Essential Tips for Designing Parts for CNC Machining Service
At Creatingway, we take full advantage of the capabilities of CNC machining to the fullest. It is how we orient our design team to follow certain design rules for manufacturing. This is, however, challenging as specific industry-wide standards have not been put in place yet. The article highlights comprehensive guidelines with the best design practices for CNC machining. This is through extensive research by our very own Creatingway experts and our long history on CNC machining service provision in compiling a comprehensive, up-to-date information list. The focus is on describing what is practicable with modern CNC systems today.
What’s The CNC Machining Process?
CNC machining is a form of subtractive manufacturing technology. The material in CNC is removed from a solid block using a variety of cutting tools that rotate at high speed, i.e., thousands of RPMs. A CAD model is the basis of the parts produced. Materials used in CNC include both metals and plastics. The advantage of CNC machining is the ability to achieving high dimensional accuracy and tight tolerances. The process suits both high volume production and one-off jobs. It is currently the better alternative in terms of cost in producing metal prototypes in comparison to 3D printing.
What’s The Main CNC Design Restrictions?
CNC offers excellent design flexibility in machining but possesses specific design restrictions due to basic mechanics. However, the limits are mainly related to:
- Machining Tool geometry
- Machined Tools access
Tool Geometry
The CNC cutting tools have a cylindrical cutting shape with a limited cutting edge. Examples include end mills and drills. During the removal of material from the workpiece, transfer of the tool geometry to the machined part occurs. A situation arises, for example, where the internal corners of a CNC part will have a radius, even with the use of a small cutting tool.
Tool Access
Removal of material from a workpiece is when the cutting tool approaches the workpiece directly from above. CNC cannot machine features inaccessible in this way. An exception exists in designing undercuts. Good design practice is aligning all elements of your model to one of the 6 main principal directions. The features include holes, cavities, vertical walls, etc. Hence, our designers should take advantage of this as a recommendation since we possess a 5-axis CNC systems for advanced workpiece holding capabilities.
It is also an issue in machining features with a large depth to width ratio. To access the bottom of deep cavities, we require special tools with long shafts for this task. It consequently lowers the stiffness of the end effector, that increases the vibrations of the tool and lowering the achievable accuracy. Hence, experts at Creatingway recommend that you design parts machinable using a tool with the largest possible diameter and the shortest possible length for enhanced accuracy.
CNC Design Rules
In the CNC industry, manufacturers continuously improve the capabilities of the technology, thus expanding the limits of what is possible. It possesses a challenge as their no specific existence of an industry-wide standard. Therefore, below is a summary of the recommended and feasible values of the most common features encountered in the CNC machined parts.
What’s The Design Tips Need To Consider?
Thin Walls
Minimum thickness of the wall
- Recommended: 0.8 mm (metals), 1.5 mm (plastics)
- Feasible: 0.5 mm (metal), 1.0 mm (plastics)
The thinner the wall, the lower stiffness of the material, which increases vibrations during machining. It lowers the achievable accuracy. Plastics are also prone to warping and softening due to residual stress and temperature increase. Thus, we recommend a larger minimum wall thickness for plastics.
Cavities and Pockets
Cavity depth
- Recommended: 4 × cavity width
For end mill tools, they possess a limited cutting depth of 3-4 times their diameter. Cavities with smaller depth to width ratio have more tool deflection, chip evacuation, and vibrations. Thus, limiting the depth cavity to 4 times its width ensures excellent results. Cavities with a depth greater than 6 ×the tool diameter we considered deep. On the other hand, It requires using specialized tooling to achieve machining in this case.
Small Features
Minimum hole diameter
- Recommended: 2.5 mm (0.1”)
- Feasible: 0.05 mm (0.005”)
We machine accurately cavities and holes using tools down to 2.5 mm in diameter. Micro-machining is anything below this limit. Furthermore, we have expert knowledge in this aspect though we recommend its best to avoid unless necessary.
Tolerances
- Standard: ±0.125 mm (0.005”)
- Typical: ±0.025 mm (0.001”)
- Feasible: ±0.0125 mm (0.0005”)
Tolerances define the boundaries for any acceptable dimensions. The achievable tolerance varies depending on the base dimension and geometry of the part.
Texts and Lettering
- Recommended: at least font size 20, 5 mm engraved
To remove less material, we prefer engraved text over embossed. Also, using a Sans-Serif-font with at least 20 font size is recommended.
In summary, CNC takes pride in informing our clients on how best to design their CNC models. Our automated software and manufacturing experts are ready to review the machinability of your designs. For any inquiries or orders, contact us now.
Creatingway is concentrated on CNC machining manufacturing, prototype machining, low-volume manufacturing, metal fabrication, and parts finishing services, provide you the best support and services. ask us one inquire now.
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