In the mass production of aluminum die-cast products and aluminum cast parts, the “mold” is the most critical component that determines success or failure. This is because no matter how high-performance the casting equipment or excellent the alloy material used, if there is even the slightest deterioration or deformation in the mold, it will immediately manifest as quality defects such as “dimensional inaccuracies,” “burr formation,” and “cooling failures,” causing serious damage to production efficiency and reliability.
A characteristic of aluminum molds is the accelerated progression of deterioration phenomena such as thermal fatigue (thermal cracking), which occurs from repeated exposure to high-temperature molten aluminum, as well as wear, erosion, and corrosion. This means it is not a structure that “breaks the more you use it,” but rather one whose “lifespan changes depending on how you use it.” In other words, the proficiency of maintenance, including inspection, cleaning, and repair, greatly influences the lifespan and quality of the mold.
From a business management perspective, extending the lifespan of aluminum molds is not just a “preservation activity” but also brings ripple effects such as avoiding mold remanufacturing costs, reducing downtime, and improving customer satisfaction through stable quality. This means that “advancement in maintenance technology becomes a strategic asset that influences manufacturing costs.“
This guide explains practical knowledge of aluminum mold maintenance that can be immediately applied in the field, structured as follows:
- Chapter 1: “Basic Knowledge of Aluminum Molds” – Understanding types and deterioration mechanisms, and knowing the factors that affect lifespan.
- Chapter 2: “Systematization of Inspection and Servicing” – How to design daily/periodic inspections and lifespan management.
- Chapter 3: “Examples of Repair and Regeneration” – Crack removal, buildup, and reproduction techniques for molds without drawings.
- Chapter 4: “Learning from Failure Cases” – Troubles and their feedback to the design stage.
- Final Chapter: “Conclusion” – Practical points for implementation in practice.
This guide is structured by comprehensively incorporating primary information, field data, and expert case studies so that readers can design for longer mold lifespan based not on “intuition” but on “theory” and “examples.” We hope this guide will be of some help to everyone involved in the aluminum casting industry.
Basic Knowledge of Aluminum Molds: Types and Deterioration Mechanisms
In aluminum casting production sites, multiple casting methods exist depending on the application, and the corresponding mold structures also differ. To optimize mold design and maintenance, it is essential to first correctly understand the “type of mold” and “its deterioration factors.”
Mold Classification (GDC/LPDC/DC) and Structure
Aluminum casting molds are broadly classified into the following three types:
- GDC (Gravity Die Casting) Molds: A method where molten metal flows in naturally by gravity. They have a relatively simple structure and are suitable for small lots. The use of cores is common, and cooling management is a key point.
- LPDC (Low-Pressure Die Casting) Molds: A method where molten metal is raised and filled under low pressure. It is often used for thick-walled parts and automobile wheels. The structure makes it easy to suppress air entrapment.
- DC (Die Casting) Molds: A method of high-pressure, high-speed filling. It is suitable for mass production and excels in dimensional accuracy and surface quality, but the thermal load and wear are extremely large.
Each structure is composed of a fixed mold, a movable mold, slide parts, cooling pipes, etc. DC molds, in particular, require many moving components and precise dimensions.
Main Causes of Deterioration: Thermal Fatigue, Wear, Erosion, and Corrosion
The main factors that shorten the lifespan of a mold can be classified into the following four categories:
- Thermal Fatigue (Thermal Cracking)
Fine cracks occur on the surface due to repeated contact with molten metal. If this progresses, it can cause leaks and dimensional defects.
- Wear
Occurs during product removal or sliding with moving parts. It is particularly concentrated around slide parts and guide pins.
- Erosion
A phenomenon where the mold surface melts away due to continuous contact with high-temperature aluminum alloy. It depends on the heat resistance of the mold material.
- Corrosion
The mold steel corrodes due to reactions with components in the cooling water or humidity in the air. This is accelerated by a lack of maintenance of the cooling system.
Since these deterioration factors progress in a complex manner, the difficulty lies in the fact that they cannot be prevented by eliminating a single factor.
Factors Affecting Lifespan: Material Selection, Cooling Design, and Injection Conditions
Mold lifespan can be significantly extended not only by “product design” but also by the following measures:
- Material Selection: It is important to select mold steel with excellent high-temperature strength, thermal conductivity, and wear resistance (e.g., SKD61). Lifespan can also be extended with heat treatment or PVD coating.
- Cooling Design: Appropriate cooling circuits and the selection of a medium (water, oil) can alleviate thermal stress and suppress thermal cracking.
- Optimization of Injection Conditions: A balance of filling speed, mold temperature, and the amount of release agent applied leads to a reduction of stress on the mold.
By systematically managing these design and operational elements, it becomes possible to design molds with lifespan in mind from the initial design stage.
