Injection Mold Design Guide [top]

Automatically shear off during mold opening. They feed the part below the parting line, hiding the gate vestige.

Keep rib height under 3 times the wall thickness to maintain structural integrity during the molding flow. 4. Mold Complexity: Undercuts & Actions

Without draft, the part will stick to the mold or be damaged during ejection. Usually 1.5 to 2 degrees for most parts.

| Defect | Root Cause in Mold Design | The Fix | | :--- | :--- | :--- | | | Rib too thick; Wall too thick. | Reduce rib to 50% of wall; core out backside of boss. | | Weld Lines | Gate too far from obstacle; No vent. | Move gate; Add an overflow well; Add vent 0.5mm from weld point. | | Flash | Clamp force too low; Venting too deep . | Increase tonnage; Reduce vent depth to 0.0005". | | Burn Marks | Trapped air compressing & igniting. | Add vents to the last place the plastic fills. | | Warpage | Uneven cooling; Non-uniform walls. | Balance cooling lines; Add ribs to stiffen against internal stress. | | Short Shot | Gate too small; Runner too long. | Increase gate cross-section; Use a hot runner. | injection mold design guide

Traditional molds use straight, drilled cooling channels placed within the core and cavity blocks. Channels should be positioned as close as possible to the cavity surface, typically 1.5 to 2 times the channel diameter from the surface, with consistent spacing to promote uniform cooling.

: This is the most critical rule. Aim for consistent walls between 1–4 mm. Non-uniform walls lead to "sink marks" (surface depressions) and "warpage" because thick sections cool slower than thin ones. Draft Angles

Maintain a consistent wall by matching the internal radius with the external radius. 💡 Pro-Tip: The "Cooling" Factor Automatically shear off during mold opening

Place the gate at the thickest section of the part. This allows "packing" to compensate for shrinkage. Never gate into thin walls adjacent to thick walls.

A mold is a precision tool made of several plates and components.

The mold base houses all internal components. Selecting the correct steel grade depends on production volume, resin abrasiveness, and surface finish requirements. Core and Cavity Steel Selection | Defect | Root Cause in Mold Design

Design outside radii to be 150% of the adjacent wall thickness to maintain uniform wall thickness. Mold Base Selection and Steel Classification

Designing a high-quality injection mold requires a deep understanding of thermodynamics, material science, and mechanical engineering. A well-designed mold ensures dimensional accuracy, minimizes cycle times, and prevents part defects. This guide covers the essential engineering principles required to design production-ready injection molds. Part Design Considerations and DFM

Ensure the vent land length is short (2mm to 3mm) before opening into a deeper relief channel (0.5mm to 1.0mm) to prevent flash. Ejection Mechanisms