I’m doing a 30 pass deep engrave of a Brass coin. The part of the design in question is simple words with in a circular form towards the outside of the coin. The engrave is the area around the text. I’m seeing an inconsistent engraving ( bands) in the horizontal and vertical passes. The effect follows if I change the engraved angle. I thought that it might be focus related but have not been able to change the outcome with that. I see a “Auto Rotate” selector and have turned that on thinking it would switch up the angle and reduce the effect that did not appear to affect it. I thought that I could add a cleaning pass as you would on the 3D slice sequence but it looks as if the only way I would add a cleaning pass would be the sub-layer option but not sure how to interject a cleaning every few engraving passes as you would in the 3D slice. The
“banding” is evident on every pass and becomes cumulative. I’m certian I’ve missed something. Looking for suggestions on this effect or potential ideas to mitigate.
TIA
David
Edit: Just thought of “Global Passes” as one of the potentials to add a cleaning sub-layer. Running both layer 30 times. Trying that when the machine frees up.
Edit 2: while adding the ^ thought, I just saw the “angle Increment” … Duh. Still looking for suggestions or thoughts. I’ve not tried either as of this writing.
A cleaning layer could help… Sometimes the fiber will weld debris back onto the object. I had to add an air assist to prevent this on some of my coins.
thanks for the response. I’ve added a cleaning pass and it is much better. The source worries me. I wonder if there is debris in the laser housing that is the cause…Edit the first few runs did not demonstrate to this extent
I did a few things at the same time (tired of wasting raw materials). 1) selected “Auto-Rotate”, 1a) Changed the angle increment (10deg) on both engraving and cleaning pass. 2) Made the engraving and cleaning passes different scan angles (45, 0). 3) Added crosshatch to the cleaning pass 4) Tried a few cycles with 2nd cleaning pass at a different scan angle but deemed it unnecessary as the first thee changes look as if it resolved the issue. 5) I also varied the cleaning pass settings on test passes (still learning there). Made a list of items to follow up and test but don’t want to get to far distracted.
What I saw in this piece and its design was without cross hatch parts of the deep parts of the engraving did not get the benefit of the cleaning pass, the cross hatch was a second pass from the opposite direction and caught those parts. Without crosshatch there was a “shadow” left all on the same side of the piece at a certain depth. I’m still considering how and if that effect can be used. The whole project left a list of follow-ups like that. I plan on doing more of these so it will give an opportunity to discover more.
The “banding” appears to be an artifact of the lens and focus height, (given the same power/speed settings etc.). The first indicator was this artifact (or similar) can be replicated somewhat when you conduct a “focal height optimization” test (Moving the head while engraving using the sight and sound method). This was a 70x70 lens at 90% power and the artifact stayed with the orientation of the engraving pass. If the focal height is changed slightly you can affect the artifact. Currently up and running still with all of the changes but added a slight focal height adjustment.
Still looking for a “downside” to the cross-hatch cleaning pass with the exception of added engraving time.
