The performance and service life of die-casting molds largely depend on the processing quality and assembly accuracy of the main mold components. As core components of die-casting molds, die casting mold accessories such as blocks, guide rails, pressure plates, wear plates, and wedge blocks not only provide structural support and guidance but also directly affect the mold’s stability, clamping accuracy, and long-term operational reliability. This article will systematically introduce the processing flow of the main die casting mold components and the final mold assembly process, focusing on these critical parts.
Overview of the Overall Processing Flow of Die-Casting Mold Accessories
The processing flow of die casting mold accessories is usually divided into three main categories based on part function: mold core, mold base, and other auxiliary parts, which are then assembled and subjected to final inspection.
The processing flow of the mold core usually begins with rough machining. Depending on the structural complexity, rough forming is completed through manual machining or CNC machining, followed by heat treatment to improve the material’s hardness and wear resistance. After heat treatment, the mold core parts enter the precision machining stage, where cavity dimensions, contour accuracy, and surface quality requirements are achieved through manual machining, CNC machining, electrical discharge machining, and wire cutting. Some parts with simple structures or high repeatability can utilize mold-saving processes. After precision machining, the die casting mold core parts are inspected for dimensions and quality to ensure they meet design requirements.
The processing flow of the mold base focuses on structural stability and assembly accuracy. First, the material is cut, and then rough machining is performed to form the basic structural dimensions. Subsequently, the die casting mold base parts undergo heat treatment to obtain good overall mechanical properties. After heat treatment, precision machining is performed to ensure critical accuracy requirements such as guiding surfaces, mounting surfaces, parallelism, and perpendicularity. After precision machining, preliminary assembly and inspection are carried out to confirm correct fit, before proceeding to the subsequent overall assembly process.
Other components (such as standard parts and auxiliary structural parts) are processed according to actual needs. All such parts must be inspected before assembly to ensure that dimensions, tolerances, and quality meet assembly standards.
After all parts have been inspected, all qualified components are unified into the mold assembly process for the assembly and debugging of the complete die-casting mold. After assembly is complete, a final inspection is conducted to comprehensively verify the overall structure, motion coordination, and assembly accuracy of the mold, ensuring that the mold is ready for stable production.
Machining Process of Main Parts of Die Casting Molds
The mold core, slider head, and vent block are interconnected parts that perform different functions in a die casting mold. The mold core is primarily used to form the internal cavity structure of the casting. Its shape and size directly determine the internal contour and dimensional accuracy of the casting, making it a critical component affecting product quality. The slider head, as the connecting and load-bearing part of the slider assembly, reliably connects the core or insert to the slider body. During the core pulling and resetting process, it ensures that the parts move stably and accurately with the slider, thus achieving the forming and demolding of complex lateral structures. The vent block plays a crucial role in venting the mold cavity, promptly releasing gases through micropores or grooves during the filling process, reducing casting defects such as porosity and looseness, and improving the density and overall forming quality of the casting. These three components work together to ensure the forming accuracy, operational stability, and casting quality of the die casting mold.
Mold Cores/Sliders/Vent Blocks
Key Machining Points ：
- Lifting ring holes, ejector pin holes, insert pin holes, and cooling water holes;
- Mold surface, runner, and mating surfaces;
- Hardness
Machining Process for Mold Cores/Sliders/Vent Blocks:
① Manual Rough Machining
Machining content: Drilling pre-holes for ejector pins/insert pins/inserts, drilling cooling water holes, drilling threaded bottom holes, and tapping.
Machining methods:
a. Machining on a vertical milling machine: Tapping (for cooling threads, lifting rings, etc.) or pre-holes for ejector pins/insert pins of small molds can be processed on this equipment;
b. Deep hole drilling machine machining: Common pre-holes for ejector pins/insert pins or cooling water holes can be processed on this equipment.
② CNC Rough Machining
High pressure die-casting mold CNC machining includes rough machining and semi precision machining
a. Machining content: CNC machining quickly removes excess material from the blank to form the die casting mold prototype. Note that sufficient allowance should be left for finishing;
b. Machining precautions:
Because the mold core will deform after heat treatment, sufficient allowance must be left during rough machining. The amount of allowance depends on the size and complexity of the die casting mold. Too little may result in insufficient material for finishing, while too much may lead to a decrease in hardness after finishing. Generally: 0.5mm for small molds, 1mm for medium-sized molds, and 1.5-1.8mm for large molds.
③ Heat Treatment (vacuum quenching, increasing material hardness);
I. Role and precautions of heat treatment:
a. Heat treatment can change the metallographic structure of the material to ensure the necessary strength and hardness, dimensional stability at high temperatures, wear resistance, corrosion resistance, fatigue resistance, and machinability of the material;
b. The heat-treated parts must be free of cracks, require minimal deformation, and minimize residual internal stress;
c. The quality of heat treatment plays a very important role in the service life of die-casting molds. Improper heat treatment often leads to cracking and premature failure of the mold.
