Does focus height for an engraving/etching job remain constant between varying materials?
For instance, ablating coated metals vs engraving wood. If I have determined a 9mm focus height is ideal for painted aluminum, can I safely assume it’s also 9mm for most everything else?
What about other variables, such as line interval and scanning offset?
I’ve tried to measure line width at various focal lengths and line intervals on wood (using a crack ruler and magnification) but it’s really hard to tell what’s best because of the heat affected zone (overburn, caramelization, whatever one chooses to call the transitional area at the edges of the beam).
Does focus height for an engraving/etching job remain constant between varying materials?[/quote]
Yes and No. The focus height on the surface of the material, say 9mm will be the same regardless of the material. However, if you are cutting something really thick and want the focus to be in the middle of the material, the you’ll have to account for that.
For instance, ablating coated metals vs engraving wood. If I have determined a 9mm focus height is ideal for painted aluminum, can I safely assume it’s also 9mm for most everything else?[/quote]
Yes
What about other variables, such as line interval and scanning offset?[/quote]
Line interval may need to be adusted based on the material and the look you’re going for. Soft white pine versus Hardboard will yield different results in appearance.
I’ve tried to measure line width at various focal lengths and line intervals on wood (using a crack ruler and magnification) but it’s really hard to tell what’s best because of the heat affected zone (overburn, caramelization, whatever one chooses to call the transitional area at the edges of the beam).[/quote]
Get a good quality masking material for laser cutting to aid in the smoke residue. Do a the material test found in LightBurn under Laser Tools. You can change the interval beforehand and again afterwards and go again. It’s hard to give specific settings because of different lasers. Only through emperical data you obtain yourself for your laser will be of use. Yes, the are some basic starting points/settings but to fine tune… well, that’s on you. Sorry.
With coated metals, it’s far more definitive.[/quote]
With my wood tests, I see a color gradient across the width of the line. The middle ~80% of the total width is relatively consistent while the ~10% at either edge of the line is ragged and coloring is lighter compared to the middle. This makes it less clear to me where “good” focus is. I look at a 10mm range and half of the range makes me think, “I don’t know…they’re all pretty much the same except this edge is a bit sharper and that line has more consistent color across the total width.” I even tried sanding to 600 or scraping to help define the edges better. An interval test produces a similar “I’m not sure” result between maybe .08 and .13
With the coated aluminum, the lines have a crisp edge with no gradient. They simply get wider or narrower. I can very easily see a difference in width. Same with the interval test; the lines either overlap or they don’t.
I can’t get decent pictures of what I’m seeing. I don’t have a digital microscope. Just a loupe, and trying to get a picture thru that is ugly. Terrible lighting and contrast.
It’s kinda like the difference between two circles, where one has been antialiased and the other has not.
I clamp down all my test cards so they’re as flat as I can get them. Usually less than 1mm.
I have a powered Z axis, so I never did a ramp test in the traditional sense. I have run both the in-built LB focus test and my own variations of the same. Making offsets in .5mm steps from 3mm to 15mm distance above surface. With the aluminum it’s obvious my tightest beam is at 9mm. With scraped basswood (nearly a glossy surface), everything from about 7-12mm is similar with the minor edge variations I mentioned above.
