Some time ago I thought I came up with an original idea of a laser tool path displayer, only to be shown that they already exist. The advantage of such a device is that it displays the tool path the exact position that the machine will cut. This means you can safely know where to screw down your work and not cut though a screw, also you can use scrap bits of timber and know if your work will fit into it.
Obviously it would need to get the information from mach in order to display the path.
I was wondering a few things........
Would any one be interested in designing the laser device and posting a build guide.
Could Mach be made to do this ?
Do any of you see an advantage of such a device?

It should be quite cheap to make using a $10 dollar laser a mirror and some soliniod device.

Any thoughts?

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You are a sick man

Benny,

why not get hold of a disco laser and rob the lens system out of it, most of them use steppers to drive the mirror so you could connect the two steppers to your PC.

Mach should drive it OK.

The trig to point the lens in the right place is going to be the hard bit!

Graham.

Someone in CNCZone posted this link http://elm-chan.org/works/vlp/report_e.html
Looks like a good head start , but not as cheap as I was hoping .

Brian, I know why you say that. I dream up the ideas, and expect guys like you to make them happen.
Hows that coil winder script going? ( Whip whip )

Benny,
I used to design and build Professional Laser display hardware. I can give you a little info on this stuff.

First, it is a great idea. I thought it would be nice too.

The problem in the laser world is nothing is cheap. Pro optical galvanometers (scanners) are ~$1500 a set without power supply, a nice 635nm 10mw (red) laser diode is ~$50, now you have to have something that can drive the galvos ~$2000 and up.

Scanners use a balanced +-10v pp analog input,no step and direction here.
The other problem is your scan rate has to be high enough for the persistence of vision trick to work. If not you just see a dot running around. you also have to have galvos that have a high scan angle ( or a really tall ceiling)
 There is some cheap Chinese patent infringing knock-off stuff that probably be kluged together but that is still in the ~$600 range and you still have to figure out how to get g code to scanner.
Another issue, mach 3 is not fast enough. You could probably tweak a grex and use the analog output, that would get you closer to the 20,000 to 80,000 points per second the good stuff runs at.  i think the g rex analog out is only 8 bit though. In other words you would only have a resolution of +128 -128 for a total of 256 x  by 256 y. But the good news is you could modulate the laser intensity to simulate depth.

Scanners don't ever make a full revolution. They are limited to (for good ones) 80 degree optical.
Stepper motors won't work because of... well it is a stepper. You see the detentes. You could go to a very fine micro step and maybe get sort-of acceptable resolution out of them but then you have the speed problem again. With a gazillion micro-steps you have to send the data that much faster to keep the scan rate up high enough for persistence of vision to work.   

OK, assuming we got all of that worked out we have the, geometric correction, linearity ,focal point size, diversion thing to work out.

What you are seeking is the holy grail for laser nerds like my self. I have spent the last 20 years trying to come up with a $10 dollar high quality scanner set. The systems i used to build were in the ~$250,000 range, unfortunately to do this stuff well ain't cheap ;(

Now on to Chan's stuff. He has spent years perfecting his creation. And i must admit that he has done a bang up job. He is using some very tweaky electronics with an even tweaker feed back system, and getting great results!
There is another guy named Norm and he is building some home brew stuff, inspired by Chan.

http://24.200.192.31:81/LaserShow/LaserShow.htm

He is using a much better (simpler)  feedback system. He is also doing great stuff! I have my own version on the back burner but the mill is eating all of my time.

A cheap video projector taped to the roof would work just as well and be a lot cheaper!

Any way it is fun to think about, let me know if you come up with anything ,we will make millions.

Chad
 

Yeh I have come to the same conclusion Chad.
I cheap video projector would do the trick. Use a dual screen setup of Mach, make a long Mach screen that spans across the two monitors, and have the current tool path display, show on the second monitor.
This option can be done NOW with no programming needed and just a video projector.

I still like the idea of flickering lasers though. Pity about the expence and complication of getting it to work.