How to Use Collision Detection in SOLIDWORKS
Contents
Collision Detection in SOLIDWORKS checks whether assembly components touch while you move or rotate a part. It is useful for testing mechanisms such as hinges, sliders, levers, and linkages because it shows where motion is blocked before you manufacture the assembly.
This guide explains how to run the check, choose the right components, stop at first contact, and troubleshoot a part that will not move as expected. The commands are in the Move Component and Rotate Component PropertyManagers.
Collision Detection vs. Interference Detection
The two tools answer different questions:
- Collision Detection checks for contact encountered as you manually move or rotate a component.
- Interference Detection evaluates the assembly in its current position and reports overlapping volume or coincident geometry, depending on its settings.
Use Collision Detection when you want to test a range of motion. Use Interference Detection in SOLIDWORKS when you need a static check of the assembled model. For a design review, it is often sensible to use both: test motion first, then calculate interferences at important positions.
Before You Start
Open the assembly and confirm that the component you want to test is allowed to move. A fixed part cannot be dragged, and fully defined mates can remove all of its remaining degrees of freedom. If needed, review how to unfix a component in SOLIDWORKS and verify that the mates represent the intended mechanism.
Do not suppress necessary mates simply to make a part move. Collision Detection follows the motion permitted by the assembly. Incorrect or missing mates can produce a motion path that the real mechanism could never follow. The guide to mating parts in SOLIDWORKS covers the basic setup.
How to Run Collision Detection
1. Start Move Component or Rotate Component
On the Assembly toolbar, click Move Component or Rotate Component. Move Component is normally the better starting point because a component constrained by mates can translate, rotate, or follow its allowed path as you drag it. For more detail on the controls, see how to rotate and move parts and assemblies.
2. Enable Collision Detection
In the PropertyManager, expand Options and select Collision Detection. SOLIDWORKS then checks for contact as you drag or rotate the selected component.
3. Choose What to Check
Under Check between, choose one of these options:
- All components: checks the moving component against the entire assembly. This is the broadest check, but it can be slower in a large model.
- These components: checks only against the components you select. Add the relevant surrounding parts to the selection box, then click Resume Drag. This is usually the more efficient choice when you are testing one mechanism or local area.
Selecting only the parts that can realistically contact one another reduces unnecessary calculations and makes the result easier to interpret. Run a broader check later if other nearby components could also enter the motion envelope.
4. Decide Whether to Check Mated Followers
Select Dragged part only when you want to check only the component you directly selected to move. Clear it when other components move because of mates and their collisions also matter. For example, a dragged link may drive a second link into a housing even when the original component remains clear.
5. Stop at the First Collision
Select Stop at collision to stop the dragged component when contact is detected. This makes the limiting position easier to inspect and helps you identify the faces that define the available travel. It is particularly useful when measuring the maximum angular or linear movement of a mechanism.
Collision Detection is a design aid, not a tolerance or manufacturing-clearance calculation. A model that stops at nominal face contact may still need an intentional gap for coatings, deflection, thermal expansion, fastener access, or assembly variation.
6. Set the Advanced Options
- Highlight faces: highlights the contacting faces so you can see exactly where the collision occurred.
- Sound: plays an alert when SOLIDWORKS detects a collision, if sound is available on the system.
- Ignore complex surfaces: limits detection to supported analytic surface types, including planar, cylindrical, conical, spherical, and toroidal surfaces. This can improve performance, but it can also omit contact involving other surface geometry.
Leave Ignore complex surfaces cleared when complex faces are part of the area you need to validate. Use it only as a deliberate performance tradeoff, not as a default for a final check.
7. Drag the Component Through Its Motion
Move or rotate the component slowly through the full intended range. Test both directions and pay attention to any mated followers. When a collision is found, inspect the highlighted faces and note the component position. Repeat the test after changing geometry, mates, or clearances.
The example below shows a barrel stopping when it reaches the surrounding part.
Physical Dynamics Is a Different Mode
Physical Dynamics is another option in the same area. Instead of simply stopping at contact, it can let a dragged component push or rotate other free components within the motion allowed by their mates. This is useful for exploring contact-driven movement, but it is not a substitute for a Motion Analysis study or engineering simulation.
Physical Dynamics works best when the assembly has only a few remaining degrees of freedom and the required mates are already present. For a time-based mechanism study, continue with Motion Analysis in SOLIDWORKS.
Why Collision Detection May Not Work
The component will not move
Check whether the component is fixed, fully constrained, or locked by a mate. Use Move Component without Collision Detection first. If the part still cannot move, the problem is the assembly constraints rather than collision settings.
The wrong parts are being checked
If These components is selected, confirm that every relevant obstacle appears in the collision-check selection box. Click Resume Drag after changing the selection. If a mated follower is missing from the check, clear Dragged part only.
A contact appears to be missed
Drag more slowly, turn on Stop at collision, and make sure Ignore complex surfaces is cleared when the contact area includes complex geometry. Also confirm that the parts are resolved and that the expected bodies and components are visible.
The assembly is slow
Use These components and select only the mechanism and nearby obstacles. Test one motion path at a time. Simplified configurations can help, but do not suppress geometry that defines the actual clearance.
Finish With a Static Interference Check
After the moving test, place the assembly at critical positions and run Interference Detection. Collision Detection finds contact during the path you manually test; it does not prove that every possible position, clearance, or tolerance condition is acceptable. A final review should include the endpoints, tightest-clearance positions, and any configuration used for manufacturing.
For a clean handoff, record the tested configuration, the components included in the check, and whether complex surfaces were ignored. That makes the result repeatable when the assembly changes.
