Injection Mold Development Process Explained: From Design to Production
The quality of an injection-molded part is 70% determined by the mold. A mature “mold + molding” solution requires design, steel, machining, mold trials, and production to work together. This article walks through the complete process.
1. Requirement Confirmation
- Part information: 3D model, 2D drawing, material, color, and surface requirements (gloss / mold texture / leather grain).
- Volume forecast: annual volume and peak demand, which determine the number of cavities and the mold life class.
- Assembly relationships: whether the part mates with others, and the tolerance requirements.
- Special requirements: transparent parts, inserts, flame-retardant, food-grade, etc.
2. Mold Design (DFM)
The core of the mold design stage is the manufacturability review:
- Parting surface and ejection: choose the parting surface so the part ejects cleanly with no undercuts or dead corners.
- Runner system: gate location and type, which affect fill, weld lines, and appearance.
- Cooling system: cooling channel layout affects cycle time and distortion.
- Ejection system: ejector pin layout, avoiding stress whitening and distortion.
- Number of cavities: balanced against volume and cost; 1, 2, and 4 cavities are common.
- Shrinkage compensation: scale dimensions up according to material shrinkage.
3. Steel Selection
Mold steel is selected according to part requirements and life:
| Class | Typical Steel | Application |
|---|---|---|
| Standard | P20 / 718 | General structural parts, medium volume |
| High polish | NAK80 / S136 | Transparent parts, cosmetic parts, high-gloss surfaces |
| Wear resistant | H13 / 8407 | Glass-filled / highly filled materials |
| Long life | Hardened S136 | High volume, long life |
4. Mold Machining
- Cavity / core: CNC machining centers (Haas and others), EDM, and wire EDM (Sodick and others).
- Precision fits: controlled precision on critical dimensions to ensure the mold closes without misalignment or flash.
- Surface treatment: polishing, mold texture, nitriding, etc.
5. Mold Trials (T0/T1/T2)
Mold trials are the key validation step for a mold:
- T0 (first trial): verify fill, ejection, and basic dimensions, and identify structural issues.
- T1/T2: rework the mold based on T0 feedback, progressively closing in on tolerances and appearance requirements.
- Dimensional report: measure critical dimensions with CMM / optical measurement equipment and issue a report.
- Sample approval: the customer confirms assembly and appearance on the physical sample.
6. Mass Production and Quality Control
- Process window: establish injection pressure, speed, temperature, holding pressure, and cooling time.
- First-article inspection: full dimensional and appearance inspection on the first part of each shift.
- In-process inspection: periodic sampling during the production run.
- Final inspection: sampling to AQL before shipment.
- Scrap control: tightly control common defects such as weld lines, sink marks, flash, and short shots.
7. Lead Times
- Mold development: 15–35 days depending on complexity.
- Small-batch delivery is possible right after mold trials.
- Production scheduling: coordinated by the APS system, with standard production orders completed within 10 days.
8. Maintenance and Life
- Regular maintenance: clean the parting surface, descale cooling channels, lubricate moving parts.
- Spare inventory for wear parts: ejector pins, sleeve ejectors, sprue bushings.
- Mold life: from several hundred thousand to over a million cycles, depending on steel and maintenance.
Summary
The value of an integrated “mold + molding” solution is that design, material, process, and inspection are connected end to end, so the part maker and the mold maker cannot pass problems back and forth. Bring a supplier with full-process capability into the DFM review early in the project; it can significantly shorten development time and reduce production risk.
Cremage provides integrated mold development and injection molding solutions, equipped with Haas machining centers, Sodick wire EDM, and all-electric servo injection molding machines, with first-article, in-process, and final inspection control throughout. For molding solutions or mold feasibility assessments, please contact us.