Tips to Know When Preparing CAD Model for CNC Milling

Whether you are machining metal or plastic, preparing a Computer-Aided Design (CAD) drawing is the first step to achieving the perfect finishing. However, the journey from vision to execution is not so straightforward that you can simply begin production on your Tabletop CNC Mill the moment you have the idea. 

Creating 2D or 3D designs that can be reproduced faithfully requires a high level of detail and extensive simulation to maintain optimum accuracy. Plus, the CAD file that you create must be compatible with the Tabletop Milling Machine to minimize errors and create high fidelity design prototypes.

So, if you are looking for tips on how to create such CAD models, we have a few useful tips that can help. Read on to know more!

Wait Until You Have the Details

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You may be tempted to start creating your CAD models the moment an idea or inspiration hits you. However, you will have to practice restraint and allow the design to marinate for some time. Once you have a firm visualization of the concept, proceed with committing it on paper by preparing a detailed technical drawing covering critical features or dimensions of the part, construction lines, finishing preferences, tolerances, etc. Continue refining this design and its details until you are absolutely satisfied with the sketch, and only then proceed with making the CAD model.

Optimize Design for Manufacturing Considerations

While a Tabletop CNC Mill is a manufacturing powerhouse, it has its own set of limitations. As such, in the process of preparing a CAD model for a CNC mill, pay close attention to the specifications of design intricacies such as cavities, holes, edges, walls, etc. 

Some of the best practices that can help in this regard include:

• End mill tools can typically cut to a depth that is three to four times their diameter. Hence, limit the depth in proportion to the diameter of the tool.
• Take the diameter of the cutting tool into account while calculating internal corners, curvature, and edges. Increase the corner radii by 1mm from the recommended value to get top-notch finishing.
• Use T-bone undercut for actualizing right-angled internal corners while 3D modeling.
• As wall thickness can impact the durability and strength of the material, practice care to dampen vibrations. Ideally, the minimum allowable thickness should be 0.8mm in the case of metals and 1.5mm in the case of plastics.
• Use reamers or boring tools for holes that call for tight tolerances. Also, carefully plan these holes well in advance before integrating them into the CAD models.
• While adding threads to your CAD file, keep the size at M6 (or higher) for best results. Avoid anything less than M2.

Such considerations will optimize your CAD design for manufacturing.

Eliminate Overlapping Geometry

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Overlapping or stacked vectors in a CAD file will cause the CNC mill to work and rework over the same area repeatedly. As a result, it will render the material weak and can potentially introduce design flaws. Hence, check your model to eliminate any overlaps or stacks to allow the manufacturing to take place smoothly and without unnecessary movements. 

Ideally, you should fuse all the geometry into a single layer to reduce any redundancies. To achieve such results, you will have to:

• Delete any duplicate copies of the design objects and elements that may exist.
• Fuse all the overlapping lines and consolidate them into a single drawing.
• Combine different sections of the design to ensure seamless design alignment.
• Minimize vector lines to the lowest possible number of nodes without compromising on the design quality.

In addition to the above measures, pay attention to exporting only the necessary parts of the model while converting the CAD drawing into its CAM counterpart.

Want to Integrate Text?

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If some form of textual matter is a part of a design, you will also have to make design considerations for these in your CAD model. Typically, such text is used to brand the finished product with the company logo, include manufacturing details, or inscribe part numbers or other identifiers. To ensure the seamless transfer of text onto the part, maintain a 0.5mm spacing between each individual character of the textual content. Also, pick clear and legible fonts like Verdana, Arial, or Sans-Serif, etc., to ensure that the text is recessed and concise.

Finally, Practice Until You Reach Perfection

One simply cannot learn CAD modeling without continuous practice. Given that the learning curve for CAD is steep, you will have to dedicate ample time, energy, and resources to mastering the art. And even if you feel at some point that you have “made it,” some design will come your way and leave you stumped.

Therefore, make learning a continuous process to acquire more knowledge and stay up-to-date. Refer to tutorials and become a part of forums that can contribute to your skills. Also, share your work to get feedback and constructive criticism to gain perspective. In this way, you will find yourself gradually making your way from being a noob to an expert in almost no time!

About the Author:

Peter Jacobs

Peter Jacobs is the Senior Director of Marketing at CNC Masters. He is actively involved in manufacturing processes and regularly contributes his insights for various blogs in CNC machining, 3D printing, rapid tooling, injection molding, metal casting, and manufacturing in general.