3D model
Floating parts that touch nothing.
A part that touches nothing in the design is usually in the wrong place. Sometimes the model is right and something is missing: a gasket, a ring or a shim that does have to be ordered.
Published 21 September 2026
01 What it is
Floating parts, briefly explained.
A floating part is a part whose bounding box touches no other part. There is literally air around it. The distance to the nearest part tells you what is going on.
A few millimetres almost always means something belongs in between that is not modelled. Centimetres or metres almost always mean the part was fixed wrongly or moved along.
How you notice it
- A part moves along when you pull on something else, or does not
- The fitter asks what exactly a part has to be attached to
- A small gap between two flanges on the section of the drawing
- A part sits far outside the rest of the model
In a check
This shows up as caution in the check of the 3D model. You judge what has to be done about it.
02 Example
What it looks like.
Example design GRP-2210 (demo)
- Part
- BV-050 ball valve
- Nearest
- FLG-050-PN16 weld flange
- Distance
- 2 mm
- Probable cause
- Flange gasket not modelled
Two millimetres is exactly a gasket. The model does not have to be changed, but the gasket does have to be on the BOM, otherwise it is not ordered.
How it comes about
- A removed relation or constraint, after which the part stays on its last spot
- A gasket, O-ring or shim that does sit between the parts in reality but is not modelled
- A part inserted from another design that brings the old origin with it
- A replaced part that has slightly different connection dimensions
03 Approach
Find, fix, prevent.
How to find it
You find floating parts by looking per part whether it touches anything, and if not, how far away the nearest part is. That distance determines how you judge it.
- 1 Open the STEP in the free check.
- 2 Go through the lines about loose parts: it says which part is nearest and how many millimetres lie in between.
- 3 Click the line to see where the part is.
- 4 With a few millimetres: see whether the missing gasket or ring is on the BOM. With more: check the placement in the CAD.
Fix
- Fix the part in the CAD again to the part it belongs to, instead of sliding it to the right spot by hand.
- If a gasket or ring belongs in between, put it on the BOM, even if you do not model it.
- With replaced parts, check whether the connection dimensions are still correct.
Prevent
- Model gaskets and shims, or give them a fixed place on the BOM.
- After every major change, check whether all parts are still fixed.
- Make the check on loose parts part of the release, not of the assembly.
With BOMproof
Every release, without having to think about it.
BOMproof puts your STEP model, your PDF drawings and your Excel BOM side by side and points out every deviation: with a pin in the 3D model and a balloon on the drawing. You tick off what is correct.
04 Frequently asked questions
Floating parts.
01 Is a floating part always wrong?
No. A few millimetres between two flanges is often a gasket that is not modelled, and that can be a deliberate choice. That is why a small gap gets a different message than a part that stands completely loose in space.
02 What is a normal gap?
That depends on your product. In the free check a gap up to and including 3 mm counts as "probably a gasket or ring" and is shown as a comment; larger distances get more emphasis.
03 Can I also see this in my CAD package?
An interference check finds parts that intersect each other, not parts that touch nothing. For that you have to look at the distances between the parts.
05 Often seen together
Other errors from the same corner.
You never want to hunt for this error by hand again.
Upload your model, your drawings and your BOM and let BOMproof check them against each other. Book a demo with your own design.