Mold Design Drawing Dimensioning Examples
A comprehensive guide to proper dimensioning techniques for injection mold parts and assemblies, featuring industry-standard practices and detailed examples for various mold components.
Fundamentals of Mold Dimensioning
Accurate dimensioning is critical for manufacturing high-quality injection mold parts. Properly dimensioned drawings ensure that each component fits together precisely, functions correctly, and meets all design specifications. This guide presents industry-proven dimensioning techniques for various mold components.
Table of Contents
1. Mold Assembly Drawing Dimensioning Examples
Mold assembly drawings require careful dimensioning to ensure all injection mold parts fit together correctly. Due to the large number of dimensions typically required, it's standard practice in industry to omit section lines from major sectional views to maintain clarity and readability.
These drawings must clearly show the relationships between all injection mold parts, including their relative positions and critical interfaces. Assembly dimensions focus on overall sizes, parting lines, alignment features, and important gaps or clearances between components.
Properly dimensioned assembly drawings serve as the master reference for manufacturing, assembly, and quality control processes. They ensure that each team working on the project has a clear understanding of how all injection mold parts should come together in the final product.
The dimensioning strategy for assembly drawings should prioritize functional relationships between injection mold parts over individual component details, which are typically covered in separate part drawings.
Key Dimensions in Layout Drawings:
- • Overall mold dimensions (length, width, height)
- • Positioning of guide pins and bushings
- • Location of sprue and runner systems
- • Placement of main injection mold parts
- • Distance between cavity centers
Section View Dimensioning Considerations
Section views in mold assembly drawings require special dimensioning techniques to clearly communicate the internal structure of injection mold parts. Leader lines with balloons are commonly used to identify and reference different components.
The numbered components in typical mold assemblies include:
Best Practice for Assembly Drawings
When dimensioning mold assemblies, focus on the relationships between injection mold parts rather than repeating dimensions that appear on individual component drawings. This reduces redundancy and minimizes the chance of errors from conflicting dimension values.
2. Moving Mold Plate (B Plate) Dimensioning Example
The moving mold plate, commonly referred to as the B plate, is one of the most critical injection mold parts that requires precise dimensioning. Its structure includes various features that must be accurately positioned and sized to ensure proper functionality of the entire mold system.
Plate Structure
- • Mold frame dimensions
- • Cooling channel layout
- • Screw hole positions
- • Ejector pin holes
- • Return pin holes
- • Distance分型 mechanisms
- • Side core-pulling features
X & Y Dimensioning
Coordinate dimensioning method is standard for X and Y directions, using the mold centerlines as the primary datums. This ensures consistent positioning of all features relative to each other and to other injection mold parts.
Z Dimensioning
Height dimensions utilize linear dimensioning with the plate's bottom surface as the reference datum. This provides a consistent reference point for all vertical measurements across related injection mold parts.
Ejector Pin Hole Identification
Different ejector pin through-holes must be clearly identified using distinct symbols, with their sizes and quantities specified. This ensures proper installation of these critical injection mold parts during assembly.
Common Ejector Hole Symbols:
Each symbol should be accompanied by a size specification (e.g., Ø5.0) and quantity (e.g., 8X) where multiple identical features exist. This simplifies both manufacturing and assembly processes for these injection mold parts.
Critical Considerations
When dimensioning cooling channels in the B plate, ensure that dimensions include both centerline positions and hole diameters. Proper spacing between cooling channels and other injection mold parts is essential to prevent interference and ensure effective temperature control during molding operations.
3. Fixed Mold Plate (A Plate) Dimensioning Example
The fixed mold plate, known as the A plate, follows dimensioning principles similar to those used for the B plate. As one of the primary injection mold parts, its accurate dimensioning is crucial for ensuring proper alignment with other components in the mold assembly.
The A plate typically contains the cavity features that form the outer surfaces of the molded part. Its dimensioning must precisely locate these cavities relative to the mold centerline and other critical features to ensure part accuracy and proper alignment with corresponding features on the B plate.
Like the B plate, X and Y dimensions use coordinate dimensioning from the mold centerlines, while Z dimensions reference the plate's primary mounting surface. This consistency between these two critical injection mold parts ensures they will properly mate during assembly.
Special attention should be paid to the dimensioning of sprue and runner systems in the A plate, as these features directly affect the flow of molten material into the cavities. Proper dimensioning here ensures balanced filling and optimal part quality.
Key A Plate Features:
- • Cavity positions and dimensions
- • Sprue and runner geometry
- • Guide pin bushing locations
- • Locating ring position
- • Fastener hole patterns
- • Cooling circuit layout
Dimensioning Comparison: A Plate vs. B Plate
| Feature | A Plate Dimensioning | B Plate Dimensioning |
|---|---|---|
| Primary Datums | Centerlines (X,Y) and front face (Z) | Centerlines (X,Y) and back face (Z) |
| Main Features | Cavities, sprue, runners | Cores, ejector systems |
| Fastener Holes | Through holes with counterbores | Tapped holes or through holes |
| Guide Features | Bushing bores | Guide pin bores |
Maintaining consistency between the dimensioning systems of the A and B plates is essential for ensuring these critical injection mold parts work together seamlessly. This consistency extends to datum references, tolerance schemes, and feature identification methods, creating a unified documentation system for the entire mold assembly.
4. Inner Mold Insert Dimensioning Example
Inner mold inserts are precision injection mold parts that form the detailed surfaces of the molded product. Their accurate dimensioning is critical because they directly influence the final part's geometry, surface finish, and functionality. These inserts are typically made from high-quality tool steels and require tight tolerances to ensure proper fit within the mold plates and to produce consistent parts.
