How to Design Plastic Parts Injection Molds with SOLIDWORKS Plastics

SOLIDWORKS Plastics is powerful simulation software that helps you optimize the design process of plastic parts and injection molds. The software is fully integrated with SOLIDWORKS applications so you can analyze and modify part designs while optimizing shape, fit, and function.

The process of designing plastic parts and injection molds is easy with SOLIDWORKS Plastics. First, you need to create or import your part or mold model. You can then analyze and optimize your design using the various tools and features provided by the software.

One of the important functions is to simulate the flow and filling process of plastic materials. By setting the appropriate parameters, such as injection speed, pressure, and temperature, you can simulate the flow of plastic material through the mold. This helps you determine the optimal injection point, gate location, and cooling system design to ensure part quality and performance.

In addition, SOLIDWORKS Plastics provides the ability to analyze the strength and durability of parts. You can use the finite element analysis tools in the software to evaluate how a part performs under different load and stress conditions. This helps you identify potential weaknesses and make improvements accordingly to increase part reliability and longevity.

In addition to analysis capabilities, SOLIDWORKS Plastics provides a rich set of design tools that enable you to quickly create and modify part and mold models. You can use modeling tools to draw, trim, and merge geometry, as well as add dimensions and constraints. In addition, the software also supports the import and export of multiple file formats to facilitate collaboration with other CAD software.

In summary, SOLIDWORKS Plastics is a powerful simulation software that can help you optimize the design process of plastic parts and injection molds. With its integrated analysis tools and design capabilities, you can improve part quality and performance by considering form, fit, and function simultaneously during the design process. Whether you’re a beginner or a professional, plastic part and injection mold design can be made easy with SOLIDWORKS Plastics.

What is Plastic Injection Molding?

Plastic injection molding is a manufacturing process that involves injecting molten plastic material into a mold cavity, where it cools and solidifies to form the desired part shape. The mold cavity is usually made of metal and consists of two halves: a fixed mold (cavity) and a movable mold (core). The mold also contains features such as sprues, runners, gates, and vents that facilitate the flow of plastic material and the removal of air and gases.

Plastic injection molding is widely used to produce a variety of products, such as automotive parts, medical devices, consumer electronics, toys, and packaging. Plastic injection molding offers many advantages over other manufacturing methods, such as high production rate, low labor cost, high design flexibility, and good dimensional accuracy.

Benefits of SOLIDWORKS Plastics for Product Development

The integration of SOLIDWORKS Plastics in your workflows provides several benefits when you develop plastic parts and molds. With SOLIDWORKS Plastics, you can:

Predict and avoid manufacturing defects in plastic parts and injection molds, such as short shots, weld lines, sink marks, air traps, and warpage.
Evaluate part manufacturability while you design, reducing costly rework and improving part quality.
Optimize mold design and process settings to minimize cycle time and maximize efficiency.
Validate different material choices and part configurations with ease.
Leverage the SOLIDWORKS user interface and data integrity for ease of use and data reuse.

Capabilities of SOLIDWORKS Plastics

SOLIDWORKS Plastics is offered in three product bundles: SOLIDWORKS Plastics Standard, SOLIDWORKS Plastics Professional, and SOLIDWORKS Plastics Premium. Each bundle provides different capabilities to suit your needs.

SOLIDWORKS Plastics Standard: This bundle allows you to ensure part manufacturability during the design process. You can analyze how melted plastic flows during the injection molding process to predict manufacturing-related defects. You can also evaluate the final shape of the ejected part due to flow-induced and thermal stresses.
SOLIDWORKS Plastics Professional: This bundle builds upon SOLIDWORKS Plastics Standard to analyze mold designs. You can quickly analyze single-and multi-cavity, and family mold layouts including sprues, runners, and gates. You can also estimate cycle time and optimize feed system design.
SOLIDWORKS Plastics Premium: This bundle includes SOLIDWORKS Plastics Professional with advanced simulation functionality to analyze mold cooling line layouts and part warpage. You can optimize cooling line design to minimize cycle time and decrease manufacturing costs.

