Precision Mould Parts – The Precision Core & Selection Guide for Industrial Manufacturing

Introduction: Why Are Precision Mould Parts the "Invisible Cornerstone" of Modern Manufacturing?

In high-end manufacturing sectors such as automotive components, electronic devices, and medical equipment, "precision" is the core standard that determines product quality and market competitiveness. The key to upholding this standard lies in Precision Mould Parts. From the guiding and positioning of moulds to the detailed control of injection moulding, the tolerance, material, and performance of every precision part directly impact the mould’s service life (which can be extended by over 30% on average), production efficiency (reducing scrap rates by 15%-20%), and the consistency of the final product.

This article systematically analyzes the core types, key selection factors, industry application scenarios of precision mould parts, and how to enhance the stability of manufacturing processes through high-quality parts – providing practical references for manufacturing buyers, mould engineers, and factory managers.

I. What Are Precision Mould Parts? Analysis of Core Types & Functions

Precision Mould Parts refer to high-precision components used in mould systems to achieve key functions such as positioning, guiding, ejection, and cooling, with dimensional tolerances controlled within the range of ±0.001mm to ±0.01mm. Their core value lies in ensuring "macro production stability" through "microscopic precision". The common types and their functions are as follows:

Part Type (English)	Core Function	Application Scenarios	Precision Requirement
Guide Pins/Bushings	Ensure accurate positioning during mould opening and closing to prevent cavity misalignment	Injection moulds, stamping moulds	Coaxiality ≤ 0.002mm, surface roughness Ra ≤ 0.4μm
Ejector Pins	Eject the formed product from the mould cavity to avoid product deformation	Plastic injection moulds, die-casting moulds	Straightness ≤ 0.003mm/m, diameter tolerance grade g5
Core Pins	Form complex structures such as holes and grooves in products, determining the detailed dimensions of products	Electronic connector moulds, medical device moulds	Dimensional tolerance grade IT3-IT5
Cooling Inserts	Optimize the temperature distribution of the mould, accelerate product cooling and setting, and shorten the production cycle	Large automotive plastic part moulds, thin-walled product moulds	Hole diameter tolerance grade H7, thermal conductivity ≥ 45W/(m·K)
Sprue Bushings	Connect the injection machine to the mould, guide molten plastic into the cavity, and reduce material flow resistance	Hot runner injection moulds	Inner hole surface roughness Ra ≤ 0.2μm

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II. How to Select? 5 Key Factors Affecting the Performance of Precision Mould Parts

For buyers and engineers, incorrect selection may lead to frequent mould failures (such as guide pin wear and ejector pin breakage), reduced production efficiency, or even mass product scrapping. The following 5 factors are the core basis for selection:

1. Material: Choose "Wear-Resistant" or "Impact-Resistant" Materials Based on Working Conditions

Material directly determines the service life and application scenario of the part. Common options and their characteristics are:

SKD61 (Hot Work Tool Steel): High-temperature resistant (up to 600℃) and thermal fatigue resistant, suitable for cooling inserts and die-casting mould parts;
SKH51 (High-Speed Steel): High hardness (HRC62-65) and wear-resistant, suitable for core pins and high-precision ejector pins;
SUS440C (Stainless Steel): Corrosion-resistant and rust-proof, suitable for medical moulds and food packaging mould parts;
Brass/Bronze: Low friction coefficient, suitable for light-duty guide parts (such as guide bushings for small moulds).

2. Precision Grade: Match Product Requirements to Avoid "Excessive Precision" Cost Waste

The precision grade of precision mould parts needs to match the tolerance requirements of the final product, not the higher the better (the cost of high-grade precision may increase by more than 50%):

Ultra-Precision Grade (Tolerance ±0.001mm): Suitable for electronic chip carriers and optical component moulds;
High-Precision Grade (Tolerance ±0.003mm to ±0.005mm): Suitable for automotive precision components and medical device moulds;
Standard Precision Grade (Tolerance ±0.01mm): Suitable for moulds of daily plastic parts (such as home appliance casings).

3. Surface Treatment: A "Protective Layer" to Enhance Wear Resistance and Corrosion Resistance

Proper surface treatment can extend the service life of parts by 2-3 times. Common processes include:

Nitriding: Improves surface hardness (up to HV1000 or above) and enhances wear resistance, suitable for guide pins and ejector pins;
Chrome Plating: Reduces friction coefficient and prevents rust, suitable for sprue bushings and guide bushings;
PVD Coating (Physical Vapor Deposition): High-temperature resistant and anti-sticking, suitable for hot runner-related parts.

