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Error in converting tear shape cut from pipe via sheet metal to flat pattern

Question asked by Jake Martin on Jul 27, 2015
Latest reply on Jul 27, 2015 by Daen Hendrickson

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Hi there,

I am currently designing an outlet for a piece of equipment and I am having issues converting the piece to its flat pattern. This is the final product:

I am attempting to select the sheet metal piece which is a section cut from pipe in solidworks. I want to then convert the piece to its flat pattern so that I can convert it to a dxf and cut it from sheet metal on plasma cam. The following are the steps to creating the first version I attempted that worked in the program just fine:

This is the first cut in the sheet metal pipe. This angle is what determines the height of the piece when attached to the outlet. The second/final cut is simply a right angle to the original cut that also passes through the vertex of the part:

The next step is to simply unfold:

Now this works great as you can see. The issue comes when I want to increase the height of the outlet to allow for more airflow. Below are the following steps:

The height of this piece is just over 1.4, whereas the base is the normal length of 1.25 (though not labelled in this picture). The next picture is the issue I am facing:

It appears that something to do with the dissymmetry between the lengths is preventing the part from being unfolded. Any thoughts on how to skirt this issue?

Thanks!

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John Stoltzfus Jul 27, 2015 2:04 PM

This type of sheet metal cut has been a tough one for SW, try this;

In the right plane, (I'm assuming the first picture is from the right side), draw a small rectangle for a cut extrude, (you only need like .001"), you need to go through all both directions, that cut edge is what you select for the sheet metal feature..

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Jake Martin @ John Stoltzfus on Jul 27, 2015 2:28 PM

I made the pipe in sheet metal from the start hence the seam, sorry if that wasn't clear in the previous pictures. Do you think starting from a boss extrude and converting to sheet metal later would be better understood by the software?

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Jake Martin @ Jake Martin on Jul 27, 2015 2:30 PM

Also, where exactly should the rectangle extrude go?

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Matthew Simkovic Jul 27, 2015 3:32 PM

in the first version you used only one angle dimension and constraints. in the second you added a dimension (.807)? have you tried just adding another angle dimension for the second cut referencing the top of the pipe and a 45° dimension?

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Dennis Bacon Jul 27, 2015 10:13 PM

Something screwy is going on here. I no longer see my reply but I know it must have been here since I got a like from John.

Here it is again. By the looks of your screenshots your cuts are not normal to the sheet metal. See how mine looks.

You are correct in starting with sheet metal (don't convert) but when you make your cuts make sure that "normal" is checked in the cut extrude manager.

I think what John was getting at was that it might be a good idea to have a little bit of flat or straight edge at sharp ends. SW is sort of fickle and sometimes will not flatten without it. I had no problems flattening (before and after changing the angle) with the sharp corners but this is not always the case.

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Dennis Bacon @ Dennis Bacon on Jul 27, 2015 4:13 PM

Holy Smoke,, There are 3 separate posts on this.

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Daen Hendrickson @ Dennis Bacon on Jul 27, 2015 4:39 PM

Yeah, what he said!

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7 Replies

John Stoltzfus Jul 27, 2015 2:04 PM
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This type of sheet metal cut has been a tough one for SW, try this;

In the right plane, (I'm assuming the first picture is from the right side), draw a small rectangle for a cut extrude, (you only need like .001"), you need to go through all both directions, that cut edge is what you select for the sheet metal feature..
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- Jake Martin @ John Stoltzfus on Jul 27, 2015 2:28 PM
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  I made the pipe in sheet metal from the start hence the seam, sorry if that wasn't clear in the previous pictures. Do you think starting from a boss extrude and converting to sheet metal later would be better understood by the software?
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  - Jake Martin @ Jake Martin on Jul 27, 2015 2:30 PM
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    Also, where exactly should the rectangle extrude go?
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Matthew Simkovic Jul 27, 2015 3:32 PM
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in the first version you used only one angle dimension and constraints. in the second you added a dimension (.807)? have you tried just adding another angle dimension for the second cut referencing the top of the pipe and a 45° dimension?
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Dennis Bacon Jul 27, 2015 10:13 PM
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Something screwy is going on here. I no longer see my reply but I know it must have been here since I got a like from John.
Here it is again. By the looks of your screenshots your cuts are not normal to the sheet metal. See how mine looks.
You are correct in starting with sheet metal (don't convert) but when you make your cuts make sure that "normal" is checked in the cut extrude manager.
I think what John was getting at was that it might be a good idea to have a little bit of flat or straight edge at sharp ends. SW is sort of fickle and sometimes will not flatten without it. I had no problems flattening (before and after changing the angle) with the sharp corners but this is not always the case.
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- Dennis Bacon @ Dennis Bacon on Jul 27, 2015 4:13 PM
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  Holy Smoke,, There are 3 separate posts on this.
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  - Daen Hendrickson @ Dennis Bacon on Jul 27, 2015 4:39 PM
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    Yeah, what he said!
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Error in converting tear shape cut from pipe via sheet metal to flat pattern

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