Different design standards and concepts; Different design basis; Different design processes; Different acceptance standards.
Product molds rarely use templates for reverse engineering; they are generally based on customer's 3D and 2D drawings. A product mold fully adheres to customer's mold standards in its design philosophy. Mold quality, specifications, and lifespan fully comply with customer's mold design specifications. Mold design and manufacturing are entirely based on customer-confirmed mold drawings. Mold packaging, transportation, and delivery dates are strictly in accordance with mold contract. A complete solution is provided to customer.

 

Before receiving a commercial mold order, mold manufacturers must conduct a risk assessment. This assessment should evaluate whether company's technical capabilities, manufacturing equipment, processes meet customer's requirements, whether company has experience in designing and manufacturing similar molds. For commercial mold projects, a dedicated project engineer should be designated as communication point with customer. This project engineer must undergo professional training, clearly understand customer's needs, know which questions must be asked and which should not. Large mold manufacturers should establish a mold project department and develop a series of mold processes. Project engineer should create a paper file for each mold, ensuring one file per mold and consistency between mold and file. Customer design materials, including mold design standards, product drawings, mold design specifications, injection molding machine data, product design change notices, plastic property tables, and communication emails, should all be bound in file for easy organization of mold review meetings and verification.
Commercial molds have higher requirements than production molds; clearly, export molds fall under category of commercial molds. Aforementioned design processes and considerations for production molds are also fully applicable to commercial molds. In addition, commercial molds involve following processes.

DFM stands for Design for Manufacturability. It primarily studies physical design of a product and interrelationships between various parts of manufacturing system, applying it to product design to integrate the entire manufacturing system for overall optimization. DFM can reduce product development cycles and costs, enabling smoother production. European and American clients often request DFM documentation before placing orders. Mold suppliers bear significant responsibility for their DFM assessments, as they directly impact rationality of mold design and stability during mass production. Therefore, meticulous attention to detail and item-by-item evaluation according to requirements are crucial.
Manufacturability-oriented product design refers to product design that meets manufacturing requirements, possessing good manufacturability, enabling product to be manufactured with the lowest cost, shortest time, and highest quality. Intense market competition has gradually revealed drawbacks of traditional product development models: due to disconnect between product design and manufacturing, it's difficult to consider manufacturing requirements during product design phase. Products designed by product designers often have poor manufacturability and assemblability, turning product development process into a repetitive cycle of design, manufacturing, design modification, and remanufacturing. This results in numerous design modifications, long development cycles, high costs, and low quality. Phrase "repeatedly modifying until things are done right" perfectly encapsulates traditional product development process. Moreover, sometimes "even repeated modifications don't guarantee things will be done right," leading to product development failure.
Concurrent engineering refers to a systematic approach to designing products and their related processes (including manufacturing and support processes) in an integrated and parallel manner. It's a means of implementing a manufacturing-oriented design process. This method requires product R&D designers to consider all factors throughout product's entire lifecycle, from concept formation to product obsolescence, including quality, cost, schedule, user requirements, from outset. Only by starting with product development and collaborating with mold designers can concurrent engineering achieve its goals of improving quality, reducing costs, and shortening development cycles. For example, Canon, a Japanese printer brand, consistently employs concurrent engineering in its printer product development. Product drawings undergo three Design for Manufacturing (DFM) reviews before mold development begins, and these three DFM reviews are conducted collaboratively with mold manufacturer.
It is well known that design phase determines 80% of a product's manufacturing cost. Similarly, many quality characteristics are fixed during design phase. Therefore, considering manufacturing factors during design process is crucial, and designers should be aware of these factors. To improve efficiency, companies should have their own DFM system, categorized and maintained. DFM documents should be dynamic documents that change with environmental conditions, managed by a core committee whose members should include personnel from design, manufacturing, marketing, project, and quality control (QC) departments.
Through DFM activities, mold manufacturers can intervene in customer's product design phase, strengthening relationships with customers. They assist customers in improving product design capabilities, providing expertise, optimizing and enhancing product quality, reducing potential problems, and offering comprehensive solutions. Simultaneously, they gain a deeper understanding of customer's design intent, enabling better control of later costs. On the other hand, for mold manufacturers, ability to fully communicate with clients on various technical issues during DFM activities in the early stages of project initiation lays a solid foundation for successful mold review meetings, facilitating parallel development of product and mold design work, thus shortening product and mold development cycle.
When creating DFM documents, any problems with plastic parts and molds need to be proactively assessed, and insightful solutions proposed. For issues where several possible design solutions are difficult to determine, these should be clearly expressed and discussed with client for a joint decision. DFM documents should avoid simply raising questions without providing solutions; instead, client should answer questions and propose mold design solutions. A standardized template should be used for DFM documents, ensuring an aesthetically pleasing, clear, and eye-catching layout, as this document represents company's image.

