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How to Create an Extrude-Cut on a Curved Surface

Jesse Ortman on August 6, 2015 at 2:22 PM

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Sometimes you will find yourself in a situation where you need to create an extrude-cut on a curved surface.

Take the following part for example:Extrude Cut on a Curved Surface in SOLIDWORKS

There is not a single flat face on this part (other than the 3 primary planes) on which to base a classic 2D sketch for your cut.

The challenge is to create a blind cut into the model and have the bottom face of the hole maintain the shape of the original face before the cut. For now we will assume no draft is necessary.

At this stage, there are questions we need to answer before proceeding:

  • What direction does the cut needs to be in? 
  • Does the cut need to be perpendicular to one of the primary planes of the part? 
  • Do you need the cut to be a cut into the model with a blind depth? 
  • Does the cut need to have draft?
  • Does it go ‘through all’?

Answering these questions will help frame the proper technique to use.

There are many approaches to a part like this. Here we will focus on using commands OTHER than ‘extrude-cut’ to get the job done.

First let’s get the outline of the cut etched onto the face of the model.

The first step is to use the TOP Plane to sketch out a few splines and tangent arcs. Below are side and top views with the plane and sketch visible.


Extrude Cut on a Curved Surface in SOLIDWORKS

Next use the ‘projected curve’ command to get the 2D slot shape to sort of well, project, itself down onto the surface:

Extrude Cut on a Curved Surface in SOLIDWORKS

Next we will just copy the surface we want to start our cut on using the offset surface command with an offset value of 0. This is essentially a ‘copy surface’ command. The result is a free standing surface body that looks just like the original one on the solid model. This is a great way to keep the original solid model untouched while working on new geometry.

Extrude Cut on a Curved Surface in SOLIDWORKS

It will be on this surface that we will use the ‘surface trim’ command. Select the previously created curve, and the suface created in the offset surface step and then use the ‘keep selections’. The result is shown here:

Extrude Cut on a Curved Surface in SOLIDWORKS

Then run a simple ‘offset surface’ command. The offset value will end up being the depth of your hole.

Here we did a 6mm offset resulting in 2 surface bodies:

Extrude Cut on a Curved Surface in SOLIDWORKS

 

Run a surface loft from the top body down to the bottom body, knit the 3 surface bodies together and you will now have a solid body that looks like this:

Extrude Cut on a Curved Surface in SOLIDWORKS 

NOTE: Make sure to look at the ‘solid bodies’ folder in the feature manager tree – some bodies may be hidden, and some bodies could have remained as surface bodies if you didn’t choose the ‘Try to Form Solid’ option during your surface knit.

Extrude Cut on a Curved Surface in SOLIDWORKS

Finally, use the ‘combine’ command with the ‘subtract’ option to ‘CUT’ this new solid body into the previous solid body: (initial solid body showing as blue outlines in the picture for clarity)

Extrude Cut on a Curved Surface in SOLIDWORKS

The final part:

Extrude Cut on a Curved Surface in SOLIDWORKS

There are many different ways to skin this cat. This was just one example. How many different ways do YOU know how to get this task done?

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