II. Selection of hardness for mold core/slide head/vent block:
a. The hardness after quenching is generally 44-48 HRC;
b. Higher hardness is more conducive to demolding and provides better wear resistance, but it also increases brittleness;
c. Larger inserts should have relatively lower hardness, while smaller inserts should have relatively higher hardness; complex shapes should have relatively lower hardness, while simple shapes should have relatively higher hardness (general recommendation: below 280T: HRC48; 280T-650T: HRC46; 800T-1200T: HRC45; above 1200T: HRC44; tolerance range ±HRC1);
d. The more uniform the hardness after quenching and the smaller the difference in hardness values for the same workpiece, the better.
III. Heat Treatment Process: Quenching → Tempering → Tempering → Tempering
④ Benchwork Finishing
a. Processing content: Grinding the bottom surface, milling the X/Y datum surfaces;
b. Processing precautions: Because the mold core will deform after heat treatment, the first step after heat treatment is to find the three original processing datum points for the mold in the X/Y/Z directions. The Z-direction datum can be processed using a surface grinder, and the X/Y direction datums can be processed using a horizontal milling machine (precision edge milling machine).
⑤ CNC Finishing
a. Processing content: Maximizing the removal of excess material remaining after rough machining of the blank;
b. Processing precautions:
Currently commonly used programming software includes: MasterCAM, Cimatron, UG, Powermill, etc.;
Currently commonly used CNC machine tools are three-axis machines. Due to the limitations of the machine tools and tools, many surfaces and mating surfaces on the mold core cannot be fully processed and can only be processed in the next process; other advanced CNC machining machine tools include 4-axis or 5-axis machines, high-speed machines, etc.
⑥ EDM Machining
a. Processing content:
Performing electrical discharge machining on excess material or areas requiring high precision that cannot be completed by CNC machining;
b. EDM machining principle: EDM (Electrical Discharge Machining) is a process method that removes material through the electro-corrosion effect during pulsed discharge between the tool electrode and the workpiece electrode in a certain medium. It can process various materials with high melting point, high hardness, high strength, high purity, and high toughness.
c. The basic processing methods of EDM include:
Profiling method: This method involves designing and manufacturing tool electrodes with opposite convex and concave shapes, and the same dimensions and accuracy requirements as the workpiece, for surface erosion processing;
Generating method, also known as the trajectory method: This method involves creating a two-dimensional digital control program based on the required shape of the workpiece’s processing surface. A simple cylindrical electrode (generally a copper electrode) rotates while simultaneously moving along the CNC trajectory for electrical discharge machining. This method is generally used for machining threads.
⑦ Wire EDM (WEDM)
a. Processing content: Cutting out ejector pin holes and insert/part holes according to drawings and pre-drilled holes;
b. Wire EDM principle: The principle of wire electrical discharge machining is the same as that of electrical discharge forming, both based on the principle of electrical discharge erosion during pulsed discharge between electrodes. The difference is that wire electrical discharge machining does not require the production of complex forming electrodes, but uses a continuously moving electrode wire as a tool, while the workpiece moves along a predetermined trajectory to cut out the required complex part shape.
⑧ Die Casting Mold Polishing
a. Processing content: Improving the surface accuracy after CNC or EDM machining; mold polishing has two purposes: one is to increase the smoothness of the mold, making the surface of the molded product smooth and beautiful, and the other is to allow the product to be easily demolded. Mold polishing generally uses grinding stones, files, oilstones, sandpaper, pneumatic tools, ultrasonic instruments, etc., to polish the cavity surface of the mold. Generally, the die casting mold is polished to 320# oilstone or sandpaper (Ra0.4um).
Standard Insert Pin Manufacturing Process for High-Pressure Die Casting Molds
Machining Method: Grinding (removing excess material from the blank);
Machining Equipment: Pin grinding machine
Blank Material: SK*** standard insert pins; insert pins requiring higher precision require special surface treatment (surface nitriding, titanium plating, or titanium aluminum nitride coating, etc.). These pins are generally outsourced for processing.
Irregularly Shaped Insert Pins/Inserts
Machining Method: CNC/EDM/Wire cutting (machining method depends on the shape)
Blank Material: SK*** standard insert pins or ordinary H13/8418 material; those requiring higher precision require special surface treatment (surface nitriding, titanium plating, or titanium aluminum nitride coating, etc.). These irregularly shaped insert pins/inserts are generally outsourced for processing.
