Cut circles turning elliptical, polygonal or distorted is a common laser‑cutting issue. It stems from combined factors of machinery, cutting process and material. Below lists major causes and countermeasures.
‑Symptom: Regular elliptical shapes or flat spots on certain axes of cut circles. ‑Cause: Clearance or wear exists on gears, racks, servo motors, guide rails and sliders of X/Y‑axes. When the cutting head switches moving directions, tiny delay or jitter occurs due to clearance, making actual trajectory deviate from programmed path. ‑Solutions:
‑Symptom: Circle distortion appears randomly and gets worse in certain working zones. ‑Cause: Mis‑leveled machine installation, deformation induced by long‑time operation or foundation settlement. ‑Solution: Re‑level the machine and perform precision compensation with laser interferometer by factory technicians.
If mechanical parts work normally, check cutting‑process configurations.
‑Symptom: Local over‑burning or melting leading to irregular contours. ‑Causes: ‑Excessive speed: Incomplete cut‑through, delayed plasma spark, energy accumulation at corners and contour ablation. ‑Over‑high power: Heavy edge over‑burn and loss of fine details especially for thin sheets. ‑Unsuitable gas pressure: Insufficient pressure fails to blow away molten slag, resulting in dross and secondary combustion. ‑Solutions: ‑Match cutting speed and laser power for different material thicknesses. Reduce travel speed for small circles. ‑Optimize gas type and pressure setting.
‑Symptom: Rough, non‑vertical cutting section and decreased circular precision. ‑Cause: Too‑deep or too‑shallow focus broadens laser beam, weakens cutting capacity and widens kerf. ‑Solution: Set proper focal offset. Negative defocus is often adopted for thin sheets for finer kerf and smaller spot size.
‑Symptom: Poor circular symmetry and uneven dross adhesion. ‑Cause: Mismatched nozzle bore, nozzle offset or damage causes asymmetric gas flow, deteriorating slag removal and cooling performance. ‑Solutions: ‑Select proper‑bore nozzles according to plate thickness (small bore for thin sheets, large bore for thick sheets). ‑Replace damaged nozzles regularly; calibrate nozzle concentricity with alignment scope.
‑Symptom: Unstable cutting quality for circles in different positions of the same sheet. ‑Cause: Warping or internal stress of sheets triggers continuous Z‑axis height adjustment of cutting head, shifting focal point; rust or coating lowers laser‑beam absorptivity and brings unstable energy input. ‑Solutions: Use flat, high‑quality raw sheets. Pre‑treat rusty or coated workpieces or fine‑tune power parameters.
‑Symptom: Bumps at start‑cut point or rough circle periphery. ‑Causes: Improper lead‑in length; “fine circle / hole‑cutting” function is disabled on control systems (Bochu, Xunlei etc.). ‑Solutions: ‑Adopt arc‑shaped inner lead‑in instead of straight lead‑in to eliminate start‑point scars. ‑Enable the dedicated hole‑cutting function in cutting software. It will automatically optimize parameters: reduce cutting speed, adjust power and air pressure, and improve motion tracking accuracy for circular trajectories.
Systematic troubleshooting above can resolve most out‑of‑round circle cutting problems.