Designing a part that’s easy to machine is not just about aesthetics or functionality—it’s also about making sure it can be manufactured efficiently, cost-effectively, and without unnecessary delays or complications. Whether you're designing custom parts for a client or creating something for your own shop, considering how the part will be machined is key to keeping production costs down and turnaround times short.

In this blog, we’ll explore the art of part design with a focus on machinability. From material selection to feature considerations, here are some practical tips to help you design parts that are easier to machine and ultimately produce better results.

The first step in designing machinable parts is understanding the process by which they will be made. Different machining techniques, whether CNC milling, turning, or EDM, have their own capabilities and limitations. The more you know about these processes, the better you can design a part that minimizes complexity and makes optimal use of the machine's capabilities.

For example:

CNC Milling is great for creating complex features like pockets, contours, and holes.

Turning is perfect for cylindrical features and produces smooth, precise finishes on round parts.

EDM (Electrical Discharge Machining) is ideal for making intricate details and shapes, especially in hard-to-machine materials like hardened steel.

Pro Tip: 

Before starting your design, consult with your machinist or manufacturer about the best machining process for your part. Early communication can save a lot of headaches down the road.

The simplest designs are usually the easiest to machine. While complex geometries are often required for certain applications, it's crucial to consider how those complexities will impact the machining process. Features like sharp corners, deep holes, and intricate curves can require specialized tooling, longer cycle times, or more expensive equipment.

Key Considerations for Simple Geometry:

Avoid Sharp Corners: 

CNC machines struggle with sharp internal corners, as they often result in tool wear or broken tools. Instead, use radius edges (a small curve) in your designs to make it easier for the tool to navigate.

Straight Lines Over Curves: 

If possible, design features with straight lines rather than curves or arcs. Straight lines are easier to machine and typically require fewer tool changes or passes.

Avoid Deep Pockets: 

Deep pockets with narrow spaces can be difficult for milling machines to access. If deep pockets are necessary, keep them wide enough to allow the tool to cut efficiently and avoid long, expensive operations.

Pro Tip: 

If your design does require tight tolerances or complex shapes, break it into smaller, simpler features. You can often machine complex parts in stages rather than trying to machine everything at once, which saves time and reduces risk.

While tight tolerances are essential for certain applications, they can also make machining more difficult, expensive, and time-consuming. It's important to balance your tolerance needs with the capabilities of your machine.

Tips for Managing Tolerances:

Use Tolerances Where Necessary: 

Don’t over-specify tolerances unless it’s absolutely necessary. Tighter tolerances often require slower cutting speeds, more precise tools, and additional quality checks.

Design for Standard Fits: 

Standard fits (like press fits, clearance fits, or slip fits) are easier and more cost-effective to machine than custom fits. When possible, try to use standardized fits that align with common machining capabilities.

Avoid Overlapping Features: 

Features that overlap (like multiple pockets or holes) can create difficult setups, especially when they are located near each other. Try to space your features in a way that allows for easy access by tools.

Pro Tip:

Whenever possible, provide clear tolerances only for critical areas of the part (e.g., mating surfaces or assembly areas). This will reduce the amount of machining required while still ensuring the part functions correctly.

Material choice plays a huge role in how easy or difficult a part is to machine. While harder materials might be necessary for certain applications, they also increase tool wear, require more cutting power, and may slow down production times. Softer materials like aluminum or certain plastics are much easier to machine than harder alloys like titanium or stainless steel.

Material Considerations:

Consider machinability: 

Some materials, like aluminum, brass, and mild steel, are relatively easy to machine. Others, like titanium or hardened tool steel, are much more difficult and will require special tooling, longer cycle times, and higher costs.

Thermal Expansion:

Materials with a high rate of thermal expansion (like certain metals) can cause issues in precision machining. Be mindful of how your material reacts to heat during the machining process.

Consider Material Supply: 

The availability of material is another factor to consider. Some exotic or specialty materials may have longer lead times and higher costs, which can affect project timelines and budgets.

Pro Tip: 

When in doubt, consult with your machinist or supplier about the best material choice for your design. They may have insights on material properties and machining considerations that will make the process smoother.

Fixturing refers to the process of securing a part in place while it's being machined. If your part is difficult to fixture—either because of its shape, size, or weight—it can lead to setup errors, machining difficulties, or even damage to the part. By designing with fixturing in mind, you can save significant time and effort during the manufacturing process.

Fixturing Tips:

Use Flat Surfaces for Fixturing: 

Parts with flat, parallel surfaces are easier to secure in a fixture. Avoid overly complex shapes that make it hard to clamp or hold the part steady during machining.

Consider the Machining Sequence: 

Plan your part’s machining process ahead of time to ensure you can machine each feature without compromising the part’s stability or access.

Design with Tool Accessibility in Mind: 

Make sure that your design doesn’t trap the tool. It’s important to ensure that each feature can be accessed by the cutting tool without interference from other features or the fixture itself.

Pro Tip: 

Where possible, include features in your design that can be used for fixturing, such as through-holes or flat faces. These features will help machinists easily secure your part and reduce setup times.

Using standard, off-the-shelf tooling rather than custom or specialized tools can save both time and money. Keep your design in line with commonly used tools, such as drills, end mills, and inserts, to reduce tooling costs and minimize setup complexity.

Standard Tooling Tips:

Use Common Hole Sizes: 

Avoid using non-standard hole sizes that require special tooling. Stick to common sizes like 3mm, 6mm, 10mm, etc., unless absolutely necessary.

Design with Tool Lengths in Mind: 

Ensure that your design accommodates the standard tool lengths and cutting diameters available in your shop, which will prevent issues with tool reach or clearance.

Pro Tip: 

Always ask your machinist about any potential tooling restrictions or limitations before finalizing your design. They may have recommendations for more efficient tooling options.

The more operations a part requires, the more time it will take to machine. When designing parts, consider how many steps are involved in manufacturing and how to minimize unnecessary movements or tool changes.

Design Tips to Reduce Operations:

Combine Operations When Possible: 

If you can design a part in a way that allows multiple features to be machined in one setup or with fewer tool changes, it will reduce production time.

Think About the Final Finish: 

Designing parts with easier-to-machine surfaces can reduce the need for extensive post-machining processes like grinding, polishing, or deburring.

Pro Tip: 

Optimize your design for concurrent operations, like simultaneous milling and drilling, to reduce cycle times and tool change frequency.

Part design and machinability go hand-in-hand. While the ultimate goal is to create a part that performs well in its intended application, it’s equally important to design it in a way that minimizes manufacturing complexity. By understanding the capabilities of the machine tools, choosing the right materials, designing for easy fixturing, and avoiding unnecessary features, you can make the machining process much smoother, faster, and more cost-effective.

The art of part design isn’t just about innovation—it’s about balancing creativity with practicality. Keep these tips in mind when designing your next part, and you’ll find that producing high-quality, machinable components becomes a much easier task.