[ynneb]

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?

[vacpress]

ben,

it would seem easier to have the device load gcode and interpret it directly? otherwise mach would need provisions to extract the vector information from the on-screen display and somehow transmit just the area of interest to the scanning head...

i would imagine if someone out there has done a project to draw line-art vector images with a laser, this could be 'easily' adapted.

i would think the real challenge must be having the laser. job start point, etc, line up....

[Geof]

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

I think you are being very optimistic here. It is correct that all you need in principle is a laser and a mirror controlled by two solenoids; actually they would not be simple solenoids but would have to be something similar to a speaker coil which can be precisely moved like a servo. However, there are two big challenges: The first is the angular accuracy required in the positioning of the mirror. The mirror would need to be above the work area by at least twice the maximum dimension to be scanned and the image on the work area would have to be precise to within maybe 0.010". For a 50" maximum dimension this means the mirror has to be controlled to within 1 part in 5000 which is quite precise. The second challenge is doing it fast enough; you have to write a line with the laser spot which means you have to come back to every spot on the line at least 30 times a second in order for persistence of vision to give the impression that a line exists. This combination of precision and speed will not be easy to obtain without some fairly sophisticated engineering.

[slp_prlzys]

check this out, could be a good start. http://elm-chan.org/works/vlp/report_e.html

[ynneb]

Geoff, since its main use would be for roughly knowing the position the tool will travel along, I dont know if the accuracy you are talkning about would be needed.

Slp_prlzys, Thats a very good link indeed. Thanks for that.

Vaccy,
Since I made this post, a friend mentioned the idea of using DLP technology. That got me thinking about another idea. If instead of using a laser you used an old low res video projector. You could then have your computer set up as a dual monitor set up. Make the tool path display on the second monitor. This would mean there would not need to be a math processor thing happening, and is just a projected display of the existing toolpath on the work piece.
You should be able to calibrate it using the lens focas, visual settings, and by moving the video projector the right distance away.

[Geof]

That got me thinking about another idea. If instead of using a laser you used an old low res video projector. You could then have your computer set up as a dual monitor set up. Make the tool path display on the second monitor. This would mean there would not need to be a math processor thing happening, and is just a projected display of the existing toolpath on the work piece.
You should be able to calibrate it using the lens focas, visual settings, and by moving the video projector the right distance away.

Damn, why didn't I think of that :frown: . I had looked into one of these laser systems for my big gantry machine but the price was horrifying. Your video projector idea is terrific. Just abour everything should be available off the shelf. You would need a PC running a simple G code interpreter with some ability to scale the display and just a mounting point for the projector above thre machine. The only minor inconvenience could be having to dim the shop lights because the projector would be further away than normal but even this may not be necessary with a high powered projector.

[ynneb]

Yeh the more I think about it the easier it would be to use a video projector.
In Mach3 it is easy to make a wide screen that spans over a dual monitor setup. If you had the toolpath display that mach already has, on the second monitor, and the second monitor was a video projector, essentially you have every thing you need.

How simple, nothing special needs to be done, cheap second hand low res monitor, and a screen tweak for mach that any one can do.

If anyone wants to give this a try, and doesnt know how to make a mch3 wide screen, let me know and i will do it for them.

I must admit the flickering laser is cooler though.

[Graham S]

You are probably right to try the projector idea but I wouldn't spend too much in case you can't tweak it as well as you would like. Another problem would seem to be that the toolpath view scales with the toolpath so perhaps it would be better to project your CAD, you could draw a box the size of your work table and always put your cad in that, then do view:zoom:window and select the box, full screen preview and you are away.

Graham

[vacpress]

i think you could find old, crude 'overhead projector LCD screens' on ebay.. ive got one i got for free and never used much..

http://cgi.ebay.com/INFOCUS-BOXLIGHT...QQcmdZViewItem

http://cgi.ebay.com/Infocus-1600GS-5...QQcmdZViewItem

http://cgi.ebay.com/nView-ViewFrame-...QQcmdZViewItem

[ViperTX]

Just a thought....but you most likely don't want to see the entire tool path since that would take some time to display that info....maybe just the perimeter or any islands around a place where you could have a fastener....

[plexer]

Why not just mount it instead of the tool and run it really fast around an outline of the piece you are cutting?

Ben

[Geof]

Why not just mount it instead of the tool and run it really fast around an outline of the piece you are cutting?

Ben

And don't blink while it is doing it or you will miss it.

[plexer]

ok maybe not too fast then.

My versalaser cutter if you open the lid turns on a visible laser light instead of the co2 one and it's useful for seeing where your piece will be cut out.

Ben

[dhweizel]

i live in argentina and in recent expo was expossed a cutter machine (for textile materials with a oscilating knife) that displays the cut path using exactly a video projector to a mirror and the mirror is about a meter of the cutting table and the monitor shows the path to cut so the projector and the mirror project them into the cutting material so i can tell that the video projector idea works fine.

Sorry about my english

[joecnc2006]

I still like the OHP aproach, I have a few LCD panels and using an OHP with mirror may work, because you can possition it however you like on the work piece.

[DennisCNC]

I have been working on this idea for a while. This is what I dug up so far. China sells pretty good quality 18Kpps ILDA compatible projectors for like under $400. I found a few sites that make and sell software that can take a DXF file and convert it to a ILDA signal to send to the projector, at least that is what they say. Still trying to contact some of those people to get more details. So far it looks like a system can be built just under $1,000. And it will be as good of quality projection as the $19,000 SL laser that comes with a FREE dell pc!!! When the sales guy told me that the PC is free my hand when for the card :nono:
Now that is profit!

[joecnc2006]

I was thinking a little more on this, why not just print dwg file or tool path onto a transparency then place the work piece vertical and use an OHP to show the tool path on it. Once you have the right distance from OHP to workpiece or wall it will be easy setup from there on with OHP on roller cart.

or just use a mirror above the cnc table and shine the OHP to it and onto workpiece.

Hope this makes sence..