Banding on solid black fills.

[Dan Kozakewycz]

I am having issues with vertical banding when engraving anodised aluminium. Initially I noticed this when trying to engrave a photograph but have now discovered it to be an issue on black vector fills, which rules out artwork as the cause of the problem.

Here is the banding under the loupe



I engraved the same black filled square twice, one above the other but slightly displaced in the X axis. The banding appeared in the same location on the X axis, which again rules out the artwork and points to an issue with the laser, at certain points on high power settings the dot size appears to be fluctuating.

I know from searching this forum that these issues are rarely solved but I was hoping that having ruled out the artwork, there might be a narrower band of possible causes for the issue?

Cheers

Dan

[Michael Hunter]

Unless the bearings and belts on your machine are supernaturally perfect, there is likely to be some oscillation of the lens holder following each change in direction.
You might be able to prove whether this is happening to you by doing a wide engraving, rather than the tiny square.

Fixes are :
Use a higher resolution.
If already at the highest resolution, slightly de-focus so that the beam is a bit wider.

[Dan Kozakewycz]

It will do it on wide engravings too. The photo I was doing was A3 size and the banding was noticeable in the lighter areas.

I will give a higher resolution a go, hopefully that will fix it.

[Scott Shepherd]

Dan, can you report your settings? DPI sent over as, speed/power/ppi, all the settings in your "advanced" settings.

[Dan Hintz]

Looks like the dot size is fluctuating on initial entry into a line (getting the tube to start lasing is not fast enough), so you may need to turn up the tickle a tad... you can see that every other line is leaving an entry mark, which says the end of the line is still at the same power as the middle, but the beginning isn't up to full power.

Second, it looks like you're getting full coverage (so dpi is good), but that also looks like bare aluminum... until you post your power, I'm going to guess you have your power way too high and you're completely blowing away the oxide layer down to bare metal.

[Dan Kozakewycz]

Hi Dan

I know you're an advocate of using low power on anodised aluminium, but I did a test ramping down the power from 100% and 70-100% produced much the same response, 40-70% produced varying (darkening) shades of silver and anything below 40% produced absolutely no mark whatsoever. This material needs quite a lot of power to produce a decent mark I have found, your recommended settings of 20P/100S did not work at all. Perhaps you're basing that on a much more powerful laser?

I also tried 100% and decreasing the speed, which again didn't produce much difference!

Good analysis though, I hadn't noticed the entry points. How do I adjust tickle settings in JC 10.3?

[Dan Kozakewycz]

Scott, settings were 333dpi, 100P/100S, DPI 1000, correction 20.

[Ross Moshinsky]

Increase to 500 DPI. Speed up the laser 5%.

[Dan Kozakewycz]

How do you mean, it's already at 100%?

[Ross Moshinsky]

How do you mean, it's already at 100%?

It's a rule of thumb. If you can't speed up, then you use less power. Same idea.

[Dan Hintz]

Hi Dan

I know you're an advocate of using low power on anodised aluminium, but I did a test ramping down the power from 100% and 70-100% produced much the same response, 40-70% produced varying (darkening) shades of silver and anything below 40% produced absolutely no mark whatsoever. This material needs quite a lot of power to produce a decent mark I have found, your recommended settings of 20P/100S did not work at all. Perhaps you're basing that on a much more powerful laser?

I also tried 100% and decreasing the speed, which again didn't produce much difference!

Good analysis though, I hadn't noticed the entry points. How do I adjust tickle settings in JC 10.3?

I never provided you with any initial settings, so I'm not sure where you got the 20P/100S settings from (it's what I used on my ULS with a cartridge measuring 70W+)... if you pulled those from another thread, then I based those settings upon the power of the system used in that thread (probably mine). We don't know what machine you have (and therefore the max raster speed) or what power cartridge you're working with, so we can't suggest appropriate power/speed settings. If you're working with a 140ips Trotec Speedy with a 60W cartridge, I'd suggest something in the area of 40P/100S.

You're at 333dpi, which has significant overlap on a 2" lens and should be okay for simple shapes like the square, but for high-definition images I'll typically use 500 dpi (or thereabouts).

[Scott Shepherd]

Scott, settings were 333dpi, 100P/100S, DPI 1000, correction 20.

Correct should be at zero for rastering. I'd also do the 500 dpi. Your wattage is a little less than ours, so I'd guess that you'd be at 500dpi, 70% power, 100% speed, and 1000 PPI.

Correction used to be for vector only, so there was a default value in that field. In 10.2, they made it have an impact on rastering, and it's generally a value you want at 0, unless you are having specific issues where you need to bump it up, but I'd start at 0.

Don't worry about the tickle for now. Let's get you engraving with the right settings before you start messing with anything else.

[Dan Kozakewycz]

The correction factor was actually set by the Trotec engineer when he was here setting it up. In honesty, I don't know what it does, but as he recommended it, I have left it as is!

[Dan Kozakewycz]

Sorry, I picked up 20P/100S from another thread, yes. Mine is a 40w Speedy 100 (180cm/s maximum speed I think).

[Scott Shepherd]

The correction factor was actually set by the Trotec engineer when he was here setting it up. In honesty, I don't know what it does, but as he recommended it, I have left it as is!

Dan, the correction factor had a change come to it, so what used to be right is now wrong. Please change it and start there. You should NOT be starting with any value in the correction for rastering. Vectoring? Yes. Rastering? No. It WILL cause engraving quality issues if you have it set too high (or anything at all in some cases).

Please try it at 0 and if you believe it makes something worse, then simply change it back. Or, better yet, copy that material, name it something else like "experimenting" and then change it to zero in that one so you can always go back to what he set it at.

This change causes me headaches. With a value in there, it can mess up how text (or anything else) engraves and since it defaulted with a value in it (which it did nothing in the past), now it's default is set to a value, so it messes things up by DEFAULT. They need to change that default value to zero since they changed it's function. It's a bug, in my opinion, that needs to be corrected.