Un-even burning

[Jason Lippert]

In these photos you can see the way the plastic is burning fine in some areas and light in some others. I've done several of these signs today and the light areas seem to be in the same spots regardless of whats on the sign. I've messed around with settings and I'm running these 100sp 80p 300 dpi. The plastic is taped with engravers tape, so it's flat. What's going on here :confused:
My table is pretty dang level. Optics clean. Am I expecting too much to not have to do 2 passes on these? Any suggestions would be awesome.

[Larry Bratton]

What kind of material is it? Rowmark, IPI, type? and what is the cap thickness?

[Brian Robison]

Hi Jason.
In the photo it looks like it was started before the tube warmed up or with the lid open.
Can you go up to 100% power? It should keep your time the same. Increasing dpi would help but 300 dpi should be fine and increasing dpi would slow the cycle.

[Jason Lippert]

Well the material is Rowmark Lasermax, .003 Cap Thickness. As far as the tube being warm, the laser has been running almost non-stop for around 4 or 5 hours.

[Joe Pelonio]

Wow, I'd not expect that on a 75 watt. When that's happened to me it's always a focus issue. More often than not it's warped material, but it also can be caused by low spots due to wear on the vector grid honeycomb. Try taping it onto a sheet of sacraficial 1/4" material, like MDF, then re-focus and try again.

Oh, another time I found that a small hunk of a previous job had fallen between the vector grid and table, causing it to be out of level.

[Larry Alles]

Jason,

This happened to me one time and I found that the lens was dirty.
Cleaned the lens and everything lasered fine.
Also try cleaning the encoder strip under the metal hood where the lens goes back and forth.

[Brian Robison]

Hmmm. The reason I mentioned the laser not being warmed up is that the top of the "C" is chopped off as if
it were running without firing.

[Jason Lippert]

Brian, I see what you mean about the top of the "C", but it is engrave bottom up, so it just hasn't finished the top of the letter yet. And Joe, I took a look at the vector table and I did notice a dip in the left side of the table. I wish there were more than 2 support beams under the honeycomb. It would protect from dents etc. much better. Hopefully me flipping the grid will help a little.

[Frank Corker]

Jason, I'll tell you now, the left hand side of your carrier (laser bed tray) is lower than the right. Reasonably easy to sort. At the front of your machine is the white cover which is held on by a few screws. When it's removed you should be able to see the drive belts running across the machine and also see the bottom of the carrier.

Lower the table down to a specific height. Lets use a spray can with the lid on. Put the spray can in the middle on the FAR RIGHT hand side of the carrier as far as it can go. Lower the bed so that the bed is JUST touching the top of can but you can still move it out to the left. Now slowly slide it across to the left and I bet you any money you cannot get it over the FAR LEFT.

Okay, let's assume I am right. Turn the power off but leave the tray where it is. If you touch the belt you will find that it has ribs running across it. Slide your hand (without gripping the belt) to either the left or right hand side, you will see that it goes over a cogged wheel. Using a gentle pressure, slide it off the cogged wheel leaving the belt slack. Now using a bit of finger manipulation (this is not brute force but similar to removing the top off a soda bottle) grab hold of the cogged wheel and turn it. Depending on which wheel you are turning you will find that the table will rise or fall. Manipulate the cogged wheel until the can fits perfectly under the left AND right sides. Slide the belt over (gently) and it will engage the ribs into the cogs.

Run your test piece again and I will eat my hat if it doesn't work. I have lots of hats and I have never eaten one of them!

[Joe Pelonio]

Brian, I see what you mean about the top of the "C", but it is engrave bottom up, so it just hasn't finished the top of the letter yet. And Joe, I took a look at the vector table and I did notice a dip in the left side of the table. I wish there were more than 2 support beams under the honeycomb. It would protect from dents etc. much better. Hopefully me flipping the grid will help a little.
I flipped mine and got another 6 months out of it, but then the replacement from Epilog was only like $30+-.

[Joe Pelonio]

Jason, I'll tell you now, the left hand side of your carrier (laser bed tray) is lower than the right.
Run your test piece again and I will eat my hat if it doesn't work. I have lots of hats and I have never eaten one of them!
Be sure to put some Coleman's mustard on that hat Frank, it'll go down easier.

