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Rich Harman
12-16-2013, 6:34 PM
My Reci 80W tubes are constructed such that they have an inner glass tube (that the cooling water flows through) which is supported only by a single small vertical glass tube at the back and another single vertical tube at the front. For proper cooling flow the tube must be oriented with these support tubes vertically. If this tube were mounted in a traveling gantry it seems that the inside tube would be susceptible to breakage when the gantry accelerates aggressively - such as when vectoring small details where the gantry is moving so quickly that it appears to be vibrating. If the tube were rotated 90 degrees then the supports would be in line with the acceleration forces - which would seem more desirable.

My question is, is anything special done when fitting a glass laser tube into a gantry, or are the tubes just fine without any alterations?

Dave Sheldrake
12-16-2013, 6:42 PM
Tubes are fine in mine Rich, I have 150's and 180's in gantry mounts. much over 50mm per second and gantry machines start to struggle but their acceleration length settings are different to chassis mounted machines anyhows so the forces applied are over a longer time period.

For example a line 5mm long in the Y-Y axis even if it is set to 100mm per second won't actually reach that as the acceleration distance is too short for the motors to achieve anywhere near that. The belts, motors and gears are a lot bigger but the top speed of flatbeds is very often slower on an average.

cheers

Dave

Ernie Balch
12-16-2013, 8:37 PM
Why mount on a gantry when mirrors are so much lighter and you can have the laser tube in a fixed location? Lots of mass means slow acceleration. The fastest engraving machines have put a lot of effort into keeping the moving parts very light. Running water lines to a moving glass tube might cause a problem with stress on the connections and even flow of cooling water.

Rich Harman
12-16-2013, 9:11 PM
It makes sense for larger machines, not intended for speed. The farther the beam has to travel the less forgiving it is to misalignments. When gantry mounted the beam path remains relatively short. Having the tube in a fixed location would mean a beam path almost 3 times longer. Also, the beam can be confined safely inside a gantry, an enclosure for large machines is not practical. I am sure there are some other reasons too...

Dave Sheldrake
12-17-2013, 9:25 AM
On the 25 series HX machines the first two mirrors are within 6 inches of each other, worst case scenario if the tube was chassis mounted is a beam path with 2.5 meters in between mirror one and two. At that distance optical movements and divergence can be a huge problem.(there are other technical reasons of why long beam paths are counter productive to both form and mode)

At 1 degree of angular change on a mirror the beam at the next mirror moves 43 mm's. (the mirrors are 30mm diameter on gantry machines) the spot size also increases by a huge amount at that distance. At 150 mm distance the beam moves 2.6mm at the second mirror per degree of angular change.

As Rich said safety is also an important consideration, a 2.5m beam path that isn't enclosed is going to be a pretty big hazard for users. Big machines aren't really designed to be used as engravers, most have big number tubes and long focal lengths making them less well suited to fine detail work.

Big engravers like my Vytek use Galvo heads and moving beds to achieve speed over large areas but lens costs can be considerable (as well as initial machine price)

cheers

Dave