How do I create a Celtic knot from scratch in Aspire using the Celtic Weave gadget and Extrude and Weave?

Overview

Celtic knots are one of the most impressive things you can make with Aspire. Two tools work together: the Celtic Weave Creator gadget, which produces the vectors for a grid-based weave pattern, and the Extrude and Weave tool, which turns those vectors (or hand-drawn freeform knots) into a 3D over-under weave. For the Extrude and Weave options themselves, see the entry on how Extrude and Weave works.

Method 1: Celtic Weave Creator Gadget (Fastest for Grid Patterns)

Best for rectangular or square grid-based Celtic patterns: panels, borders, picture frames and decorative tiles.

Step 1: Open the Gadget

Open Gadgets > Celtic Weave Creator from the Gadgets menu (it is not in the Modeling tab).

Step 2: Define the Knot Grid

Define the size of the weave grid you need, then click Update Grid Size to see the change in the Weave Preview Image.

Step 3: Design the Crossing Pattern

Click the interactive Weave Preview Image to cycle through the options at each intersection. There are three: Cut Vertical, Cut Horizontal and Cut Neither. Use the Reset Grid Content button to reset the preview at any time.

Step 4: Create the Cross-Section and the Artwork

1. Choose the cross-section you want and click Create cross-section to add it to the 2D view
2. Click Apply to convert the weave design into vector artwork in the 2D view. You can change the preview and click Apply again to update the artwork as often as you like.
3. Click Close when you are happy with the design

Re-editing: if you re-select the unedited weave pattern in the 2D view and re-open the gadget, it shows your current weave in the preview for further editing.

Step 5: Create the 3D Weave with Extrude and Weave

1. Open Extrude and Weave in the Modeling tab
2. Select the main weave pattern vectors (not the cross-section vector) and click Use Selection in the Drive Rails section. The rails turn orange.
3. Select the cross-section vector, then click anywhere on the weave rails in the 2D view to apply the cross-section to them
4. Tick the Weave option
5. Adjust Z Over and Z Under to control how pronounced the over-under effect is. The documented example uses 70% Z Under and 130% Z Over, which is a good place to start. A bigger gap gives a more dramatic weave.
6. Click Apply to create the 3D weave component

Method 2: Freeform Knot from Drawn Vectors

For custom Celtic knot shapes (circular, triquetra, irregular) that do not fit a rectangular grid.

Key Rule: a Center Line Vector

Experienced users on the software maker's forum draw a center line vector of the whole knot first, which should end up as one closed vector. The center line traces the middle of all the knot strands as a simple continuous path.

Drawing tips:

• Use a reference image of the knot you want
• Trace the center path of the strands as a single vector and join all the segments
• Aim for a closed loop (start and end nodes connected)
• Keep the vector's start point off a crossing. A forum project showed a small mismatch at the center of a knot whose start point sat on a crossing; moving the start point to a nearby node that is not on a crossing fixed it.

Apply Extrude and Weave

1. Select the closed center-line vector(s)
2. Open Extrude and Weave and click Use Selection
3. Select the cross-section vector. A small arc, about 1/4 inch in diameter, is a common choice, and a double arc gives two humps on each strand. The cross-section can be nearly any open shape within reason.
4. Tick the Weave option
5. Click Apply

Toolpath Setup for Celtic Knots (starting points to test)

3D Component Approach (full relief)

1. Create the 3D weave component
2. Use a 3D Roughing toolpath with a 1/8 or 1/4 inch ball nose to clear bulk material
3. Use a 3D Finishing toolpath with a small tapered ball nose (1/32 to 1/16 inch tip) for sharp detail in the grooves. A smaller tip gives sharper groove corners but a longer cut time.

Hybrid V-Carve Approach

1. Create the 3D weave component and a 3D Finishing toolpath
2. Add a V-Carve toolpath over the same area to deepen and sharpen the grooves, since a ball nose rounds them over

Background Clearance (Making Knots Pop)

To isolate the knot against a cleared background:

1. Draw a boundary rectangle or circle around the knot
2. Create a Pocket toolpath inside the boundary but outside the knot vectors
3. Use a 1/8 inch end mill for clearing

This removes the background material and leaves the 3D knot raised above a flat field.

Machining Tips from the Community

• Tapered ball nose bits with a small tip give the sharpest results for finishing a knot
• Use a small stepover on the final pass. Try your own feed rate and stepover on scrap first, because the right numbers depend on your machine and bit.
• Hardwoods (walnut, maple, cherry, oak) usually give the sharpest detail and cleanest over-under definition. Softwoods can tear at fine detail points.
• A dark stain wiped into the grooves, followed by a light sanding of the surface, gives strong contrast