7 Steps to Laser Powder Bed Fusion (LPBF) Metal 3D Printing

Understanding the specified vocabulary in the comprehensive description of the Laser Powder Bed Fusion (LPBF) process used by One Click Metal, we can further explain the intricate steps involved in this advanced 3D metal printing technique. Here’s a detailed explanation of the LPBF workflow, integrating the requested terms to underscore the technology’s complexity and versatility:

First, here is an introduction to One Click Metal. Established in 2019, aims to democratize industrial metal 3D printing with its innovative solutions, including the MPRINT and MPRINT+ 3D printers, alongside the MPURE powder handling system. The MPURE system, a key component for powder management and recycling, integrates seamlessly with the 3D printers to offer a streamlined, end-to-end workflow. This setup minimizes technical complexities and ensures a clean working environment, marking a significant step forward in making advanced metal additive manufacturing accessible and efficient.

The system’s user-friendly nature is largely due to its innovative cartridge system for managing powdered materials. The MPRINT+ features four cartridge slots, capable of holding up to 11kg of feedstock each, offering an ample 250% surplus compared to the print volume. This design significantly reduces the need for frequent material replacements and minimizes operational interruptions. Additionally, each cartridge is equipped with a distinct NFC tag, allowing for real-time monitoring of material levels and preventing the mixing of different metal types, enhancing both convenience and safety.

The BOLDSERIES addresses the challenges of powder management through its innovative cartridge system, enhancing safety and cleanliness in the process. By distinguishing between supply and overflow cartridges, it effectively eliminates the possibility of mixing materials. This system also greatly diminishes the user’s exposure to the powder, making the handling process safer. Additionally, the design allows for most of the powder to be recycled, promoting efficiency and sustainability in operations.  An overview of the powder handling is below.

1. Data Creation and Preparation

Preparing a 3D model for printing involves several critical steps to ensure that the model is printable and will produce high-quality results. Here’s a summary of the key considerations for creating a printable 3D model, highlighting common pitfalls and how to avoid them:

1. Watertight/Non-Manifold

Issue: Models must not have any holes in their surface to be printable. A non-watertight model has gaps that would allow water to flow out if it were filled.

Solution: Ensure your model is manifold by checking for and closing any holes, creating a completely sealed volume.

B.. Wall Thickness and Volume

Issue: Every surface of your 3D model needs a defined wall thickness. Models designed for visual purposes may lack this, but 3D printers require specific information about wall thickness to print correctly.

Solution: Assign a wall thickness to every part of your model, considering the minimum printable thickness based on the chosen material.

1. Auto Intersections/Internal Overlapping/Self-Intersecting Surfaces

Issue: Models that look good externally may have internal intersections that confuse printers, making the model unprintable.

Solution: Design your model considering a 2D space first to avoid internal complexities. Utilize Boolean operations to merge overlapping elements properly.

1. Reversed Faces/Inverted Normals/Surface Orientation

Issue: Inward-facing or reversed faces occur when the surface of your model faces the wrong direction, potentially invalidating the volume for printing.

Solution: Check your model to ensure all normals are correctly oriented outward.

1. Grouped Models

Issue: Uploading designs with separate shells as a single file can lead to order cancellations.

Solution: Upload separate objects individually to avoid complications. For multiple identical designs, use quantity discounts or design a grid container for small parts.

1. Small Details and Embossed/Engraved Text

Issue: The smallest features of your design, including text, must meet size requirements to be visible on the final print.

Solution: Adhere to the minimum detail size guidelines for your chosen material to ensure clarity and readability.

1. Hollowing and Escape Holes

Issue: Solid models are more expensive and can trap unused material inside during printing.

Solution: Design your model to be hollow with escape holes to allow excess material to be removed, reducing cost and preventing defects.

1. File Resolution and File Size

Issue: The STL file format translates designs into triangles, and improper resolution settings can lead to heavy files or visible triangles in the final print.

Solution: Set a tolerance of 0.01 mm when exporting to STL to balance detail and file size, ensuring that the print quality is high without creating an unnecessarily large file.

These guidelines underscore the importance of meticulously preparing your 3D model for printing. Resources, tutorials, and material guides can provide further assistance. When using an online 3D printing service, models are often checked for these issues before printing, helping to catch any potential problems. Keeping these considerations in mind will help avoid common pitfalls and ensure your 3D printing project is successful.

