Trying to make a radiused dish

[betacrash]

i am trying to make a 12' and 15' radius dish for ukulele building. i made the profiles of both radiuses with ease, the problem is making a part file of this. basically needs to be made into a "parabola". I have access to vcarve if you it can be done with that. Any help or suggestions would really help. Thanks -shawn
12' radius DWG

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15' radius DWG

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[betacrash]

dude, sorry about the braindead sentence at the end. i may have fallen asleep. i was just saying that I have access to V carve and if anyone could help or give suggestions it would be appreciated. thanks. -shawn

[fleinbach]

Shawn,

Your drawings are of a 2D profile and not enough information to figure out what you are trying to do. If you could supply more detailes someone may be able to help you

[betacrash]

i need to make something like this
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[paco]

What if you put the straight edge perpendicularly to what it is on the picture?

I can tell if it's cupped or bent...

If it's bent and you don't need high accuracy, go for the sander.

If it's cupped and/or need extra accuracy, go for a 3D model. In that case, I could help...

[fleinbach]

You will need a program like Artcam or Rhino to create the 3D. V carve will not carve out a parabolic shape.

[paco]

Something like this?...


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[bill.young]

If the "top view" of the dish is either circular or elliptical than you could use the newest version of the Extruder in ShopBot Labs. Follow the instructions to create the profile toolpath of the cross-sections then start the Extruder. Tell it to do a circular extrusion from 0 to 360 degrees and set the inside radius to 0.0001 or something small like that. A value of 0.0 for the radius will currently give an error...I never thought of this use for the Extruder but will fix it soon.



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[bill.young]

FYI, the Extruder has been updated to fix the problem with extrusions that have a 0 radius, to make it easier to do these sort of bowl shapes. You can get the new version in ShopBot Labs (http://www.shopbottools.com/files/LabFiles/extrupdt.htm)

[betacrash]

that is exactly what I need (both Paco and Bill). This dish is used to shape ukulele backs and sides. Would you recommend using a box core bit? would this take too long?

[myxpykalix]

bill, I downloaded the updated software but looked thru all my shopbot folders to see where to put it to overwrite the older version but couldn't find it anywhere. Where do i put this update and how do i access the extruder thru shopbot control panel? thanks

[bill.young]

Jack,

The Extruder isn't included in the ShopBot software...it was from one of the Bill's Corner articles. It's a standalone program so it can be unzipped to and run from anywhere you want...your desktop will work fine.

If you downloaded the original Extruder program from the Bill's Corner article just put this update in the same folder...the updates don't overwrite the originals in case there's a problem with the newer version. You don't need to have the original to use the new one, though...it just gives you some samples to try out.

Bill

[myxpykalix]

thanks

[bill.young]

Shawn,

Sorry, I missed this question last Thursday.

" Would you recommend using a box core bit? would this take too long?"

To use the Extruder to create your files you would HAVE to use a round-nose bit like that to get the right profile offset, though my guess is that you would end up using one no matter what system you used to generate the files because the round-nose bits do a nice job shaping curvy surfaces like that.

The time question is hard to answer...it's always a tradeoff between cutting time and sanding time. The quick example I did uses a pretty small stepover and the estimated cut time is about 20 min at 1.5" per sec cutting speed. You could make that much shorter with a smaller stepover and bigger segments in your profiles but would end up having to sand more.

Bill