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Dome Flat Pattern 1
- Thread starter atcoast
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Thanks for the picture - it really helps!
First of all, I don't think you'll be able to do this with CATIA V5, without some manual efforts. CATIA's current flat pattern capabilities only work with ruled surfaces, which is not what you have. Also, your dome shape is not made by bending, but rather by a forming/stamping operation that stretches and thins the material. And, based on the material being used, I don't think you'll have good results if you cut the holes first and then try to form the dome shape.
That being said....
One way to get an approximate flatpattern is to project the cutout shapes onto the plane of the flanges. That might be close enough.
A more acurate method would be to calculate the stretching ratio between the dome and the flat by measuring the distances between the centerpoint and the diameter of dome and flat shapes, and then using the ratio to redraw the cutout shapes on the flat. Since the part looks like it's pretty thin gauge, I don't think it matters if you use inside, outside or neutral measurements for this.
Have fun! And let us know if you find a easy solution to this.
First of all, I don't think you'll be able to do this with CATIA V5, without some manual efforts. CATIA's current flat pattern capabilities only work with ruled surfaces, which is not what you have. Also, your dome shape is not made by bending, but rather by a forming/stamping operation that stretches and thins the material. And, based on the material being used, I don't think you'll have good results if you cut the holes first and then try to form the dome shape.
That being said....
One way to get an approximate flatpattern is to project the cutout shapes onto the plane of the flanges. That might be close enough.
A more acurate method would be to calculate the stretching ratio between the dome and the flat by measuring the distances between the centerpoint and the diameter of dome and flat shapes, and then using the ratio to redraw the cutout shapes on the flat. Since the part looks like it's pretty thin gauge, I don't think it matters if you use inside, outside or neutral measurements for this.
Have fun! And let us know if you find a easy solution to this.
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- #4
The picture of your part was available earlier, but it's disappeared again, but if I remember correctly, it's not a deep dome, and it looks like a surface of revolution. If the slots are pierced from the blank first, then the latitudinal strips are bound to distort in the forming die, as well as the flange becoming non-circular, whereas if the slots are pierced after forming then, for cost reasons, the punches will be parallel, so that some slot edges will be angled.
What is the flat-wrap for? The flange of formed part will probably be trimmed last, and the 3 bolt holes being pierced at the same operation - to guarantee positional accuracy, it would be better to do it then, rather than add another operation. Without knowing exactly what this part is for it's not easy to imagine how much distortion you can accept, or how precise the flange profile has to be.
A dome is a synclastic surface, which is not readily developable, although several approximate methods have been tried over the years, I have used circular sectors to make templates for cutting out gores of carbon fibre to lay up on a paraboloidal mould. If they are kept narrow enough then a reasonable result may be obtained.
Another interesting way of developing a spherical form is the so called Orange Peel method, which is a spiral segment strip.
Anyway, back to your case, if you want to know what size blank sheet to start off with, you could assume it will be a circular piece and an approximate way of finding its radius would be to assume that the unpierced blank will have the same volume after forming, and that enough pressure will be on the blankholder to control wrinkling. Use the area of a centre cross-section of the flanged dome, including enough radius for the lugs, to find the length of a narrow rectangle whose height is the thickness of the sheet blank. This will be the radius of the blank, and add a bit on for trimming.
There is no instant Catia function to do it, that would take the fun out of it. The key to making the part is the tooling, and how much money can be spent on it.
If the Catia model has the slots having edges that are exactly normal to the dome surface, at any point, then the cost of making even one part would be phenominal, if the production engineering process was driven totally by the V5 model geometry. I would model the part according to how it was going to be made, not forgetting that the material thickness could reduce by up to 15% in the stretched area.
What is the flat-wrap for? The flange of formed part will probably be trimmed last, and the 3 bolt holes being pierced at the same operation - to guarantee positional accuracy, it would be better to do it then, rather than add another operation. Without knowing exactly what this part is for it's not easy to imagine how much distortion you can accept, or how precise the flange profile has to be.
A dome is a synclastic surface, which is not readily developable, although several approximate methods have been tried over the years, I have used circular sectors to make templates for cutting out gores of carbon fibre to lay up on a paraboloidal mould. If they are kept narrow enough then a reasonable result may be obtained.
Another interesting way of developing a spherical form is the so called Orange Peel method, which is a spiral segment strip.
Anyway, back to your case, if you want to know what size blank sheet to start off with, you could assume it will be a circular piece and an approximate way of finding its radius would be to assume that the unpierced blank will have the same volume after forming, and that enough pressure will be on the blankholder to control wrinkling. Use the area of a centre cross-section of the flanged dome, including enough radius for the lugs, to find the length of a narrow rectangle whose height is the thickness of the sheet blank. This will be the radius of the blank, and add a bit on for trimming.
There is no instant Catia function to do it, that would take the fun out of it. The key to making the part is the tooling, and how much money can be spent on it.
If the Catia model has the slots having edges that are exactly normal to the dome surface, at any point, then the cost of making even one part would be phenominal, if the production engineering process was driven totally by the V5 model geometry. I would model the part according to how it was going to be made, not forgetting that the material thickness could reduce by up to 15% in the stretched area.
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atcoast - will allow you to link to pictures you host for free
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