Advice on whats going wrong here..

[Kieran Mannings]

http://img697.imageshack.us/img697/8369/iffy.jpg


I can do a whole bed of these engravings 18 peices exact same design, but usually one comes out like this with miscoloured lines the rest will be perfect. I'm new to the whole world of laser engraving so any help would be appreciated, machine is a Trotec Speedy 100. Any help would be great :)

[Larry Bratton]

What is the material? Looks like it may not be completely flat.

[Dee Gallo]

To narrow it down a little, some questions:

1. is it always the same one in the same place on your table?
2. is it always the same stripes in the same place in the same color?
3. have you checked your table level lately?
4. are the pieces heavy and possibly unevenly spaced to make the table unlevel?
5. were the pieces taped together and this is from the residue?
6. were the pieces machined and the substrate possibly irregular on the surface or have oil or something on them?

It would be helpful to be able to determine if it is the laser or the document or the substrate causing the problem. Have you tried running a test using some other material to see if happens?

I know I'm not a lot of help, but I have a lot of questions!

:) dee

[Kieran Mannings]

Hi,

Thank you for your replys.

The material is flat, it is brushed aluminium.

1. is it always the same one in the same place on your table?

Certain positions are more prone to it, the lines normaly occur when the laser starts a new engraving next to the current one that is already running as the second starts a little futher down the page.

2. is it always the same stripes in the same place in the same color?

Strips occur in different places, mostly the same colour.

3. have you checked your table level lately?

I dont think there is a problem with level of table but shall certainly check that out.

4. are the pieces heavy and possibly unevenly spaced to make the table unlevel?

Items are not heavy, would not effect table.

5. were the pieces taped together and this is from the residue?

The items have never been taped together.

6. were the pieces machined and the substrate possibly irregular on the surface or have oil or something on them?

The peices have been machined, they are cleaned before being engraved. Substrate could be irregular I guess..

Thank you for your help! Any further advice much appreciated..

[Jon Colley]

Try going to Settings>Options>Process Options>Quality and turn on High Quality Engraving mode.

Let me know if this fixes the issue. If the material is very sensitive, this can help.

[Kieran Mannings]

Unfortunately I don't think I can activate that because I only have the basic version of job control, is it worth upgrading to expert? I've not missed any features from expert so far.

Kieran

[Dee Gallo]

AHHHH - aluminum! That has always caused trouble for us. It seems to conduct differently at whim. You're going to need more expert advice from those who have experience if you're going to get controlled and consistent results. How big are the pieces?

Sorry, dee

[Kieran Mannings]

Dee,

No problems :) I guess it could just be down to material but on a normal run 17 will engrave fine one will turn out like that.

It just would be good to cut down on waste, when I do small runs one or two it is noticable that these marks occur when one peice is already engraving then the laser gets a bit further down the page and the item next to it starts engraving ( as item next to it has a design further down on the surface) then the first engraving will go from a perfect clean engrave to looking like the above, just a bit odd.

The product surface is 90mmX90mm.

Kieran

[Dee Gallo]

Are you using air assist? Maybe there is some kind of gassing occurring which causes a chemical reaction or oxidation in a stripe... shooting in the dark here, it's an intriguing situation. Can't wait to find out the exciting conclusion! Where are all the chemists and metal experts???

[Michael Kowalczyk]

Hey Kieran,
Are you the one I just spoke to in GA? Either way Welcome to the Creek.
Well first thing that comes to mind is--- are your lens and mirrors all cleaned and aligned properly?

Does it happen in the same quadrant or is it all over the table?

example:
1__2__3__4__5__6
7__8__9_10_11_12
13 14 15 16 17 18

(Hope it lines up like I typed it, Well it didn't recognize extra spaces so I put _ in)
So does it happen around the
bottom right(17,18)
top right (5,6)
Top Left (1,2,)
Bottom Left (13, 14)


If you have the master file of the logo, try making a new file and make sure your black is 100% black.

Also make sure your firmware is up to date. I had an issue with banding and an update cleared it. Also what John posted to make it a high quality engraving may help but not sure if that is available in basic. Might be in expert. I don't have my laser on otherwise I would check.

Hey John, is it available in all 3? I have Expert so not sure what does not come with expert.

Thanks and ...

[Richard Rumancik]

. . . Certain positions are more prone to it, the lines normaly occur when the laser starts a new engraving next to the current one that is already running as the second starts a little futher down the page. . .

It sounds like you have them nested together in close proximity so that you can get the maximum parts in minimum space. (Possibly a good strategy to minimize raster travel.)

