1. Calculations for solar concerntrating dish. (How to go about it)

If I wanted to make a mold for a 1 x 1 metre square reflective solar dish, and the focalpoint was to be 3metres away, how would I go about it?
How would I then ceate code to then cut this mold via 3 axis CNC.

2. Soler Concentrator

Hi Benny
I believe that if you do a Google search for parabolic reflector or solar cooking you will find a lot of information. I do not have the details but I have read a lot about it in the past few years. Hope this helps.
Regards
Don
(domar)

3. Thanks Don, I was wanting to be lazy and hoped there was an CNC optical calculator plugin/program that spat out Gcode acording to a few inputs, like dish diameter, shape, and focal point, etc.
Surley there is a geek who has already worked on such a program

4. Benny,

What a thought-provoking question.

The math isn't all that difficult:
http://www.analyzemath.com/parabola/parabola_focus.html

For a dish with a 1 meter diameter, (haven't seen any square parabolas) the depth of the dish would have to be 1/48 of a meter in order to have a focal distance of 3 meters.

How to make the thing is a different story. Haven't seen any CNCs that offer parabolic interpolation, but I'm sure that they exist.

5. Thanks guys, I think I have found a sollution, and it even has a free geek calculator program too
http://www.cerebralmeltdown.com/cncs...bola/index.htm

6. There ceratiainly are machines that cut parabolas... I'm cutting one right now! (but no-where near that size). I do them all the time.

I've written a program that calculates the X and Z values from the relevant input data.

If you give me the base radius of curvature, (the eccentricity will be 1 and the conic constant -1, naturaly) and the step size in X I can get all the sag values.

7. Originally Posted by ImanCarrot
There ceratiainly are machines that cut parabolas... I'm cutting one right now! (but no-where near that size). I do them all the time.

I've written a program that calculates the X and Z values from the relevant input data.

If you give me the base radius of curvature, (the eccentricity will be 1 and the conic constant -1, naturaly) and the step size in X I can get all the sag values.
One of the first projects I did when I got a cnc mill here that was a long time personal goal was to write a parabola macro...the part I made with it has been proudly displayed next to my desk for 12yrs!

...man, that was fun to do!!

8. Guys, it sounds like you're generating a parabola from many X, Z values on a lathe (or X,Y,Z on a mill). Do you know of any machines that do this in hardware or firmware, as with circular and linear interpolation?

Would be nice...

9. Fizzissist you are right: I got the exact same buzz, they won't let my software go cos it's apparently too "commercially sensitive".

What's all that about?! What is that! *rant*

I wrote it in my spare time, when the machine was running lol.

Bloody Bean Counters who know fek all about anything apart from how to wreak the economy.. sorry went off on a rant then (4am here and too much hassle).

 And if they did have a bloody clue, even an inklink about how much it takes to develop and make a "thing" the would probably employ 30 "comittee" folk who knew fook all about making things and 1 person who actualy made it.

Grrr..

sorry for rant.

10. Eurisco, sorry, I posted and edited at the same time as you must have.

Picture a cone coming out of your desk.

Picture two slices going through it perpendicular to your desk- you'd be left with a circular bit.

Picture a slice going at, say 30 degrees..what would you have hehe,

A parabola. (alothough some call it hyperolas an shiit, prolate spheroids, blah blah blah.. i know how to make em)

Aspherics are a diferent matter entirely

I do this for a living.

[Edit again] I find it best to do the maths and generate the X nd Z co-ords, copy and paste that to a dummy job file with small steps, like 0,001mm steps, not sure if you could smooth the machine into following an aspheric form... would be very interested if anyone would contradict![/Edit]

11. Solar Collector

Hi Benny
It seems that you are on your way by the responses on the zone. I should have mentioned this in my last post. I do not want to tell you how to suck eggs but please be aware that with such a focal length there is a real risk of somebody getting in front of it. With a short focal length this is not so much of a risk. Certainly the potential for eye damage and or serious burns almost instantly.
By the way I would like to have a talk with you next time we meet as I have some ideas to discuss.
Regards
Don
domar

12. Thanks Don, a weapon is my intention. We have a serious ant problem

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