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Establishing a Maintenance System: Daily Inspections, Periodic Servicing, and Lifespan Management
Aluminum molds are assets directly linked to product accuracy and production stability. Therefore, establishing a maintenance system based on “prevention” and “planning,” rather than one-off repairs, ultimately leads to cost reduction and improved product reliability.
Below, we introduce the specific approaches and benefits of three pillars that can be implemented on-site: daily inspections, periodic servicing, and lifespan management.
Daily Inspections: Frequency and Procedures for Cleaning, Lubrication, and Visual Checks
Daily inspections are said to be “a 3-minute lifespan extension,” and while often overlooked, they are one of the most effective management activities.
- Target Items:
- Removal of dirt (foreign matter, casting residue) from the molding area
- Lubrication of guide pins and slide parts
- Checking for cracks, discoloration, and rust
- Frequency:
- Implemented daily before and after use
- In shift-based workplaces, using a checklist for each shift is effective
- Key Points:
- If excessive residue of release agent is left during cleaning, it can cause corrosion or carbonization.
- Abnormal noises or a sense of違和感 (strangeness/discomfort) in moving parts are signs of initial deterioration. Do not ignore them.
Periodic Servicing: Dimensional Accuracy / Deformation Detection / Parts Replacement
The purpose of periodic servicing is to visualize “invisible deterioration.” A maintenance cycle of “every 30,000 to 50,000 shots” is a common guideline.
- Main Tasks:
- Measurement of parting line surface dimensions (e.g., with a Mitutoyo 3D measuring machine)
- Visualization of thermal deformation by heat checking
- Replacement of guide bushes, ejector pins, etc.
- Important Mindset:
- “Replacing based on early signs” is overwhelmingly cheaper than “fixing after it breaks.”
- Even a deformation of ±0.01mm can directly lead to burrs and dimensional defects, so quantitative evaluation of differences of 0.1mm or less is necessary.
Lifespan Management: Introduction of Predictive Maintenance and Utilization of Record Management
The final stage of mold management is “lifespan management.” This involves quantifying and recording usage history and deterioration trends to build a system that allows for judgment before trouble occurs.
- Effective Tools and Measures:
- Automatic counting of usage shots (IoT-compatible machines)
- Comparison of measurement results every 3 months (accumulation of change data)
- Photographing and recording of crack/wear locations
- Benefits:
- Reduces sudden stops by up to 80% by optimizing repair timing
- Eliminates waiting time for parts procurement and processing by planning repairs in advance
- Improves repair accuracy and delivery time prediction by sharing records with external vendors
The era of relying solely on “luck” and “experience” for mold lifespan is over. Predictive maintenance based on records and measurements is the very source of competitiveness in modern manufacturing.
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Repair and Refreshment Case Studies: Optimization of Crack Removal and Buildup Regeneration
In the operation of aluminum molds, cracks and wear are unavoidable phenomena, but the “choice of repair method” can make a significant difference in the subsequent mold lifespan and product quality. This chapter explores hints for technology selection and operational improvement through three on-site repair case studies.
Case 1: Failure Case in Crack Welding Repair and Improvement Measures
An automotive parts manufacturer used the conventional method of grinding out fine cracks in aluminum die-casting molds with a rotary tool and regenerating them with buildup welding. However, there were issues with work efficiency and repair accuracy.
- Problems:
- The rotary tool could not completely remove the thin remaining aluminum oxide film, leading to the inclusion of bubbles (pinholes) during welding.
- The crack reappeared after several thousand shots post-repair.
- Improvement Measures:
- Introduced chemical pretreatment (next section) to enable complete surface removal.
- Thoroughly reviewed welding wire material (heat-resistant alloy system) and managed preheat temperature.
As a result, recurrence in the same area was significantly reduced. It became clear that not just the technical work, but “integrated process management from pre-treatment to post-treatment” is important.
Case 2: Improving Work Efficiency with Chemical Cleaning using MC-G [S Company Case]
At S Company, the pre-treatment for buildup welding during crack repair required significant effort. The thinly adhered aluminum alloy was invisible to the naked eye, and traditionally, judgment was made based on the presence or absence of sparks, requiring the removal process to be repeated multiple times.
- Improvement Measure Introduced: Apply Meka Mold Clean MC-G, leave for 15 minutes → wipe off → perform buildup.
- Effects:
- Removal process was shortened by up to 50% or more.
- The incidence of welding defects was reduced.
- Operator’s subjective judgment was reduced, realizing a repair system with reproducibility.
The person in charge at S Company commented, “Standardizing the work has also reduced the burden of training,” making the introduction of chemical cleaning a good example of on-site improvement.
