acrylic banding

[Rodne Gold]

If things are really bad , it's often largely cured by converting the fill to a bitmap of 90% black.. you can try adding some random noise to the bitmap..essentially you are decorrelating the fill.

[Bert Kemp]

Thanks Rodney I'll try that also

Banding often arises cos the laser puts a lot of heat into the materials and they expand and contract
Try a teeny bit out of focus and reduce your scan gap ..ie a little more gap tween y axis scan lines

[Keith Downing]

Yes I did take it out about an 1/8" it helps a little also.

I usually go a bit more out of focus than that to achieve the "melt" effect. About 1/4 to 1/2" depending on the acrylic and power settings.

Might be too much for your design, but can't hurt to try if you're already testing.

[Michele Welch]

OK, really stupid question, but I've asked it several times and never got a concrete answer. When you say take the lens "a bit out of focus", are you talking moving it up (away from the material) or down (towards the material)? I've never had a straight answer. Forgive the ignorance!!!

[Tony Lenkic]

Michele,

I prefer to move table down but it may be fine either way.

[Keith Downing]

OK, really stupid question, but I've asked it several times and never got a concrete answer. When you say take the lens "a bit out of focus", are you talking moving it up (away from the material) or down (towards the material)? I've never had a straight answer. Forgive the ignorance!!!

Technically you could do either and be lasering out of focus. However, I always move the table further when trying to melt the acrylic by manipulating the focus. And here's the reason.

When you move the material closer, you are actually moving the focal point into the material. So, if your power is too high, you could inadvertantly end up with a focused beam at a point near the bottom of the engraving. When I'm doing this, I want the opposite. I want the beam to kind of spread out and blur the lines ever so slightly as it burns into the acrylic.

But feel free to play with it and see what works best for each individual project. There are so many factors to consider (power, speed, interval, focus, material, air assist, ambient temperature, etc). It's never a bad idea to try different combinations for yourself.

[Gary Hair]

I think this is about the best reasoning I've read for which direction to focus! The other one is that it gives you more room between the substrate and the lens instead of less.

Technically you could do either and be lasering out of focus. However, I always move the table further when trying to melt the acrylic by manipulating the focus. And here's the reason.

When you move the material closer, you are actually moving the focal point into the material. So, if your power is too high, you could inadvertantly end up with a focused beam at a point near the bottom of the engraving. When I'm doing this, I want the opposite. I want the beam to kind of spread out and blur the lines ever so slightly as it burns into the acrylic.

But feel free to play with it and see what works best for each individual project. There are so many factors to consider (power, speed, interval, focus, material, air assist, ambient temperature, etc). It's never a bad idea to try different combinations for yourself.

[Bert Kemp]

After running about 7 different tests I found reducing the scan gap or DPI worked best. Final settings
325mmps speed
40% Power
Scan gap .0847 or 300 dpi
Banding hardly noticeable
Thanks for all the suggestions
This is how it came outSOF FIXED 2 (Copy).jpg

[Bert Kemp]

Thanks everybody its done see previous post

[billy fayo]

i do mostly acrylic work. i get banding about every 2 weeks. all i do is clean my mirrors and lens. works every time. i take the lens out and clean it. not just a quick clean with a qtip.

[Scott Marquez]

Thanks everybody its done see previous post

Wow!!
I missed your your final outcome, watch out Bert you may soon find yourself busier than you care to be.
Keep up the great work.
Scott

[Bert Kemp]

Thanks Scott, I already had someone inquire about doing something similar as a memorial for her father.

[Mike Null]

Bert
Nice work on the layout!