With the significant advantages that die casting offers, maintaining quality and consistency is critical in each completed part. To ensure manufacturers constantly produce parts that optimally perform, they must be made within certain parameters or tolerances.
This article will dive into the basics of die casting tolerances, including different tolerance levels and factors that can affect these levels.
What are Die Casting Tolerances?
Tolerances in die casing refer to the deviation allowed based on the part’s nominal dimension. This means that the actual dimensions of the molded product may still be accepted even if it doesn’t have exact specifications, as long as it’s within the tolerance limits. Typically, the acceptable value for each dimension is given as a specific range, like +/- 0.005 inches.
Why is tolerance important in die casting? Simply put, tolerances ensure the performance and functionality of the finished part.
Precision and consistency are important in most industries that use molded parts, like aerospace, medicine, and automotive markets. If the completed part goes beyond the allowable tolerances, either it won’t fit properly once assembled or could compromise the integrity and competency of the final product.
Factors that Contribute to Die Casting Tolerances and How to Avoid Them
Several factors can affect die casting tolerances, with each potentially impacting the ability to achieve tight tolerances and requiring specific strategies to address them. In this section, we’ll discuss these criteria and look at ways how to prevent possible issues.
Part geometry and complexity
First on the list is the component’s design. Specifically, the overall geometry and how complex the part is modeled.
Components with a simple design will typically have basic geometric shapes, making it easier to mold and require lighter tolerances. Conversely, complex designs may have more complicated geometric shapes, thus having tighter tolerances to achieve efficient operation.
When working with complex components, make sure to carefully assess its overall design and consider how the parts integrate with each other. Molds should have enough detail and spacing, so the molten material can capture every millimeter upon pouring.
Material properties and composition
Another important factor is the type of material used in creating the molded component. Not all materials respond to heat and pressure the same – some expand more than others, for example. If tolerances are not properly set, this could lead to molded parts with poor dimensions that won’t function well once assembled.
Taking this in mind, always consider the properties of the material to be used for a specific project. Understand how each material reacts to heating, pressure, and other factors, and set an allowable limit accordingly.
Die design and construction
The design and construction of the die play a big role in how the component will look and function. As the base of any molded component, the die cavity must have the right measurements to properly imprint the design on the molten material. It should also be able to handle the combination of high temperature and pressure.
When designing the die, always allow for a minimum tolerance limit of around ±0.005 inches. Additionally, select a durable material when making the die to ensure it can be used multiple times during the molding process without affecting the molded component’s quality and consistency.
Casting process variables
Now that we’ve discussed the components needed to create the parts, time to look at other variables that can affect the final product. Key factors here include the temperature of the molten material, the pressure applied to the mold, and the overall production speed.
To achieve the ideal result, there should be a fine balance between these factors. The production speed must be properly calibrated to allow enough cooling time for the molten material. There should also be enough pressure to force the materials to fuse together, or else the completed part won’t have the right durability.
Post-processing operations
Production doesn’t end at the molding process, as the array of post-processing tasks can also affect the final component’s tolerance levels. These would include the machining, heat treating, and surface finishing applied to the molded part.
For the best results, it’s important to account for which secondary processes will be used on the component and add them to the tolerance level. For instance, surface finishing adds a later of material over the molded component, so this has to be considered on the part’s allowable limits.
Types of Tolerances in Die Casting
As a global component manufacturer, Raidy Mold practices a standardized process when casting die molds that guarantees tight tolerances. Here are some general inputs regarding various tolerance levels used during die casting and some best practices for setting allowable limits to guarantee precision production.
Parting Line
Typical molds consist of two halves that are clamped together during the molding process with no separation. But as it receives the molten plastic or metal and pressure is applied to the mold, it may open slightly, causing a thicker output than what’s expected. If left unchecked, it can lead to a defective part that won’t function properly.
This is where die casting tolerances for parting lines come in. This refers to the allowed limit for the mold to open up as the molten material enters the cavity or projected area. Proper tolerance calibration ensures that the products have consistent quality, dimensions, fit, and performance.
Seasoned engineers recommend a permissible tolerance level of +/-0.25mm or +/-0.01 inches. However, material type has to be considered as well, as some materials like aluminum would require a higher allowable limit.
Linear Dimensions
As the liquid material is poured into the mold, it will cool down and solidify, forming the desired part. While the material is taking shape, factors like temperature fluctuations and deformities within the mold can cause the material to shift away from the intended design.
Thus, when it comes to casting linear components, the focus is placed more on the allowed deviation of the casted part’s dimensions. This tolerance limit is intended to account for the anticipated dimensional shift during the molding process.
For most linear molding processes, precision is key to achieving a desirable outcome, especially when working with Aluminum as a material. As such, the allowable deviation is +/-0.12mm or +/-0.005 inches.
Moving Die Components
Complex die molds will often have movable sections that allow the final component to perform complicated functions. As these parts need to be in perfect alignment to operate properly, even a slight deviation can cause the parts to misalign during assembly. If the tolerances for these parts are too light or too loose, it will result in a faulty final product.
That’s why when checking the tolerances for moving die parts, it’s important to consider the acceptable limits for the moving parts to operate. Most experts recommend starting with a benchmark tolerance level for the moving parts and then maintaining them throughout the molding process. Additionally, inspectors should also regularly check these tolerances to ensure they’re within acceptable limits, leading to efficient mold operation.
Tolerance levels for moving die parts are typically set at +/-0.005mm or around +/-0.002 inches. However, experts suggest increasing tolerance levels to accommodate the material’s properties. Aluminum alloy, for example, will require a higher tolerance compared to other materials.
Dimension Tolerances vs. Geometric Tolerances Explained
There are two types of tolerances when it comes to designing and creating functional components: dimension and geometric tolerances. Let’s look at their differences and how they help in ensuring the final product meets acceptable levels.
Dimension Tolerances
This refers to the allowances given to the completed part’s basic dimensions, including its shape, length, width, or thickness. The variation allows for the part to go over certain levels while staying at optimal levels of functionality.
Geometric Tolerances
Complex parts that have multiple features require proper alignment and precise orientation. Geometric tolerances count the allowable variation between the features of a specific part, like its flatness, parallelism, and angularity.
How Different Materials Influence Die Casting Tolerances
Each material has its own properties and dimensional stability, making material selection important in maintaining tolerance levels in the die casting process.
Let’s take aluminum alloy, for example, one of the main materials Raidy Mold uses in die casting products for customers. With its better dimensional stability and lower thermal expansion coefficients, aluminum allows for tighter die casting tolerances.
Some points to consider when choosing a material for a die casting project:
The part’s performance requirements – some materials have more flexibility, resistance, and durability than others, so it’s critical to work with a material that matches what the project needs.
Manufacturing process capabilities – depending on the molding and secondary processing that will be implemented in the production, certain materials will work better than others.
Cost allowances – budget also plays a big role in material selection, as some materials cost more based on their inherent properties and tolerance allowances.
Tighter Tolerances Equals Consistent Products
Tolerance levels play a key role in maintaining the consistency and quality of every completed product. By knowing what influences a product’s tolerances, manufacturers can properly manage the output and guarantee their performance.
For aluminum die casting products with tight tolerances, trust Raidy Mold as your manufacturer of choice. With nearly three decades of production expertise, we’ve mastered the art of manufacturing various products for multiple industries. We also offer a range of customization options for bespoke production requirements. contact our team today for a free consultation.
