# Unrolling a curve

I have some curves measuring a length of 36 and 40. I need to know the length of steel I need to purchase so I need to know what the size of these surfaces are prior to curving.yellow moon plates only.3dm (57.9 KB)
I’m really a beginner and the posts i’ve seen so far regarding this seem to talk about scripts of which I know nothing

Lingums, I see Pascal already suggested Lenght and DimCurveLenght. In a prior post you seemed to have trouble with DimCurveLength. You said “with style leader chosen, I pick the start point, then it asks me for the next point.in leader…if I try and pick anywhere along the curve it just jumps off into space somewhere…whats happening?”

Pardon me if I’m being too simple, but as you stated you’re a beginner, maybe you misunderstand how a leader works. A leader is a line with an arrow on one end and annotation or dimension text at the other. Normally one would put the start point near the curve being measured and the next point away from the curve, where you want the text to appear, not “anywhere along the curve”, and then finish the command with a right click or Enter. This differs from other dimension commands where you are asked to pick a start and end point to measure between; the command already knows the length of the curve, it is asking where you want the start, mid and end points of the leader line to be placed.

If you understand all of this and the leader still “jumps off into space somewhere”, then I don’t know what is going on. It works normally when I try it here.

Length = 46.05 centimeters is that what you are looking for?

As per Mark’s point about a simple question, I hope I’m wrong but are you looking to create that in sheet steel? When I read “plates” I presumed it is a sectional detail of a sheet.

If you’re looking to get something rolled you’d need arc and chord lengths and you won’t be able to recreate that unless it’s being pressed, of course it’s pencil bar and it’s being CNC formed as a wire shape that’s a different story…

Hi Eddy that sounds right but how did you get it…I am getting steel rolled into this shape by the fabricator who opened up the Rhino drawing in Solid Works and seemed to have understood it because he’s already quoted me on it. Its just that I have to purchase the steel and didnt want to look too stupid not knowing the size of flat sheet steel I need to buy.

I am trying to use Rhino to calculate the lenght of metal sheet or plate I need to purchase which I can give the fabricator to do the rolling. they have solid works and seem to have been able to open the Rhino drawing up in that and have quoted me on the rolling. I just didnt want to look really stupid by asking them the size of metal sheet I need to purchase. I know the width but can’t figure the length. Eddyf has figured it out…thanks but I’d like to understand how to do it myself.
The tool icon I am using is the one highlighted in this jpeg image which says " curve length dimension"… t
As you can see in the Rhino snapshot I’ve clicked at the beginning of the curve and have gone to click at the end of the curve
As soon as I click at the end of the curve it jumps to a point below the curve on the perpendicular underneath and asks me for “next point in leader” I think I have even used this command once before so don’t understand why its not working now. I am using windows 8. I’ll upload the actual drawingyellow moon plates only.3dm (57.9 KB)

Try using DimCurveLength in the Front view, not in the Perspective view, The command does not appear to work properly in the Perspective view. Also have a look at “Help” for the command.

Another approach would be to unroll the curved surfaces using UnrollSrf and then dimension the unrolled surfaces. This is a more general method for determine the size of pieces to be used for forming with rolls.

Just grab the squiggly edge curve and use the command Length.

It was trying to do it in perspective view! when I did it in front view I could measure it

all working thank you sooooo much!

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Hi Lingums,

I’d be interested to know how they are forming the sheet, would you be able to shed some light on this? I understood that CNC rollers were limited in there application and required particular dims - arc and chord lentghs, I may be way behind the times with what’s available.

maybe its even more old school than that, no cnc at all. just rolling and bumping on a brake press. Not sure what the final material thickness or final size is.

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At first glance it looked like it was 1.8m long but then I realised it was 360mm x 5 - you’re probably right but it’d be done by eye on a brake press, each one would be different? I can’t imagine it’s done with rollers at 360mm long… In the past when I’ve had sheet steel formed it’s been pretty basic shapes, even at larger firms.

Lingums, you’ll have to buy a piece of steel longer than the edge length. The rolling machine will need a “lead in” at each end which stays straight and is cut off later.

John