Common-line nesting
Shared-edge cut planning: compatible parts, kerf ownership, cut-side quality, sequencing, dimensional checks and realistic savings.
Tags: production, planning, nesting, cutting
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Two 100 × 50 mm rectangles have 600 mm of separate nominal contour. Sharing a 50 mm edge reduces unique contour to 550 mm, saving 8.33% of contour or 3.0 s at a constant 1,000 mm/min. This omits kerf offsets, leads, pierces, rapids and support features. On a fixed centerline, increasing symmetric kerf from 1.0 to 1.2 mm retreats each edge by 0.1 mm. Verify both part edges.
Hypertherm describes a common pass forming two adjacent edges in compatible sheet, plate or slab layouts. Hypertherm, ProNest: Common Line Cutting, January 23, 2017
Confirm both parts meet dimensional, edge-quality and identification requirements after separation.
Distinguish shared cuts from linked cuts
Hypertherm lists Common Line Cutting separately from Chain and Bridge Cutting in its ProNest modules. Sharing an edge, linking profiles into a continuous cutting route and retaining connecting material are different operations. Confirm the selected CAM operation rather than interpreting every reduction in pierces as common-line cutting. Hypertherm, ProNest optional modules
A common-line plan may also include ordinary independent profiles, internal features and skeleton cuts. Describe which edges are shared and which remain separately processed. Do not delete duplicate-looking geometry from the part master merely to force a shared path: retain the nominal part definition and make the manufacturing relationship explicit in the nest.
Establish eligibility before optimizing
Group parts by actual stock compatibility: material and grade, thickness, condition, required surface, traceability and approved cutting process. Also preserve permitted rotations, grain or rolling direction, handedness and side-specific finish. An attractive arrangement must not silently mirror a handed component or mix stock identities.
Review each candidate shared edge against its requirements:
| Input | Planning question |
|---|---|
| Nominal geometry and tolerances | Can one path satisfy both adjoining boundaries? |
| Edge angle, taper and finish | Are both sides of the cut acceptable? |
| Leads and corners | Can entry, exit and junctions avoid critical finished surfaces? |
| Support and release sequence | Will remaining cuts occur while parts are still controlled? |
| Identification and removal | Can each completed part retain its required identity? |
For example, a weld-preparation bevel and a square finished edge are not automatically compatible merely because their plan-view outlines coincide. Resolve the actual three-dimensional cut and process capability.
Define who owns kerf compensation
Kinetic's Primecut SmartCluster documentation says its common-line geometry is explicitly offset using the specified kerf and its common cuts are marked kerf none, while outside cuts retain ordinary kerf treatment. It warns that this arrangement prevents adjusting shared-cut kerf at the machine. That is a specific implementation rule, not an instruction to disable compensation globally in every CAM system. Kinetic, SmartCluster: Common Line and Common Crop Cutting
The older Primecut manual workflow is explicitly marked deprecated. It defines its requested Kerf Offset as center-to-cut-edge distance, equivalent to a radius rather than a full cut width. This illustrates why a field labeled “kerf” must be interpreted using its own documentation and version. Kinetic, deprecated Manual Commonline Cutting
By comparison, Autodesk's 2015 CAM-Duct/Profile Master help describes setting an inter-part margin consistent with the configured kerf, enabling Common Line Cut when writing NC, and inspecting the resulting NC. A visible spacing in the nesting interface therefore need not represent an extra strip that will remain between finished parts. Do not transfer that historical workflow to a different release without checking its implementation. Autodesk 2015, Common Line Cutting
Record the nominal geometry, actual process kerf basis, CAM compensation, postprocessor and controller settings together. Applying another offset to an already compensated shared path can invalidate both adjacent parts.
Protect both sides and the cut sequence
Kinetic warns that plasma's preferred cut side can compromise one adjacent part, and its SmartCluster guidance distinguishes cutting patterns whose direction changes affect taper. A shared path cannot give both adjoining edges the same side of one directional cut. Confirm both edges against their actual tolerances rather than inspecting only the favored part. Kinetic, SmartCluster process limitations
Review the posted sequence for repeated segments, unwanted extra pierces and cuts through already open gaps. Determine when internal features, common boundaries and final release cuts occur. Address thermal movement, loss of support, tip-up and safe head travel for the actual process and table. Removing a separating skeleton strip can change how the work is supported; a nest preview alone cannot prove stable execution.
Avoid a blanket rule that common-line cutting always reduces distortion or pierces. Savings depend on the resulting sequence, process and geometry, including leads, acceleration, corner behavior and any additional holding or cleanup operations.
Original bounded path-length example
Assume two identical 100 × 50 mm rectangular parts. Each independent nominal outline has perimeter 300 mm, so two independent outlines total 600 mm. Arrange the parts to share a 50 mm edge:
- The two original outlines count that boundary twice: 100 mm.
- One shared pass counts it once: 50 mm.
- Ideal unique contour length becomes 550 mm, a 50 mm or 8.33% reduction.
- At an assumed constant 1,000 mm/min, this represents 3.0 s of ideal cutting-motion time saved.
This original model concerns nominal straight contours only. It excludes kerf offsets, leads, pierces, rapids, corners and support features, and supplies no achievable tolerance or cycle-time promise.
As a separate sensitivity calculation, suppose a fixed centerline is planned for a 1.0 mm full kerf but the actual cut is 1.2 mm, symmetrically about that centerline. Each adjacent edge retreats an additional 0.1 mm. If the other boundaries are unchanged, each part loses 0.1 mm of width at that edge. This is a hypothetical symmetric-cut model; it does not represent plasma taper or establish an adjustment method.
Release and acceptance
Compare plans using conforming output, actual cycle time, material consumption and downstream work. Report retained remnants separately from scrap. A shorter toolpath that increases rework or prevents a required edge finish may be the worse plan.
Before production, confirm the posted NC against part revisions, counts, stock identity, shared boundaries and compensation ownership. Measure representative adjoining parts, including shared-edge dimensions, squareness/taper and critical junctions. Define acceptance and revalidation for kerf drift, consumable changes, new material/thickness or changed software/postprocessor settings.
The handoff should include stock and part identities, nest revision, permitted orientation, shared-edge map, process/kerf basis, posted program, removal sequence and inspection requirements. Distinguish a proposed nest from released production and completed inventory transactions.
Source versions
Reviewed 2026-11-01. Hypertherm's cited article is dated January 23, 2017; Autodesk's cited help belongs to its 2015 documentation. The retrieved Kinetic and ProNest module pages expose no separately verified technical issue date, so none is inferred from crawl dates. Primecut's deprecated manual method is identified as historical. Numerical examples and the release checklist are original planning guidance, not machine settings or a company policy.