1.What is the role of "3D printing substrate"?
Mechanical support: Securely supports the part as it is being formed during printing.
Heat conduction: Rapidly dissipates the enormous heat generated by the laser/electron beam, controlling thermal stress and deformation.
Metallurgical bonding: Forms a strong metallurgical bond with the first layer of the printed part.
Fixing and positioning: Provides a reference plane for the entire printing process.
2.How feasible is it in theory?
Material Compatibility: If the part to be printed is made of low-carbon steel or stainless steel, then using a cold-rolled steel coil with the same or similar composition as the substrate can theoretically achieve metallurgical bonding. This is the most important prerequisite.
Surface Flatness: High-quality cold-rolled coils have a very flat surface, meeting the stringent requirements of SLM for substrate flatness (typically within tens of micrometers).
Cost and Availability: Compared to custom-forged or milled substrates, cold-rolled coils of specific specifications may be less expensive and have faster delivery.
3.What are the major challenges and limitations?
Insufficient Thickness and Rigidity:
SLM substrates typically require thick plates (15mm or more) to withstand the enormous thermal stress and prevent warping during printing. Standard cold-rolled coils (usually 0.3-3.0mm thick) are too thin, lacking rigidity and highly susceptible to deformation.
Internal Stress Issues:
Cold-rolled coils inherently possess significant residual internal stress. Under the high-temperature thermal cycling of the printing process, this internal stress is released and superimposed on the printing thermal stress, leading to severe substrate warping and even printing failure.
Size Limitations and Fixing:
Cold-rolled coils are produced in rolls and require cutting and leveling before use as flat substrates. Securely mounting them on the printer's heated substrate platform requires specialized and reliable clamping designs to prevent edge warping.
Surface Condition:
The rust-preventive oil film, slight oxide layer, or roughness on the surface of cold-rolled coils can hinder the spread of the first powder layer and the initial bonding between the laser and the metal, often requiring rigorous degreasing, cleaning, or even surface finishing (such as milling).
4.What is the essential difference between this and "chip carrier board" applications?
Chip carrier boards: require insulation, high frequency and high speed, and thermal matching; cold-rolled coils are excluded due to their conductivity.
3D printing substrates: require electrical and thermal conductivity, high strength, and metallurgical bonding; cold-rolled coils are theoretically possible due to their metallic nature, but are limited by mechanical and process details.
5.What are some practical conclusions and suggestions?
For mainstream SLM processes (printing high-value, high-precision parts):
Using ordinary cold-rolled coils as substrates is not recommended. Standard substrates of the same material, specifically forged, heat-treated, and milled for 3D printing, should be used. This is the most reliable and lowest-risk option.
For printing large components such as DED and WAAM:
Using thick steel plates (potentially hot-rolled or normalized, rather than cold-rolled) as deposition platforms is common practice. Here, the "substrate" is more like a "workbench," with relatively lower performance requirements.
For R&D or specific scenarios:
For low-cost prototyping or printing large, simple parts made of the same material as cold-rolled coils, rigorously treated cold-rolled sheets can be used. The treatment steps must include:
Cutting and stress annealing to eliminate internal stresses.
Surface milling to ensure flatness and cleanliness.
Designing a reliable fixture system.
Conducting thorough process testing and validation.