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best practice for bending a tub with a normal cut & splitting it

Question asked by Lauritz Berg on Oct 1, 2020
Latest reply on Oct 5, 2020 by Kevin Chandler

 I am looking for a good solution/a best practice for the following case:

1. How to set up the part

We have a part that we bend many times to achieve a fairly round profile.
i.e. this kind of profile:
round tub profile


In SolidWorks I can either

  1. draw this profile & make a sheet metal piece out of this
  2. or make sketched bends onto a flat piece & bend it to my gusto


Both versions have advantages & disadvantages:

+quick to draw-slower to draw
+lightweight on resources-can be extremely heavy on resources
+normal cut (see later chapter) works fine-normal cut (see later chapter) can cause great headaches
+splitting the part is lightweight on resources-splitting the part can be extremely heavy on resources
-not a very accurate representation of the real part+accurate representation of the part

-needs an extra drawing to be bent that needs to be modified according to the drawn part every time (more error prone)

+drawing included correctly within the part

-to put it properly onto the brake press we need an extra configuration that shows all the bends

+can be put onto the brake press easily

+easy to modify/mate to, because it just has a few faces (fewer errors)

+horrible to modify/mate to because wrong faces are often automatically selected

-not very accurate flat pattern for pieces where the thickness varies a lot

+accurate representation of the flat pattern especially for varying thicknesses


What is the best practice on how to set up a part like this?


2. How to make the normal cut

I'll go more into detail regarding those problems, starting with the normal cut.
This piece has a number of bends in it to make it nice and round:
flat pattern with bend lines
The normal cut is made from the side of the bent piece to ensure a flat piece (gate) can cover this later on.

normal angled cut on the right planenormal cut closeup

The normal cut works fine on Version1 like this and gives a nice flat pattern (optimize geometry is not checked).
Setting up Version2 the same way yields the following result (optimize geometry unchecked):
cut failed

with optimize geometry checked it looks like this:

If I set up the cut a bit different, I can get the desired result, but for every thickness I need to adjust the length accordingly, because more material gets cut off:


What is the best practice on how to perform a normal cut on this part?




3. How to set up the part split correctly

Next part of the agenda would be to split this huge piece into the pieces that the manufacturer/the equipment can handle them. The available sheet size can also vary quite a bit and sometimes seams should be avoided in certain areas later on.
Right now we have one main piece as an envelope in the higher assembly. Most of the parts get mated to this piece.
Then we split this piece into the desired size mostly depending on sheet availability.
What is the best practice to split the part now? Right now we have multiple configurations of the part depending on the sheet size, i.e. part# - sheetsize - split#

We tried derived sheet metal parts at one point, but the flat pattern gave tons of errors for those pieces when we changed too much.


This leads sometimes to a whole lot of configurations, because depending on the sheet thickness sometimes the part geometry has to change a bit too (means we have another variable in there - thickness!).
Version1 is not as heavy on the resources here, but Version2 is a real bummer here, because it will rebuild all the configurations with ALL the bends in it.


Is there a best practice on how to handle this? Is there a way to get away from multiple configurations? Or how to make derived sheet metal parts work properly (especially the flat pattern)?


4. Getting the (real life) bent part to look like the model

When bending so many bends it does not according to the model perfectly.

Here the die i.e. goes 'into' the previous bend starting from the second bend, because the distance is smaller than the die size. Perfectly hitting those bend lines depends i.e. on the operator, the brake press, the cut quality... So there is another inaccuracy. The cut quality can also be an issue.

In real life the part itself is always too short at the bottom (& part of the radius is also too short). So the flat piece (gate) that should cover the opening actually does not fit:

The only good way out for us was to add material to the flat pattern. The split part with multiple configurations though now tries to add this to EVERY configuration that gets flattened manually (which our nesting software does automatically. it does not take the flat pattern configuration(!)). The only way to suppress this feature it to flatten every configuration that does not need it & suppress this feature.
In addition the bounding box for the flat pattern is now wrong & shows the wrong measurements.


Is there a better way to add material to a flat pattern/to modify a flat pattern? What is the best practice here?


I did attach a part (panel-test.sldprt) with out current idea for a set up for those kind of parts & also a part where the sheet metal was set up with a profile.
Thank you for your time.