How to Convert Images for CNC Engraving
CNC engraving machines carve designs into material using a rotating bit that follows precise toolpaths. Unlike laser engravers that burn images pixel by pixel, CNC machines need vector paths or highly optimized raster data to generate clean cuts. Feeding the wrong image format into your CNC software produces rough, inaccurate results or may not work at all.
The conversion process for CNC is more involved than for screen or print use. You need to think about toolpath generation, bit size relative to detail level, and whether your design requires 2D engraving, 2.5D relief carving, or full 3D machining. Each approach has different image format requirements.
This guide covers the practical steps to convert any image into a CNC-compatible format, whether you are engraving signs, plaques, decorative panels, or custom parts.
Step-by-Step Instructions
- Determine Your Engraving Type
CNC engraving falls into three categories. Line engraving follows vector paths and requires SVG or DXF files. V-carving traces letters and shapes with varying depth for a chiseled look, also using vector paths. Relief engraving (2.5D) uses grayscale heightmaps where white is the highest point and black is the deepest cut, requiring grayscale PNG or BMP files. Know which type you need before converting your image.
- Convert Raster Images to SVG for Line Engraving
If your CNC software requires vector paths, you need to convert your raster image (JPG, PNG) to SVG. Use an image tracing tool to convert pixel data into vector paths. Clean up the traced result by removing unnecessary nodes and simplifying curves. The cleaner your vector paths, the smoother your CNC toolpaths will be and the faster the machine will run.
- Create Grayscale Heightmaps for Relief Carving
For 2.5D relief engraving, convert your image to grayscale where brightness represents depth. White areas remain at the surface and black areas are carved to full depth. Convert your color image to grayscale, then adjust levels to ensure you are using the full brightness range from pure black to pure white. Export as PNG or BMP at the resolution matching your CNC machine's step-over distance.
- Set Resolution Based on Bit Size
Your image resolution should match what your CNC bit can physically reproduce. A 1/8-inch bit cannot carve details smaller than 1/8 inch. Calculate the minimum feature size based on your bit diameter, then ensure your image resolution does not include details smaller than that. Over-detailed images waste machining time without visible improvement. For most CNC engravings, 150 to 300 DPI at the final carving size is sufficient.
- Export in the Correct Format
For vector-based CNC work, SVG is the most widely supported format. For raster-based relief carving, use PNG (lossless, smaller files) or BMP (universal compatibility with older CNC software). Avoid JPG because its compression artifacts create unwanted surface texture in relief carvings. Save at the exact dimensions of your intended carving area.
Format Requirements by CNC Software
Different CNC software packages accept different file formats. Carbide Create works with SVG and PNG for both vector and pixel-based operations. Vectric VCarve and Aspire accept BMP, JPG, PNG, and TIFF for relief modeling and SVG and DXF for vector work. Easel by Inventables accepts SVG for vector carving. Fusion 360 can import SVG, DXF, and use image files as height maps for 3D operations.
If you are unsure which format your software requires, SVG is the safest bet for 2D line and V-carve work, and PNG is the safest for relief carving. Both are widely supported and maintain quality through the conversion pipeline.
- SVG: Universally accepted for vector toolpath generation
- PNG: Preferred for relief carving heightmaps (lossless compression)
- BMP: Compatible with older CNC software that does not accept PNG
- DXF: Alternative vector format for CAD-based CNC workflows
Optimizing Images for Clean Toolpaths
The cleanliness of your CNC output depends on how well your image converts to toolpaths. Noisy images (from JPG compression or low-quality sources) generate noisy toolpaths, which means the bit chatters and produces rough surfaces. Start with the highest quality source possible, use lossless formats, and apply a slight Gaussian blur to eliminate noise before generating toolpaths.
For text and logos, vector formats always produce cleaner results than raster because the machine follows smooth mathematical curves rather than approximating pixel edges. If your design contains text, convert it to outlines in SVG format rather than engraving from a raster image.
Quick Format Conversion
imageconvert.co converts between image formats entirely in your browser. Convert your source images to PNG or BMP for relief carving, or prepare raster files for vector tracing. No file uploads, no accounts, and no file size limits. Your workshop designs stay private on your device.
Frequently Asked Questions
What is the best image format for CNC engraving?
It depends on the engraving type. For line engraving and V-carving, SVG (vector) produces the cleanest results. For relief carving (2.5D), grayscale PNG is ideal because it preserves exact brightness values without compression artifacts. BMP is an alternative for older CNC software.
Can I use a JPG file for CNC engraving?
You can, but it is not recommended. JPG compression creates artifacts that translate into unwanted surface texture in relief carvings and rough edges in line engravings. Convert your JPG to PNG first to lock in the current quality, then use the PNG file for your CNC workflow.
What resolution should my image be for CNC engraving?
Match the resolution to your bit size and step-over distance. For most hobby CNC machines with 1/8-inch bits, 150 to 200 DPI at the carving size is sufficient. Professional machines with smaller bits can benefit from 300 DPI. Higher resolution than your bit can physically reproduce just wastes machining time.
How do I convert a photograph for CNC relief carving?
Convert the photo to grayscale, then adjust levels so the brightest areas are pure white (surface) and the darkest areas are pure black (maximum depth). Increase contrast to separate foreground from background. Export as PNG at your desired carving dimensions and 200+ DPI.
Convert images to PNG for CNC work