Saving time on large engraved panels

A question of time:
On panels with a lot of engraved lettering I notice that the time required to burn the panel can sometimes run into hours.

I have seen on the internet a method of refocusing the laser to give a wider kerf and decreasing the line spacing when engraving.

I like the crisp line detail when cutting with a kerf of .2mm so I experimented with engraving with lines.

To compare both methods I set the parameters for both engraving and cutting to be the same.
EG. for cutting: 20mm per sec @ 60% power 1 pass
For engraving 20mm per sec .2 line spacing, 45 degree angle and 1 pass (My kerf is .2mm wide)

Lightburn:
In lightburn I used a script font to measure the varying widths within each letter. At 20 mm high the widest width was 3mm. That meant that to completely burn the 3mm widest section of the letter I would need 7 lines spaced at
.2mm apart.
Selecting the font in wireframe mode I used the offset shapes tool ,set to

  • .22 offset* > inward
  • corner
  • select resulting objects

I repeated this setting 7 times and the resulting text was as below

Using the DISPLAY function it estimated that to line engrave this text would take 45 secs
Using the same text and font , but set to fill, the resulting time was estimated to be 1min 50 secs

This is a saving on this one word only of 65 sec, or 40% Over a large text file the saving in time would be considerable.

I would be interested in hearing from anyone who has tried this method with their resullts and thoughts on engraving this way

Note: I try for a true black engraving that is sharp , not to deep and easy to clean up

John

Edited by Lliam to include text and images from PDF in post.
line engraving.pdf (136.5 KB)

Interesting idea John, I think this will generate a path very similar to the ‘Offset Fill’ layer mode: LightBurn: Offset Fill

Below is a comparison of standard Fill vs Offset Fill:
image
image

The main thing to watch out for with this method is the Speed, as there are typically a lot more direction changes in shapes such as text. If your speed is too high (depending on the shape this can be as low as 600mm/min (10mm/sec)) you might start to have issues with overshoot and/or occultations.
In the example below I have increased the Line Interval to 0.400 and increased the Speed to 2500mm/min (41.5mm/sec) to show what this can look like:

For shapes with rounded corners, or if you are careful with the speed, Offset Fill can be a really good timesaver.

Lliam, Thanks for the reply,
Not having used offset fill before I was supprised as to how similar the methods were. I notice, when watching the laser work that the mumber of lines that make up each letter, waries.
It appears that each letter or shape is filled with different number of lines. Is this a function of the algarithm that creates the offset fill , and if so can it be manipulated. ( I cant see any place where it can be). The reason is to eliminate the faint centre left in the letter or shape.

A further question on defocusing the laser with the offset fill.
Do I use the top of the beam or the bottom of the beam to achieve wider lines.
Or does the emblaser automatically focus back to the rop of the workpiece.

Hi John,

OFFSET FILL:
The line count (or offset count) is set by the Line Interval, based on the outline of the original shape.

The offset is created from the outside-in, with spacing at the Line Interval setting. When the lines become so close that the following offset would over-shoot the centre-line, no more offsets are added in that area.

This can mean that on shapes such as text, with varying widths, you can have some areas where the inner lines land very close in one area, and far apart in another - like in the image below. You can see from the overlay with the green lines at the same spacing, the next offset would have over-shot the centre mark.

Generally I try to ‘tune’ the Line Interval to achieve a compromise between these areas, however sometimes this is not possible with the current iteration of this feature, as you indicated.

DE-FOCUSING:
LightBurn calculates the optimal focus based on the values provide in LightBurn for ‘Support’ and ‘Material’ and the Focus Calibration value entered.

The Z-Offset value will add an offset to the optimal focus calculated, de-focusing the laser.
Which direction you move ( + for down, - for up) does not make much practical difference in terms of beam shape/quality, however you can run into clearance issues if lowering the Laser Unit too much. For this reason I would tend to add a negative (upwards) Z-Offset value.

~ Lliam

Lliam,
continuing our conversation , I have experimented with all forms of fill, using your suggestions.
I have discarded my original idea of generating a line fill as it is the same as the offset fill.
That said I wanted to ensure that there was no small amount of material left in the centre of the text or graphic. My experiments showed that if you enter an amount of 92% of the Kerf in the line spacing, the algorithm will fill completly the text or graphic. (MY kerf is .2mm so I enter.185)
Being concerned about shudder being created with small quick movements of the laser head I dropped the speed to 15 mm sec.
The resulting job was acceptable for blackness in the text and the speed was reuducd to 7 mimutes per job on a plaque of 150mm x 90 mm.

novelty plaque

Hope this helps other community members looking to reduce engraving times.
John

Hi John,

Great results! Thanks for sharing this.