Common Challenges When Demolding
1. Deformation and warping
Warpage occurs when the cooled part loses its shape and does not conform to the final product shape. Warpage is typically caused by uneven cooling rates or stresses within the forming system. It is particularly acute when the thermoplastic material shrinks and expands during the crystallization phase of cooling. Consequently, this warpage is aggravated by changes in wall thickness, mold temperature, and varying material cooling rates. Warpage results in parts that are out of specification or unusable. However, some control over the cooling process is essential to reduce the risk of warping thin-walled components. Key considerations include mold temperature control, cycle time optimization, and wall thickness uniformity.
deformation during demolding
2. Part Glue to the mold
Part sticking, or adhesion, occurs when the part adheres to the surface of the mold cavity. This problem occurs for several reasons, such as the need for more MR, a rough mold surface, or insufficient cooling. These factors cause the part to pull out of the mold. The part material also plays a role. For example, thermoplastics have higher coefficients fan data of friction; therefore, the tendency to stick is strong. Characterizing the mold surface with coatings or appropriate selection of release agents can limit adhesion, allowing for smooth ejection of the part.
3. Discharge marks and surface imperfections
Ejection marks are marks left on the surface of the part by the action of the ejector pin. These marks are interference marks of the ejector pins when removing the part. The marks may be caused by poor mold maintenance or inefficient processing conditions, including scratches, imperfections, or uneven surfaces. A practical design of the ejector system should be made to reduce the marks left by the ejector on the product. Engineers should choose the correct location of the pin, properly maintain the mold surface, and polish the surface.
Ejection marks appear during demolding
Best practices for effective demolding
Successful demolding of castings requires attention to several factors, including mold design, cooling times, and appropriate lubricants and release agents.
1. Improve the mold design to extract the part
Mold design is a definitive plan that is essential to facilitate demolding. One of the concerns is the draft angle, which stipulates the separation of the part from the mold cavity. The draft angle should be between 1 and 3 degrees. However, the value can be higher for certain parts and types of materials.
Additionally, it is essential to minimize undercuts and features that could trap the part in the mold design. This approach can significantly reduce sticking.