topic Betreff: Problems with Solid Combine Function. Cut, and Join leaves material. in Fusion Design, Validate & Document Forum

Problems with Solid Combine Function. Cut, and Join leaves material.

jdlake1 — Sat, 17 Jan 2026 08:25:07 GMT

When using the Combine function when designing, I keep running into the problem of material being left over. I am designing a mold, and am using the Combine function with the part and the mold half I have already modeled to cut the other half of the mold to the exact opposite. Is the combine function not accurate? How am I supposed to use the tool if it keeps leaving unclean solids that often gets even more miss matched if i try to clean it up?

I attached a photo of the issue.
The red surfaces are the ones it left over after the combine/cut function. The cross hatching seen of dark grey (part) and red (left over material) shows a clear picture of what was being used to cut the cavity/core. Both sides were created with the Combine function in one form or another.

Betreff: Problems with Solid Combine Function. Cut, and Join leaves material.

g-andresen — Sat, 17 Jan 2026 09:33:41 GMT

Hi,

Please share the file for reply.

File > export > save as f3d on local drive > attach to post.

günther

Re: Problems with Solid Combine Function. Cut, and Join leaves material.

TheCADWhisperer — Sat, 17 Jan 2026 17:14:23 GMT

@jdlake1 wrote:
Is the combine function not accurate?

I doubt it.

Re: Problems with Solid Combine Function. Cut, and Join leaves material.

jdlake1 — Sat, 17 Jan 2026 18:57:31 GMT

I cannot share the file. The design is not mine to share.

I currently do not have many if any sketch constraints, since most of the solids are imported. Will that cause an issue? If so what would be the best way to solve it?

As you can tell from the screenshot i posted, the part is complex. I cant just redesign/resketch it from scratch.

Re: Problems with Solid Combine Function. Cut, and Join leaves material.

TheCADWhisperer — Sat, 17 Jan 2026 20:25:43 GMT

@jdlake1

My guess is the issue is related to Face Draft.

If you are using imported, can't you Extrude-Intersect a rectangle of only the area in question - export that, import and reproduce the issue and Attach here.

This would be only a tiny area of the model protecting the intellectual property. (Consider this carefully that you would not violate IP.)

Re: Problems with Solid Combine Function. Cut, and Join leaves material.

johnsonshiue — Tue, 20 Jan 2026 22:06:40 GMT

Hi! You may want to check the interference between the two bodies to see why some material is left over after the Boolean operation. Go to Inspect -> Interference Analysis -> select the two target bodies.

Many thanks!

Re: Problems with Solid Combine Function. Cut, and Join leaves material.

rosie_lucas1 — Mon, 26 Jan 2026 20:35:53 GMT

Hello @jdlake1 ,

Just checking in—did the responses shared by @TheCADWhisperer and @johnsonshiue help clarify your question?

If so, please consider clicking the "Accept Solution" button on the post(s) that solved your problem. Doing so helps others in the community easily find useful answers.

If your question still needs more attention, feel free to reply here with an update. This way, other members can jump in with further suggestions or guidance to help you move forward.

All the best,

Rosie | Community Manager

Re: Problems with Solid Combine Function. Cut, and Join leaves material.

jdlake1 — Tue, 27 Jan 2026 19:15:18 GMT

I have been very busy with work lately, sorry for the late reply. I ended up reimporting the part files fresh, and making all the my sketch geometry fresh and locked down. ( Cut profiles ) That fixed the issue in this scenario. I have had similar issues even after keeping the sketches locked down. Seems like when i use the Cut to selected face i will sometimes get a small step. Probably only less than .0001" But it is still a pain. I will look into the Interference Analysis tool that johnsonshiue mentioned when i have time. But i have had to just move forward and work with the discrepancies for now.

When this project is done i will try to recreate the issue i had and section out a portion of the solids as TheCADWhisperer suggested. If the interference analysis tool doesn't help me solve it.

Thanks.