Mold design specifications are documents concerning mold design specifications. Mold design engineers should review and understand contents of mold design specifications item by item, and mold design drawings should fully comply with requirements of mold design specifications.

 

There are two types of mold review meetings. The first type is a mold review meeting between mold manufacturer and customer. In Japanese-owned companies, this is also called a mold agreement meeting. Review focuses on identifying structural problems in product and mold, proposing improvement measures, determining parting line, ejection method, gate. All review content must be marked in pencil on product drawings and written into mold design specification. After review is completed, relevant review records are filled out, stamped on drawings, and signed by both parties for confirmation. The second type is an internal review meeting within mold manufacturer. Upon receiving a mold order, mold manufacturer should immediately organize a mold review meeting. This meeting should be organized by project engineer, convening mold designers and manufacturers, mold follow-up personnel, testing personnel, trial mold personnel. Through review meeting, customer product information is promptly communicated to every employee, allowing for timely identification and resolution of problems.
Three key elements of mold review are parting line, ejection method, and gate design. These three elements also determine mold structure. Once these three elements are determined, basic structure of a mold is essentially finalized. Final document of mold review meeting must include these three elements.
Key points of a mold review meeting are: Discuss mold requirements, structure, and processing methods; Refer to past problems encountered with similar molds and anticipated high-risk issues, thoroughly discuss and implement preventative measures.
Regardless of type of review meeting, focus is on product drawings, mold design challenges and key points, customer mold standards, and injection molding machine parameters. Following points should also be noted during mold reviews:
1) Component demolding analysis, review of important dimensions and tolerances
First, conduct component demolding analysis (to determine rationality of component structure design and whether there are any unnecessary undercuts). For each injection molded product, mold opening direction and parting line should be determined at the beginning of design phase to minimize core-pulling mechanisms, eliminate impact of parting line on appearance. After determining mold opening direction, product's reinforcing ribs, snaps, protrusions, and other structures should be designed to align with mold opening direction as much as possible to avoid core pulling, reduce seam lines, and extend mold life. After determining mold opening direction, an appropriate parting line can be selected to improve appearance and performance. Understand product's assembly relationships, confirm critical dimensions, allow for adjustments (addition allowance). Review reasonableness of assembly tolerances in product design. For parts with particularly strict tolerances, inserts should be used in mold. For tolerances that are difficult to guarantee using conventional methods, modification suggestions should be made to customer. For parts that may require dimensional adjustments, consider using independent insert designs. This should be proposed in advance for improvement during subsequent mold design. If components require common mold design, consider design of replacement inserts. Does it have a forced demolding structure? Forced demolding is only possible when inner and outer recesses are relatively shallow. At the same time, plastics with sufficient elasticity have a higher probability of successful forced demolding. Decisive factor for successful forced demolding is whether plastic part has room for deformation.
2) Draft Angle
Based on parting line of product, propose draft angle. For parts with deep cavities, a suitable draft angle must be selected. An appropriate draft angle can prevent product roughening. Draft angle for smooth surfaces should be greater than 0.5, for finely textured surfaces greater than 1, and for coarsely textured surfaces greater than 1.5. Inquire and confirm reference point for draft angle. Clarify whether parts of component structure design without draft surfaces will be handled by mold factory (such as pillars, ribs, etc.).
3) Analysis of injection molding issues such as glue thickness, shrinkage, deformation, and air trapping:
