Many companies turn to the common and trusted practice of Computer-Numerical Control (CNC) machining when designing new products. This process quickly manufactures prototypes and parts with superior strength and tight tolerances. To maximize CNC machining and accelerate production, designers must recognize specific production rules and avoid making mistakes that hinder the prototyping process. Taking time to assess and enhance the CNC machining design condenses the manufacturing cycle and optimizes efficiency and product quality.
A leading expert in pre-production manufacturing services, Advantage Engineering delivers strategic and flexible CNC rapid prototyping to bring your products to life. We serve as the manufacturing launchpad for a diverse group of industries and can give you the advantage by helping you with custom CNC prototyping for your product. Here, we offer various factors to consider when designing CNC prototypes.
Keep the Design Simple
With CNC rapid prototyping, machining multiple simple parts is always easier than machining one complex piece. Avoid implementing features into your design that are tedious or difficult to produce, as machining these intricate parts wastes labor and resources. If you must include complex pieces, divide them into simpler parts and assemble them to keep the overall prototype more streamlined.
Be Clear and Concise with Text
Some custom CNC machining applications include text or marks, such as company logos, serial numbers, and unique signs. Smaller and more complex text results in longer run times, so choose larger size text if possible. You should also select recessed text over raised markings as it is easier to attain your desired look by removing excess material with a milling tool.
Avoid Using Tiny Features
Refrain from including minuscule features in the design, such as micro-holes. Small parts can be useful for some prototypes, but they can be difficult to process if they exceed the minimum tool diameter of the machine. You must utilize various cutting tools on the corner materials, which extends the processing time. To mitigate the need for time-consuming and complex tool changes, add a radius to the small internal edges and corners of the part. This radius will also reduce wear and tear on tools and enhance cutting speeds.
At Advantage Engineering, we can craft features as small as 0.019 in (0.5 mm). We also offer a 10-foot travel and 50-ton crane to accommodate a broad range of part sizes, ensuring customers no job is too big.
Get the Tolerance Right
Although there are custom CNC designs for various prototypes, most CNC parts do not need a unique tolerance. Therefore, abstain from assigning too many tight tolerances as they generate extended machining periods. Only utilize tight tolerances on vital part surfaces and features to keep a reasonable machining time. Standard tolerances will suffice for the less crucial elements of the part.
Make Thin Walls Thicker
Parts must be durable enough to endure pressure from numerous hard tools, including carbide and high-speed steel. If the walls are too thin, the part will chatter, distort, or potentially break, making it difficult to machine promptly. Conversely, walls that are too thick may also hinder the process. Engineer designers and QC support can help you optimize your design based on the materials used.
Use Standard Hole Sizes
Standard-size holes are easy to CNC machine quickly with standard drill bits, saving time and providing more accurate dimensions. Non-standard holes, on the other hand, must be processed with end mills or reamers and limit the depth and diameter. At Advantage Engineering, we deliver precision machining to prototype designs with boring, cutting, and gun drilling.
Improve Tapped Holes
When it comes to tapped holes in CNC-machined components, only two or three turns are needed to hold the bolt tighter — increasing the length of the thread in a hole does very little. Going deeper multiplies the risk of tap breakage and extends the tapping operation time. Avoid using a thread longer than three times the hole’s diameter.
Limit Cavity Depth
The cutting tools used in CNC milling services usually operate best with cavity depths up to two to three times their diameter. To ensure success, the depth of the cavity should not exceed four times the diameter of the tool. If the cavity is too deep, the CNC component may suffer from deflection, fracture, tool hanging, and issues with chip evacuation. If the cavity must be deeper, try to create parts with variable depths to achieve optimal results.
Select the Right Thread Size
Utilizing the correct thread size is critical to optimizing your design. The suggested size for CNC-machined parts is M6 or higher, and the proper thread length is three times the nominal diameter. If the component has threads smaller than M6, adding an unthreaded length to the bottom of the hole that measures 1.5 times the nominal diameter can help. If your thread size is larger than M6, thread the hole throughout the length. It's best to avoid using thread sizes smaller than M2 and design holes that can't be threaded.
Remove Unnecessary Machining
Always seek to avoid prototype designs that require unnecessary machining. Extra machining makes manufacturing processes and lead times longer, stifling your production rate. Instead, simplify your design by cutting off excess material or eliminating purely aesthetic features. If you're unsure about the state of your design, Advantage Engineering offers design for manufacturing (DFM) support with CNC milling services to help clients determine the feasibility of their designs.
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Optimize your custom CNC design with Advantage Engineering. We guide our customers through challenging prototypes to ensure manufacturability and adhere to tight deadlines. Using CNC machining, additive manufacturing, injection molding, and urethane casting, we also assist in bringing prototypes to low-volume production efficiently. For more information about CNC rapid prototyping and our other pre-production services, contact us or request a CNC quote today.