CraftMold STL formwork walls
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Free tool · STL

Trim STL bottom online

Remove a specified thickness from the bottom and get a flat, closed base.

or drop your file hereASCII and binary STL · up to 200 MiB · up to 4 million triangles

Processed on your device. Download the model or create a project.

Load a model to see the preview

Drag to orbit · scroll to zoom

STL

Make a flat base

Height before → after: —

The model is not scaled — only the bottom layer is removed.

Adjust manually

Dimensions, mm

— × — × —

Choose an STL to get started.

Change dimensions

STL has no units. We interpret dimensions as millimeters.

Change one dimension to scale all dimensions proportionally.

Choose the bottom

On upload, the model is automatically aligned with its detected base. For another plane, press Select bottom plane on the main screen, then hover over the required side and click the highlighted plane.

How to make an STL base flat

On upload, the tool looks for a contact patch and levels the model with it. Check the selected bottom: select a plane with the pointer, or restore the STL orientation. Enter how many millimeters to remove, measured from the lowest point. The cut is capped with a flat surface while preserving the remaining geometry. For an uneven base, a small cut is suggested for the main contact patch. Raised feet and rounded protrusions do not require cutting the whole model up to their height. Check the orange highlight: this estimate is approximate and does not guarantee stability. No preset is suggested when a flat contact patch is detected or there is insufficient evidence for a confident estimate.

Example: trim 0.2 mm from the bottom

An 80 mm tall model has an uneven base. Enter 0.2 mm: after trimming, the height is 79.8 mm. The new cut is flat and closed.

Trimming removes only the part below the plane. The remaining model keeps its scale, so details and distances retain their dimensions. Changing dimensions in the settings is a separate operation that scales the entire model proportionally.

Supported models

The tool checks and prepares the mesh for trimming. Closed parts may touch each other. If the geometry engine cannot obtain a valid solid and cap the cut, the tool shows an error.

Runs in your browser

Your file is uploaded only when you choose Create project. Download free without an account or engraving. The current source is loaded from the project on every visit. Creating a project temporarily saves the prepared model in this browser; that copy is removed after a successful upload.

STL trimming questions

What if the STL dimensions are wrong?

STL does not store units. This tool interprets coordinates as millimeters. If the dimensions are wrong, open Change dimensions and enter one correct dimension in mm. The others change proportionally. Then enter the trim thickness.

Why does processing fail?

Open holes or serious damage can prevent a closed solid. Supported junctions and touching parts are handled during mesh preparation. If preparation fails, repair the damaged parts in a mesh editor and load the STL again. For large models, also check the limits: 200 MiB and 4 million triangles.

Can I download the result without signing up?

Yes. Download the processed STL for free without an account or engraving. Your model is processed on your device. Creating a project uploads it to the server. To return to the original geometry, press Undo trim.