Is glue thickness reasonable, even, and easy to mold? Glue thickness less than 0.5mm is difficult to mold. For thicker glue areas or base of pillars, is it necessary to reduce glue thickness to prevent shrinkage? Confirm method and size of reduction. Areas prone to deformation need to be reviewed, predicted, analyzed, and countermeasures proposed in advance. Review mold for problems such as sharp corners, thin sheets, excessively deep ribs, and insufficient slider stroke. Whether ejector pins or inserts are used for venting at air trapping points, and whether inserts are used to vent at mold core at air trapping points. Clarify whether "volcano" venting at base of pillars is handled by mold factory and confirm "volcano" parameters.
4) Plastic Material and Shrinkage Rate
Reviewers should be familiar with molding characteristics of commonly used plastics; Review and confirm plastic grade and raw material supplier, and confirm shrinkage rate; For plastics containing GF (glass fiber), shrinkage rate will be significantly reduced, and shrinkage rate will be inconsistent in different directions.
5) Textured Surface (Confirmation of Product Surface Treatment Information)
Confirm range and texture grade of textured surface. Consider designing a slider core-pulling mechanism for 0° textured surfaces.
6) Parting Line (PL)
Parting line should fully consider product's appearance, mold opening direction, processing difficulty, define parting surface position clearly. For R-corners that are difficult to machine, it is recommended that customers cancel or change them. Draft angle of insertion surface should ideally be 3~5 (not less than 2). Consider strength of mold core and insertion/penetration surfaces.
7) Fillets
Insufficient fillet radius may cause stress concentration in product, leading to cracking. Insufficient fillet radius may cause stress concentration in mold cavity, leading to cavity cracking. A well-designed fillet radius can also improve mold processing technology, such as allowing cavity to be directly milled with an R-cutting cutter, avoiding inefficient EDM. Different fillet radii may cause parting line movement; different fillet radii or chamfers should be selected based on actual situation. Necessary internal R-corners in product can improve plastic flow properties, facilitate injection molding process adjustment, and easily solve shrinkage problems.
8) Insert Status and Ejector Pin Position Confirmation
Confirm necessity of inserts based on mold processing difficulty and venting conditions. Confirm type and size of inserts related to paper-through and textured surfaces. Conduct a preliminary analysis to determine if ejector pin arrangement can prevent ejection deformation and whether there is suitable space to design ejector pin positions. Mold manufacturer needs to provide final ejector pin layout drawing for customer confirmation.
9) Inserts
Inserting inserts into injection molded products can increase local strength and hardness, but it also increases product cost. Inserts are generally made of copper, but can also be other metals or plastic parts. Portion of insert embedded in plastic should be designed with anti-rotation and anti-pull-out structures, such as knurling, holes, bends, flattening, shoulders, etc. Plastic around insert should be appropriately thickened to prevent stress cracking of plastic part. When designing inserts, their positioning method in mold (holes, pins, magnetism) should be fully considered.
10) Slider Mechanism
Confirm size, stroke, and drive method of slider mechanism. For larger strokes, a hydraulic cylinder should be used. Review whether sliders interfere with each other and whether movement is smooth. Fixed mold slider.
11) Lifter Mechanism
Confirm stroke and angle of lifter, and review whether there is interference with product.
12) Gate
Confirm gate type (two-plate or three-plate mold, hot runner or cold runner), size, location, number. Review deformation and weld line of product, analyze shrinkage incomplete injection. Review whether gate removal is easy. Review impact of gate parameters on product molding process, predict whether there will be shrinkage, deformation, or other problems. Analyze whether wall thickness of injection points in same direction is similar; a large difference in thickness can easily lead to deformation. Design of runner and gate needs to consider whether plastic part and solidified material in runner will automatically drop or be picked up by a robotic arm.
13) Mold Base Specifications and Grades, Mold Material and Heat Treatment
Based on product condition and customer requirements, confirm mold base specifications, grade, and mold material. For products requiring a high mirror finish, mold core material should be a high-grade imported steel with high mirror polishing performance, such as NAK80 or S136H. For materials that release corrosive gases during molding, such as POM and PVC, mold core needs to be made of stainless steel, such as 420SS. Molds containing GF materials require heat treatment such as quenching. For molds requiring a lifespan of over 1 million cycles, appropriate materials should be selected and heat treatment should be performed. Is it required to engrave mold number and usage precautions (especially for molds with side-pull sliders)?

