Machined Part Design: Mistakes to Avoid in Precision Machining
The quality of a machined part largely depends on its initial design. All too often, errors made at this early stage lead to cost overruns, production delays, and, in some cases, functional failure of the final product. At GM Precision, we support our clients throughout the entire manufacturing process to ensure an optimized design that meets the specific requirements of precision machining. In this article, we present the most common design mistakes to avoid when developing a part for machining.
Overcoming the Limitations of Machining Processes
One of the most common mistakes is designing a part without considering the capabilities and limitations of the machine tools. An overly complex part, with inaccessible geometries or overly tight tolerances, can cause extended lead times, prohibitively high manufacturing costs, or even make the part unproducible.
For instance, designing a deep cavity with a small diameter without allowing for lateral access can make the part impossible to machine using standard milling tools. It’s essential to understand the characteristics of machining methods like 3-axis milling, turning, or EDM (electrical discharge machining), and to integrate those constraints into the design process. Collaborating with the machine shop early in the project is strongly recommended.
Specifying tight tolerances without justification
Tight dimensional tolerances are often associated with increased complexity and higher costs. It can be tempting to specify extremely tight tolerances to “ensure quality,” but this can be counterproductive if that level of precision is not required for the function of the part.
A better approach is to identify critical surfaces—those that interact with other parts or endure mechanical stress—and reserve tight tolerances for those specific areas. Standard tolerances are often sufficient elsewhere. This helps reduce machining time, minimize scrap, and limit the need for detailed inspections.
Forgetting machining radii in internal corners
When a part includes pockets or grooves, it is crucial to include internal corner radii in the design. A frequent mistake is to design perfectly square internal corners, assuming they’ll be easy to machine. In reality, cutting tools—such as end mills—are cylindrical and cannot create perfectly sharp 90° corners inside a cavity.
Omitting these radii leads to technical difficulties, often requiring special tools or forcing the operator to modify the design, which slows down production. As a rule of thumb, the larger the internal radius, the faster and more economical the machining process. Always include radii that match standard tooling, while still meeting the functional requirements of the part.
Designing a part without considering assembly
A machined part rarely functions alone. It’s usually part of a mechanical or structural assembly, and its interaction with other components must be considered from the design phase. A common error is failing to plan for screw access, tool clearance for assembly, or fit tolerances between parts.
Ignoring these factors can result in a perfectly machined part… that cannot be installed or used in its final environment. It is essential to design with assembly, maintenance, and overall manufacturability in mind. Functional dimensioning plays a key role in ensuring proper fits and efficient integration.
Adding complex features that add no value
Sometimes, designers include aesthetic features, elaborate chamfers, asymmetrical pockets, or decorative textures that do not offer any real functional benefit. These design elements may seem minor, but they can significantly complicate the machining process.
It is important to make the distinction between features that are functionally essential and those that are merely decorative. Every additional operation—tool changes, repositioning, surface finishing—adds time and cost. A simple, well-thought-out part is often more effective and more profitable to produce.
Ignoring material properties in machining
Material choice plays a critical role in the design of a machined part. Some materials, such as aluminum, are easy to machine, while others, like hardened steels or titanium alloys, require specialized tooling, reduced cutting speeds, and longer cycle times.
It’s essential to choose a material that meets both the functional needs of the part and the machining capabilities of the shop. A design optimized for machining should take into account hardness, thermal conductivity, dimensional stability, and compatibility with surface or heat treatments.
Failing to consult the machine shop before finalizing the design
Designers who work in isolation from the realities of the machine shop risk making avoidable mistakes. One of the best practices is to involve machinists or the manufacturing team during the design phase to validate the feasibility of the part.
At GM Precision, we actively promote this collaborative approach. Our team is available to advise engineers and designers, suggest improvements to 3D models, and optimize designs to reduce costs and improve part performance. This early collaboration results in smoother production and higher-quality outcomes.
A well-designed part is the key to successful machining
Precision machining is not just about running a CAD file through a CNC machine. It’s about synergy—between design, material, tooling, and machine capabilities. By avoiding the common mistakes outlined in this article, designers can significantly enhance part quality, minimize production delays, and effectively control costs.
GM Precision puts its expertise at your service to support the manufacturing of your most complex parts. Contact us today to discuss your projects and leverage our precision machining expertise.