Case 3: Reproduction of Mold without Drawings and Short-Term Repair [Ishikawa Seisakusho]
Ishikawa Seisakusho received a repair request for a mold made by another company for which no drawings existed from a manufacturer in the Kanto region, and they completed the delivery within two weeks.
- Challenge:
- Wear and erosion had progressed with the structure being unknown.
- The mold was deemed unacceptable for repair by other companies.
- Response Process:
- Reverse engineering of the internal structure by a skilled craftsman through physical disassembly.
- Buildup repair using high-precision machining and re-welding.
- Precise measurement and adjustment after reassembly.
- Results:
- Achieved delivery within 2 weeks.
- 100% pass rate in quality inspection.
- Received high praise from the customer, “I can’t believe they can reproduce it this well without drawings.”
Throughout the entire repair process, establishing the three steps of diagnosis, planning, and verification, rather than just “fixing,” led to a highly reliable finish.
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Learning from Failure: Mold Troubles and Their Cause Analysis
What is essential for excellent mold operation is not success stories, but the “analysis of failures.” Signs of trouble appear as small changes, and whether the operational organization can detect them and sublimate them into recurrence prevention measures determines its maturity. Here, we organize typical failure patterns that have actually occurred and their prevention guidelines.
Cost Simulation of “No Periodic Inspection → Sudden Stop”
A mid-sized manufacturer reduced the frequency of periodic inspections to once a year while reviewing the outsourcing costs of inspection work. However, six months later, it was reported that burr defects in molded products increased sharply due to wear on the parting line surface, ultimately leading to an emergency stop of the machine.
Calculating the cost impact that occurs in such a situation, the following effects can be considered:
- Example of Assumed Costs:
- Opportunity loss due to production interruption (8 hours × 8 lines) = approx. 64 hours
- Quality claim response costs (returns, re-inspections, re-deliveries) = approx. 500,000 yen equivalent
- Surcharge for emergency repair request (2-3 times the normal rate)
While intending to save about 200,000 yen annually on inspection costs, there is a possibility that it could lead to a cumulative loss of over 3 million yen due to trouble response.
This is just a model case based on general factory operations, but it suggests the realistic risk that neglecting periodic inspections can lead to a high price.
Recurrence Prevention Measures for “Incorrect Injection Conditions → Cooling Failure”
At another site, pinholes and shrinkage cavities frequently occurred in molded products. The cause was that “the temperature setting of the casting conditions was not finely adjusted for summer outdoor air fluctuations.” This caused thermal distortion to accumulate inside the mold due to cooling failure. As a result, a part of the mold was deformed, and repair costs were incurred.
- Recurrence Prevention Measures:
- Dynamic control of cooling medium temperature according to air temperature/humidity
- Addition of “molding environment data” to record sheets
- Redefinition of injection pressure and cooling timing (referencing)
This is a good example showing the risk that “fixed ideas” about molding conditions can shorten the mold’s lifespan.
Trouble Trends and Prevention Guidelines at the Design Stage
In fact, most troubles are of a pattern that can be addressed at the design stage.
| Trouble | Prevention Measure in Design |
| Cracks | Distributed placement of cooling circuits, shapes that avoid stress concentration |
| Wear | High-hardness material + surface treatment (PVD/nitriding) |
| Deformation | Symmetrical structure design, deformation prediction by CAE |
The attitude of asking, “Could this have been prevented by design?” before saying, “It was used improperly,” is the foundation of next-generation mold management.
Sources:
- AIST｜Research Report on Surface Damage and Durability Treatment (https://www.aist.go.jp/)
- Daiwa KK｜Points to Note during Design and Production
Conclusion: 5 Practical Points for Extending Lifespan
As introduced in this guide, the lifespan of an aluminum mold can be extended not by chance, but by a trinity of “structural design × inspection management × repair technology.” Finally, let’s confirm five guidelines that can be put into practice starting tomorrow.
- Make Inspection a Habit
→ Making it a daily routine directly leads to the early detection of abnormalities.
- Visualize and Quantify Records
→ Predictive maintenance is achieved by quantitatively managing dimensions, wear, and temperature fluctuations.
- Turn Defect Patterns into Knowledge
→ Accumulating past cases and sharing recurrence prevention measures within the company are essential.
- Proper Design of Cooling and Lubrication
→ Comprehensive design related to “heat,” including a review of injection conditions, holds the key.
- Strengthen Collaboration with Specialized Outsourcing Partners
→ For tasks that are beyond your company’s capabilities, collaborate with reliable partners to ensure quality and delivery stability.
A mold is not just a “tool,” but the core of production and a corporate asset. Extending its lifespan through appropriate maintenance leads to the strengthening of the company’s competitiveness. We hope you will utilize the content of this guide for your company’s mold management system.