 

14) Molding Machine
Inquire with and confirm specifications and size of injection molding machine from manufacturer (trial molding) to determine specifications of locating ring for gate. Consider molding process (automatic or semi-automatic).
15) Number of Cavities
Review and confirm whether number of cavities is economical, reasonable, and feasible. High-precision components (such as gears and racks) should not exceed two cavities. Components with significantly different shapes and sizes, or different materials, should not be molded together.

After mold structure drawing is completed, it needs to undergo internal review. Experienced engineers will review it to ensure it fully meets customer's requirements. Internal review is based on customer's mold standards and mold design specifications. Furthermore, any non-compliant items must be corrected immediately. After internal review and confirmation, design is converted to DXF format and submitted for customer confirmation. Steel and mold bases can only be ordered after customer confirmation of product mold.
Review items emphasize aspects most closely related to injection molding, such as mold's steel, hot runner system, temperature control box, hot runner sockets and wiring methods, undercut solutions, parting line and draft angle, mold cooling water connector specifications, injection molding machine nozzle parameters, and injection molding machine die clamping method. For specific molds, there may be some special considerations requiring case-by-case analysis.
Mold drawings submitted by mold manufacturer for customer confirmation must be repeatedly checked and confirmed to be error-free. Design drawings represent mold manufacturer's image; therefore, they cannot contain any errors, omissions, or unclear expressions. Design concept and philosophy expressed in mold drawings must be unique, accurate, and conform to customer's mechanical drawing standards. Choice between first-quadrant and third-quadrant projection must align with customer's preferences.
Mold drawing confirmation is a crucial step in product mold design and a fundamental design principle for export molds. Customer confirmation of mold drawing indicates that mold specifications meet their design philosophy and that mold's installation matches injection molding machine; however, it does not guarantee correctness of mold structure. Therefore, mold manufacturer must be responsible for correctness of mold structure.

During mold transfer, following documents must be provided to customer: assembly drawing, parts drawing, mold parts list, cooling circuit diagram, purchase order, and molding condition table (one copy each), as well as one final sample/one sample with zero holding pressure. These documents must be packaged and shipped together with mold.
After mold assembly drawing design is completed, assembly drawing, water circuit diagram, and IN/OUT piping specifications must be provided to customer immediately. For hot runner molds, circuit diagrams for sensors and heaters must also be provided. Mold drawing included with mold must show final mold dimensions (any dimensional changes due to design variations must be reflected in mold drawing). During mold transfer, confirm that mold design is complete and obtain a mold design confirmation certificate. Part numbers, cavity numbers, mold weight, and country of origin should be clearly CNC-engraved on square iron.

