[Epoxy]

Hello,

First off, great forum, already read a lot of stuff here on previous projects. Registered and returned, hope you could advice me on a issues. The following is stone-coal english, im Dutch, sorry.

Currently i'm working on an art project, this project consists of a painting 'battle' with my current project, an XY router capable of holding different tools.

I designed the machine myself. Parts are handmade (frame), lasercut (those pieces needed for precision, on a Trotec Speedy 500) and 3D printed (Mendel90). All the wooden stuff is done cut from MDF, frictional parts are coated with PVA (D3 white woodglue, water diluted) thoroughly in order to resist grease. It's Y motors are mounted on the X-axis itself. All steppers are a 1:3 transmission on a rack, X-axis is 1:2. Racks and gears are also MDF lasercut. The steppers themselves are NEMA17 driven by A4988 drivers. It already might be an obvious point as in design requirements: IT NEEDS TO BE AS CHEAP AS POSSIBLE! I realize that requirements of both laser cutters and CNC machines don't combine with cheapness. Still, i just finished the Y-axis and its supprisingly smooth & stable, so i'm optimistic.

So i used the trotec, asking myself; "why in the **** aren't these machines produced in 'full plate' (244 x 122 cm) format?". I realised later that i was building a larger machine and that it might carry a laser as well (on gantry).

I'm aware of the following things;
- Nema17 is'nt going to cut it when it comes to speed; neither the drivers aren't.
- Using wood for transmission & racks are a pretty bad idea when speeds increase.
- Gantry should be lighter material. In order to reach higher speeds.

My questions;
- CO2 laser tubes and their 'beam divergency' is this going to be a problem in distances over 2 meters. And yes; is this problem solvable with different lenses?
- Why is the focal distance always controlled by moving the table height? Why not change the distance to material by moving the lens on a Z-axis?
- Is there (URL please ), a payable $300 - $600 80W (more = better) watt CO2 laser available. (Yes i Googled, lots of. Does anyone have good expierences with?)

Greeting, Tom

[Epoxy]

Attachment 272278Attachment 272282Forgot the pictures.

[Dean448]

The most important aspect of a machine is laser beam alignment. You are directing a 3 to 5 mm beam down the Y axis and then down the X axis and trying to hit the lens in the center, over the entire table. When the beam goes off center it will be blocked by the cone just below the lens. Even if you don't have a cone your cut accuracy suffers. So the larger the table the harder this gets. I question that something made from wood is stable enough to stay in alignment. Save yourself the time to redo it and use steel or aluminum. By the way you might be able to purchase the 80w tube for 500. Everything gets expensive with higher wattages.

[gavztheouch]

The z - axis is sometimes moved with the laser head.

The larger 2.4m by 1.2m machines have the laser mounted on the gantry and use ball screws to move the gantry around. If you don't need the size build it as small as you can.

[wildseyed]

On a 100 Watt CO2 laser, your dot could be as large as 8mm, and possibly more. A beam expander can distribute power over a larger area of the mirrors, assuming the mirrors are at least 30mm in diameter. Larger machines can benefit from this, but it's not cheap.