CNC milling machine cutting a metal block with high precision
Meta Description: Learn smart ways to reduce CNC milling costs through better part design: simple tips that will help you save time, cut waste, and get the best results from your CNC projects.
Designing CNC milling parts can be expensive if not done correctly. Small changes in your design can lead to longer cutting times, more material waste, or even the need for special tools, all of which drive up costs.
That’s why it’s important to know how to design parts that are not only functional but also easy and cheap to machine. By choosing the right shapes, hole sizes, and tolerances, you can reduce the time it takes to make your part and reduce overall production costs.
This blog will guide you through simple design tips that help reduce CNC milling costs without sacrificing quality. It will also provide strategies for minimizing material waste and teach you the principles of design simplification.
10 Design Tips to Reduce CNC Milling Costs
CNC milling is a reliable way to create strong, precise, and detailed parts from metal or plastic. But the truth is, CNC machining can get expensive—especially when the design is not made with cost in mind. Whether you’re making just one part or producing thousands, the way you design it affects how much time and effort the machine will take to make it. Here are 10 design tips that can help reduce the cost of your CNC-milled parts:
1. Keep Your Design Simple
The more complicated your part, the longer it takes to machine. This means more machine time, more tool wear, and higher costs. Designs with a lot of sharp corners, complex curves, or extra details require multiple tool passes or special tools. Try to stick to simple shapes. For example, go with straight edges or flat surfaces instead of deep grooves or decorative curves if they serve the same purpose. Simpler parts are faster and easier to produce, lowering each part’s cost.
2. Avoid Deep Pockets and Cavities
Deep pockets may look neat, but they cause problems. Cutting tools have limits to how deep they can go. If the pocket is too deep, the machine needs to use longer tools, take more passes, and run at slower speeds to avoid breaking the tool. All of this adds to the cost. A good rule is to keep the pocket depth no more than 4 times its width. If a pocket needs to be deep, consider redesigning the part to split the depth across multiple levels or using a different shape that’s easier to mill.
3. Use Tight Tolerances Only Where Needed
Tolerances show how exact the size of a part must be. For example, a hole with a tolerance of ±0.01mm has to be extremely precise. Making parts with tight tolerances takes more time and better tools, which increases the price. This allows the machine to cut faster and with fewer adjustments, which saves both time and money. Use tight tolerances only in parts that must fit very closely with other parts.
4. Avoid Tiny Features
Tiny holes, narrow slots, or small lettering take more time to cut and may require extra-small tools that wear out quickly. These features may also need slower cutting speeds, which means more time on the machine. If a small hole or thin wall isn’t truly needed for how the part works, consider making it bigger or removing it altogether. Features that are easy to see, touch, or clean also make the part more user-friendly and cheaper to manufacture.
5. Use Standard Hole Sizes
Standard drill sizes are fast and cheap to use. When you use standard sizes (like 3mm, 5mm, 10mm, etc.), the machine can drill the hole quickly with a ready-made tool. But if you use odd sizes, like 3.37mm, the machine must mill the hole using a special path, which takes longer. Before finalizing your design, check a list of standard drill sizes and match your holes to those numbers. It’s a small step that saves a lot of time during production.
6. Minimize Tool Changes
Each time a machine changes its cutting tool, it stops working for a few seconds or even minutes. These short breaks might not seem like much, but they add up—especially if you’re making many parts. More tool changes also mean more setup work for the machinist. Design your part in a way that allows most features to be cut with the same tool. For example, use the same diameter for most holes or keep similar depths for pockets. Fewer tool changes mean faster work and lower costs.
7. Design for Easy Cutting Directions
Machines usually cut parts from the top or side. If your part needs to be cut from multiple angles, the machinist might have to flip or reposition the part during the process. Each repositioning means extra time and care, especially if high precision is needed. Try to design your part so that all the major features can be accessed from one direction. If the part is more complex, consider breaking it into smaller, easier-to-machine parts that can be assembled later.
8. Avoid Very Thin Walls
Thin walls are tricky. They can bend, vibrate, or break during machining. They also limit the speed of the machine because the tool must cut more gently to avoid damage. To avoid this, keep metal walls at least 1mm thick and plastic walls at least 1.5mm thick, depending on the material and use. Thicker walls make the part stronger, easier to cut, and less likely to cause problems during production.
9. Combine Parts Where Possible
If your product has many small CNC parts that are later put together, check if some of them can be combined into a single part. Fewer separate parts mean less machining time, fewer setups, and lower assembly costs. However, this only works if combining parts doesn’t affect how the product functions. Sometimes keeping parts separate is better for repair or replacement. But if you can combine them without harm, you’ll reduce costs.