Designing the Injection Molding Process

The injection molding design process typically consists of two phases: Definition and Validation.

Definition Phase

During the Definition phase, you define the proper process settings and validate the runner system design. These settings depend on the selected material and the part’s thickness distribution. Typical settings include:

Injection pressure: The pressure applied by the injection unit to push the molten plastic into the mold cavity.
Injection time: The time required to fill the mold cavity with plastic material.
Packing pressure: The pressure applied by the injection unit to pack more material into the mold cavity after filling.
Packing time: The time required to pack more material into the mold cavity after filling.
Cooling time: The time required for the plastic material to cool down and solidify in the mold cavity.
Mold temperature: The temperature of the mold surface that affects the cooling rate of the plastic material.

You can use SOLIDWORKS Plastics to perform a Flow analysis to simulate how melted plastic flows during the filling phase. You can also perform a Pack analysis to simulate how the plastic material is packed during the packing phase. These analyses help you to predict and avoid potential defects, such as short shots, weld lines, air traps, and sink marks. You can also use SOLIDWORKS Plastics to evaluate the runner system design and optimize the sprue, runner, and gate sizes and locations.

Validation Phase

During the Validation phase, you validate the cooling system design and evaluate the part warpage. The cooling system design affects the cycle time and the part quality. A good cooling system design should provide uniform cooling throughout the mold cavity and avoid hot spots that can cause uneven shrinkage and warpage.

You can use SOLIDWORKS Plastics to perform a Cool analysis to simulate how the plastic material cools down and solidifies in the mold cavity. You can also perform a Warp analysis to simulate how the plastic part deforms due to flow-induced and thermal stresses after ejection. These analyses help you to optimize the cooling line layout and minimize the part warpage.

Designing the Part Geometry

The part geometry is one of the most important factors that affect the injection molding process and the part quality. A good part design should consider the following aspects:

Wall thickness: The wall thickness should be uniform as much as possible to avoid differential shrinkage and warpage. The wall thickness should also be within the recommended range for the selected material and process.
Draft angle: The draft angle is the angle of inclination of the part surface relative to the mold opening direction. The draft angle helps to facilitate the part ejection from the mold and avoid damage to the part or mold. The draft angle should be sufficient for the part geometry and surface finish.
Ribs and bosses: Ribs and bosses are features that provide structural support and attachment points for the part. Ribs and bosses should have a smaller wall thickness than the main wall to avoid sink marks. Ribs and bosses should also have proper draft angles and radii to avoid stress concentration and ejection problems.
Undercuts: Undercuts are features that prevent the part from being ejected from the mold in a straight line. Undercuts should be avoided as much as possible because they require complex mold mechanisms or additional operations to remove them. If undercuts are unavoidable, they should be minimized and located in areas that do not affect the part function or appearance.
Fillets and radii: Fillets and radii are features that smooth out sharp corners and edges on the part. Fillets and radii help to reduce stress concentration, improve material flow, enhance part strength, and improve part appearance. Fillets and radii should be applied generously to all internal and external corners and edges.

You can use SOLIDWORKS Plastics to perform a Design Advisor analysis to check your part geometry for potential manufacturability issues. You can also use SOLIDWORKS Plastics to perform a Thickness Advisor analysis to check your part thickness distribution and identify thick or thin areas.

