1. The core goal of mold design
Functional realization: Ensure that the product structure (such as buckles, threads, thin walls) is accurately reproduced, and avoid demoulding deformation.

Mass production efficiency: Optimized parting surfaces, gating systems (gate/runner design) and cooling systems (cooling channel arrangement) to reduce cycle times.

Cost control: Reduce overall costs through cavity number optimization (multiple cavities in one mold), material utilization (scrap reduction) and mold life (steel selection, surface treatment).

2. Technical details in the design process
Parting Line

It is necessary to avoid the appearance surface, and give preference to flat or simple surfaces to avoid flash caused by acute angles.

Example: The parting line of a mobile phone case is often hidden at the turn of the side curvature.

Draft Angle

Usually 1°~3°, the deep cavity or textured surface needs to be increased to 3°~5° to prevent demoulding and strain.

Special case: A 0.5° limit slope may be required for high-gloss products, but the requirements for mold polishing are extremely high.

Ejection System

The layout of the thimble needs to avoid the weak area, such as the bottom of the BOSS column with stiffeners to prevent the top white.

Special-shaped parts may be ejected by push plate or gas-assisted demoulding.

Cooling Channels

Following the "equidistant principle", the distance between the waterway and the surface of the cavity is kept uniform (usually 8~15mm).

Conformal Cooling is 3D printed to achieve conformal cooling, and the cooling efficiency is increased by 40%.

3. Depth matching of materials and processes
Plastic parts

The glossy surface is made of S136H stainless steel (HRC 48~52), and the transparent parts need to be mirror-polished to Ra0.01μm.

Cemented carbide inserts are required for glass fiber reinforcement materials to prevent runner wear.

Die castings

H13 steel is commonly used in aluminum alloy die-casting molds, and beryllium copper inserts need to be superimposed in local hot joints to accelerate heat dissipation.

Vacuum die-casting technology reduces porosity, but increases the complexity of the mold sealing structure by 30%.

4. Cutting-edge technology subverts mold design
Topology optimization conformal cooling
Through CAE simulation, the mold structure was reversely optimized, and the weight of an automobile part mold was reduced by 22% while the stiffness was increased by 15%.

Metal 3D printing
The porous conformal cooling mold manufactured by SLM technology shortens the injection cycle from 28 seconds to 19 seconds, saving more than 500,000 yuan in annual electricity costs.

AI-aided design
The AlphaTooling system developed by Google DeepMind can automatically generate gate schemes, reducing the number of mold trials by 70%.

5. Cost traps and avoidance strategies
Over-design: A home appliance company pursues a tolerance of 0.05mm, resulting in an 80% increase in mold costs, while the actual assembly demand is only 0.2mm.

DFM (Design for Manufacturing) Failure Cases:

For plastic gears without embedded metal inserts, the cost of secondary processing accounts for 35% of the total cost.

The thin-walled areas are not graded, and the injection molding is underfilled, resulting in a yield of only 68%.

6. Industry trends and future challenges
Miniaturized molds: Medical microfluidic chip molds have an accuracy of ±2μm and require nano-level EDM processing.

Challenges of composite materials: When carbon fiber reinforced PEEK is injection molded, the mold needs to be temperature resistant to more than 380°C and has an anti-corrosion coating.

Sustainable design: Detachable mold structure (modular design) increases material recovery from 45% to 92%.

Key Thoughts
A good mold designer needs to have the ability to "balance contradictions": find the best balance between shrinkage allowance and dimensional tolerance, between surface texture depth and mold release resistance, and between mold flow analysis results and actual mold tryout data. It is recommended that newcomers start with reverse engineering, disassemble classic molds (such as Coca-Cola cap molds) to learn the essence of the structure, and master tools such as Moldflow/Moldex3D for virtual verification to reduce the cost of trial and error.