from technical drawing to cad

malcolm_mccaffery · January 14

I want to create necessary drawings so I can get a die made for this item to be made out of 0.157" mild steel. It is a like bell, a round item open at the bottom.

Is there any ways to take the measurements from these drawings and input them in an object or something to get the item.

What would be the best objects / items / approach to start creating this type of item?

I expect first step is to model the finished item, which is this drawing. Then are there tools in onshape to help me create die?

How to interepret the 3'-0"R and 2 1/2"R here?

martin_kopplow · January 14

You'd create a sketch using the dimensions given, but only one half of it, up to the center axis. Then you would rotate that sketched shape around the axis to get the 3D part, and then hit the 'create drawing' menu item to get a 2D representation with 3-view and where you put on the dimensions and such. That is standard parctice.

This approach assumes the 4 curves are tangential. R usually stands for 'radius', and that's just what the curves are. You can solve that in a fully defined sketch. I'll leave you alone with the feet and inches, though - not my world.

kees_bijker · January 14

First about the interpretation of those units. 3feet and 0 inches is a far cry from 2 inches and 9/16th, so I think that is a notation mistake from whoever made the sketch. Or it is the shape of the central part of the shape with diameter 3 feet, this is feasible. What is missing is the hole position and if the whole shape is symetrical or not. I would be inclined to assume it is 3 feet center part and it is symetrical, but the question has to be asked.

Now to the bit where you can make a drawing of this sketch.

If you have this sketch as a jpg or other image, you can import it into a part studio after you made a sketch on a chosen sketch plane.

If you know the sizes you can scale the image so that it is precisely those measurements.

Then you can trace the image in a new sketch, and you can create a part from it with the revolve.

From this part you can create a technical drawing or export the sketch as a dwg or dxf.

There is a feature script for importing images and scaling them precisely, but this is a bit more advanced stuff. I do not know hopw well you are familiar with onshape, but if you know the basics of sketches you should be able to get along with that as well.

Here is a link to the tutorial of the feature script:

https://cad.onshape.com/documents/f7a45d78c374497d37c1d2cb/v/e55cc4b62eaac7ef75039ab2/e/af89d519b2985176cfd7eb55

If you have trouble, load up the image as JPG somewhere and share a link. It will take all but a few minutes to do this.

MDesign · January 14

https://forum.onshape.com/discussion/comment/112197#Comment_112197

I think your just looking through the cross section through the exact middle… 3' is probably accurate. think like a bell on a desk or an alarm clock bell

eric_pesty · January 14

Not much interpretation needed really if you just start sketching this. I think it's fair to assume the 2+9/16" and 3' radii are tangent if not given any other information.
The only thing that's not completely clear is where the 2 9/16" vertical dimension ends: it could be either at the edge of the6/16" hole (i.e. something you could measure), or at the "virtual" center point of the 3' dome, I would guess the edge of the hole as that's what you can measure but it really doesn't make much of a difference either way (only about 0.001")

If you are planning on making the die yourself then you are going to need a lot more knowledge than can be provided in a forum post…
If you just want to get the part manufactured, you can send that existing drawing you poste to any company that does this kind of work and they have all the info needed to create a die and make the part…

kees_bijker · January 14

https://forum.onshape.com/discussion/comment/112206#Comment_112206

I agree with you from an engineering point of view, but from a production point of view I would only like to state that those who receive instructions should never make assumptions, only ask questions.

This set of parameters does not define the final product without making assumptions, therefor questions meed to be asked.

I remember a teacher telling me that assumptions are the grandfather of all financial losses!

Yes I am that old 😜

eric_pesty · January 14

https://forum.onshape.com/discussion/comment/112208#Comment_112208

Fair…
Although with the given information, I don't think the tangent assumption is a big leap… A note on the drawing stating that would be helpful but in the absence of such a note and given the lack of any dimensioning on the center point of that 2-1/2" R, I think that tangency is implied (see, it's not an assumption anymore 😉)