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**1. Scope**
This procedure applies to all die casting molds used within the die casting workshop. It outlines the guidelines and precautions that must be followed during the use, maintenance, and repair of these molds to ensure their proper functioning and longevity.
**2. Reference Standards**
The following documents form an integral part of this procedure:
- GB/T 5611-1998: Casting Terminology
- GB 8844-88: Technical Conditions for Die Casting Molds
- GB 8847-88: Terminology for Pressure Casting Molds
- GB 4678.1～15-84: Die-Casting Parts
- GB 4679-88: Technical Conditions for Die-Casting Parts
These standards provide the necessary technical background and requirements for the safe and effective use of die casting molds.
**3. Use of Die Casting Molds**
Die casting molds are expensive to manufacture and require precise design and careful handling. Proper usage is essential to maintain their performance and extend their service life.
**3.1 Preheating**
Before starting the die casting process, it is crucial to preheat the mold. The preheating method depends on the equipment available:
- If a mold temperature machine is available, it should be used to heat the mold to a temperature range of 230–280°C.
- If no mold temperature machine is available, an external electric heating plate can be used as an alternative.
When using a mold temperature machine, the clamping force should be loosened before preheating to prevent excessive tightening due to thermal expansion. After preheating, the mold’s locking mechanism must be readjusted to ensure proper alignment.
**3.2 Mold Temperature Control During Production**
Molds equipped with a mold temperature machine should always be used for consistent temperature control. For molds without such equipment, the production rhythm can be adjusted, and water-based sprays can be applied to manage the mold temperature effectively.
**3.3 Pouring Temperature Control**
The pouring temperature significantly affects the mold's lifespan. It must strictly follow the temperature specifications outlined in the process card. During the trial phase of a new mold, the pouring temperature can be referenced from the "General Process Specification for Die Casting."
**3.4 Mold Surface Maintenance**
Throughout the production process, the mold surface should be monitored regularly. Any dirt or debris must be cleaned immediately, and lubrication should be applied to sliding parts to ensure smooth operation.
**4. Maintenance of Die Casting Molds**
Proper maintenance is essential to keep the molds in optimal condition and avoid premature failure.
**4.1 Basis for Mold Repair**
Mold repairs should be based on the following:
- Mold design drawings
- Mold size inspection results
- Sample out-of-tolerance reports
- Operator feedback
Repairs are carried out according to the repair orders issued by the responsible craftsman.
**4.2 Repair of Cavity Parts**
Cavity parts can be repaired or replaced depending on the extent of damage. The repaired mold must be restored to its original dimensions, shape, and surface finish, and verified through testing.
**4.3 Repair of Non-Cavity Parts**
Non-cavity components should be repaired or replaced as needed, but the original structure, surface roughness, and hardness should remain unchanged wherever possible.
**4.4 Post-Repair Inspection**
After the repair is completed, the mold must be inspected by a technician according to the drawings and repair orders. If required, a test run may be conducted. Once approved by the craftsman, the mold can be stored or put into production, and the repair order should be filed accordingly.
**5. Ongoing Mold Maintenance**
To ensure long-term performance, continuous maintenance and record-keeping are essential.
**5.1 File Establishment**
Once a mold is qualified, a file must be created containing the date of qualification, manufacturer details, usage records, repair history, and maintenance logs.
**5.2 Usage Tracking**
Each time the mold is used, a usage log must be maintained, detailing the production conditions. In case of any malfunction, production should be stopped immediately, and a technician should be notified to assess and plan the necessary repairs.
**5.3 Storage Preparation**
Before storage, the mold should be cleaned, inspected, and properly oiled to prevent corrosion and damage.
**5.4 Periodic Stress Relief Annealing**
Molds accumulate internal stress during repeated use, which can lead to cracks and early failure. To mitigate this, periodic stress relief annealing is recommended. The frequency varies based on mold size:
- For molds under 500 tons: First annealing after 5,000 cycles, then every 10,000 to 15,000 cycles.
- For molds over 500 tons: First annealing after 5,000 cycles, then every 6,000 to 10,000 cycles.
**5.5 Timely Grinding and Repair**
Early microcracks on the mold surface can propagate quickly if not addressed. Regular grinding and repair help extend the mold's life. Special attention should be given to areas prone to stress concentration, such as gates, runners, corners, sharp edges, fillets, and hole perimeters. Any signs of microcracks must be ground immediately.
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