Die Casting mold Sprue Bushing
Machining Key Points:
- Surface finish (affects the fit with the punch – preventing the punch from getting stuck);
- Surface hardness (affects lifespan – wear);
- Coaxiality (affects mold installation and punch movement)
Sprue Bushing Machining Process:
① Rough turning according to the 2D drawing (turning quickly removes excess material from the blank, ensuring sufficient allowance for finishing);
② Heat treatment (improves material hardness);
③ Fine turning/grinding according to the 2D drawing (removes excess material remaining after rough machining);
Machining process for die casting mold cooling jackets
Machining Key Points: Interference fit
- Turning (removes excess material from the blank, including rough and fine machining);
- Assembly (the processed cooling sleeve and the inspected sprue bushing are assembled together using a heated interference fit);
- Benchwork (drilling thread bottom holes and tapping)
Runner Cone Machining Process
① Rough turning according to the 2D drawing (turning quickly removes excess material from the blank, ensuring sufficient allowance for finishing);
② Benchwork (drilling ejector pin pre-holes, drilling cooling water holes, drilling thread bottom holes and tapping, etc.);
③ CNC machining according to the 3D drawing (CNC machining quickly removes excess material from the blank, no allowance is needed);
④ Heat treatment (improves material hardness);
⑤ Fine turning (removes excess material remaining after rough machining)
Block Base Machining Process
① Benchwork rough machining (drilling cooling water pipe through holes, drilling bolt through holes, drilling thread bottom holes, tapping, and rough machining of slider head positioning grooves, etc.);
② CNC machining according to the 3D drawing (CNC machining quickly removes excess material from the blank, ensuring sufficient allowance for finishing);
③ Heat treatment (improves material hardness);
④ Benchwork fine machining (grinding the X/Y/Z three datum planes);
⑤ CNC fine machining (removes the maximum amount of excess material remaining after rough machining);
⑥ EDM machining (electrical discharge machining is used to remove excess material that cannot be removed by CNC machining).
Guide Rail/Pressure Plate/Wear Plate/Wedge Block Machining Process
① Benchwork rough machining (drilling bolt through-holes, drilling threaded bottom holes, tapping, and rough machining of sliding positioning grooves and directional positioning grooves, etc.);
② Heat treatment (to improve material hardness);
③ Benchwork precision machining (milling or grinding to remove excess material remaining after rough machining);
Mold Assembly Process and Quality Control Key Points
Part fitting mainly includes several key fitting operations: firstly, the fitting of the mold core and the mold base, ensuring the installation position and overall fit accuracy of the mold core in the mold base; secondly, the fitting of the moving mold and the fixed mold core, focusing on the fitting and correction of key parts such as the parting line (PL surface), original core position, slider groove, contact surface, and support surface, to ensure mold closing accuracy and reliable movement; in addition, it also includes the fitting of other parts, such as slider components (slider head, slider base, pressure plate, wedge block, etc.), exhaust block, runner cone, sprue bushing, insert pins, ejector pins, and cylinder components, to ensure coordinated cooperation between each functional component and meet design and usage requirements.
Some requirements for die casting mold final assembly:
a. All moving parts of the mold (including sliders, ejector pins, etc.) should ensure accurate positioning and reliable movement, without tilting or jamming;
b. Fixed parts (including mold core, insert pins, runner cone, slider pressure plate, etc.) should not move relative to each other;
c. The runner transitions should be smoothly connected, the joints should be tightly fitted, the un-molded draft angle should be no less than 5°, and the surface roughness Ra≤0.4μm;
e. After mold closing, the parting surface should be tightly fitted. If there are local gaps, the gap should not be greater than 0.05mm (except for exhaust grooves);
f. The cooling water channels should be unobstructed, and there should be no leakage. The inlet and outlet should be clearly marked;
g. The mold should be equipped with lifting eye bolts to ensure safe lifting. The mold should be stable during lifting for easy mold installation.
Raidy Die Casting Mold Process
The manufacturing of die casting molds is not simply the processing of individual parts, but a systematic engineering process based on the machining of die-casting mold components and centered on high-precision mold assembly. From base blocks, guide rails, pressure plates, and wear plates to wedge blocks, the machining accuracy and assembly fit of each part directly impact the operational stability of the mold and the quality of the castings. Only through standardized processing procedures and strict assembly control can the die-casting mold ensure long-term stable operation in mass production, creating higher production value for customers.
RaidyMold, a manufacturer specializing in the precision machining of die-casting mold components and complete mold assembly, covers key parts such as mold cores, slider heads, venting blocks, base blocks, guide rails, pressure plates, wear plates, and wedge blocks. From initial process planning and strict processing control to high-standard mold assembly and inspection, RaidyMold consistently focuses on stability, durability, and reliability in mass production.
Whether you are developing a new mold or optimizing and modifying an existing one, RaidyMold can provide practical and mass-producible mold manufacturing solutions based on your actual production needs.
If you are looking for an experienced partner in die casting mold processing, mold component manufacturing, and mold assembly quality control, please contact RaidyMold and discuss your project requirements with our engineering team.