10. Pick a Material That’s Easy to Machine
Some materials are harder to work with than others. For example, aluminum is softer and easier to cut than stainless steel. This means faster cutting speeds, less tool wear, and lower costs. Before choosing a material, ask yourself: “Does this part really need to be made from a hard-to-machine metal?” If not, choose a more machinable one. You’ll still get good strength, but at a lower price.
Here’s a table showing the 10 Design Tips to Reduce CNC Milling Costs:
| Design Tip | Summary |
| Keep Your Design Simple | Avoid complex shapes; use straight lines and flat surfaces for faster machining. |
| Avoid Deep Pockets and Cavities | Keep pocket depth shallow to reduce tool wear and machining time. |
| Use Tight Tolerances Only Where Needed | Only apply strict accuracy where necessary to save cost and time. |
| Avoid Tiny Features | Small holes or thin walls take longer and are harder to machine. |
| Use Standard Hole Sizes | Stick to common drill sizes for faster and cheaper drilling. |
| Minimize Tool Changes | Design with fewer tool types to avoid delays during production. |
| Design for Easy Cutting Directions | Make parts that can be machined from one direction to reduce repositioning. |
| Avoid Very Thin Walls | Keep walls thick enough to avoid bending or breakage during cutting. |
| Combine Parts Where Possible | Merge smaller parts into one to reduce setup and assembly time. |
| Pick a Material That’s Easy to Machine | Use materials like aluminum for faster machining and lower tool wear. |
Strategies for Minimizing Material Waste
Minimizing material waste is a smart way to save money and improve efficiency in CNC milling. Wasted material doesn’t just increase costs—it also slows down production and creates unnecessary scrap. Below are five practical strategies you can apply to reduce waste without compromising the quality of your parts.
1. Choosing the Right Tolerance Standards
Tight tolerances are only necessary for features that fit or function precisely. Applying them to every part of the design can lead to more rework and wasted materials because the slightest error makes a part unusable. Instead, use tight tolerances only where they’re needed. Standard or relaxed tolerances will do for areas that don’t require extreme accuracy. This simple adjustment reduces waste and makes the machining process smoother.
2. Optimize Tool Paths
How a CNC machine moves during cutting affects material usage and production time. Unnecessary tool movements, deep cuts, or inefficient paths can remove more material than needed. Using CAM software, you can generate optimized tool paths that reduce unnecessary passes. A well-planned tool path limits material waste and protects cutting tools from quick wear and tear.
3. Choose Material Sizes That Fit the Job
Using oversized material might seem safe, but it often leads to more cutting and more waste. Instead, try to select raw material sizes that are close to the final part dimensions. Working with well-matched stock sizes reduces how much material needs to be removed, shortens machining time, and cuts down on leftovers that can’t be reused.
4. Reuse Leftover Stock When Possible
Not all leftover pieces need to be thrown away. Many can be reused for future projects, especially if they’re large enough or made from expensive materials like aluminum or stainless steel. Keep off-cuts organized by size and material so they’re easy to access later. Reusing materials reduces waste and lowers the need to constantly purchase new stock.
Principles of Design Simplification
Machinist preparing a part for CNC milling with tool setup
Simplifying your CNC milling part design is a smart way to reduce cost, save time, and improve production. A simple design doesn’t mean it’s weak or basic—it means the part is easier to machine without losing its strength or purpose. Here are some helpful tips to keep your design simple and efficient.
- Structural Optimizations to Reduce Machining Time
Avoid complex shapes that take too long to cut. Deep pockets, sharp corners, and hard-to-reach areas can slow down the machine. Instead, use flat surfaces, shallow features, and open spaces. Try to reduce the number of setups needed. The fewer times a part needs to be flipped or adjusted, the faster the job gets done.
- Remove Unnecessary Features
Extra details like decorative grooves, unneeded holes, or tight curves increase machining time. If a feature doesn’t improve the part’s function, it’s better to leave it out. Simple parts are faster to make and easier to inspect.
- Use Standard Sizes and Shapes
Stick to common hole sizes, thread types, and shapes. Special tools and rare sizes take more time and may not be available right away. Using standard options keeps the process smoother and cheaper.
- Apply Tight Tolerances Only Where Needed
Don’t make every part of your design super precise. Tight tolerances should only be used in areas where accuracy really matters. For example, parts that must fit together tightly or perform a specific job.
- Design for Easy Tool Access
If the machine’s tool can’t reach a certain spot, it might require custom setups or longer tools. That leads to more time and money spent. Keep your design open and easy to reach with standard tools.
Conclusion
Designing a CNC-milled part is not just about getting the shape right—it’s also about thinking ahead. Every design decision you make has a cost tied to it, whether it’s in time, tools, materials, or machine effort. This is why smart design is not just a skill but a strategy.
If you want to work closely with a machinist or manufacturer that will spot areas to adjust before the first cut is made, you can search for CNC milling near me. This can save hours in production and thousands in cost over time.