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4. Size & Specification: Follow the "Mould Compatibility" Principle

When selecting, it is necessary to confirm that the nominal size and installation method (such as interference fit/clearance fit) of the part match the existing mould system. For example:

The diameter of the guide pin must match the inner diameter of the guide bushing (common fit clearance: 0.001mm-0.003mm);
The length of the ejector pin must be calculated based on the depth of the mould cavity to avoid incomplete ejection due to being too short or mould damage due to being too long.

5. Supplier Qualification: Prioritize Partners with "ISO Certification + Customization Capability"

The quality of precision parts depends on production processes and quality control. When purchasing, pay attention to whether the supplier:

Has passed the ISO 9001 Quality Management System Certification (basic standard);
Has customized production capabilities (such as non-standard size and special material processing);
Provides quality inspection reports (such as dimensional tolerance testing and material composition analysis).

III. Industry Applications: Practical Cases of Precision Mould Parts in 3 Core Fields

Different industries have significant differences in the demand for precision mould parts. The following cases can help you understand the selection logic more intuitively:

1. Automotive Manufacturing: High-Temperature Resistance and Impact Resistance Are Core Requirements

Application Scenario: Moulds for automotive engine plastic parts (such as intake pipes)

Core Parts: Cooling inserts (material: SKD61, nitrided) and large guide pins (diameter: 30mm, tolerance: ±0.005mm)

Selection Reason: The forming temperature of engine parts is high (about 280℃), and the high-temperature resistance of SKD61 can prevent insert deformation; the guide pins need to withstand the high-frequency impact of mould opening and closing, and the high coaxiality design can reduce wear.

2. Electronic Equipment: Ultra-Precision and Corrosion Resistance Are Key

Application Scenario: Moulds for mobile phone charger interfaces

Core Parts: Core pins (material: SKH51, PVD-coated) and stainless steel guide bushings (SUS440C)

Selection Reason: The aperture tolerance requirement of the interface is ±0.002mm, and the high hardness of SKH51 can ensure that the core pin does not wear after long-term use; the charger needs to be in contact with current, and the rust resistance of the stainless steel guide bushing can avoid short-circuit risks.

3. Medical Devices: Sterility and High Consistency Are the Bottom Line

Application Scenario: Moulds for syringe barrels

Core Parts: Ejector pins (material: SUS440C, polished) and cooling inserts (thermal conductivity: 50W/(m·K))

Selection Reason: Medical devices need to comply with FDA standards, and the corrosion resistance of SUS440C can prevent the precipitation of metal ions; the cooling insert needs to cool down quickly to ensure that the inner wall of the syringe barrel is smooth and free of bubbles.

IV. Frequently Asked Questions (FAQ): Solving Pain Points in the Purchase and Use of Precision Mould Parts

Q1: When precision mould parts are worn, do they have to be replaced?

A1: It depends on the degree of wear. If the wear causes the product size to exceed the tolerance (such as guide pin clearance > 0.005mm), replacement is mandatory; if there are only slight surface scratches, repair can be done through polishing (e.g., Ra ≤ 0.4μm) to extend the service life by 1-2 months.

Q2: What is the usual delivery time for customized non-standard Precision Mould Parts?

A2: It depends on the material and complexity. For simple non-standard parts (such as ejector pins of special lengths) made of ordinary materials (such as SKD61), the delivery time is about 7-10 days; for parts made of special materials (such as SKH51) or with complex structures (such as special-shaped cooling inserts), it takes 15-20 days.

Q3: How to judge whether the precision of the parts provided by the supplier meets the standard?

A3: Request the supplier to provide a coordinate measuring machine (CMM) inspection report (to test dimensional tolerance, coaxiality, etc.), or conduct self-inspection with tools: use a micrometer to measure diameter tolerance (precision: 0.001mm) and a roughness tester to measure surface roughness (Ra value).

Conclusion: Choosing High-Quality Precision Mould Parts Means Choosing "Manufacturing Stability"

In the trend of industrial manufacturing upgrading towards "high precision and high efficiency", Precision Mould Parts are no longer "supporting roles" but "core elements" that determine mould performance and product quality. Whether purchasing standard parts or customizing non-standard parts, following the principles of "material matching working conditions, precision matching needs, and qualified suppliers" can help achieve the goals of "cost reduction, efficiency improvement, and quality assurance".

If you need to learn more about the selection details of a specific type of precision mould part or obtain a customized solution, you can consult us through the contact information at the end of the article – we provide full-process support from material selection to quality inspection.

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