirror the image, some vectors don't fill when lasered? But if you convert to bmp bitmap then it lasers okay?

Not sure what would be causing this . . . does it raster okay before mirroring? Have you checked that you are using colors in your vector fill that are recognized by your laser printer driver? Or is it all black fill? Maybe you could take a picture or scan an image so we can see.

[sunil jain]

Richard:
before mirroring, images engraved are perfect. i got the problem with fill 100% black

[Ed L Miller]

I'm Back! :confused:

Well my trickle problem has come back. Per Mike M's instructions I set the dip switches to

001 001

The problem was solved for only about a month, now it's back in full swing once again. I have an order of 80+ boxes to engrave this weekend and what I'm doing is having to place a cardboard cutout just enough to enclose the engraved area. This allows the mis-firing to hit the card board rather than the wood; however, after running the laser for about an hour, it gained power and went through the card board and into the wood. :(
I'm assuming I need to drop the frequency down again on the laser. It's now running at 5.5KHz and 1.5microseconds width.

Should I drop it down to the next step (4.1KHZ and 2.7 microseconds)?

I'm not sure if you change the width when you change the frequency.

Any thoughts?

Thanks
-Ed

[David Fairfield]

I get the occasional phantom line in my rastering. Its not a random event because it always appears in the same place in the drawing, every time the drawing is run though the machine, even after rebooting. Its very frustrating when it appears but I've always solved the problem by cleaning up or tweaking the drawing in minor ways. Sometimes just rotating it 180 degrees helps, or changing the scale by 1%, for examples. Also want to make sure my document dimension settings are trimmed close to the artwork, I've noted a correllation between glitches and emtpy space on the document.

I always figured it was a software problem with Adobe, so I hadn't thought of calling the Epilog tech department. Good to know there are some potentially useful hardware adjustments.

Dave

[william kennington]

I had that problem before but it turned out that the material
I was using (brushed gold) was causing the laser beam to reflect
and hit it in random places causing similar marks. Transfer tape solved the
problem for materials that may reflect the beam.