FDM 3D printing, a form of additive manufacturing, creates objects by adding material layer by layer.
Casting: Embracing a Holistic Approach
Casting involves the flow of material, much like FDM printing, where molten plastic is extruded and flows into place. Learning about casting can provide a deeper understanding of how material behaves when it's in a fluid or semi-fluid state.
Anticipating Warping and Shrinkage: Just as a cast part cools and shrinks, an FDM print can experience warping and shrinkage due to temperature differences between layers. The base layers cool and contract as new, hot layers are added on top. A designer with knowledge of casting anticipates these stresses and designs parts with features like fillets and generous radii to distribute stress evenly. They might also design sacrificial structures, like a brim, to anchor the part to the build plate and prevent warping.
Optimizing for Flow: The quality of a cast part depends on the material's ability to flow into all parts of the mold. Similarly, with FDM printing, the print head's path and material flow are critical. Understanding concepts like gate placement and runner systems from casting can help you think about how material is deposited on your build plate. This knowledge can lead you to design parts that minimize the need for complex, unsupported overhangs and tight corners that can be difficult for the FDM process to fill accurately.
Machining: Designing for Strength and Simplicity
Machining
is all about removing material, which forces a designer to think about
geometry in terms of tool access and part strength.
Understanding Anisotropy: Machining creates parts with uniform strength in all directions (isotropic properties). In contrast, FDM prints are anisotropic; they are strongest along the lines of the layers and weakest between them. A designer with a machining background is used to thinking about how a part will be stressed from multiple directions. They will consider the weak points in a printed part and orient the model on the build plate to align the layer lines with the main stress vectors, thus maximizing its strength.
Designing for Simplicity and Tool Paths: A machinist designs a part with the capabilities of a specific tool in mind. They avoid complex, inaccessible geometries that require specialized or expensive tooling. This principle is directly applicable to FDM printing. A designer with a machining mindset will create parts with minimal overhangs, simple geometries, and no internal, unsupported structures. They will recognize that complex designs require extensive support structures, which can be difficult to remove and often leave behind a rough surface finish.
By integrating the
principles of these two classic manufacturing methods, a designer for
FDM 3D printing can move beyond simply creating a cool-looking model.
They can create a part that is not only visually appealing but also
structurally sound, reliable, and optimized for the unique constraints
of the FDM process.
Gate placement is a critical aspect of casting, which is a manufacturing process that involves pouring molten material into a mold.
Key Principles of Gate Placement 🔑
The primary goal of gate placement is to control the flow and solidification of the material.
Directional Solidification: One of the most important principles is to achieve directional solidification. This means the casting solidifies progressively from the sections farthest from the gate toward the gate itself. This is because the gate acts as a reservoir, continuously feeding molten material to the part as it shrinks during cooling. To achieve this, gates are typically placed at the thickest section of the part. This ensures the thickest, and therefore last-to-solidify, section can be continuously fed with liquid metal to compensate for volumetric shrinkage.
Minimizing Turbulence: A properly placed gate promotes laminar flow, which is smooth and non-turbulent.
Turbulence can trap air and impurities, leading to defects like gas porosity and dross inclusions. Designers achieve laminar flow by: Placing the gate at a location that provides a less tortuous path for the molten metal.
Avoiding sharp corners and abrupt changes in flow direction.
Minimizing Flow Path: The gate should be positioned to minimize the distance the molten metal has to travel to fill the entire cavity.
A shorter flow path reduces heat loss, preventing the material from solidifying prematurely and resulting in an incomplete fill. Easy Removal and Minimal Impact: The gate should be placed in a non-critical location on the final part.
This makes it easier to cut off or remove the gating system after the part has solidified without damaging the casting's functional or aesthetic surfaces.
The video below explains the principles of designing a gating system for a metal casting process, which includes the placement and function of gates and runners.
Gate placement is a critical aspect of casting, which is a manufacturing process that involves pouring molten material into a mold.
Key Principles of Gate Placement 🔑
The primary goal of gate placement is to control the flow and solidification of the material.
Directional Solidification: One of the most important principles is to achieve directional solidification. This means the casting solidifies progressively from the sections farthest from the gate toward the gate itself. This is because the gate acts as a reservoir, continuously feeding molten material to the part as it shrinks during cooling. To achieve this, gates are typically placed at the thickest section of the part. This ensures the thickest, and therefore last-to-solidify, section can be continuously fed with liquid metal to compensate for volumetric shrinkage.
Minimizing Turbulence: A properly placed gate promotes laminar flow, which is smooth and non-turbulent.
Turbulence can trap air and impurities, leading to defects like gas porosity and dross inclusions. Designers achieve laminar flow by: Placing the gate at a location that provides a less tortuous path for the molten metal.
Avoiding sharp corners and abrupt changes in flow direction.
Minimizing Flow Path: The gate should be positioned to minimize the distance the molten metal has to travel to fill the entire cavity.
A shorter flow path reduces heat loss, preventing the material from solidifying prematurely and resulting in an incomplete fill. Easy Removal and Minimal Impact: The gate should be placed in a non-critical location on the final part.
This makes it easier to cut off or remove the gating system after the part has solidified without damaging the casting's functional or aesthetic surfaces.
The video below explains the principles of designing a gating system for a metal casting process, which includes the placement and function of gates and runners.
