total newbee, lots of questions

[Anodiser]

Hi all,
as the subject says, i have absolutely no experience with laser operations, but the more i read about it the more exciting it seems to be.
i am looking into building a 4 axis machine (at a later date upgrading to full 5 axis) to engrave onto anodised aluminium. there is lots of info on the net and on here and i think i have over read (easily done) and am not finding specific answers to questions.
so here goes :
(1) focusing. how critical is focusing ? if an object has some ramp shaping will 5mm matter much ?
i have seen various designs of engravers, some have the laser head quite a distance from the work piece, others have it relatively close, does having the head higher make for less critical focusing ?
(2) controllers / drivers. i see controllers have an out put for spindle power for cnc routers, how are lasers wired in, are all controllers compatible for lasers ?
(3) does lightobject do an all in package and is it relatively easy to set up ? (electroncs inc stepper motors etc)
(4) software: which software is most suitable for overlaying graphics over a 3D object which can ultimately support 5 axis engraving?

sorry for so many questions, but before i diving in head first i like to get things right and future proof first time.

thanks in advance
Clive

[Things]

1. Focusing is very critical. It ultimately determines the resolution and sharpness of your engraving. A 5mm slope may be doable with a long focal length lens, however I'd look at somehow moving the cutting bed so it always remains in focus.

2. Most lasers have 2 control schemes, PWM and TTL. TTL is simple on and off, while PWM allows you to vary the effective power (like you'd adjust spindle speed)

3. Light object currently sells XY stages, I have bought some and you can see a review in this forum. They do not offer complete laser cutter kits at this time, however I believe it's in the works.

4. Not sure about 3D compatible laser software, sorry!

Dan

[Anodiser]

1. Focusing is very critical. It ultimately determines the resolution and sharpness of your engraving. A 5mm slope may be doable with a long focal length lens, however I'd look at somehow moving the cutting bed so it always remains in focus.

2. Most lasers have 2 control schemes, PWM and TTL. TTL is simple on and off, while PWM allows you to vary the effective power (like you'd adjust spindle speed)



Dan

thank you for taking the time to reply. focal length i kind of guessed, and found a great page explaining all http://www.parallax-tech.com/faq.htm
i need to do some more searching on laser control to get to grips with it.
ive found some 5axis laser cam software and am awaiting an evaluation copy.

just one other question for now, stepper motor sizing. i plan to use linear bearings on stainless rod (20mm) for both x and y axis and belt driven, table will be 1200mm X 800mm. what kind of torque should i be looking at ?
thanks again

[geotek]

I can't imagine the optical complexity of using a CO2 laser in a 4 or 5 axis system. I know there are lasers out there that can do it, but my guess they are fiber optic, not gas tube. A laser tube is not like a small spindle motor, even a 60W tube is 1.2M in length.

[Anodiser]

I can't imagine the optical complexity of using a CO2 laser in a 4 or 5 axis system. I know there are lasers out there that can do it, but my guess they are fiber optic, not gas tube. A laser tube is not like a small spindle motor, even a 60W tube is 1.2M in length.

its not a moving head arrangement, its a standard gantry type with rotating 4th axis with another rotary table on the forth axis like this
so no more complex on the optics than a standard machine

[Things]

thank you for taking the time to reply. focal length i kind of guessed, and found a great page explaining all http://www.parallax-tech.com/faq.htm
i need to do some more searching on laser control to get to grips with it.
ive found some 5axis laser cam software and am awaiting an evaluation copy.

just one other question for now, stepper motor sizing. i plan to use linear bearings on stainless rod (20mm) for both x and y axis and belt driven, table will be 1200mm X 800mm. what kind of torque should i be looking at ?
thanks again

Do you mean the round 20mm linear bearings and shafts? If so, I'd recommend avoiding those as the ball bearings inside the bearing tend to "bind" on each other, creating sort of rough movement. This becomes obvious when you're trying to do fine detail stuff.

I build one of my laser cutter revisions using those rod and bearing combos, but quickly ditched it as the bearings weren't smooth enough (and weight became an issue too)

Dan

[Anodiser]

thank you for taking the time to reply. focal length i kind of guessed, and found a great page explaining all http://www.parallax-tech.com/faq.htm
i need to do some more searching on laser control to get to grips with it.
ive found some 5axis laser cam software and am awaiting an evaluation copy.

just one other question for now, stepper motor sizing. i plan to use linear bearings on stainless rod (20mm) for both x and y axis and belt driven, table will be 1200mm X 800mm. what kind of torque should i be looking at ?
thanks again

Do you mean the round 20mm linear bearings and shafts? If so, I'd recommend avoiding those as the ball bearings inside the bearing tend to "bind" on each other, creating sort of rough movement. This becomes obvious when you're trying to do fine detail stuff.

I build one of my laser cutter revisions using those rod and bearing combos, but quickly ditched it as the bearings weren't smooth enough (and weight became an issue too)

Dan

thanks for the heads up,
that is what i had in mind, did you drive the axis from just one side of the track or did you drive doth sides ? i would imagine pulling from one side only will result in twisting and rough running as you experienced.