I’m new to laser engraving and thus this might be an obvious question. I’m trying to engrave text on a piece of wood using offset fill. For some reason however there are alwasy missing spots in the center of the letters. I’ve tried with different fonts and different setting of the layer, both on/off for constant power and several variation between 128 and 512 lines per inch. All give approximatly the same result as seen in the pictures below. Funny the preview also show the white spaces in the middle
Am I missing something or this is how offset fill should work ?
On another note, I’ve also tried to do a normal fill but I hit another problem the laser was missing the borders of the letters creating a mothing blur effect. Even on the slowest(600) speed and with 5% overscanning it didn’t do much better.
If the distance between the perimeter lines is not an exact multiple of the fill’s Line interval, then there is no way to completely fill the remaining space: one more line won’t fit!
So, yeah, that’s how Offset Fill works and why it’s only recommended for special situations.
Because it’s a diode laser, it most likely has mechanical backlash that requires fixing:
A more detailed guide for Sculpfun lasers will give you more suggestions, including the myriad screws holding everything together:
The usual cause is having a setscrew holding a pulley to a motor shaft become slightly loose.
Run this test on cheap cardboard at suitable speeds to verify your work:
I’ve managed to solve the text issue by using normal fill with bidirectional-fill turned OFF. It looks like the two passes are miss-aligned for some reason.
Do you think this can still be related to mechanical issue ??? Also the laser is brand new, so I would not suspect any mechanical problem, may be loose belts but I did a couple of checks and they look ok
To reduce the gaps in offset fill, you can adjust the line interval. Mine runs normally at 0.1 mm. What was yours set for to get that large gap? A different font may also alleviate some of that issue.
I like to use offset fill for text because it gives a very nice outline. I encourage you to try some adjustments before you turn your back on the offset fill.
Your blurry fill text is from the machine needing a tweek to the timing. Left to right it is burning in a different place than it does right to left. That is adjustable from the software
Try as many different things as you can, so you will learn how to make the program and your laser work together.
That suppresses the symptoms by having the laser head move in the same direction across all the scan lines.
Diode lasers generally move slowly enough that the laser doesn’t lag behind the motion. The offset in your pictures looks to be on the order of a millimeter, which is much more than any possible delay due to the electronics.
“Fixing” backlash with a timing offset hides it by adjusting the timing to match the backlash. If you measure the offset at a wide range of speeds and find they’re all pretty much the same, that’s the amount of backlash.
Yes.
Not to sound dismissive, but that assumption is totally wrong.
I’m glad you were able to get satisfactory results with the scanning adjustment. I believe @ednisley is also correct though.
The amount of offset shown in your picture looks excessive and is probably the result of a mechanical issue. The scanning offset just masks it. The fact that the machine is new is even more reason to believe that something is loose, etc. as quality control is almost non existent.
When you have time, run through the mechanical testing he linked and then red othe scanning offset. A little play/slop/backlash is almost unavoidable, but I think yours is excessive.
After adjusting the scanning offset both passes are on spot