# Accurate method to wrap a sketch to a cylinder

**URL:** <https://discourse.shapr3d.com/t/accurate-method-to-wrap-a-sketch-to-a-cylinder/18024>\
**Category:** Share your creations\
**Created:** [March 15, 2022, 1:08am UTC](https://discourse.shapr3d.com/t/accurate-method-to-wrap-a-sketch-to-a-cylinder/18024 "2022-03-15T01:08:29Z")\
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**Author:** ![PEC](https://avatars.discourse-cdn.com/v4/letter/p/67e7ee/32.png) [@PEC](https://discourse.shapr3d.com/u/PEC)\
**Post date:** [March 15, 2022, 1:08am UTC](https://discourse.shapr3d.com/t/accurate-method-to-wrap-a-sketch-to-a-cylinder/18024/1 "2022-03-15T01:08:29Z")

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Hi,  
I think this has not been posted before, here is an accurate method to wrap a sketch onto a cylinder.  
 ![CleanShot 2022-03-22 at 00.35.36](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/f/f6b52277cf3a42b284037d7c4b2a92d13db8e313.gif)

Orthogonal projection of a plane onto a cylinder creates distorsion. One solution is obviously to slice the cylinder to reduce error. The following table gives an estimation of the maximum error of the projection for a given number of slices.

 ![image](https://us1.discourse-cdn.com/flex002/uploads/shapr3d/original/2X/a/a2daea0106f7aa194ff874094ac846afdf61c5d6.png)  
2 slices means projection of a plane on half the cylinder, which leads to infinite distorsion at the limit of the projection.  
With 16 slices, worse case error is less than 2%, which is not noticeable.  
With 64 slices, worse case error is about 0.1%.

The idea is to create a flatten version of the cylinder, project the sketch on the flatten version, extrude it if needed, and then wrap the cylinder to create the final shape in a systematic way, using mirror and align tools.  
It’s a five minutes process for 16 slices, as in the video, but it just requires 1 additional minute to go to 32 slices 😀 and do not require any computation at all.

_There is only one limitation: ensure there are no spline control point too close (less than 0.01mm) to any slice’s edge or extrude may fail._

This method can be extended to project a sketch onto a cone 🙂  
[Accurate method to wrap a sketch around a cone](https://discourse.shapr3d.com/t/accurate-method-to-wrap-a-sketch-around-a-cone/18234)

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