Sheetcam Hot Crack ((new)) Jun 2026

A hot crack occurs during the solidification phase of the welding or thermal cutting process. As the plasma arc or laser melts the metal, a localized pool of molten material forms. If this pool cools too rapidly, or if the surrounding metal expands and exerts tensile stress on the cooling zone, the material tears apart as it solidifies.

Hot cracks happen when the thermal contraction strains exceed the mechanical strength of the solidifying metal. Three main factors contribute to this failure:

Worn electrodes or nozzles cause erratic arcs, leading to inconsistent heat and increased stress on the material. CUMIC Steel Are you experiencing cracks on a specific material thickness or type, such as AR400/500 wear plate? Sheetcam Tutorial 7: Start Points

: Cracks often occur at the "crater" where a cut ends. You can set a rule to turn off the torch or adjust the height slightly before the end of the cut to minimize thermal shock. Preventing Cracking in Fabrication

By keeping the torch in motion while the arc shuts down, the residual heat and trailing arc are distributed along an already-cut path rather than concentrating in one static spot. sheetcam hot crack

, this defect is primarily managed by adjusting lead-in/lead-out settings, path rules, and cutting speeds to control heat input and residual stress. 1. Understanding the Causes

A lead-out allows the torch to cross past the finish line before turning off. This moves the final "extinction crater"—where the arc dies and leaves a cooling shrink point—away from your finished piece. 2. Implement Overcutting

The "hot crack" issue highlights the necessity of the CAM programmer’s expertise. A perfectly generated SheetCam file can still result in cracking if the gas pressure

The torch will continue past the start point of the circle or shape. This prevents the "hot crack" by ensuring the metal is fully severed before the arc terminates. 3. Lead-Outs A hot crack occurs during the solidification phase

When programing CNC plasma, oxy-fuel, or laser cutters in SheetCam, achieving a flawless finish requires more than just correct feed rates. One of the most frustrating defects fabricators face is the "hot crack"—a structural or visual defect left at the exact point where the torch starts or stops cutting.

Retains heat poorly compared to carbon steel, leading to massive heat accumulation. Using a combination of nitrogen shield gas and smooth arc lead-outs in SheetCam is critical.

Mill scale, rust, and surface oils act as contaminants. When melted into the cut pool, they alter the metallurgy of the edge, drastically reducing its resistance to cracking. Clean your cut lines prior to running the program. Conclusion

SheetCam allows users to define "Path Rules" that automatically reduce feed rates on small circles or tight corners. While slowing down is often necessary for accuracy, SheetCam helps users find the "sweet spot" where the torch moves fast enough to avoid the excessive heat that causes grain boundary separation (the root of hot cracking). Lead-in/Lead-out Strategies: Hot cracks happen when the thermal contraction strains

The plasma arc does not straight-line down from the torch; it trails slightly behind the torch movement. When the torch stops at the end of a path, the trailing arc catches up, concentrating intense heat in one spot.

Ensure your lead-in is long enough to keep the initial pierce puddle away from the final part edge. For thick materials, a lead-in of 6mm to 10mm (0.25" to 0.4") is recommended.

Rapid heating followed by sudden cooling creates intense localized shrinkage.