Lenses …. again

So why do we have all these different focal length lenses?


50.8mm, 63.5mm, 101.6mm, 127mm. What does this mean? 

Well, if you go back to the days of old, inches were the way to describe length.

1" = 25.4mm

so the numbers mean:

50.8mm = 2"

63.5mm = 2.5"

101.6mm = 4"

127mm = 5" 

These refer to the focal length of the lenses we use and sell – others may also be available.

In the 3040 / 6040 Corellaser-controlled machines, the standard lens is 18mm in diameter, and has a focal length of 50.8mm. We cannot change this for various reasons – mainly because the lens holder does not accommodate a different focal length.

In the Ruida-controlled machines, the standard lens is 20mm in diameter, with a focal length of 63.5mm. These can be changed – but, there are some "gotchas" to be aware of.

The only reason to go with a shorter focal length would be for greater precision, so if your client only cuts say, acrylic, and they need accuracy of 0.2mm, they may need a shorter lens. However, the 50.8 in Corellaser machines, and the 63.5 in Ruida machines are more general purpose lenses that will work for most applications.

Clients may need longer lenses however, to cut through thicker material. This is when we use 101.6 or even 127mm.

However – care needs to be taken. The 101.6 lens will (just) work in the standard lens holder tube, but it is preferable to use a flatter nozzle. A 127mm lens should have a longer lens holder tube and MUST have the flatter nozzle.

Always confirm that the client has a lens holder threaded at both ends so the longer focal distance lenses can be put at the top – and preferably sell a complete lens holder and flat nozzle with the longer lens so the client does not have to mess around and probably damage the lens while changing it.