1.Automotive Mold Types and Characteristics of Mold Processing Equipment

In recent years, the rapid evolution of China's automotive industry has driven a remarkable 20% annual growth in the stamping mold market. Molds are integral to the stamping production process, and are technology-intensive products. The quality, production efficiency, and cost-effectiveness of stamped parts directly hinge on mold design and manufacturing. Notably, in the lifecycle of a car model, the car body undergoes the shortest cycle and the most frequent changes. The design and manufacturing of body stamping molds is a pivotal aspect of car body development, accounting for approximately 2/3 of total car development time and posing a critical constraint on the rapid introduction of new models. In China, imported products make up about 50% of the mid-to-high-end mold market.

Automotive stamping molds take on diverse forms and can be categorized based on three factors: purpose, mold structure, and mold materials. They can also be classified by their primary characteristics, like their manufacturing process. The blanking mold separates material along a closed or open contour, and includes punching molds, cutting molds, incision molds, trimming molds, slitting molds, etc. The bending mold induces bending and deformation along a straight or curving line to achieve a specific angle in the shape of the workpiece, while the drawing mold transforms the sheet blank into an open hollow part or modifies the shape and size of a hollow part. Forming molds directly replicate the blank or semi-finished workpiece according to the shape of the convex or concave mold, causing only local plastic deformation in the material. Examples include bulging molds, shrinking molds, expanding molds, undulating forming molds, flanging molds, shaping molds, and more. Classification can also be done through processes: A single-process mold is a mold that finishes only one stamping process in one stroke of the press; a composite mold has only one station, and in one stroke of the press, two or more stamping steps are completed at the same time. The progressive mold (also called the continuous die) has two or more stations in the feed. One stroke of the press leads to two or more completed passes successively at different stations. The molds can also be categorized based on the specific material operations: punching and shearing molds, bending molds, drawing molds, forming molds, and compression molds. Punching and shearing molds execute tasks through precise shearing. Commonly employed forms encompass shearing molds, blanking molds, punching molds, trimming molds, edge forming molds, hole punching molds, and punching molds. Bending molds transform flat sheets into angled shapes, tailoring their application based on the part's specific geometry, accuracy requirements, and production volume. Bending molds encompass ordinary bending molds, cam bending molds, curling molds, arc bending molds, and bending punches. Drawing molds are instrumental in shaping flat blanks into seamless containers with a bottom. Forming molds utilize diverse deformation methods to alter the blank's shape, including convex forming molds, roll forming molds, edge forming molds, necking forming molds, hole flange forming molds, and round edge forming molds. Compression molds employ substantial pressure to induce metal blanks to flow and conform to the desired shape. This category encompasses extrusion molds, embossing molds, imprinting molds, and end pressing molds.

2.Comprehensive Promotion of Digitalization in the Design and Manufacturing of Automotive Molds  

Digital technology in mold production integrates computer technology or computer-aided technology into the mold design and manufacturing processes. It is internationally recognized as the pivotal factor elevating the mold industry's overall proficiency. The application of CAD/CAE/CAM/DNC technology in digital mold design and manufacturing, coupled with enterprise information management, is acknowledged as enhancing mold production efficiency, product quality, and overall enterprise efficacy. The widespread adoption of digital technology has permeated every facet of mold manufacturing.

The term "digital mold production technology" refers to the utilization of computer technology or computer-aided technology (CAX) in the mold design and manufacturing process. This advanced approach significantly enhances the design proficiency of molds, resulting in reduction of the design-to-production timeframe and overall manufacturing cycle. Moreover, it contributes to an elevation in the quality of molds. Key elements of digital automotive mold production technology include: Design for Manufacturability (DFM), which meticulously considers and assesses manufacturability during the design phase to ensure process success; auxiliary technology for profile design, including the development of intelligent profile design technology; CAE for analyzing and simulating stamping forming processes, predicting and resolving potential defects in forming; the adoption of 3D mold structure design as a replacement for traditional 2D design; and the integration of Computer-Aided Process Planning (CAPP), Computer-Aided Manufacturing (CAM), and Computer-Aided Testing (CAT) technologies in the mold manufacturing process. Guided by digitalization, this comprehensive approach tackles and resolves challenges that may arise during the mold trial process and stamping production. These facets encompass the complete journey of digital automotive mold production, from initial design to the testing phase. Together, they form an integrated automotive mold production system, delineating the trajectory of contemporary automotive mold production technology. Digital mold production technology is progressively emerging as the predominant and most mainstream technology in automotive mold manufacturing due to its evident advantages.  

