Why 'As Machined' Finishes Are Perfect for Certain Manufacturing Applications
Introduction
In the world of 3D printed parts, the "as machined" finish refers to the surface quality that a part achieves directly after printing and machining, without additional surface treatments. At the same time, many manufacturing processes involve secondary treatments like polishing, painting, or coating, the "as machined" finish can be an excellent solution for specific applications where functionality and cost-efficiency are prioritized over aesthetic quality.
This blog explores why the "as machined" finish is often the perfect choice for specific 3D printed parts, particularly in aerospace, automotive, and medical devices. We’ll also compare this finish with other surface treatments and highlight the materials most suitable for "as-machined" finishes.
How the 'As Machined' Finish Works and Quality Assessment Criteria
The "as machined" finish results from direct machining of the 3D printed part, typically using CNC machining, which can remove any support structures, refine the dimensions, and improve the overall surface quality. This finish is achieved without secondary treatments like polishing or coating. The part's surface roughness depends on the machine tool used, the machined material, and the machining parameters such as speed, feed, and tool type.
The quality of an "as machined" finish is typically evaluated through the following criteria:
Surface Roughness (Ra): The roughness of an "as machined" finish typically falls between Ra 1.6 μm and Ra 3.2 μm, which is suitable for many industrial applications that do not require a polished or mirror-like surface.
Dimensional Accuracy: One of the key advantages of an "as machined" finish is its high dimensional accuracy, with tolerance levels often as tight as ±0.05 mm, depending on the material and machining process.
Surface Integrity: The machined surface should be free from visible tool marks, burrs, and defects. It is essential to use the right cutting tools and machining techniques to ensure the surface is functional and aesthetically acceptable for the given application.
Cost-Effectiveness: The lack of secondary finishing treatments makes the "as machined" finish a more cost-effective solution for applications where surface appearance is less important than functionality and precision.
'As Machined' Finish Process Flow and Key Parameter Control
Achieving the "as machined" finish involves careful control of several steps in the manufacturing process:
3D Printing – The part is printed with the required material using 3D printing technologies like FDM, SLA, or SLS, ensuring the part is ready for the subsequent machining process.
Machining Setup – The part is fixed securely in a CNC machine, where cutting tools remove excess material and achieve the desired shape and dimensions.
Machining – The part is machined according to specific instructions, and material is removed layer by layer. The process can include drilling, milling, turning, and other methods to refine the surface and improve the part's function.
Post-Machining Inspection – The part is inspected for dimensional accuracy and surface finish quality after machining. Inspection may include visual checks, surface roughness measurements, and tolerance checks.
Cleaning – The part is cleaned to remove any residual machining debris, dust, or oils left over from the machining process.
Key parameters that must be controlled during machining include tool selection, cutting speed, feed rate, and coolant application. Properly maintaining these parameters ensures that the final "as machined" surface meets the required functional and dimensional specifications.
Applicable Materials and Scenarios
The "as machined" finish is particularly well-suited for certain materials and applications in 3D printing. Below is a table listing commonly used materials for 3D printed parts with "as machined" finishes and their primary applications, with hyperlinks to the specific materials:
Material | Common Alloys | Applications | Industries |
|---|---|---|---|
Aerospace components, medical devices, industrial machinery | Aerospace, Medical, Automotive | ||
Aerospace parts, medical implants, custom tooling | Aerospace, Medical, Automotive | ||
Automotive parts, structural components | Automotive, Aerospace | ||
Electrical connectors, heat exchangers | Electronics, Automotive, Energy |
The "as machined" finish is suitable for parts that do not require highly polished surfaces but precise dimensions and good functionality. It benefits mechanical components, aerospace structures, and automotive parts where performance is more critical than appearance.
Advantages and Limitations of the 'As Machined' Finish
Advantages The "as machined" finish offers several key benefits:
Precision: The machining process provides tight tolerances and dimensional accuracy, making it ideal for high-performance parts.
Cost-Effective: Since no additional surface treatments are required, parts with an "as machined" finish are often more affordable than those with polished or coated finishes.
Fast Turnaround: The absence of secondary processes results in faster lead times for parts that must be produced quickly.
Functionality: The "as machined" surface is ideal for functional parts, especially in applications where appearance is secondary to performance.
Limitations However, the "as machined" finish has some limitations:
Surface Finish: While the finish is functional, it may not be aesthetically appealing for consumer-facing products or parts that require a glossy finish.
Roughness: The surface roughness, although generally within acceptable limits, may not be smooth enough for some applications, especially those requiring a high-gloss finish.
Wear Resistance: Parts with an "as machined" finish may not have the same level of wear resistance as those with additional coatings or treatments like anodizing or plating.
'As Machined' Finish vs. Other Surface Treatment Processes for 3D Printed Parts
The "as machined" finish is often compared to other surface treatment processes such as polishing, anodizing, and powder coating. Below is a table comparing the "as machined" finish with these processes:
Surface Treatment | Description | Roughness | Dimensional Accuracy | Applications | Cost |
|---|---|---|---|---|---|
Directly machined surface from the 3D printed part without further finishing | Ra 1.6-3.2 μm | High (typically ±0.05 mm) | Mechanical parts, structural components | Cost-effective, no additional processes | |
Smooths the surface to a high-gloss finish | Ra < 0.1 μm | Excellent (tighter tolerances) | Jewelry, consumer parts | Time-consuming and expensive | |
Electrochemical process to form a protective oxide layer | Smooth, Ra < 0.5 μm | Excellent (typically ±0.05 mm) | Aerospace, automotive parts | Moderate cost, adds corrosion resistance | |
Electrostatic application of a protective layer | Smooth to slightly rough, Ra 1-3 μm | Moderate (typically ±0.1 mm) | Automotive, exterior parts | Moderate cost, adds protection and color |
Application Cases for 'As Machined' Finishes in 3D Printed Parts
The "as machined" finish is commonly used in industries where precision, functionality, and cost-efficiency are the primary concerns. Some notable application cases include:
Aerospace: Machined aluminum structural components show improved dimensional accuracy, essential for assembly and fitting.
Automotive: Custom parts like engine components and brackets are machined to precise tolerances, ensuring proper function under high-stress conditions.
Medical: Machined parts, such as surgical instruments and medical device components, offer high precision without requiring further aesthetic treatments.
Consumer Electronics: Machined prototypes for testing and validation, ensuring dimensional accuracy and functional performance.
FAQs
What is the "as machined" finish, and how is it achieved?
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