2. Data Preparation for Metal 3D Printing

Supports Generation: Essential for metal 3D printing, supports are generated for the component using software like MPREP. These temporary support structures are vital for overhangs and certain angles during the laser sintering process. Support structures are essential in metal 3D printing, a process where parts are constructed layer by layer from a digital file. These supports are crucial for maintaining the stability and integrity of the model during the printing process. They serve multiple purposes:

1. Connection to Build Platform:

Supports ensure the model is securely attached to the build platform, preventing movement that could lead to inaccuracies.

1. Stress Absorption:

They absorb internal stresses that occur during the printing process, minimizing the risk of deformations or structural failures in the finished part.

1. Preventing Deformations:

For parts of the model with walls or overhangs that have angles less than 45° relative to the build platform, supports are necessary to prevent building errors and deformations, as these angles typically cannot sustain themselves during the printing process.

After the printing process is completed and the part is built successfully, the support structures are removed. This is often followed by sandblasting to finish the surface of the part. However, some signs of the removed supports might still be visible on the final product, indicating where they were attached.

3. Print Preparation in 3D Metal Printing Work

Preparing the build chamber for the One Click Metal MPRINT system involves inserting powder supply cartridges and the build module, highlighting the precision of metal 3D printing systems. The process also includes loading the print job and inverting the build chamber to create an optimal environment for metal printing.

1. Filling with Inert Gas:

The build chamber is first filled with an inert gas, such as argon or nitrogen. This step is crucial because it displaces oxygen and other reactive gases from the chamber, preventing the metal powder from oxidizing during the heating and melting processes. Oxidation can compromise the quality and mechanical properties of the final part.

1. Heating to Optimal Print Temperature:

The build chamber is then heated to the optimal print temperature. Preheating the chamber helps to reduce thermal gradients within the built environment, which can lead to warping and residual stresses in the finished part. The precise temperature depends on the metal powder used but is typically high enough to ensure good powder flowability and proper fusion of particles.

4. Printing Process Using Powder Bed Fusion Technology

Powder Supply: Demonstrating the core of powder bed fusion processes, metal powder is supplied from cartridges.

1. Spreading the Metal Powder

A recoating blade or roller spreads a thin layer of metal powder over the build platform. The thickness of this layer is typically around 50 micrometers (μm), though it can vary depending on the machine and the desired resolution of the print. This step is critical for achieving fine detail and high surface quality in the finished part. The uniform distribution of powder ensures consistent melting and solidification across the entire layer.

1. Scanning and Bonding

Laser Scanning: A high-power laser then scans the cross-section of the part to be printed, following the pattern defined by the slice taken from the 3D model file. This process selectively melts (in the case of SLM) or sinters (in the case of DMLS) the metal powder according to the part’s geometry.

Bonding Metal Particles: The laser’s heat energy causes the metal particles to fuse together, forming a solid layer that matches the current cross-section of the part. This bonding process is what builds the part’s structure, layer by layer. The precision of the laser and the control of the scanning process are key factors in determining the resolution, strength, and accuracy of the finished part.

5. Unpacking Process in Metal 3D Printing

Post-printing, the build module is transferred to a cleaning station like MPURE for removing excess metal powder, showcasing the careful handling required in metal 3D printing work.  The cartridges are designed to work seamlessly with the company’s MPURE station, streamlining the powder management process. This system automates the depowering of parts, assesses the powder’s suitability for reuse, and efficiently recycles unused powder through an ultrasonic sieve, all while ensuring users avoid direct contact with the material. This integration simplifies the workflow and enhances safety by minimizing exposure to loose powder.

6. Separation of the Component

While wire EDM is traditionally favored for detaching parts from the build plate, a growing number of machine shops are opting for bandsaws due to their speed and the necessity of finishing part bottoms regardless. However, materials like Inconel, which become harder when worked, can pose challenges for bandsaw removal. Cost-wise, wire EDM services at a local machine shop typically range between $200 to $300 per plate and take several hours, depending on the parts’ quantity and size, in contrast to the bandsaw’s ability to accomplish the task in mere minutes.

7. Post-Processing of Metal Parts

Removing support structures and finishing the surface are crucial post-processing steps in the 3D printing process. Techniques like shot peening (beams) or sandblasting improve the surface quality, while heat treatment processes can enhance material properties, ensuring the final metal part meets strict design guidelines and material specifications.

This detailed overview of the LPBF process, enriched with specific terminology, illustrates the sophisticated nature of 3D printing methods and technologies, especially in the realm of metal additive manufacturing. It emphasizes the critical stages from data preparation to post-processing, required to achieve high-quality metal parts with complex geometries, aligning with the rigorous standards of industries like aerospace, automotive, and medical devices.