Focal Distance

[Ray Beaty]

What is checking the focal distance and how is it done?

[gary l roberts]

Well, it is the distance from the lens to the work surface. Your laser lens works like an hour glass with the optimal effective area of the beam in the narow band between the two bulbs of the hour glass. Too high ,too low and you lose effective cutting or burning energy.

[walter hofmann]

Hi there
take a piece of thin wood the length or your table put about 1/2 inch piece under it on the right side and cut a line there with very less power
than look where the line is the thinnest and measure there the distance from the ;laser head to the wood plus the thicknes of the wood,
this is your focal distance for max power.
greetings
waltfl

[Mike Null]

Walt

On the machines I've operated you do not include the thickness of the wood.

[Doug Novic]

Many lenses are labeled as 25mm, 50mm or 100mm. This nomenclature is the distance from the bottom of the focal lens to the top of your work piece. I use a 50mm and a 100mm depending upon what I am cutting. The 50mm gives a finer engraving. If you do not know your lens' particular distance check with the manufacturer of your machine. Does anyone out there know of a way to ascertain what lense is which without doing test burns?

[Rich Harman]

Does anyone out there know of a way to ascertain what lense is which without doing test burns?

Yes, simply hold the lens above a table and use it to focus an overhead light to the smallest spot. Whichever lens is furthest away from the table when the the light makes the smallest spot, that is the longer focal length.