CNC, EDM and Grinding Combination Machining for Precision Parts

Wire EDM Routes

2D through-profiles, narrow slots, and internal corners commonly trigger CNC roughing followed by wire EDM.

1 start hole or accessible edge is required; the wire path limits fully enclosed features without an entry.

Sinker EDM Routes

3D ribs, blind sharp corners, and deep cavities commonly require CNC roughing, electrode manufacture, then sinker EDM.

1 electrode strategy must account for wear, flushing, and inaccessible cutter paths.

Grinding And Tooling Routes

Flat datum faces favor CNC, heat treatment where specified, then surface grinding; journals favor cylindrical grinding.

Multiple interacting mold features usually need CNC, EDM, grinding, fitting, and inspection under one revision plan.

Route Selection By Condition

Pre-hardened tool steel usually permits milling before finish grinding; hardened steel often shifts intricate profiles to wire or sinker EDM. Stainless may work-harden, so controlled cutting conditions and stock allowance matter.

Heat treatment can move datums and critical geometry. Define the heat-treatment state, post-treatment grinding stock and inspection datum on the drawing.

Electrode And Carbide Considerations

Copper and graphite are electrode materials, not interchangeable finished-part materials; electrode wear, feature size and finish target guide selection. Carbide is conductive but difficult to cut conventionally, making EDM plus diamond grinding a considered route.

Geometry And Access

Cavities, deep ribs, micro features, and sharp internal corners need explicit dimensions and section views. Identify where cutter access is restricted and where wire EDM or sinker EDM is permissible.

Threads, profiles, and mating bores belong on the drawing with callouts, thread standard, class, depth, and applicable datum references.

• Show cavity floor and wall requirements
• Dimension micro features from stable datums
• State internal-corner radius or EDM requirement

Datums And Tolerance Notes

Three datum references can establish a repeatable inspection and assembly scheme. Apply geometric tolerances to the features that affect location, sealing, motion, or interchangeability; avoid tightening all dimensions by default.

Surface texture, burr direction, edge breaks, and coating allowance belong in drawing notes. State whether final dimensions apply before or after coating.

• Define primary assembly datum
• Identify critical-to-quality features
• State coating thickness allowance

Identification And Inspection

Part numbers, revision marks, and traceability engraving require location, character height, depth limit, and prohibited surfaces. Put visual placement in the CAD model and controlled requirements on the drawing.

Inspection plans should name the critical dimensions, measurement method, sampling expectation, and report format. SUUXIANG can review these inputs against machining access and the proposed process route before production.

• Keep marks clear of sealing faces
• Link inspection records to drawing revision
• Provide mating-component context

Datum And Sequence

Three datum references should govern setups, electrode locations, and final inspection. Machine rough stock first, stabilize heat treatment where specified, then EDM and grind from controlled references.

One revision-controlled setup plan should identify which operation establishes each critical feature. This prevents a wire path or ground face from masking an earlier location error.

Allowance And Thermal Control

0.02 mm of final grinding stock is not a universal rule; the drawing review must define stock by material, geometry, and distortion risk. Insufficient stock leaves EDM texture or heat-treatment movement; excess stock raises grinding heat and cycle time.

One documented electrode offset and wear-compensation method is required for critical cavities. Coolant condition, spark strategy, wheel dressing, and dwell time should be controlled where they affect burn, taper, or profile.

Measurable Acceptance Criteria

Five acceptance items commonly need explicit limits: size, flatness, parallelism, profile, and surface finish. Define measurement datum, instrument, sampling quantity, and report requirement with each critical-to-quality feature.

100% inspection may be appropriate only for identified critical features, not assumed for every dimension. Require burr limits, edge-break definition, and evidence that mating faces remain free of damaging recast, grinding burn, or raised material.

• Datum-referenced flatness and parallelism
• Profile tolerance with inspection method
• Ra target and measurement direction
• Burr height or approved edge condition

DFM And Process Ownership

Before quotation, request a marked-up drawing review identifying tool access, electrode strategy, wire path, grinding stock, datums, and unresolved tolerances.

One supplier can own the tolerance chain only when it plans each handoff and verifies the final features against the same revision.

Engineering And Material Evidence

For each order, request programming controls, electrode drawings where applicable, material certificates, and the proposed heat-treatment sequence.

Generic statements about CNC, EDM, or grinding do not prove that hardened-state distortion and finishing allowance were considered.

Inspection And Program Control

At first article, request the inspection plan, measurement method, report format, and disposition route for nonconforming results.

Capacity discussions should identify loading assumptions, critical-machine dependencies, revision communication, and escalation contacts before release.

Define Functional Datums

Datum A must reflect the mating or assembly surface, not merely the easiest face to measure. Unclear datums can shift a tolerance stack; identify functional datums and measurement alignment on the drawing.

Specify Only Necessary Precision

±0.01 mm tolerances and unspecified finish requirements can add grinding operations without improving function. Assign tight limits and Ra values only to critical features, with permissible alternatives elsewhere.

Plan EDM And Heat Treatment

Wire EDM leaves an inside corner radius related to wire size, while sinker EDM requires an electrode strategy. State minimum internal radii, heat-treatment sequence, and machining or grinding allowance before release.

Keep Process Ownership Connected

One owner must control CNC, EDM, grinding, fitting, and revision status when dimensions cross processes. Separating them obscures responsibility; approve a linked routing, inspection plan, and report format before comparing piece price.

RFQ And DFM Gate

Step 1: submit 2D drawings, CAD, quantity, material grade, heat-treatment state, application context, and target date.

Step 1: agree CTQ dimensions, datums, surface requirements, machining access, EDM strategy, grinding stock, and measurement method before quoting.

Prototype And First Article

Step 2: approve a prototype sample against the released revision, especially for core inserts, pins, electrodes, or connector-tooling details.

Step 2: review first-article results, deviations, inspection records, fit evidence, and corrective actions before pilot authorization.

Pilot To Production Release

Step 3: pilot builds confirm repeatable routing, inspection frequency, approved material evidence, packing protection, and shipment batch size.

Step 3: release production only after revision ownership, change notification, delivery cadence, traceability records, and improvement feedback are defined.