Sample review after trial molding includes three aspects: appearance review, dimensional review, and mold forming stability review, as well as mass production confirmation. Sample reviews are generally marked on plastic part sample with a colored pen, and written information is recorded on 3D drawing of plastic part. Written information mainly records sample defects and their locations, whether dimensions and tolerances are out of tolerance, problems encountered during mold trial molding process, etc. All above information should be compiled into a document, archived, and distributed to relevant mold-making personnel for improvement.
For continuous molding of 100 or more batches, appearance and key dimensions of initial and final batch samples must meet drawing requirements (MT plates can be used as substitutes); Sliders, ejector pins, and insert surfaces must not have scratches or abnormal movements (such as unstable ejection); guaranteed production quantity must be at least 500,000 batches; mold design specification cycle must be met; a temperature control machine (water-cooled) (adjustable from 25 to 65℃) must be used during mold trials.
Injection Mold Trial Part Review: Appearance. Check if surface texture is correct, if there are impurities in material, and if there are any dents or scratches on product surface; Parting Line. Check for burrs at parting line and for any pulling (note that pulling can easily occur at hole locations, leading to hole deformation); Gate. Infer weld line location based on gate distribution and check weld line; how to remove excess material at gate; whether areas far from gate are fully filled; if glass fiber is added to raw material, scratches are likely to occur at gate, and fiber floating is likely to appear on product surface; Deformation. Plastic products often experience internal shrinkage deformation, which cannot be fundamentally avoided. Therefore, design should consider adding necessary ribs or reasonable structures to prevent deformation; Shrinkage. Shrinkage usually occurs on the back of thick plastic parts and ribs; Stress Marks. Stress marks usually occur on the back of thin plastic parts and ejector pins or sleeves; Ejector Pins. Is distribution of ejector pins uniform and reasonable? To avoid assembly interference, ejector pins are usually recessed into product by 0.05~0.1mm. During product ejection, check if back of ejector pins is whitened, and whether ejector pin burrs exceed design requirements. To prevent sticking to front mold, if an undercut structure is added to top of ejector pin, it will be reflected on product after demolding. Customer confirmation is required, and it should be repaired in subsequent processes; Slider, Insert, and lifter. Marking lines will appear around sliders, inserts, and lifters. Are these within design limits? During demolding, lifter positions are prone to scraping; Inserts. Insert injection molding (e.g., sheet metal parts, nuts, etc.). After injection molding, nuts are heat-fused. At this point, it's necessary to determine torque, pull-out force, and whether there is excess glue; Marking. Material/Date/Cavity Number/Product Number/Version Number/Recycling Mark; Printing. Silk screen printing/pad printing/spray painting/laser engraving... (usually requires corresponding tooling/fixtures); Critical Dimension Measurement. Measure and verify critical dimensions. There are three ways to handle non-conforming dimensions: mold manufacturer improves, accepts (providing an allowable range), or modifies drawing tolerances.
During trial molding, when defects are found in sample, following aspects should be analyzed in detail.
What kind of defect occurred? Where in product did it occur? What was its severity? How frequently does defect occur (every time, or sporadically)? How many cavities are there? Do injection molding defects always occur in same cavity? Does defect always occur in same location? Was this defect anticipated during mold design and manufacturing? Is defect clearly visible at gate, or in a location far from gate? Was cooling water (electric heating or gas) connected as required during trial molding process?
During sample review, nature of problem should be clarified: is it a mold problem, an injection molding process problem, or some other issue?
DMAMIC process can be used in sample review. DMAMIC is an important tool for process improvement in 6O management. 6O management is not only a concept but also a methodology for achieving performance breakthroughs. It transforms concepts into actions and goals into reality. DMAIC refers to a process improvement methodology consisting of five phases: Define, Analyze, Measure, Improve, and Control. It is generally used to improve existing processes, including manufacturing, service, and work processes.
DFSS is an abbreviation for Design for Six Sigma, referring to a design methodology for new processes and products.

 

