How to Trim Surface in SOLIDWORKS

The Trim Surface feature removes part of a surface body using another surface, plane, sketch, or set of edges as the trimming tool. It is commonly used in surface modeling, imported geometry repair, molded shape development, and cleanup work before knitting surfaces into a solid.

Open the Trim Surface command

1. Open the part that contains the surface body.
2. Go to Insert > Surface > Trim.
3. Choose the trim type.
4. Select the trimming tool.
5. Select the regions to keep or remove.
6. Preview the result and accept the feature.

Choose standard or mutual trim

Standard trim uses one or more trimming tools to cut a selected surface. This is the common option when a sketch, plane, or surface is used to remove part of another surface. Mutual trim is used when several surfaces trim each other and you choose which regions remain.

If you are new to the command, start with standard trim. It is easier to understand because one tool is cutting one target surface. Use mutual trim when several surfaces intersect and you need to keep a specific combination of regions.

Select the trimming tool

The trimming tool can be a sketch, plane, surface, face, or edge set depending on the geometry. A sketch trim is useful when you want a controlled outline. A surface trim is useful when one surface defines the cutting boundary for another. A plane trim is useful for quickly removing material on one side of a flat reference.

Make sure the trimming tool actually intersects the surface being trimmed. If the tool stops short, extend the surface or sketch so the trim can solve cleanly.

Keep or remove regions

After selecting the tool, SOLIDWORKS shows surface regions that can be kept or removed. Zoom in before confirming the selection. On complex surfaces, it is easy to click the wrong side of the boundary or leave a small region behind.

If the preview does not show the expected regions, the tool may not fully cross the surface, the surface may have gaps, or the trim direction may not be clear.

Trim before knitting

Trim Surface is often used before Knit Surface. After surfaces are trimmed to their final boundaries, Knit Surface can join them into a single surface body. If the knitted body encloses a watertight volume, SOLIDWORKS may be able to create a solid from it.

Before knitting, rotate the model and inspect the trimmed edges. Clean edges make the next surface operation easier and reduce the chance of small gaps causing solid conversion problems.

Troubleshooting failed trims

If the trim fails, check whether the trimming tool intersects the target surface completely. Extend the surface, extend the sketch, or use Split Line if the model needs a clearer boundary. Also check for imported geometry with bad edges or tiny gaps.

For complicated models, perform several simple trims instead of one large trim. Smaller surface operations are easier to diagnose and usually rebuild more predictably.

If the model comes from imported geometry, repair obvious surface gaps before trimming. A trim feature can only work as well as the surfaces and boundaries it is given.