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Parabolic Dish
« on: January 09, 2017, 06:42:22 PM »
This is for the more advanced g-code wizards: Can anyone post an example g-code program to cut a parabolic dish?
I am not (yet) familiar enough with the g code command set to accomplish this. Even just a small, six inch diameter program would be helpful in learning the math involved. I know that it is possible to cut a ramp. Having tried this last night:
M3
Z0
X14 Z-.25 F6
M5
results in a groove which tapers from the stock's surface, to a depth of 1/4" across a span of 14 inches at a feed rate of 6 inches per minute.
What I am looking for, is similar g code for cutting a circular pocket. With a starting depth of 0, a center depth of .5 inches, and a finishing depth of 0 (at the opposite side of the circle). I.E. a DISH! How would one express this, in g code? I know that the machine is capable, I just ain't smart enough to communicate to it the steps such a cut involves!
HELP!
Thanks in advance -Michael

Offline RICH

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Re: Parabolic Dish
« Reply #1 on: January 10, 2017, 06:43:05 AM »
Maybe consider using a Cam program.
Cambam can do what you want to do from a 2D  drawing or  it's cad.

Beats hand coding, FWIW

RICH

Offline Tweakie.CNC

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Re: Parabolic Dish
« Reply #2 on: January 10, 2017, 07:01:01 AM »
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.
(No subject)
« Reply #3 on: January 10, 2017, 07:02:29 AM »
Hi Michae

I think you're problem is better solved using a 3d cad program to construct the surface and then a CAM programme to generate the gcode.
In your 3d cad programme you will need to generate a parabola and then rotate it to form the surface (parabolic dish).
In order to generate the parabolic line you will need to look up the formula that describes it, y=x^2
You should be able to generate the points required using chosen values of y.

I hope this helps
Brian

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Re: Parabolic Dish
« Reply #4 on: January 10, 2017, 07:17:42 AM »
Tweakie,
Good reply and it  will help for sure, but it utilizes MeshCam for the pathing and there is learning curve with MeshCam and to get the file  there.
The parabolic  calculator is worth downloading also.

Don't recall if  there is a wizard for a parabola using the mill.
There is one for the lathe though.

RICH

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Re: Parabolic Dish
« Reply #5 on: January 10, 2017, 07:25:38 AM »
Quote
I think you're problem is better solved using a 3d cad program to construct the surface and then a CAM programme to generate the gcode
.

A easier way would be to use the calculator, get the points, put into 2d CAD and it have it drawn.
Even that  requires some level of experience.

CamBam can do it all and there is info in the manual on how it's done.

A number of ways, but, my thoughts are what is free and needs the least amount of know how to do.

Rich

Offline RICH

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Re: Parabolic Dish
« Reply #6 on: January 10, 2017, 07:27:25 AM »
Mike,
Is this for a mill or lathe?

RICH
Re: Parabolic Dish
« Reply #7 on: January 10, 2017, 08:22:21 AM »
Quote
I think you're problem is better solved using a 3d cad program to construct the surface and then a CAM programme to generate the gcode
.

A easier way would be to use the calculator, get the points, put into 2d CAD and it have it drawn.
Even that  requires some level of experience.

CamBam can do it all and there is info in the manual on how it's done.

A number of ways, but, my thoughts are what is free and needs the least amount of know how to do.

Rich
Does not dish mean 3D?

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Re: Parabolic Dish
« Reply #8 on: January 10, 2017, 08:24:22 AM »
Quote
I think you're problem is better solved using a 3d cad program to construct the surface and then a CAM programme to generate the gcode
.

A easier way would be to use the calculator, get the points, put into 2d CAD and it have it drawn.
Even that  requires some level of experience.

CamBam can do it all and there is info in the manual on how it's done.

A number of ways, but, my thoughts are what is free and needs the least amount of know how to do.

Rich
No disrespect Rich but is it not better offer advice without out disrespecting someone else's, freely given advice?

Brian

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Re: Parabolic Dish
« Reply #9 on: January 10, 2017, 05:09:35 PM »
Thanks to everyone for all the advise. However, I have since solved my problem. I used MeshCAM Art to carve the dish.
I simply drew a 3" diameter circle, and colored it black. Imported the bitmap image into MeshCAM Art, and used the Shape Editor with the following specifications:
Shape: Round
Angle: 33 degrees
Starting Depth: .01"
Height Limit: No Limit
Subtract.
Then generated the tool path, using a 1/4" endmill as the roughing tool, and a 1/8" endmill as the finishing tool.
The result was a dish with a depth of .556" at it's deepest point (center of circle), which feathered out to zero around it's perimeter. Works for me, this cut was used to create a "funnel" which is used to guide a pinball into it's return trough slot. I was already aware that MeshCAM Art could handle it. I was simply curious to learn the math involved in manually coding such a cut. I did attempt to use the Newfangled Wizard for a circular pocket. However, there do not appear to be fields available to control the cutting depth other than a flat bottom cut. I did try editing the resulting g code, to plunge the Z deeper between each pass. Which did a pretty fair job. But it was a spiral cut, which resulted in a "threaded" spiral, in the surface. As opposed to the desired smooth slope I was looking for.
Again, THANKS everyone!
-Michael