As computer software continues to advance, the conditions for widespread adoption of CAD/CAM/CAE technology have matured. Enterprises are urged to intensify efforts in CAD/CAM technology training and technical services while expanding the application scope of CAE technology. The development of computers and networks facilitates widespread promotion of CAD/CAM/CAE technology, fostering collaboration across regions, enterprises, and institutions in the industry. High-speed scanners and mold scanning systems, equipped with functions ranging from model scanning to processing desired models, play a pivotal role in shortening the mold development and manufacturing cycle. Installing fast scanning systems on existing CNC milling machines and machining centers facilitate rapid data collection, automatic generation of processing programs for different CNC systems, and the conversion of CAD data into different formats, enabling "reverse engineering" in mold manufacturing.  

In addition to CAD software, the design process of automotive stamping molds incorporates extensive use of finite element simulation software to enhance the design process. Notably, AutoForm, a professional software developed in Switzerland, specializes in simulating the rapid prototyping of thin plates. It can simulate and debug processes such as stamping forming, hydraulic bulging of thin plates, and tailor-welded plates. When used in conjunction with other software functions, it supplements the drawing process, aiding in the design and simulation of single-step parts forming.

In recent years, bolstered by a series of national policies and market-driven changes, digitalization and intelligence have emerged as the new core directions in the domestic mold industry. This shift represents a proactive response to the numerous challenges faced in the current domestic mold development industry.

3. Mold Core and EDM Processing

The customized mold center consists of an EDM machine tool, a CNC high-speed machining center, a material warehouse, and a robot. A task management system orchestrates the processing sequence, prioritizing tasks based on established task priorities. The material warehouse includes 8 UPC workpiece pallets and 70 to 180 ITS electrode clampers with identifiable chips. Robots and machine tools can both precisely and reliably identify any workpiece and electrode through these identifiable chips.

 The mold center operates reliably 24 hours a day. Workpieces will undergo CNC processing and EDM electrical discharge processing after a single clamping, which markedly enhances processing quality, doubles processing speed and output, and reduces the mold production cycle. The integration of diverse processing techniques via system automations have emerged as a prominent trend in mold manufacturing technology. By combining EDM and high-speed milling into a unified processing unit, respective advantages are maximized, leading to improved production efficiency, shortened manufacturing time and mold production cycle, heightened mold processing accuracy, and enhanced machine tool utilization—ultimately resulting in reduced mold processing costs.

Upon accepting a processing task, the mold center initiates the process from establishing a processing project in the CAD/CAM software and building the workpiece processing and electrical processing programs. The central control system manages the machine tool, workpiece handling, pallet clamping, electrode clamping, tool selection, machine tool processing startup, finished workpiece unloading, and workpiece storage and retrieval in the material warehouse. All movement of objects is automatically executed by robots controlled by the mold center. Workers only need to load the workpiece pallet into the material warehouse of the processing unit at the loading and unloading station. Through automation solutions, machine tools with two different processing methods are integrated  seamlessly into comprehensive and efficient processing workpieces.  

The integration of high-speed milling and EDM mirrors the trend of mold processing technology progressing towards higher efficiency and lower costs. This integrated automation solution is best supplied by manufacturers proficient in both EDM machines and high-speed milling machines. Collaborating with manufacturers adept at both processes ensures unbiased insights into the process and aids in making informed investment decisions. This holistic solution also streamlines equipment maintenance and repair, optimizing equipment operation efficiency.  

Despite the formidable challenges posed by high-speed milling, electric discharge machining (EDM) is irreplaceable due to its unique characteristics and processing of complex mold surfaces; deep, narrow, and small cavities; sharp corners; narrow slits; grooves; deep pits and other intricate features. The future of EDM applications lies in processing complex and precise small cavities and micro-cavities, removing tool marks, as well as intricate tasks like processing sharp corners, narrow slits, grooves, deep pits, and patterns. EDM will continue to increase efficiency, automation, surface integrity, precision, and scale in response to sustainable development and green EDM strategies.

4. Single-step Precision Processing of Automotive Molds

Fine processing’s purpose is to complete the processing all at once, thus greatly reducing fitter reprocessing, post-sequence compensation, manual trimming and the dependence of mold quality on the fitter skills. For example, the gap between the cutting edges of the upper and lower molds can be processed directly into place without the need for a fitter to open a gap. The convex/concave molds can be directly installed without debugging. The drawing model surface has high smoothness and no cutter marks, thus the grinding and fitting of the inner cover can be reduced. The drawing mold does not need to be removed or pushed. There is no need to clean the root when grinding concave corners and overcutting. Through refined processing and the use of high-level standard parts, the machining and assembly quality of the parts are consistent, so that the so-called "direct assembly method" of benchwork manufacturing has become the standard of modern mold production. To achieve refined processing, we must start from mold design, CNC programming and CNC machining, such as using CAE technology for refined mold design. The drawing molds are designed for different feed amounts. Various draw beads are designed for different parts of the same set of molds, and the cross-sections of the draw beads are variable in different parts of the same set of molds. Anti-rebound, anti-over-drawing treatment and minimum pressing surface design can greatly reduce profile processing, clamp repair and trial mold hours. Refined processing is mainly reflected in the improvement of mold surface processing accuracy and processing precision. It requires high-speed precision CNC milling machines with high stiffness, high precision, and high-speed characteristics as well as the use of high-speed tools. At the same time, CNC programming technology must be adopted. Relevant processing methods include contour processing; maximum length forward processing with a lateral step of 0.3mm and 30° tilt angle finishing to avoid "zero cutting", which improves the surface accuracy of the mold; and concave fillet overcutting that does not require root rectification.