Definition: What kind of defect occurs? When, where, how frequently, and what is defect rate? Analysis: What are relevant factors causing this defect? What are main factors? What is root cause? Measurement: MAS (Measurement System Analysis) analysis, including visual inspection of appearance quality, internal quality analysis, measurement of dimensions and color (visual inspection or colorimeter). Improvement: Develop effective solutions and plans to improve injection molding defects (what methods to use), organize their implementation and follow-up. Control: Consolidate improvement results (record complete injection molding process conditions), summarize and standardize defects caused by this type of structure, and apply this improvement method to other similar products, achieving goal of learning by analogy and applying knowledge to other situations.
Possible causes must be considered. Material issues must be checked, such as: Is material dry? Is raw material quality good? Is recycled material good quality (free of long rods, other impurities, dirt, excessive dust, etc.)? Is recycled material ratio appropriate, and is process control accurate? Mold issues must be checked, such as: Are water and air lines connected correctly? Is cavity clean? Is mold cavity damaged? Injection molding machine issues must be checked, such as: Is machine's check valve broken? Is barrel worn? Is actual injection pressure reached?
It is worth noting that, generally, if injection molding process can operate stably for more than 24 hours without any problems, production process parameters are considered stable and reasonable. Therefore, problems arising during stable production should not be attributed to process parameters; other issues should be investigated.
Defects found in injection molded products can have multiple causes. Methods for determining cause are twofold: experience and systematic verification. Before verification, it is essential to be familiar with detailed information regarding plastic properties, injection molding machine, injection mold, plastic product, and to clearly define purpose of verification.
Time window for injection molding. Quality of injection molded parts is guaranteed only within a "certain" parameter setting range. This "certain range" is often referred to as injection molding time window. Only parameter settings within this time window can produce injection molded parts with a low scrap rate. Assuming a quality problem occurs during production, the first step is to check all parts of injection molding machine and mold to ensure processing temperature is correct, check material drying status, and compare set values of each parameter with actual data. Procedure for changing parameters. When troubleshooting by changing process parameters, only one parameter should be changed at a time, and change should be recorded immediately. Especially when changing melt temperature and mold wall temperature, to evaluate injection molded parts, it is essential to first confirm that required set temperature was reached during production.

Common mold shipping methods include: land transport, sea transport, and air transport. For sea transport, vacuum packaging with aluminum foil is required to prevent rusting. Packaging boxes should ideally be made of engineered wood to avoid hassle of fumigation. If solid wood is used to make crates, fumigation for pest control is required, and its effectiveness is limited to 21 days; after this period, fumigation must be repeated.
1) Mold Shipping Document Preparation and Arrangement
Within one business day of receiving customer's mold shipping notification, project engineer will confirm with manufacturing department mold accessories (including electrodes) and related engineering technical documents that need to be transported with mold. Project engineer will also instruct manufacturing department to clean mold, disassemble it, drain water from pipes, prepare mold packaging materials, and vacuum pack it with aluminum foil. Within one business day of receiving customer's mold shipment notification, project engineer prepares all relevant technical documents for mold and notifies quality engineer to conduct a pre-shipment mold inspection. Within one business day of receiving notification, quality engineer conducts a final inspection of mold, completes "Pre-shipment Mold Inspection Checklist," confirms that all mold issues marked on checklist have been resolved and mold is ready for shipment. On same day as receiving customer's mold shipment notification, project engineer confirms address and contact information with customer, shipment method, provides mold dimensions and weight, as well as packaging dimensions and weight. Estimated shipment time must also be informed to customer. Within two hours of receiving detailed shipment information from customer, project engineer forwards relevant documents to sales department. Within two business days of receiving all shipping information, sales department confirms specific shipment time and mold arrival time with project engineer, quality engineer, finance department, relevant shipping company, informs both customer and project engineer. Within one business day of confirming mold delivery time, project engineer shall complete "Mold Delivery Notification," submit it to Quality Department and Finance Department for confirmation, and provide all documents and forms used in "Project Management Process," as well as customer's mold delivery notification email and final sample to supervisor for final review and confirmation. Shipping department can only arrange mold delivery after receiving a fully confirmed "Mold Delivery Notification." Note that engineer must provide following information before mold delivery: "Mold Design Review Form," "Mold Production Notification," "Mold Injection Molding Condition Table," "Dimensional Inspection Report," "Mold Inspection Report," "QA Mold Delivery Inspection Report," and "Mold Delivery Document Checklist." Before the mold is shipped, project engineer needs to provide customer with standard photos of mold as required. Note that photos of cleaned mold must be shown. Mold photos must be archived during mold delivery.

 

2) Follow-up on mold operation and handling of abnormalities after mold delivery
Within one week of mold arriving at customer's location, project engineer will confirm following: Whether customer has received mold, related accessories, and relevant technical documents; Whether mold was intact during transportation; Whether customer's trial molding or production went smoothly. If any abnormalities occurred during trial molding or production, engineer will proactively help customer solve problems and propose solutions; Follow up on the handling results and communicate with customer to request the commencement of a new project. Within one month of customer receiving mold, department manager will send an email to survey customer satisfaction.