Choppy or bad lettering
Choppy lettering is nearly always too many nodes in the vectors, often from a traced image. The machine decelerates for every tiny segment, so the result is both slow and visibly faceted. Simplify the vectors or use real font outlines.
Carved text that looks faceted rather than smooth, with visible flat segments on curves, wobbles along what should be straight strokes, or ragged corners. The machine often sounds like it is stuttering through the letters.
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Most likely causes
- Far too many nodes in the vectors, usually from a traced imageMost common
A trace of a low resolution image inherits every pixel stair-step as real geometry. The toolpath follows every tiny node, and so does the machine. See vector troubleshooting. - Arc fitting disabled in the post processorOccasional
Curves are output as thousands of tiny straight lines instead of arcs. Enable it if your controller supports arcs. Most modern posts already do. - Dull V-bitCommon
The tip makes the corners. A worn tip makes them round and ragged. See V-bits. - Low acceleration settingsOccasional
The machine physically cannot change direction fast enough to follow fine detail smoothly. - Mechanical backlashOccasional
Lettering reverses direction constantly, which is exactly where slack shows. See backlash. - Text too small for the bitOccasional
A tip with a flat cannot cut a detail narrower than that flat. - Material that cannot hold the detailOccasional
Red oak pores and softwood fibres crumble fine lettering regardless of everything else.
Diagnostic steps
- Count the nodes on one letter in your design software. A handful per letter is right. Dozens or hundreds is the answer.
- Listen to the machine through the lettering. A stutter or a buzz on every curve means it is decelerating for tiny segments.
- Check the CAM time estimate. Lettering that estimates far longer than its size suggests is segment-bound.
- Look at the corners under a loupe. Rounded where the vector is sharp means the tip is worn or the bit has a flat. Ragged means the wood.
- Cut the same text in MDF. If it comes out clean, the wood was crumbling the detail.
Fixes, in order
- Use real vector text rather than a traced image wherever possible. Convert it to outlines before toolpathing.
- Simplify the vectors. Most design software has a node reduction or curve fitting command. Use it, then check the shape still looks right.
- Re-trace from a higher resolution source if you must trace, and clean up afterwards.
- Enable arc fitting in the post processor.
- Fit a sharp V-bit. Keep one specifically for final lettering.
- Check for backlash and fix any mechanical slack.
- Increase the text size or choose a narrower V-bit angle if the detail is simply too fine.
- Change material if the wood is crumbling the detail.
Why it happens
A smooth curve described by a few Bezier curves gets converted by CAM into a small number of arcs or a smooth chain of moves, and the machine can run through it at speed. The same curve described by 800 tiny straight segments becomes 800 separate moves, and the controller has to decelerate at the end of each one because it cannot know the next one continues smoothly.
The result is a machine that crawls through the lettering while making a stuttering noise, and a carve where each of those tiny segments is visible as a flat. The design file caused both.
Prevention
- Type text in the design software and convert it to curves there. Never trace a screenshot of text.
- When you must trace, start from the largest and cleanest source you can get, then run node reduction and look at the result.
- Keep one sharp V-bit for lettering only, and retire it to roughing when the tip goes.
- Match the text size and the wood to each other before you toolpath.