Realizing precision mold manufacturing relies not only on technical excellence, but also on effective management. For example, experience is very important in the precise design of mold surfaces, and a strict technical management system must be in place. At Toyota, fitters are not allowed to modify the mold during the initial mold trial. A mold surface designer must be present when debugging the mold to record defects in the trial mold. Changes in draw beads and draw fillets must be measured on site and recorded one by one. The continuous accumulation of such data has enriched the company's design experience and ensured more precise future designs.  

The adoption of high-speed cutting technology has significantly enhanced mold surface processing precision, enabling accurate treatment of mold surfaces. In Western economies with advanced technology, high-precision machining of edge inserts has advanced to the point where matching gaps are no longer need in the mold closure. Certain foreign automotive mold manufacturers are able to skip processes like filleting corners, aligning edges, creating gaps, or rectifying roots after processing. Remarkably, mold surfaces don't require subsequent grinding. Extensive utilization of forming process simulation technology, three-dimensional mold design technology, high-speed processing, and online measurement technology have all substantially heightened the reliability of mold design and manufacturing. In some overseas companies, trial pressed part pass rates exceed 80%. There is no need for mold modifications. The ultimate goal in precision mold manufacturing is to minimize the fitter's role to mere assembly and minimal repairs, eventually progressing to a stage where mold repairs become entirely unnecessary.

5. Automotive Mold Rapid Prototyping Method

Rapid prototyping method (RPM) primarily revolves around the creation of a physical model (master mold) through rapid prototyping. It utilizes various replication methods such as metal spraying, electroplating, composite material pouring, precision casting, etc., to swiftly produce the key components of the mold, such as convex parts, concave molds, or the mold cavity and core. The manufacturing cycle typically ranges from 1/5 to 1/10 of the traditional CNC cutting method, with costs being only 1/3 to 1/5. Rapid prototyping has been a significant advancement in manufacturing technology over the past two decades, representing a fusion of CAD technology, CNC technology, material science, mechanical engineering, as well as electronic and laser technology. It stands out as one of the most advanced methods for part and mold formation. RPM technology offers advantages like lower costs, short design and manufacturing cycles, as well as moderate precision, and can be applied directly or indirectly in mold manufacturing. Speeding up product development cycles leads to a competitive edge in the market, making rapid, economical molding technology an effective means of competition. Compared to traditional mold processing, rapid, economical molding stands out for its short molding cycle, cost-effectiveness, and precision. Overall, it presents itself as a mold manufacturing technology with robust comprehensive economic benefits. Looking ahead, ongoing advancements, improvements, and applications of new technologies in rapid prototyping and rapid economical mold-making are anticipated. Rapid molding technology, characterized by a short molding cycle, straightforward processes, easy scalability, low costs, and the ability to meet specific functional needs, proves to be a swift, convenient, and practical approach to mold manufacturing. It is particularly well-suited for new product development, trial production, process and functional verification, as well as multi-variety and small-batch production. In the face of increasing enterprise competition and the ever-shortening product development cycles, rapid molding technology is well-positioned to capitalize on emerging opportunities and expand its influence. As industrial production progresses, the heightened attention from product developers and the mold industry, coupled with ongoing research and the emergence of new technological achievements, highlights the vibrant developmental trajectory and robust vitality of rapid molding technology.

6. Conclusion 

The robust growth of China’s automotive industry in recent years has been a catalyst for significant advancements in the automotive mold sector. To address the pressing demands of users for high precision, rapid delivery, and cost-effectiveness in mold manufacturing, the mold industry must persist in enhancing production capabilities and expansive adoption of cutting-edge manufacturing technologies. Only through this will they be able to cater to diverse industry needs for fundamental mold components. Looking ahead, emphasis should be placed on reshaping the industry's internal structure and elevating technological development standards. This entails integrated technology, advanced equipment, product branding, management informatization, and fostering international operations among mold enterprises. This development trajectory is pivotal, propelling the transformation of China’s mold industryinto the future.

 Images and text sourced from Machine Tool World