Tuning The Focal Length on The Stock 2" Head
This documentation is specific to the Thunder Nova series stock 2" (50.8mm) focal length lens assembly.
We have typically used 6mm (1/4") as the reference for focus but it can vary. Thunder Laser actually specifies the focal distance as 4.5mm~6.5mm:
The information immediately below is from the OEM Document and references the Thunder OEM HR head, NOT the TL-USA Beam Buddy HR Head. That data is greyed out. For a comparison of the 2", OEM HR head, and the TL-USA Beam Buddy head, see the attachment at the end of the article linked here: Dot Test-2” vs. US-HR (Beam Buddy)
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TYPE
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DOT SIZE
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FOCAL DISTANCE
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FUNCTION
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STANDARD 2"
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0.0039″(0.099mm)
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4.5mm~6.5mm
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Cutting material less than 10mm, Engraving photos within 500 DPI
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4"
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0.0039″(0.099mm)
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9.0mm~11mm
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Cutting material more than 10 mm
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HR (HI-RES) HEAD
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0.0078″(0.198mm)
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3.0mm~4.0mm
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Engraving photos up to 1000 DPI, cutting material less than 1mm
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Additionally, the acrylic that comes in the toolbox is not exactly 6mm thick, it's more like 5.93mm.
So what this means is, while the 'out of the box' configuration is likely fine, there is some fine tuning that can be done to ensure your foc.
The first step is to understand focus.
Here is the full article:
Now you need to find your optimum focal point. The standard way to do that is to to a 'ramp test'. This is where you vector engrave a line across a ramped surface so you can identify and quantify your optimal focal distance.
A ramp test can be tricky on a Thunder. since the head is designed to be somewhere around 6mm away from the surface of the material, you don't have a lot of room for error.
LightBurn has a built-in focus test. You must be sure to set it up correctly or else you risk a head crash or other issue:
https://forum.lightburnsoftware.com/t/focus-test-questions/15152
Here are the links to some discussions on focus the test:
https://forum.lightburnsoftware.com/t/focus-test-questions/15152
https://forum.lightburnsoftware.com/t/how-does-the-focus-test-work/6655
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