Maybe you should show us a sketch of the part pattern you are using. But what seems to be happening is that the laser decides it needs to change the length of "sweep" across the table as the next item becomes part of the raster pattern. When this happens, obviously the maximum travel, acceleration and deceleration profiles change. This might be causing the energy that is actually delivered to change. Of course, it shouldn't, but things don't always work the way they should in theory. It could be a firmware bug that doesn't normally matter or show up in most cases with most materials.

It's possible that your material is especially sensitive to energy level - maybe you are hovering around a threshold point. Perhaps a few % drop in energy will change appearance more dramatically than what would happen on most substrates.

I might suggest that you line them up in a regular x by y array instead of staggering, and see if you get a 100% yield that way. Since there is an outer annular "border" on each piece the x-stroke would be fairly constant if you have several parts lined up in each row. What would be the time penalty for this arrangement? Can you still get 18 pieces on the table at a time?

I'm not sure, but I think the high quality mode that Jon suggests makes full-width sweeps for ALL raster lines - thereby guaranteeing constant velocity for each line - if that is the case, it may help. Again, you'd need to determine the time penalty.

[Jon Colley]

Richard is correct. The workaround in Basic mode is to put a thin line (0.005" thick will do) on either side of the job and this will force the laser to engrave the whole width. This will force it to engrave everything with the same speed and the results should improve. There is a time penalty as Richard suggested but with certain sensitive materials you must do it this way to get perfect results.

[Kieran Mannings]

Jon- thank you that is a great idea, I wouldn't have thought of that! I shall give that a go tomorrow. I did a big job today and kept a good eye on the whole engraving process, it does seem that the banding problems occurs when it starts engraving the whole page not 1/6th of it so hopefully that will fix it!

Michael- Lens and one mirror all checked and cleaned today, I will have to do the other tomorrow as I did not have tool to hand to get service panel off. This made engraving a little sharper (must have been dirty) but banding still there.

The problem happens all over the table but as said above it starts when a wider sweep begins ( heres to hoping full sweeps will make consistent engravings! finger crossed)

The vectors are all 100% black, I will also update firmware tomorrow if possible, I think mines a bit behind.

Richard: As you say I think the sweep is the problem, I don't think the parts are specifically sensitive to energy levels as I can adjust power from 65 to 85 with no real different in engraving finish. In terms of layout of parts I don't fully understand what you mean.. they are set out in three rows of 6 pieces at the moment and that covers most of the bed. When engraved one at a time there is not problem, time is not an issue so if a fix means the machine is busy for longer that is fine, but if it means I am busier and have to swap parts in and out then it less desirable as I can be doing other work at the moment whilst the engraver plugs away.

Thank you for your help guys,

I'm hoping cleaning the third mirror, drawing a line around the whole lot so there is a consistent sweep and possible firmware update will sort this out, finders crossed for tomorrow!

Kieran

[Richard Rumancik]

. . . when I do small runs one or two it is noticeable that these marks occur when one peice is already engraving then the laser gets a bit further down the page and the item next to it starts engraving ( as item next to it has a design further down on the surface) then the first engraving will go from a perfect clean engrave to looking like the above . . .


. . . The problem happens all over the table but . . . it starts when a wider sweep begins

Kieran, I am still trying to understand what you meant in both these messages.

Attached are two layouts showing the raster engraving strokes in two hypothetical cases. If you really have a 3x6 array as you say, I can’t understand why there is a problem, as you have almost full strokes across the table. Jon’s suggestion was to add the green lines outside the pattern – but in this case I would be surprised if adding them affects the results, as the difference between the longest stroke and shortest stroke isn’t very much, and stroke length changes gradually as the raster works down the pattern.

Since you said in the first quote that “one piece is already engraving” and then “the item next to it starts engraving” I started to visualize a staggered layout as shown in layout 2. But I could not visualize the full layout. If you have a layout such that the stroke length changes by 100% suddenly, then you may encounter a problem with this engraver. In the second case, with two items staggered, bounding lines as Jon suggested could be added to make the stroke constant, at the expense of laser time, as you are engraving a lot of white space.

You say it happens all over the table, but with a 3x6 array, I don’t see where the stroke length is changing so drastically in that pattern such that it would create a problem.

[paul mott]

Kieran,

Your picture reminds me of the "banding" issue I am still getting from time to time with gray scale images.
From suggestions of others, I am currently working on the mathematical variations in the bit / gray scale patterns but at times the problem still persists.
I am still getting drawn to investigate power variations from the PSU at startup of a line but getting measurements here is going to prove difficult.

I don't know if this helps but this image is typical of the problems I am having, so you are not alone. (the edge of the band is just visible on the bridge of her nose)

Paul.

http://www.cooperman.talktalk.net/files/27_files/image800.jpg