Edit an imported STL by filling its existing hole, cutting a smaller hole in a new position, and downloading the edited mesh without changing the plate's outside size.
This article was written with AI assistance using a recorded online modeling walkthrough. All instructional screenshots show the actual editor.
Use a closed plate STL with the dimensions below in a mesh editor that supports cylinder primitives, union and difference. The screenshots show one recorded workflow. For another model, measure its bounds and hole positions first; the coordinates in this exercise are not universal defaults.
- Plate width × depth × thickness: 70 × 40 × 6 mm
- World X bounds: -35 to 35 mm
- World Y bounds: -20 to 20 mm
- Bottom / top Z: 0 / 6 mm
- Existing through-hole: Diameter 10 mm, center X = -18 / Y = 0
- New through-hole target: Diameter 6 mm, center X = 18 / Y = 0
STL stores a triangle mesh rather than the original sketches and dimensions. This lesson adds and removes material with separate tool bodies; it does not recover the source feature history. The simple plate is a practice model for this editing technique.
01. Import an editable STL
In the illustrated editor, start a new Mesh Model project, then choose File → Import model and select your STL. Keep Model editable enabled and click Import. Select the imported entry in the Browser and set its Name to Imported Plate, pressing Enter to commit the name.
02. Check the starting size
Click the navigation cube's Top face, then use Measure to select the two outer vertices along the plate's long top edge. The practice plate reads 70.00 mm; remove the measurement with Delete and return to Select.
The coordinates below assume the bounds in the starting specifications. For a different STL, establish its actual size, hole center and top/bottom positions before placing either cylinder; camera zoom does not change those dimensions.
03. Create a plug for the old hole
Click Create cylinder and place it on empty grid beside the plate. Set Name to Hole Plug and press Enter, then enter these values in Dimensions.
- Radius: 5.2 mm
- Height: 6 mm
The old hole has a 5 mm radius; the extra 0.2 mm creates radial overlap with the surrounding material.
04. Place the plug inside the old hole
With Hole Plug selected, expand Transform and enter the world coordinates below. Keep all rotations at zero and Scale Ratio at 1.
- Pos X / Pos Y / Pos Z: -18 / 0 / 0 mm
- Rot X / Rot Y / Rot Z: 0° / 0° / 0°
The plug spans Z = 0–6, matching the plate's bottom and top, so it fills the bore without adding material above or below the plate.
05. Combine the plug with the plate
Select Imported Plate first, then hold Ctrl and select Hole Plug in the Browser. Click Combine operation, check Imported Plate as Combine target 1 and Hole Plug as Combine target 2, and leave Keep source parts off.
Click Confirm and name the result Filled Plate. The old opening should disappear into one continuous top face.
06. Create the new hole cutter
Click Create cylinder and place another cylinder on empty grid. Name it New Hole Cutter, press Enter, and set these Dimensions.
- Radius: 3 mm
- Height: 8 mm
This makes a 6 mm diameter opening; the extra cutter height lets it cross both faces of the 6 mm plate.
07. Position the new opening
Expand the cutter's Transform section and enter the world position below. Keep all rotations at zero and Scale Ratio at 1.
- Pos X / Pos Y / Pos Z: 18 / 0 / -1 mm
- Rot X / Rot Y / Rot Z: 0° / 0° / 0°
The cylinder now spans Z = -1–7, extending 1 mm beyond each plate face, with its center 36 mm along X from the old hole.
08. Cut the smaller hole
Select Filled Plate first, then Ctrl-select New Hole Cutter. Click Cut operation, check Filled Plate as Target part and New Hole Cutter as the only Tool part, and keep Keep source parts off.
Click Confirm and name the result Edited Plate. The preview and result should show an open hole on the right, with the old left opening filled.
09. Download the edited STL
Select Edited Plate and choose File → Export STL. Set Currently selected models and check the count is 1; leave Project precision selected, then click Download in browser to save the STL.
Import the downloaded file into your slicer using millimeters and place the broad bottom face on the build plate. The exercise uses chosen modeling dimensions rather than a tested hardware clearance.
Finished result
The edited mesh is one plate with the original 70 × 40 × 6 mm envelope. Its old 10 mm hole is filled, and a 6 mm through-hole sits at X = 18 / Y = 0. The exported STL carries the resulting geometry; a native project can retain the tool bodies and editing workflow. Save that project separately if you need to revisit the edit.
Practical tips
Match a filling tool to the plate's exact thickness, but extend a cutting tool beyond both faces. That combination preserves the exterior while avoiding a cut that only touches a surface. When changing one hole in another STL, measure that local region and move or resize the tools; scaling the whole model would also change its other dimensions.
Adapted from the original recorded STL-editing lesson by the Reactor 3D Team. No physical print or hardware-fit test is claimed.
