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  • Writer's pictureRhys Andersen

Navigate Manufacturability Challenges: How to Translate Designs from 3D Printing to CNC Machining

In the ever-evolving landscape of modern manufacturing, the intersection of 3D printing and CNC machining is becoming increasingly significant. Each technology boasts unique strengths and has its own drawbacks.


One particular challenge from both sides is that 3D printing and CNC machining are very distinct processes with inherent differences in manufacturability. This means that transitioning a design from 3D printing to CNC machining introduces several complexities that your designs will need to adapt to account for. In this article, we'll explore these challenges and provide some industry tips for translating 3D print design features for effective CNC machining.


What is the difference between 3D Printing and CNC Machining?

3D printing, or additive manufacturing, builds objects layer by layer, enabling intricate geometries and complex internal structures. In contrast, CNC (Computer Numerical Control) machining is a subtractive process, removing material from a solid block to shape the desired form. These two processes are literal opposites, and that means that designs for a 3D printed object and a CNC machined product will differ greatly to play to the manufacturing strengths.


While 3D printing shines in prototype development and complex designs, CNC machining is revered for its precision, durability, and suitability for mass production. While most 3D printed products are plastic (though metal 3D printing is becoming more popular), CNC machines are able to mill from a larger variety of materials including metals. This makes CNC machined parts more durable and lowers the risk of warping that often plagues plastic 3D printed parts.


5 Challenges in Translating 3D Print Designs to CNC

So now you've moved from prototyping to large-scale manufacturing (or maybe changed your mind about 3D printing) and need to figure out how to convert your 3D printing design to work for a CNC. First, we'll explain some of the challenges to keep in mind during this process. Then we'll go over specific CNC machining concerns and give you the insider scoop on the best ways to translate a product design from 3D printing to CNC manufacturing.


1. Inaccessible Geometries:

3D printers can easily create designs with overhangs and nested geometries. CNC machining, however, faces significant challenges with such designs due to tool accessibility limitations. If you have a lot of internal structures necessary for your design, you'll have to stick with 3D printing or machine your product in parts.


2. Material Considerations:

Materials react differently in each process. We talked a little about the importance of considering what material you will use in our post on how to choose to 3D print or machine your part. Keep in mind that a design optimized for 3D-printed plastic may not be directly translatable to metal CNC machining.


3. Thin Walls:

Thin, tall walls, which are easily achievable in 3D printing, present significant manufacturing challenges in CNC machining. Thin walls may vibrate or deflect under cutting pressure, impacting surface finish and tolerances.


4. Deep Pockets:

Similarly, the depth of pockets is limited by the length of available tooling. If you are hoping to have a design CNC manufactured, you will need to confirm with your manufacturer exactly what dimensions will be possible. If you are looking to do this as a DIY CNC project, you might need to invest in a capable product. Tools with a suitable reach-to-diameter ratio are essential, with companies like Helical Tools offering an excellent selection.


5. Free Form Surfaces:

Free-form or organic surface features, easily achievable in 3D printing, incur a significant cost increase in CNC machining due to the additional time required to achieve a desirable surface finish. Minimizing or limiting the use of such design elements to areas where they are absolutely necessary can greatly improve cost-efficiency and manufacturability.


4 Design Considerations for CNC Machining

With these important challenges in mind, you can be better prepared to make sure your 3D printing design translates well to CNC machining. Let's cover four specific CNC machining design considerations for you to cross off your list before uploading your design.


1. Understanding Tool Access:

Effective CNC design requires a comprehensive understanding of tool accessibility. The most cost-effective parts are typically designed for top-down or 3-axis tool access. Specialty cutters or 5-axis machining strategies can address features like shallow undercuts but often at increased costs.


2. Sharp Internal Corners:

Avoiding sharp internal corners is crucial in CNC machining. A rotating tool necessitates a radius in corners at least as large as the cutting tool itself. Larger radii are preferable to prevent full tool engagement, which can cause chatter or poor surface finishes.


3. Internal Structures:

Creating internal cavities or complex internal geometries is particularly challenging in CNC machining due to the need for physical tool access to all areas of the part. Because of this, you might opt to stick with 3D printing or greatly simplify your design to ease manufacturing burdens.


4. Surface Finish and Tolerances:

While 3D printing can produce detailed textures, CNC machining provides superior surface finishes and tighter tolerances, considerations crucial to design translation. These are major advantages of CNC machining over 3D printing that are helpful to know when choosing the manufacturing method right for your design.


2 Tools for Adapting 3D Printed Designs for CNC Machining

While these challenges and design considerations might seem like impossible barriers, you actually don't need to start from scratch or do it all on your own. We've got two helpful tools you can use to translate a product design from 3D printing to CNC manufacturing.


1. Getting Design Modification Strategies from Manufacturers:

Adapting a design for CNC machining may involve simplifying geometries or redesigning features for tool accessibility. Complex designs might need to be split into multiple, simpler parts for assembly. Reach out to your local manufacturer to get the specs on their machines and discuss the manufacturability of your design idea.


2. Utilizing CAD Software and Other Programs:

CAD software can simulate CNC machining processes, aiding designers in modifying and optimizing designs for CNC feasibility. Additionally, programs such as Fusion 360 also offer tools such as Accessibility Analysis and Minimum Radius Analysis which help to locate problematic features.


Conclusion

Successfully transitioning a design from 3D printing to CNC machining hinges on understanding the distinct manufacturability constraints of each method. While both processes offer unique advantages, careful consideration and adaptation are key to ensuring a design is not only manufacturable but also retains its intended functionality and aesthetic integrity.


If you are considering transitioning a design from 3D printing to CNC machining, don't hesitate to reach out: Consult with our team of manufacturing experts at Method Mfg to optimize your design for the best possible outcomes.

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