Insert Drawing Components:
- • Insert body dimensions
- • Threaded hole positions and sizes
- • Cooling channel details
- • Parting line locations
- • Critical surface finishes
- • Heat treatment specifications
Typically, insert drawings combine several elements including screw holes, cooling channels, and machining details in a single document due to the relatively simple shape of these injection mold parts. This consolidated approach improves clarity and reduces documentation while maintaining all necessary information.
Important Considerations for Insert Dimensioning
- Orientation and Datum Features: Directions and reference corners must be accurately marked according to the moving mold side to ensure proper installation and alignment with other injection mold parts.
- View Selection: Use the minimum number of views needed to fully describe the part, with dimensions for each feature concentrated on a single view whenever possible.
- Critical Surfaces: Face-to-face and slide surfaces must be clearly identified with text annotations to ensure proper machining and assembly.
- Parting Lines: Positioning should match the assembly drawing, with reference corners clearly marked and datum features aligned with the overall mold assembly.
- Heat Treatment: For hardened inserts, specify the required HRC hardness value and include sufficient machining allowances for post-heat treatment processes.
- Draft Angles: Technical requirements must specify draft angles for cavity surfaces (typically 1.5°), with all dimensions referring to the larger end of tapered features.
Dimensional Tolerancing for Precision Inserts
Inner mold inserts, being critical injection mold parts, often require tighter tolerances than other components. The table below shows typical tolerance ranges for various features:
| Feature Type | Typical Tolerance Range | Rationale |
|---|---|---|
| Forming Surfaces | ±0.01mm to ±0.02mm | Directly affects part dimensions |
| Mounting Surfaces | ±0.02mm to ±0.05mm | Ensures proper fit in mold plates |
| Hole Positions | ±0.02mm to ±0.05mm | Aligns with corresponding features |
| Cooling Channels | ±0.1mm to ±0.2mm | Functional but less critical |
Proper dimensioning of inner mold inserts ensures these precision injection mold parts can be accurately manufactured and properly integrated into the overall mold assembly. By following the guidelines and best practices outlined above, designers can create drawings that clearly communicate all necessary information to manufacturing teams, resulting in high-quality molds that produce consistent, dimensionally accurate parts.
5. Slide Component Dimensioning Example
Slide components are complex injection mold parts used to create undercuts and complex geometries in molded products. Their dimensioning requires careful consideration due to their moving nature and precise fit requirements with other mold components. Proper dimensioning ensures slides function smoothly throughout the mold's lifecycle while maintaining the required part geometry.
Slide Dimensioning Principles
- Symmetrical slides should use centerline dimensioning for balanced features
- Asymmetrical slides use a major flat surface as the primary datum
- Height dimensions reference the bottom surface for consistency
- Front surfaces are preferred for length datums when available
- Rear surfaces serve as length datums when front surfaces are unavailable
- All slides require a machining tab on the top surface for fixturing
Machining Tab Requirements for Slides
All slide components, as critical injection mold parts, must include a machining tab on their top surface to facilitate secure clamping during manufacturing processes. These tabs are temporary features that can be removed after final machining if they interfere with mold operation.
Tab Design Considerations:
- • Position must ensure stable clamping during machining
- • Size should provide sufficient contact area for secure holding
- • Location must avoid interference with other injection mold parts
- • Thickness should be adequate to prevent deflection during cutting
- • Must be placed to allow access to all critical surfaces
- • Should be easily removable if not required for mold operation
Standard Tab Dimensions:
Minimum Length:
25mm (1.0")
Minimum Width:
15mm (0.6")
Typical Thickness:
5-10mm (0.2"-0.4")
Distance from Edge:
10-15mm (0.4"-0.6")
Tab Identification:
Clearly label tabs on drawings with "MACHINING TAB - REMOVE IF NOT REQUIRED" to ensure proper handling during mold assembly.
Slide components present unique challenges in dimensioning due to their complex geometries and functional requirements. By following established guidelines and maintaining consistency with other injection mold parts, designers can create slide drawings that facilitate accurate manufacturing and ensure proper integration into the overall mold system. Attention to detail in slide dimensioning directly contributes to mold performance, part quality, and overall production efficiency.
Dimensioning Standards & Best Practices
Consistent dimensioning practices across all injection mold parts are essential for ensuring manufacturing accuracy, assembly efficiency, and final part quality. Adhering to established standards helps streamline communication between design, manufacturing, and quality control teams, reducing errors and rework.
General Dimensioning Guidelines
- Use the minimum number of dimensions needed to fully define each feature without redundancy
- Place dimensions on the view that most clearly shows the feature's shape and size
- Group related dimensions together for clarity and ease of reference
- Avoid crossing dimension lines and keep them a consistent distance from views and each other
- Use appropriate tolerance values based on feature criticality and manufacturing capabilities
- Clearly identify datum features that serve as references for dimensioning
- Use standard symbols for common features (threads, chamfers, radii) to improve drawing clarity
Injection Mold Specific Considerations
- Maintain consistent datum references across related injection mold parts for proper alignment
- Clearly dimension parting lines and their relationship to critical part surfaces
- Include sufficient dimensions for cooling channels, including diameters, positions, and depths
- Specify draft angles on all mold surfaces that contact the plastic material
- Dimension all interface surfaces between moving and stationary injection mold parts
- Include dimensional requirements for all wear surfaces and guide features
- Specify surface finish requirements for all critical forming surfaces
Dimensioning Symbols Commonly Used for Injection Mold Parts
By following these dimensioning standards and best practices for all injection mold parts, design engineers can create clear, comprehensive drawings that effectively communicate design intent to manufacturing teams. This clarity reduces errors, speeds production, and ensures that all components work together seamlessly in the final mold assembly. Consistent dimensioning practices also facilitate better communication between different departments and suppliers, creating a more efficient and effective manufacturing process from design through production.