[ynneb]

Maybe this has been done b4 but I have never heard or seen it.

How many time have you wondered what the actual cutting path on your work piece was going to look like before it was cut?

Have you ever had a sheet with a blemish on it in a small place and wanted to make sure you avoided the blemish?

Have you ever wanted to know where you could safely screw down you work without driving the router through your screw?

Anouncing the "Ynnebulator laser tool path displayer"

Well its more a concept than a finished project. If you had a $4 laser diode and a small mirror on an X,Y pivit that was controlled by rapidly moving solinoids ( Similar to DLP video display technology) With the correct driving electronics you could project your tool path directly onto your work.

The idea is free to exploit by any talented electronics person. I guess it may need to be worked into a program like Mach2 in order to produce an output to show the tool path.

I bet the next post made will be someone telling me its already been done.

[Graham S]

Essentially a difficult project in its own right. A very cool idea but is it needed if you do your drawings within a box that shows the working area of your machine and then zero the machine to that box.

If I could make such a thing I would build a rapid prototyper with it rather than a collision detecter. Assuming I could find a UV laser

[ger21]

Why don't you just buy one.

http://www.carterproducts.com/produc..._id=3&cat_id=7

[ynneb]

Gerry there is a word that rhymes with bird and starts with T.

He he......i had a feeling it would have already been done. Is there anything in this world that hasnt already been invented. Arrrhhhh

[Graham S]

I can think of a reason you wouldn't buy one and it begins with h.

HOW MUCH!!!!!! :O

[arvidb]

I have experience with laser show equipment.

If you were to make a laser tool path display on your own, there are two issues:

1) Unless you are prepared to have a very dark room whenever you use it, you would need more than the <5 mW a standard red laser pointer puts out. And this means expensive.

2) The scanners are very expensive if you want any accuracy at all.

I actually tried to build a laser scanner using a 5 mW 635 nm (i.e. high visibility red) laser pointer, with first surface mirrors glued to metal axles that turned in ball bearings, driven by (slaughtered) speakers. It worked for simple "moving to the music" displays but were very weak even in a very dark room.

Also, no accuracy. You need a closed loop scanner (this is a servo system just like a servo motor/driver) to get positional accuracy.

Arvid

[ynneb]

Unless you are prepared to have a very dark room whenever you use it, you would need more than the <5 mW a standard red laser pointer puts out. And this means expensive.

These days you can get very bright and cheap lasers that can be clearly seen in daylight.

2) The scanners are very expensive if you want any accuracy at all.

Accuracy is not that important for just knowing where to put a hold down screw, or where to avoid a bad patch in the material.

[arvidb]

Benny, it was not my meaning to "cast down" your idea, I'm just sharing my (quite substantial) experience with lasers in display applications.

You will need a lot more laser power when you scan a connect-the-dots picture than when just holding the dot stationary. A normal laser pointer is clearly visible indoors in the middle of the day, but even scanning a simple circle on the wall it is difficult to see under the same conditions.

When I talk about accuracy here I'm not talking 1/10 of a millimeter. It would be difficult to build scanners that can hold even say +/-5 mm (+/-0.25 inch) at 0.5 meter from the scanner or so. I'm just saying it's a difficult project if you build it yourself, or expensive if you buy it.

Feel free to use my knowledge in this area, I'd be glad to help! It is a cool project .

Arvid

[Graham S]

Benny, if you are scanning the laser to make the image then it is effectively only at a given position for a very short time that means that you need a bright laser to be able to see the image.

If you want the beam to follow the tool path slowly (slower) then that is different.

If you just want to have a go then get a pair of steppers and a pair of mirrors. You could use belt drives to increase resolution, some quick calcs should tell you how much you need. You then need to just run the g-code, the problem is that the x,y coordinates in the g-code need to be modified because the angle will be arctan(a/b) where a is the distance in x from the point beneath the laser and b is the height of laser above the bed.

Words to that effect anyway.

You might be able to write a gcode converter program to do this.

It would be fun to make some nice patterns anyway using this technique but without the conversion you will get compression of the tool path in certain areas and stretching in others.

Graham

[Graham S]

Ooops some of my post repeated Arvid's.

The solution is slow scanning then. Resolution may still be a problem even if you measure it in clamp widths rather than microns.

G

[Graham S]

I'm gonna make some pretty patterns anyway

[arvidb]

Posting within the same minute!

I didn't even think about the possibility to go slow. Sometimes working for some time with a technique can make you very blind to alternative solutions!

Arvid

[edit: spelling]

[Graham S]

What about using a tool path verification program to print out the tool path and then make a projector to project it.

Now I really must do some work

[arvidb]

Regarding resolution:

With the scanner 0.5 m above the table, the movement of the spot for one full step of a 200 steps/rev stepper is about 16 mm right below the scanner (it gets better the further to the sides you get).

With 3:1 reduction and microstepping it might work? Let's see, one full step at 600 steps/rev gives about 5 mm/step, so even using only half-stepping the resolution is down to 2.6 mm. Should work!

Edit:

No, I realised this is wrong. The beam angle is twice the angle of the mirror, so you would get 31 mm/step for the 200 steps/rev stepper. And 5.2 mm/step with 3:1 reduction and half-stepping.


Arvid

[buscht]

I just came back from the IWF show in Atlanta. These things are available for about $16,000 to $18,000 U.S. dollars.

http://www.sl-laser.com/pdf/SL4002_GB.pdf
This model along with the Carter system seemed very popular.

[pmurray]

ynneb,

Interesting idea!

Your concept, I believe, is being studied but, applied as a solution to a different type of problem: “embedded servo” for high-precision CNC – this is a technique analogous to what is used in a disk drive – get the position information as close to where the data is for the R/W heads to follow or, in the case of CNC, get the position information on the material for the cutter to follow.

Unlike today’s techniques where position information is relatively far removed from where the cutter is, thus flexures between where encoders are and the point on the material at the cutter are usually not accounted for, an embedded technique would essentially use a scheme of having the cutter close the loop and follow a point-source of light that is projected and traced out on the material.

Still, many problems to solve with this method. . . You might have a chance to be a pioneer.

plm

[creative_mind]

Just a thought...how about using several cheap laser diodes and use them together to give out a brighter beam? I'm sure there is some way to "bend" the beam and illuminate all in the same path.

[Graham S]

For you reference a just waved my 1mW HeNe about as fast as I could by hand and could see the beam fine. I should think that is faster than steppers can manage. Galvo's can of course go MUCH faster!

Graham

[ESjaavik]

Why not use mass production items?
LED projectors are not very expensive now. Especially if you can get an old low-res projector on the used market. Then use on of the available backplot programs to generate an image of the toolpath. Hang it above the machine at a height that give the correct image size and off you go. It will not have resolution to make fine lines, but for placing the cut on a sheet, avoiding clamps, holes already cut and such it will be fine.

[ynneb]

All I know is that the laser I have, shines onto two offset spinning angled mirrors in series will sufficiently make large paterns on my wall in daylight. I know the lasers of old and how dim they are, but these lasers will work for what I am thinking of.

As for for accuracy, I guess that gets down to the driving electronics for the mirror solinoids. It is my guess that while the circuit may be difficult to design, the actual circuit would only cost $50 - 100 bucks max.