How does the Slice Model tool work for creating multi-layer 3D carvings that exceed machine depth?

Overview

Slice Model divides the composite model into horizontal Z-slices, and each slice becomes its own component. It is for parts that exceed the Z depth of your machine gantry, the cutting length of your tools or the thickness of the material you are using. Each slice is cut separately, and the slices are re-assembled to make the finished full-depth part.

Slice Model only cuts in Z. It does not divide a panel into sections across X and Y. To split a component sideways, use Split Component (Aspire) or separate jobs.

When You Need Slice Model

• The model is taller than the available material. A 4 inch deep relief cut from 1 inch thick boards needs four slices, each cut from a 1 inch board and glued up.
• The model exceeds your machine's Z travel. For example, the machine has 3 inches of Z travel but the model needs 5 inches.
• The tool's cutting length is too short. A ball nose that only cuts 2 inches deep cannot make a 3 inch model, so slice it into two 1.5 inch sections.
• Deliberate lamination. Each slice can be a different material or species of wood.

Slice Model solves a DEPTH problem (Z). Tiling toolpaths solve a LENGTH or WIDTH problem (X or Y): the model stays the same but the cuts are divided into machine-sized sections for a bed smaller than the job. They are sometimes used together on very large, deep projects: slice the model first, then tile the toolpaths of any slice that is still wider than the machine bed. See the Toolpath Tiling Manager in the official documentation.

How to Use Slice Model

1. Hide any components you do not want included. Only the visible composite model is sliced.
2. Open Slice Model (Model menu, Create Component From... > Slice Model, or the Modeling tab icon). The top of the form shows the thickness of the current composite model and the material thickness.
3. Choose how to set up the initial slices in Model Slicing:

• Slice Thickness: each slice is the thickness you specify (for example 0.75 inch to match your boards). Tick From Top to slice from the top down. The final, possibly thinner slice is whatever height remains. With From Top ticked it is at the bottom, and with it unticked it is at the top. For example, a model 4.75 inches thick with a 2.0 inch slice thickness and From Top ticked gives slices of 2.0, 2.0 and 0.75 inches, with the 0.75 inch slice at the bottom. Use this method when slice thickness must match the stock you have.
• Number of Slices: divides the composite model thickness equally. For example, a 3.96 inch model with 3 slices gives three slices each 1.32 inches thick. Use this when the exact thickness does not matter.

4. Optionally tick Create Boundary Vectors, which creates a vector boundary for each slice on the same layer as that slice's component preview. These can define the machining regions for each part, so you do not have to draw them by hand, and they can be used as a profile toolpath to cut each slice to its final silhouette before assembly (useful for dimensional letters, tiered bases and layered carvings).
5. Click Slice Model. Each slice becomes a component in the Component Tree.

After slicing: each slice is its own component that can be shown or hidden independently, given its own toolpaths and moved into position on the job. The Component Tree keeps a copy of the original components as well as the new slice components, so the model can look very thick. Delete, undraw or move components before going further, and hide the originals before calculating toolpaths on the slices.

Editing the Slice Heights

The Slice Heights section controls the details of each slice. It shows a height bar and a list of the slice heights by Z value. It edits the heights at which the model is sliced, not the slices themselves.

• Change a slice height: select it in the list, enter a new value and click Apply. This may adjust the thickness of the neighboring slices.
• Add slices: enter a Z height and click Apply, or double-click the height bar at the position you want.
• Remove a slice height: select it in the list and click Delete. The slices on either side merge into one.

3D view while slicing: red areas are included in the selected slice. Green areas are above the slice height and will be sliced flat. The slice happens between the red and green areas. You can also double-click the model to set the active slice height to that height, Shift + double-click to insert a new slice height, and Shift + mouse wheel to nudge the active slice height, which is useful for removing thin slices. Check whether a slice boundary falls through a face or fine detail and move it to a less conspicuous area.

Assembly Planning

Slicing needs planning for assembly:

Registration (alignment):

• Plan dowel holes or pilot holes in each layer before machining so you can line the parts up. Aligning several layers of an organic relief by eye is very hard.
• Using a consistent machine origin and coordinate system for every layer helps them align when stacked.

Fragile areas:

• Review each slice for thin or fragile geometry before machining.
• Thin features at a slice boundary may snap during handling. You can adjust a slice height slightly so fragile areas do not fall at the cut plane.

Slice thickness strategy:

• Match the stock thickness you have (for example 1.5 inch slices from 1.5 inch material).
• Very thin slices mean many glue joints, alignment trouble and fragile edges, so use the fewest slices that work.
• Plan the glue-up before slicing: grain direction, alignment features (dowels) and clamping access all matter.

Labeling: number the slices and mark top and bottom, front direction and slice (for example "Slice 1 of 3, bottom") before removing each from the machine, and photograph the stack before glue-up. Dry-fit all slices before applying glue.

Glue-up:

• Use standard wood glue and clamps for most applications.
• Protect the carved surfaces when clamping, for example with foam or padding.
• Stack and align all slices before applying glue, then glue one layer at a time.

Practical Example: Deep Relief

A carver wants a 4 inch deep shell relief but only has 1 inch thick material:

1. Model the full 4 inch relief.
2. Open Slice Model and set Slice Thickness to 1 inch.
3. Four slice components are created.
4. Hide the original components.
5. For each slice, position it in the material, then calculate 3D roughing and finishing toolpaths and cut it from 1 inch material.
6. Stack the slices in order, align them, and glue.
7. Sand the seams at the glue lines.

Common Mistakes

• Not hiding unwanted components before slicing. Every visible component is included.
• Not planning registration holes.
• Setting a slice thickness larger than the available stock. Each slice must fit within your material.
• Making slices too thin for the detail in the model.
• Forgetting that the original components remain in the tree. If you calculate toolpaths without hiding them, the originals and slices both contribute to the composite and the depth is wrong.