# Why subtraction doesnot work out
**URL:** https://discourse.shapr3d.com/t/why-subtraction-doesnot-work-out/27934
**Category:** Modeling Questions
**Created:** [September 15, 2023, 4:01pm UTC](https://discourse.shapr3d.com/t/why-subtraction-doesnot-work-out/27934 "2023-09-15T16:01:56Z")
**Posts on this page:** 3
**Page:** 1
### Author:  [@RossiWu](https://discourse.shapr3d.com/u/RossiWu)
#### Post date: [September 15, 2023, 4:01pm UTC](https://discourse.shapr3d.com/t/why-subtraction-doesnot-work-out/27934/1 "2023-09-15T16:01:56Z")
Ipad12.9 6th 16g model
Ipados: 16.5
desktop doesn’t work out too, but I can do it on NX10
[subtraction not work out.shapr](https://discourse.shapr3d.com/uploads/short-url/1Oj2JZWtwz27XSX4jHPEzC7JvZn.shapr) (267.2 KB)
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### Author:  [@TheBum](https://discourse.shapr3d.com/u/TheBum)
#### Post date: [September 15, 2023, 11:52pm UTC](https://discourse.shapr3d.com/t/why-subtraction-doesnot-work-out/27934/2 "2023-09-15T23:52:06Z")
I don’t read Chinese, but is it possible that you had “All” selected for “Keep originals of”? It would also help to see the left sidebar so we can see what objects are being created.
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### Author:  [@Cjacob](https://discourse.shapr3d.com/u/Cjacob)
#### Post date: [September 18, 2023, 11:39pm UTC](https://discourse.shapr3d.com/t/why-subtraction-doesnot-work-out/27934/3 "2023-09-18T23:39:53Z")
Hello RossiWu,
I had the same problem the other day. Managed a work around via export and reimport with another CAD program, same as what you did.
On yours we have observed the following, see ACIS error. And as I also discovered as well, the geometry needs to be “right” otherwise it won’t subtract, even as simple as an angle not be exactly correct can interfere with the operation.