[Nigel Morgan]

HI Joe,

The table you got from Epilog for $30 was it 24" x 18" honeycomb

[Frank Corker]

Looking at the photgraph this has nothing to do with the honeycomb. He has the solid stainless steel sheet down, that is self supporting and shouldn't be causing this effect without him having seen it. If he puts the stainless steel sheet down and removes the honeycomb cutting piece first and still has the problem I'll be right.

Another even simpler test. Put a golf ball in the middle of the table (not trapped in one of the little holes mind you) and if it runs to the left, the table is out.

[Joe Pelonio]

HI Joe,

The table you got from Epilog for $30 was it 24" x 18" honeycomb
No, mine was 12"x24", and that's for JUST the honeycomb.

[AL Ursich]

I am a rookie at this but, what would the result look like, turning the sample shown in the picture 180 degrees and burning the sign on sign to half split the troubleshooting. A light image on a previously good burned area will show a Laser Problem vice a Material problem. Half Splitting, Table/Laser or Material.

AL

[Brian Robison]

Hi Joe,
I looked at the standard honeycomb grid for my Mini 18 and got a price of about $150.00!!!:confused:
If Al's laser is made like mine, a damaged vector grid can cause the flat bed (stainless sheet) to not seat properly and be out of level and flat.

Frank, that's a good tip on the table. I'll try that just for fun. BTW, for the golf ball trick to work you'd better have the machine perfectly level, eh?

[Joe Pelonio]

Hi Joe,
I looked at the standard honeycomb grid for my Mini 18 and got a price of about $150.00!!!:confused:
If Al's laser is made like mine, a damaged vector grid can cause the flat bed (stainless sheet) to not seat properly and be out of level and flat.

Frank, that's a good tip on the table. I'll try that just for fun. BTW, for the golf ball trick to work you'd better have the machine perfectly level, eh?
Mine's a 3 year old legend, no stainless sheet, no vaccum table. The honeycomb is just 1/2" or so thick 12x24 so that's probably why it was less.
I hope so, and that it hasn't gone up that much in 18 months since I bought it!

[Jason Lippert]

Although I have not had to run any larger material today. I did check out what Frank suggested. (seeing as there was hat eating involved) I used a large can as suggested and much to my surprise I could slide the can all the way over. Now to be fair, Frank did not specify what kind of tolerance I should give to looking at each side. My guess is that there is a quite small variance. Perhaps a 1/16th or less. I also checked towards the back and front and found everything pretty level. Next I tried the ball trick. I don't have a golf ball here so I tried a foam ball. It stayed wherever I put it. So I guess I'm pretty level. I was really hoping this would give me some answers. On to other possibilities. What about mirror alignment? Too much to think about today. Thanks for the input everyone!;)

[Joe Pelonio]

Bad mirror alignment should result in bad engraving all over.

Now that we know the tables level, check the x-beam. Do a manual
focus, then turn the laser off, move the head around and see if it stays in focus all the way across.

Oh Fraaaannnk! Hope you are hungry!

[Frank Corker]

Jason,

I'm sorry to hear that, the reason why I said it was with such conviction, mine did EXACTLY what yours is doing. Always in the same area (coincidentally on the left hand side too) My adjustment worked. For my mind, the laser beam cannot be striking at the same level on the left hand side and your picture appears to show a slight gradation as it moves over to the right.

Despite my continued belief that it is the problem, a deal is a deal. I have had my hat with a rice and french fries, lightly seasoned with a bit of black pepper. If anyone wants the recipe, please PM me. Do not be offended by caustic replies, which will continue until I leave this hospital.

[Peck Sidara]

Jason,

I think there's too much inconsistency with the bleeding of the red to be caused by one specific thing. Possible causes:

*Laser beam alignment, possibly.
*table level, possibly.
*material not being perfectly flat, possible.

Just looking at the attached images, it appears to me that maybe, just maybe some of the dust that is getting swept back as you're doing the bottom up engraving may be affecting the top word over the first several letters and the bottom word over the first few letters.

Make sure you have the latest firmware and driver.

Whatever it is, it's either something very minor or a series of minor things causing this.

One option is to apply just a tad bit more power or a slight decrease in speed to take the depth just a little lower.

I know it's not the answer you're looking for but it'll give you some ideas. The next step would be to contact our tech support group.