Quick answer: Mold routing is the controlled sequence that creates datums, removes stock, manages heat treatment, produces inaccessible geometry, finishes surfaces, fits interfaces and verifies steel before assembly. The best route protects the drawing intent and leaves correction stock where later evidence is still needed.
Route From Datums and Risk
Start with released mold drawings, BOM, steel condition, datums, CTQs, surface and steel-safe map. Identify features affected by heat treatment, actions, shutoffs, polish or later fitting. Process planning should show when each datum is created and protected.
Separate rough, semi-finish and finish stock. Do not finish uncertain dimensions before the operations most likely to move or damage them.
Prepare Material and Heat Treatment
Verify steel identity, size, condition and certificates as required. Rough machine with balanced stock where distortion matters. Define stress relief, hardening, tempering, nitriding or other treatment from component duty and supplier procedure.
Inspect hardness, distortion and remaining stock after treatment. Plan straightening or grinding without removing the allowance needed for final fit.
Process Control Map
| Operation | Best suited task | Handoff control |
|---|---|---|
| CNC milling | 3D forms, pockets, cooling, plates and electrodes | Datum, stock, tool reach and surface allowance |
| EDM / wire EDM | Deep ribs, sharp internal details, inserts and profiles | Electrode/wire offset, recast and finish allowance |
| Grinding | Flat, parallel and precise fit surfaces | Heat, datum and thickness control |
| Polish/fitting | Surface requirement and assembled steel interfaces | Boundary, direction, witness and dimensional protection |
Use CNC for Geometry and Access
Mill plates, pockets, 3D surfaces, circuits and electrode blanks from controlled setups. Choose tools and approaches around access, deflection, corner radius, finish and stock. Record program revision, coordinate system and setup datums.
Inspect critical intermediate features before they become inaccessible. Tool length and deflection can create form error even when the program is correct.
Define an inspection hold point when later machining would remove the original setup reference or cover the feature.
Use EDM and Wire EDM Deliberately
Sinker EDM creates deep ribs, sharp internal details and textured surfaces using electrodes; wire EDM creates through profiles, inserts and precise openings. Control electrode identity, wear strategy, offsets, flushing and surface grade.
Remove or manage recast and microcracking according to component need. Protect shutoffs and polish zones from unnecessary EDM texture. Verify start holes and wire paths do not compromise cooling or strength.
Grind, Polish and Fit
Grinding establishes flatness, parallelism, thickness and sliding fits. Polishing follows a controlled direction and sequence for release or optical/cosmetic targets. Texture requires prepared steel, draft and a repair plan.
Fit inserts, parting, shutoffs, slides and interlocks through measurable contact and clearance. Avoid using hand fitting to hide upstream datum error. Record intentional clearances and witness boundaries.
Inspect and Release Each Handoff
Use in-process, CMM, optical, hardness, surface and circuit checks appropriate to the feature. Compare steel dimensions with the correction map. Label electrodes, inserts and revisions so rework is traceable.
Dry-assemble and cycle actions before T1. Close nonconformance through authorized disposition. Final routing records should explain how the released tool was made, not merely list machine hours.
Process Control Checklist
- Release drawings, BOM, steel, datums, CTQs and correction stock.
- Plan rough, heat treatment, stress relief and finish sequence.
- Protect datums and inspect after distortion-sensitive operations.
- Define CNC setup, reach, deflection, finish and stock allowance.
- Control EDM electrodes, wear, offsets, flushing and recast.
- Specify grinding, polish, texture and fitting boundaries.
- Inspect inaccessible features before later assembly.
- Retain routing, revision, nonconformance and release records.
Illustrative Routing Choice
Illustrative engineering example—not a claimed CKMOLD customer result: A hardened cavity has deep thin ribs and an optical outer surface. The route semi-finishes the cavity before heat treatment, grinds datums after hardening, uses EDM for the ribs with a defined finish allowance, then CNC-finishes and polishes the optical area without crossing the rib electrodes into it.
Implementation Questions
Why is EDM used in injection mold manufacturing?
It can produce deep, narrow or sharp internal geometry that is difficult to reach efficiently with rotating tools.
When should heat treatment occur?
The route depends on steel and duty, but rough machining often precedes treatment and final datums and surfaces follow distortion control.
Can polishing correct machining error?
Polishing removes small surface amounts for finish; it should not be used to hide form, datum or dimensional errors.
What makes a routing record useful?
It links component revision, material, operations, datums, inspection, nonconformance and final release so work is traceable.
Implementation Resources
Apply the Injection Mold Manufacturing Routing review to your released design. Share the function, exact resin, annual volume, CTQs, cosmetic limits and launch timing through the CKMOLD project form. If CAD is relevant, send it directly to jerry@ckmold.com; the form does not require an upload.