at last installing a 2.5" lens

[sebastien laforet]

my machine has not the "standard" head construction. the tube that holds the lens is way smaller than the classical 25mm tube, so it was not possible to use the tubes with recess at 2.5 and 4" interval from the nozzle. the bottom of the tube is still threaded with a M22, so at least you can connect standard nozzles.

i had not taken care of this at the moment of buying, so i had bought a 20mm/2.5" new lens to test, and a tube for it, and a nozzle (because my nozzle was for 18mm lens). the nozzle was a 22mm thread, so it fit my tube (i could not fit the tube that came with the order to the head, it was too large), but the nozzle was way too short for the laser cone after the lens, so an awful part of the beam was hitting the inside of the nozzle, and the result was pityfull.

somehow, i could test the lens using the ring that olds the lens in place in my old setting : the ring is screwed "upper" the lens to maintain it in the recess of the nozzle. but instead i put the lens upper in the tube, and could use the ring to maintain it "from the bottom". well, the lens was upper, but still not enough. i could nevertheless test without nozzle, and it was mainly ok (for setting focal point and do some test cut) except that without nozzle i could not add air and protect the lens from the fumes...


many months later, i finally got a ring extender for my tube, but even with it, the cone of power was still hitting the nozzle if i put the lens "on" the top of the ring...

finally, using a short nozzle with a large bottom aperture, and using the inner ring to fix the lens at the most upper position in the tube (which it is NOT designed for, but it works), it worked!

and the good news is that not only it works, but i get significantly more cutting power, with less problem relative to focal distance. i can cut at 40mm/s what i used to cut at 27mm/s, and with less burning. is it due to the focal difference (probably), the size of the lens (do 2mm more count?), the quality of the lens (coming from cloudray, same as the 50mm i had already)... the result is here.

next time, i will order one or two more extension rings from cloudray to set the nozzle further to the bottom so it won't get hit by the laser beam, and try to use a nozzle with a smaller hole at the bottom to get more airflow.

i have also to try some engraving a see what sort of precision i get with this lens.


i am disappointed that so much trouble occurred because the constructor of my machine used some non trivial design of the head with a smaller tube that adds no value vs. the standard tubes that you can see everywhere. and, they are not even compatible with K40 design... joy of non-standardization!

[Gene Uselman]

Sebastien, you have been fighting that machine for literally years. It was clearly never designed for a 100w tube. You have my sympathy. Gene

[sebastien laforet]

well, after the initial problems with the frame extension for the 100W laser, the machine is pretty decent. chinese quality, so i have to live with the problems and find my own ways to work-around, but overall i can do a lot for a fraction of the cost of an epilog or trotec.

i am also actively trying to push the limits and find new ways to get more of it, but as a hobbyist with few time for this, the project advances slowly, so the impression i am constantly fighting the machine... most of the time, it works just as expected, so there is nothing to tell about.

i'll try to get more tests on the cutting power of those lenses. i am still very impressed by the gain i had with just a small lens change, and i ask myself why do the chinese vendors continue to ship 100W machine with 1.5" or 2" lenses which are mostly designed for engraving, and not for cutting (and, if you get a 100W laser, it may better be for cutting), where a 2.5" or even 4" lens would do a better job, especially since those lenses are basically the same price.