Top surfaces with modifiers are interpreted as bottom surfaces when slicing for Snapmaker U1 #682

New Issue

MrUnknownDE · 2026-04-05T16:25:50+02:00

MrUnknownDE commented

2026-04-05 16:25:50 +02:00

Originally created by @scrith on 2/20/2026

Is there an existing issue for this problem?

I have searched the existing issues

OrcaSlicer Version

2.3.1

Operating System (OS)

Windows

OS Version

Windows 11

Additional system information

No response

Printer

Snapmaker U1 / Bambulab P1S

How to reproduce

Create a model with multiple top surfaces
Add a second object to the model that will encompass one surface that is not the topmost surface
Import the STEP or 3MF into OrcaSlicer and change the object type of the second object to a modifier
Change the modifier object setting to iron all top surfaces
Slice
Preview the gcode

Actual results

The resulting gcode is treating the area of the model modified by the second object as a bottom surface not a top surface and does not add ironing, but only when slicing for the Snapmaker U1. When the same model and the same modifier is used and sliced for the Bambulab P1S the modifier works as expected.

Prepare

Preview

This does not happen with a manually added modifier object though, only with the imported body that is changed to the modifier type.

This also does not happen if the custom modifier object has no settings changes.

Expected results

The object in the imported model should function the same as adding a primitive shape modifier and treat the top surface as a top surface.

Project file & Debug log uploads

orca smu1 modifier slicing issue.zip

debug_Fri_Feb_20_11_22_00_33880.log

Checklist of files to include

Log file
Project file

Anything else?

No response

*Originally created by @scrith on 2/20/2026* ### Is there an existing issue for this problem? - [x] I have searched the existing issues ### OrcaSlicer Version 2.3.1 ### Operating System (OS) Windows ### OS Version Windows 11 ### Additional system information _No response_ ### Printer Snapmaker U1 / Bambulab P1S ### How to reproduce 1. Create a model with multiple top surfaces 2. Add a second object to the model that will encompass one surface that is not the topmost surface 3. Import the STEP or 3MF into OrcaSlicer and change the object type of the second object to a modifier 4. Change the modifier object setting to iron all top surfaces 5. Slice 6. Preview the gcode ### Actual results The resulting gcode is treating the area of the model modified by the second object as a bottom surface not a top surface and does not add ironing, but only when slicing for the Snapmaker U1. When the same model and the same modifier is used and sliced for the Bambulab P1S the modifier works as expected. Prepare <img width="1530" height="761" alt="Image" src="https://github.com/user-attachments/assets/4a348cb0-563c-4dbc-9dfa-59b93a759e30" /> Preview <img width="1645" height="1379" alt="Image" src="https://github.com/user-attachments/assets/5ddd9d0c-04aa-42ff-a139-6a7cd1ecddac" /> This does not happen with a manually added modifier object though, only with the imported body that is changed to the modifier type. This also does not happen if the custom modifier object has no settings changes. ### Expected results The object in the imported model should function the same as adding a primitive shape modifier and treat the top surface as a top surface. ### Project file & Debug log uploads [orca smu1 modifier slicing issue.zip](https://github.com/user-attachments/files/25450731/orca.smu1.modifier.slicing.issue.zip) [debug_Fri_Feb_20_11_22_00_33880.log](https://github.com/user-attachments/files/25450985/debug_Fri_Feb_20_11_22_00_33880.log) ### Checklist of files to include - [x] Log file - [x] Project file ### Anything else? _No response_

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Reference: github/OrcaSlicer#682