Designing the Mold Geometry

The mold geometry is another important factor that affects the injection molding process and the part quality. A good mold design should consider the following aspects:

Parting line: The parting line is the line where the two mold halves meet. The parting line should be located in areas that do not affect the part function or appearance. The parting line should also be smooth and continuous to avoid flash or mismatch defects.
Ejector pins: Ejector pins are features that push the part out of the mold cavity after cooling. Ejector pins should be located in areas that do not affect the part function or appearance. Ejector pins should also have proper size, shape, number, and distribution to provide uniform ejection force and avoid deformation or damage to the part or mold.
Runner system: The runner system is a network of channels that connects the injection unit to the mold cavity. The runner system consists of a sprue, a main runner, sub-runners, and gates. The runner system should be designed to provide balanced and efficient material flow, minimize pressure loss, reduce cycle time, and avoid defects such as jetting, hesitation, or cold slugs.
Cooling system: The cooling system is a network of channels that circulates coolant fluid through the mold cavity. The cooling system consists of cooling lines, connectors, fittings, pumps, valves, sensors, etc. The cooling system should be designed to provide uniform and sufficient cooling throughout the mold cavity, minimize cycle time, reduce energy consumption, and avoid defects such as warpage or dimensional instability.

You can use SOLIDWORKS Plastics to perform a Mold Layout analysis to create a preliminary mold layout based on your part geometry. You can also use SOLIDWORKS Plastics to perform a Runner Balancing analysis to optimize your runner system design based on your material properties and process settings.

Conclusion

Designing plastic parts and injection molds using SOLIDWORKS Plastics can significantly streamline the product development process, improve part quality, and reduce time-to-market. SOLIDWORKS Plastics is a powerful simulation tool that allows engineers and designers to analyze and optimize plastic part designs and injection mold configurations before manufacturing.

Part Design Optimization: SOLIDWORKS Plastics enables designers to optimize plastic part designs by simulating the injection molding process. By analyzing various design iterations, designers can identify potential issues such as air traps, weld lines, sink marks, and warpage. This information helps in making informed design decisions to improve part quality and manufacturability.
Material Selection: The simulation capabilities of SOLIDWORKS Plastics aid in choosing the most suitable plastic material for the intended application. By analyzing different material options, engineers can evaluate their flow behavior, cooling rates, and potential defects. This ensures that the selected material meets the required performance and cost objectives.
Mold Design Evaluation: With SOLIDWORKS Plastics, designers can assess the injection mold design to avoid common molding defects and optimize cooling channel layouts. The simulation provides insights into the mold filling pattern, temperature distribution, and potential issues like air entrapment and uneven cooling. This information helps in refining the mold design for optimal part quality and production efficiency.
Prediction of Part Warpage: Warpage is a common issue in plastic parts due to non-uniform cooling during the molding process. SOLIDWORKS Plastics allows designers to predict part warpage and analyze the impact of various design and process parameters. By understanding potential warpage issues early in the design phase, engineers can make necessary adjustments to minimize or eliminate warpage in the final product.
Gate Location Optimization: Proper gate placement is crucial in injection molding to ensure uniform filling and minimize part defects. SOLIDWORKS Plastics provides insights into the gate locations and their impact on the flow of molten plastic. Designers can experiment with different gate locations to find the optimal configuration that results in high-quality parts.
Mold Cooling Analysis: Cooling is a critical aspect of injection molding that affects cycle times and part quality. SOLIDWORKS Plastics enables designers to analyze mold cooling performance, identify hot spots, and optimize cooling channel layouts. Efficient cooling reduces cycle times and improves part consistency.
Design Validation and Iteration: By using SOLIDWORKS Plastics in the design process, engineers can validate their designs before physical prototyping or production. This reduces the need for costly and time-consuming trial and error iterations, leading to faster development cycles and cost savings.
Collaboration and Communication: SOLIDWORKS Plastics facilitates collaboration between designers, engineers, and mold makers. The simulation results can be easily shared and communicated, allowing for a better understanding of potential design and manufacturing challenges.

In conclusion, SOLIDWORKS Plastics is a valuable tool for designing plastic parts and injection molds. It empowers engineers and designers to optimize part designs, select appropriate materials, evaluate mold designs, predict part warpage, optimize gate locations, analyze mold cooling, validate designs, and enhance collaboration. By leveraging the simulation capabilities of SOLIDWORKS Plastics, manufacturers can achieve high-quality plastic parts, reduce development time, and ensure successful injection molding processes.