1. Is all mold opening information confirmed?
Confirmation content: plastic material, number of mold cavities, mold material, standard parts, appearance requirements (glossy, leather grain), subsequent processing technology (painting, electroplating), material shrinkage information, UDB files, etc. Information that is unclear or not provided should be noted in DFM report and fed back to customer as soon as possible to ensure design progress.

 

Confirmation content: glue injection position, number of gates, and gate type. Based on past experience, consider pros and cons of various glue injection methods, determine several glue injection plans, then conduct a detailed analysis by MOLDFLOW. Final glue injection plan is determined based on comparative analysis of analysis results.

 

Confirmation content: product wall thickness analysis, mainly analyzing uniformity of wall thickness of main appearance surface, whether turning transition is smooth, and whether there is a sudden change in wall thickness. According to different plastic material, analyze thickness ratio between ribs and main surface to avoid micro-epimorphism of product surface.

 

Countermeasures
3. Add a heating rod and temperature sensor to upper mold near weld line to control molding temperature at weld line and improve weld line quality.
Through these three measures, weld line and appearance requirements of product surface have been basically met.

Draft analysis: product appearance surface demoulding analysis, mechanism movement direction demoulding angle analysis. Especially for appearance surface with leather grain, leather grain code and leather grain demoulding angle should be clearly defined. If there are any problems, feedback product optimization suggestions to customers.

 

Countermeasures
2. In design of subsequent grille molds, a holistic structure must be employed to ensure reliable positioning of upper and lower molds. This structure has been demonstrated in AP11-MY11, mold number M110049.

Parting line confirmation: When dealing with parting line, especially when it comes to appearance A surface and functional parts, product appearance requirements and functional requirements must be met first, then consider how to optimize parting line, simplify mold structure, facilitate mold design and development.

 

Problem Description: In Mold H project, mold number M090338, designer lacked an understanding of product's appearance requirements when designing slider. They adopted a design with three small sliders. This resulted in excessive parting lines on visible surface of product, impacting appearance. This was particularly evident in the center slider parting line, leading to customer complaints, as shown in image above.

Mechanism design: Design concept and analysis of demoulding mechanism should be designed based on principles of mechanism simplification, reliable demoulding, and cost saving. If there are indeed problems with product shape, mechanism cannot be demoulded, or mechanism is too complicated to be conducive to mold safety and life, mechanism concept should be given, product optimization and modification suggestions should be fed back to customer.

 

MOLDFLOW analysis: Through MOLDFLOW analysis, analyze existing injection defects (such as trapped air, weld lines, glue shortage, deformation, etc.), whether they meet product requirements, and provide targeted suggestions for next step of mold design. Select the best injection position and number of injection ports. Determine injection pressure, machine specifications, molding cycle and other information.

 

2. Grid mold
1. Selection of injection scheme
Position and number of injection ports, as well as whether to select a sequential valve hot runner system, should be selected based on product injection volume, surface requirements, molding cycle, product deformation requirements, etc. According to past experience, it is ideal to select a multi-point open hot runner to cold runner while injecting glue. In order to eliminate and control weld lines, a sequential valve hot runner system is often used.

 

2. Overall mold structure design
Upper mold of this mold is an integral one, and lower mold is a framed structure. Main problems are: 1. Mold strength is affected; 2. Positioning of upper and lower molds of mold is unreliable, resulting in misalignment, and leather surface is easily scratched; 3. Processing accuracy and assembly requirements are high. Improvement measures: 1. Add support columns to strengthen lower mold; 2. Add upper and lower mold insertion surfaces to improve misalignment. 3. Use an integral structure to ensure life of mold and stability of product production.

 

Problem Description: Due to lack of experience, this mold design utilizes a single-piece upper mold and a framed lower mold. Problem is that lower mold is a modular structure, and this type of mold has a large dropout. When injection pressure is high, lower mold core tends to flip, causing damage to product's surface during mold opening.
3. Locking structure design
Main problems of grille mold locking: upper and lower drop of molding part is large, and lateral force generated when closing mold is large, which is easy to cause upper and lower molds to misalign, resulting in product breakage and leather texture damage. Design measures are as follows: 1. Upper and lower molds must have separate and reliable positioning; 2. Upper and lower mold insertion surfaces around mold must have wear-resistant adjustment plates to facilitate mold matching; 3. Main parting surfaces of upper and lower molds must have pressure blocks to facilitate mold matching; 4. Slider is a moving part, and inclined wedge surface cannot be used as a positioning part.

 

4. Thin steel insertion surface protection design
In order to protect safety of insertion part, especially thin steel part, design must have a protection design. Methods and measures: There should be differences in design of angles of insertion surfaces around mold. Local insertion angle is smaller than angle of insertion surface of thin steel forming part to ensure that insertion force caused by mold closing error is dispersed during mold closing to protect thin inserted steel material.

 

5. Improvement measures to eliminate product weld lines
This mold uses a 5-point open hot runner, and weld lines at two places are more obvious. Improvement measures: 1. Add a venting insert made of breathable steel material to lower mold at weld line to reduce trapped air; 2. Design an overflow groove at weld line to overflow cold material; 3. Add a heating rod at weld line of front mold to locally control and improve molding temperature. 4. To completely eliminate weld line, a sequential valve hot runner system must be used.

 

Problem Description: In Touran GP2 project, M090044, due to a lack of understanding of grille's appearance requirements, company focused solely on injection balance, ignoring weld line issues. This mold's injection solution employed a five-point open hot runner system. Product exhibited two noticeable weld lines, which, due to open hot runner system, could not be resolved with process adjustments, as shown in image above.
6. Consider demoulding problem of multiple lifters
Lower mold buckle of this mold adopts lifters for demoulding. Main problems are: 1. Three sides of lifter are wrapped by glue, and wrapping force is large; 2. There is no angle in direction of backward movement of lifter, and demoulding resistance is large; 3. There are too many lifters, processing error and injection pressure are uneven, resulting in uneven force during ejection and difficulty in demoulding. Improvement measures: 1. Optimize product shape and reduce demoulding resistance; 2. Add product demoulding positioning parts to ensure reliable product demoulding. 3. Change direction of lifter movement to ensure balanced demoulding on the left and right.

 

Problem Description: Touran GP2 project MO90045, this mold has 30 parts on lifter. During ejection, part follows lifter, preventing normal part removal.
7. Pay attention to use of flat ejector pins
On grille molds, avoid use of flat ejector pins as much as possible. Because product and mold are large, ejection force of product is large, and small flat ejector pins are easy to break. For example, when ejecting ribs, flat ejector pin can be changed to a straight ejector or ejector block.

 

Improved Solution: When adding flat ejectors is necessary for deep bone placement, consider using solution shown above to ensure adequate strength.