How do I create a lithophane in Aspire using Create Component from Bitmap: full workflow, material, and settings?

Overview

A lithophane is a 3D relief carved in translucent material. It looks faint in normal light, but when backlit it shows a photographic image with full tonal depth. Light areas of the photo become thin (more light passes through) and dark areas stay thick (less light). In Aspire you make one with Create Component from Bitmap and a 3D finishing toolpath. VCarve Pro owners can preview with Lithophane mode but have no Create Component from Bitmap; see the entry on whether VCarve Pro can make lithophanes. Photo V-Carve is a different technique (see the last section).

The Core Principle

Normal photo carving: dark areas are deep cuts. Lithophane: light areas are deep cuts (more material removed means thinner material and more light through).

This is the opposite of a standard bitmap-to-component conversion, so invert your image: either in your image editor before you import it, or by selecting the bitmap and using Edit Picture with the Invert option, which turns white to black and black to white.

Material Selection

The material must be translucent (lets light through) but not transparent (you want the light to diffuse). Common options:

Thickness: many makers start with 1/4 inch (6 mm) to 3/8 inch (9 mm) material. The carving leaves only a thin layer in the lightest areas (often around 0.03 to 0.05 inch, but test on scrap).

Image Preparation

1. Convert to grayscale in an image editor
2. Adjust levels and contrast. High-contrast images make better lithophanes, and flat, low-contrast photos give weak results.
3. Invert the image (or invert it later with Edit Picture, see above)
4. Apply a slight blur to reduce noise that would make the cut surface rough
5. Save as a grayscale TIFF (16-bit if possible for smoother gradients)

More image tips:

• Boost contrast aggressively. A flat, low-contrast image produces a flat, unreadable carving.
• Simplify busy backgrounds. They compete with the subject, so remove or blur them.
• Use a Black and White conversion with color channel mixing in your image editor rather than simple grayscale, and adjust the sliders to emphasize skin tones.
• Check midtones. If everything is mid-gray the carving looks flat, so push darks darker and lights lighter.
• Use the Add Border option in Edit Picture to fade the edges of the image into the material smoothly.
• Check which way the first component models. Light photo areas must come out THIN and dark areas THICK. If the light areas are raised, undo, invert the image (Edit Picture > Invert) and convert again.

Aspire Workflow (Create Component from Bitmap)

Step 1: Job Setup

• Create a job matching your material blank and set the thickness to the blank thickness (for example 0.25 inch)
• A common approach is to put Z zero at the machine bed or spoilboard, so you can control the gap below the model
• Choose a higher Modeling Resolution (such as High) if the piece is large and has fine detail. Standard is acceptable for many parts, and higher settings are slower.

Step 2: Create the Component Directly from the File

• Make sure no bitmap is selected in the 2D view
• Click Create Component from Bitmap and browse to your inverted grayscale image
• The software creates the component directly from the file (see the Create Component from Bitmap entry for why this matters for 16-bit images)

Step 3: Set the Component Height

• Open Component Properties (double-click the component in the tree)
• Set Shape Height to the maximum carving depth you want. Values around 0.10 to 0.15 inch are common starting points.
• Keep the combine mode on Add

Step 4: Material Setup, Gap Below Model

• In the model positioning section, Gap Below Model positions the model by the gap between the bottom of the model and the bottom surface of the material
• This gap controls how much material remains at the thinnest point, so it controls the contrast of the lithophane. Too thick and the image looks flat. Too thin and you risk cutting through, leaving bright holes.
• Many makers start around 0.03 inch (0.75 mm). Treat that as a starting point and test on scrap.

Step 5: Smooth the Component

• Apply several passes of Smooth Components (3 to 5 is a common starting point) to reduce photo noise. This also reduces jagged toolpath moves and improves surface quality.

Step 6: Calculate a 3D Finishing Toolpath

• Tool: a 1/16 inch ball nose for small pieces (such as 6 by 8 inch), or 1/8 inch for larger pieces
• Stepover: a small percentage of the tool diameter for maximum detail (for example 3 to 8%)
• Strategy: Raster, with the angle at 45 degrees for a photographic look
• Boundary: a vector around the image
• Many makers cut a lithophane in a single finishing pass without a roughing pass. Test your own setup.

Typical Settings from Experienced Makers (starting points)

• Material: medium brown Corian with a small metal flake
• Bit: 1/16 inch or 3/64 inch, 3-flute spiral solid carbide ball nose, single pass
• Scale height: about 0.10 to 0.12 inch depending on size
• Gap below model: about 0.05 inch
• Tool: 1/4 inch shank tapered 1/8 inch ball nose
• Smooth the component before the toolpath to reduce cut time

Lithophane Preview Mode

The Toolpath Preview form has a Lithophane mode. It shades the preview to look like a semi-transparent material lit from behind: the thinnest areas are brightest and the brightness drops to the lowest at full material thickness. It works with whatever material or solid color is selected, and a slider next to the option adjusts the brightness to suit the material and lighting. Use it BEFORE cutting to check the lithophane will look right.

Cutting Time

Lithophanes take a long time. A 6 by 8 inch piece with a 1/16 inch ball nose at a small stepover can take several hours. To cut time without losing much quality, smooth the component more before toolpathing, use a 1/8 inch ball nose for larger pieces, or raise the stepover slightly for first test pieces.

Not the Same as Photo V-Carve

The Photo V-Carve toolpath uses a V-bit to etch a copy of the selected bitmap into the surface of the material, and it is available in both VCarve Pro and Aspire. It is a surface engraving viewed by reflected light, not a translucent relief with varying thickness, and it takes a V-carving or engraving tool. Use it for photo plaques, and use the Create Component from Bitmap workflow above for a backlit lithophane.

Common Mistakes

• Using a low-contrast image, the single most common cause of poor results.
• Not inverting when the light areas model high: the image appears reversed when backlit, because the light areas block the light.
• Using extruded acrylic. It melts and gums up the bit, so use cast acrylic.
• Setting the carving depth too deep for the material, so the thin areas break through. Leave a thin skin even in the lightest regions.