Sheetcam Hot Crack [updated] [HD]
In SheetCam, apply a (an arc or line away from the part scrap).
In CNC cutting, this manifests as a small, fracture-like crater or a literal split at the entry or exit point of a cut. It compromises both the structural integrity of the part and its visual appeal. Primary Causes of Hot Cracking in CNC Cutting
The most effective way to eliminate a hot crack is to use the feature in SheetCam. An overcut instructs the torch to continue moving past the starting point of the cut along the waste side or the perimeter line before turning off.
Imagine cutting a long, thin rectangular slot inside a 1/2" steel plate. As the plasma travels down the long side, the steel on both sides of the kerf tries to expand. But it is trapped by the cold, solid surrounding material. The result? Elastic strain. When the torch finally closes the loop (the "cutout"), the trapped energy releases violently. The plate flexes, and a hot crack shoots across the narrowest point. sheetcam hot crack
Set up SheetCam rules to prevent the plasma torch from crossing over, or cutting too close to, an already cut area. This avoids re-heating a cold part, which causes thermal shock. Summary Checklist for SheetCam Optimization Action for Preventing Hot Cracking Feed Rate Increase to reduce total heat input. Pierce Delay Reduce to prevent excessive dwell. Lead-In Use smooth, long arc lead-ins. Cutting Rules Avoid cutting near recent heat-affected zones.
When we talk about a hot crack in SheetCam, we are usually referring to . This happens when the cutting torch has to slow down to navigate a sharp corner. As the machine decelerates, the torch dumps more energy into a smaller area for a longer period.
The evaluation version of SheetCam is limited to approximately 180 lines of G-code . Many cracks fail to bypass this reliably or cause the software to revert to evaluation mode mid-job, ruining expensive material. In SheetCam, apply a (an arc or line
To fix the problem in SheetCam, it helps to understand why it happens on the cutting bed. Hot cracks are typically driven by three factors:
If your hot cracks are occurring on sharp corners or small internal holes rather than the final closure point, the issue is likely due to machine deceleration. CNC machines must slow down to navigate sharp angles, which causes the plasma arc to burn wider and create a hot-crack appearance.
When a plasma torch cuts metal, it creates a localized pool of molten material. When the torch reaches the end of its programmed path and the arc abruptly extinguishes, the sudden drop in temperature causes the surrounding metal to contract rapidly. Because the center of the molten pool cools last, the tensile stresses pulling outward from the cooling perimeter tear the center apart, leaving a microscopic or visible crack. These cracks are highly problematic for several reasons: Primary Causes of Hot Cracking in CNC Cutting
The allure of free software is understandable, but the risks far outweigh the benefits. Using a "sheetcam hot crack" exposes users to several severe dangers.
High thermal expansion coefficients combined with low thermal conductivity trap heat, increasing localized stress.
: Reducing the feed rate (e.g., to 50%–70%) as the torch approaches a tight corner (less than 45°) helps achieve smoother results and prevents excessive heat buildup that can lead to cracking.
If the sheet is clamped too rigidly or the part geometry prevents natural expansion and contraction, stress accumulates directly in the weld/cut zone.