Need Help!- Flattening out a cone ???

[Mr. LocoMartin]

I need to be able to draw a cone and then flatten it out so I can cut a piece a sheet metal to make a cone from.
I have V23.
Can someone give me a short step-by-step on how this might be done ?

Thanks in advance for your time and effort.
Martin

[wjfiles]

Measure the slope height of your cone.
Draw a full circle with the height being the radius.
Take the diameter of the base of your cone multiply by 3.1416.
Mark that distance around your circle.
draw a line from your start point to the centre and another from the finish point to the centre
the result will be a blank that will form a cone when rolled.
WJF

[Weldtutor]

Originally Posted by Mr. LocoMartin I need to be able to draw a cone and then flatten it out so I can cut a piece a sheet metal to make a cone from.

Check THIS LINK, with pictures. It might also help.

[HuFlungDung]

Originally Posted by wjfiles Measure the slope height of your cone. Draw a full circle with the height being the radius. Take the diameter of the base of your cone multiply by 3.1416. Mark that distance around your circle. draw a line from your start point to the centre and another from the finish point to the centre the result will be a blank that will form a cone when rolled. WJF

WJF,
I'm just trying to follow along here

To clarify, by "slope height", you mean the length of the line joining the base of the cone with the virtual apex, is that right? Not the slope height of the truncated cone?

[jhop2]

I'm not good at explaining. If you send the thickness, large diameter, small diameter and height of cone to jim@muellermfginc.com I will draw it and email a DXF file to you.

Jim

[HuFlungDung]

Ok, I'm a noob at sheetmetal, so this is what I understood from the post above and I propose a cone with 8" diameter base, 6" diameter top, and 6" height, like a transition from an 8" to a 6" stovepipe.
(Note: through similar triangles, the slope of the cone is 1/6, therefore the apex height for a cone with a base radius of 4 would be 24)

The 24.331 radius is the radial distance from the base of the cone to the apex as measured along the hypotenuse. I determined this graphically in CAD, but could be computed as:
A^2= B^2 + C^2
A^2= (4)^2 + (24)^2

Now in the real world, I suppose you could lay a tape along the circumference of the 24.331 radius circle, and measure out the arc length of 8*Pi, but instead I computed the angle subtended by comparing the ratio of the circumference of the base circle of the cone with the circumference of the circle having the cone apex radius:
(4/24.331)*360 = 59.184°

I might be wrong, but I did print out the thing and cut it out with scissors and rolled it. It looks right.

The picture is a bit blurred, but the blue colored area would be the flat layout, the magenta is just a side view of the desired cone.

If I have errored, please advise. Thanks.

[ger21]

Try this. Draw a side view of the cone. If it's truncated, extend the sides to find the center of two circles you'll draw (one circle if not truncated).

Use the formula to find the angle. R2 is the radius of the top of the actual cone. R1 would be the bottom of a truncated cone, or 0 for a cone.

There may be an error in my notes on this, but I don't have time to check right now. I'll check later.

[BurrMan]

Originally Posted by Mr. LocoMartin I need to be able to draw a cone and then flatten it out so I can cut a piece a sheet metal to make a cone from. I have V23. Can someone give me a short step-by-step on how this might be done ? Martin

Hi Martin,
Since BobCad has no way to draw an arc by it's "length", there will need to be a conversion with "Radians".

If you draw a cone with a 2 inch radius base, 5 inches high. Here is a step by step.

You need 2 values from your cone. The Circumference in length and the S (Slanted) value.

A 2 inch radius circle is 12.5664 in length.

The S length is 5.3852

To draw the arc we need an angle so we first need to get the radians by using the S value as radius and Length value derived from circumference.

To get the radians the equation is L/R. So, 12.5664/5.3852 = 2.3335

Mutiply by Radians (one Radian is 57.2958)

2.3335*57.2958 = 133.6997

This is the angle for the arc to draw in BobCad. The connection of this arc is the surface of the cone.

I used 0 as a start and a 0,0,0 point to snap to, but you can make it as hard as you want.

[tjones]

Nice sight with several pages of free layout info. (even if they are trying to sell something)

http://www.sheetmetallayoutcalculator.com/

[cheubach]

Try the demo at this site I have purchased the entire suite and it will save a ton of time. I have had to layout many pipe reducers by hand but this just saves a lot of time. You just impute the large dia, the small dia and the take out or face to face dim and it will plot it out to a dxf file which you can then import to BC or any other cam app to produce the cut files. It will work for concentric and eccentric reducers.
It is a great deal for around $100+/- US. But if you just need one I believe the timed trial is fully functional.

http://www.tyharness.co.uk/sheetmetal/

I hope this helps, I know it is always better to know how to calculate the parts for yourself and I do encourage you to do so but maybe this will give you the time to learn it later when your not pushed for time.