Machined Part Design: Mistakes to Avoid in Precision Machining
The quality of a machined part largely depends on its initial design. All too often, errors made at this early stage lead to cost overruns, production delays, and, in some cases, functional failure of the final product. At GM Precision, we support our clients throughout the entire manufacturing process to ensure an optimized design that meets the specific requirements of precision machining. In this article, we present the most common design mistakes to avoid when developing a part for machining.
Overcoming the Limitations of Machining Processes
One of the most common mistakes is designing a part without considering the capabilities and limitations of the machine tools. An overly complex part, with inaccessible geometries or overly tight tolerances, can cause extended lead times, prohibitively high manufacturing costs, or even make the part unproducible.
For instance, designing a deep cavity with a small diameter without allowing for lateral access can make the part impossible to machine using standard milling tools. It’s essential to understand the characteristics of machining methods like 3-axis milling, turning, or EDM (electrical discharge machining), and to integrate those constraints into the design process. Collaborating with the machine shop early in the project is strongly recommended.
Specifying tight tolerances without justification
Tight dimensional tolerances are often associated with increased complexity and higher costs. It can be tempting to specify extremely tight tolerances to “ensure quality,” but this can be counterproductive if that level of precision is not required for the function of the part.
A better approach is to identify critical surfaces—those that interact with other parts or endure mechanical stress—and reserve tight tolerances for those specific areas. Standard tolerances are often sufficient elsewhere. This helps reduce machining time, minimize scrap, and limit the need for detailed inspections.
Forgetting machining radii in internal corners
When a part includes pockets or grooves, it is crucial to include internal corner radii in the design. A frequent mistake is to design perfectly square internal corners, assuming they’ll be easy to machine. In reality, cutting tools—such as end mills—are cylindrical and cannot create perfectly sharp 90° corners inside a cavity.
Omitting these radii leads to technical difficulties, often requiring special tools or forcing the operator to modify the design, which slows down production. As a rule of thumb, the larger the internal radius, the faster and more economical the machining process. Always include radii that match standard tooling, while still meeting the functional requirements of the part.
Designing a part without considering assembly
A machined part rarely functions alone. It’s usually part of a mechanical or structural assembly, and its interaction with other components must be considered from the design phase. A common error is failing to plan for screw access, tool clearance for assembly, or fit tolerances between parts.
Ignoring these factors can result in a perfectly machined part… that cannot be installed or used in its final environment. It is essential to design with assembly, maintenance, and overall manufacturability in mind. Functional dimensioning plays a key role in ensuring proper fits and efficient integration.
Adding complex features that add no value
Sometimes, designers include aesthetic features, elaborate chamfers, asymmetrical pockets, or decorative textures that do not offer any real functional benefit. These design elements may seem minor, but they can significantly complicate the machining process.
It is important to make the distinction between features that are functionally essential and those that are merely decorative. Every additional operation—tool changes, repositioning, surface finishing—adds time and cost. A simple, well-thought-out part is often more effective and more profitable to produce.
Ignoring material properties in machining
Material choice plays a critical role in the design of a machined part. Some materials, such as aluminum, are easy to machine, while others, like hardened steels or titanium alloys, require specialized tooling, reduced cutting speeds, and longer cycle times.
It’s essential to choose a material that meets both the functional needs of the part and the machining capabilities of the shop. A design optimized for machining should take into account hardness, thermal conductivity, dimensional stability, and compatibility with surface or heat treatments.
Failing to consult the machine shop before finalizing the design
Designers who work in isolation from the realities of the machine shop risk making avoidable mistakes. One of the best practices is to involve machinists or the manufacturing team during the design phase to validate the feasibility of the part.
At GM Precision, we actively promote this collaborative approach. Our team is available to advise engineers and designers, suggest improvements to 3D models, and optimize designs to reduce costs and improve part performance. This early collaboration results in smoother production and higher-quality outcomes.
A well-designed part is the key to successful machining
Precision machining is not just about running a CAD file through a CNC machine. It’s about synergy—between design, material, tooling, and machine capabilities. By avoiding the common mistakes outlined in this article, designers can significantly enhance part quality, minimize production delays, and effectively control costs.
GM Precision puts its expertise at your service to support the manufacturing of your most complex parts. Contact us today to discuss your projects and leverage our precision machining expertise.