I resized a 3D model and now it is too tall, too flat, or lost its detail. What changes when I scale a model?

What changes when you scale

Four things move when a model changes size, and only the first is obvious.

1. Height. The Auto Scale Z option decides this. Checked, the Z height grows and shrinks in proportion with X and Y. Unchecked, the height stays constant however you scale the footprint.
2. Slope. With Auto Scale Z off, shrinking packs the same height into a smaller footprint, so every wall gets steeper. Enlarging does the reverse and the model looks flatter.
3. Detail against the bit. The bit does not shrink with the model. Fine features that carved well at full size can become smaller than the tool can reproduce.
4. Model resolution. Resolution is spread across the whole job area, so a much larger job has coarser detail at the same setting.

Steps for a clean resize

1. Select the component and open Set Size (or press T for the transform tool). Keep the XY Link checked so the footprint is not distorted.
2. Decide on Auto Scale Z. Leave it checked to keep the model's proportions. Uncheck it when the height must stay where it is, for example to stay inside the board.
3. Open Material Setup and read Model Thickness. It must be less than the material thickness. If it is not, use Scale Model Height and Set Exact Height... to bring the whole composite model down.
4. If you had to reduce the height a lot and the model looks lifeless, in Aspire you can try Emboss Component instead of plain height scaling (see that entry; VCarve Pro does not have this tool).
5. Recalculate the 3D toolpaths and run the preview. The official documentation says to use the preview to judge finish quality and detail, and to move to smaller tooling or a smaller stepover if it falls short.
6. For a job that grew large, revisit Modeling Resolution. The official guidance suggests High for parts over 18 inches that still have small details, and Highest for very large parts over 48 inches with small details.

Pro tips

• To resize the job and the design together, open Job Setup and turn on the option to scale the design with the job size. The software then offers to recalculate the toolpaths. For resizing a whole finished project (vectors, text and toolpaths together), see the entry on resizing a whole finished project to a different size.
• In Aspire, a Texture Area component behaves differently. Resizing it changes the area covered, not the size of each tile.
• As a rough guide from one published relief article, a 1/8 inch ball nose suits pieces under 12 inches and a 1/16 inch suits very fine detail. Confirm with the preview.