Mold Texture in CNC Manufacturing(electroplating Martin)
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- source:DAHLER CNC Machining
Understanding Surface Finish
Surface finish refers to the texture of a part's surface. It is quantified in roughness average (Ra) measurements that describe variations in height across the surface. A lower Ra value indicates a smoother surface. Typical Ra values range from around 63 microinches (μin) for rough finishes like deck grip tape up to 4 μin for polished surfaces.
CNC machining can replicate any surface finish within the machine's capabilities by moving the cutting tool in small, finely spaced paths. The spacing between toolpaths, stepover distance, feed rates, cut depths, and other parameters can be adjusted to create different patterns and textures. Common surface patterns like horizontal or vertical stripes can be programmed, as well as more complex simulated textures.
Benefits of Textured CNC Parts
Here are some of the benefits of adding texture to CNC machined parts:
- Improved aesthetics - Texture adds visual interest and a custom feel to parts. Logos and branding elements can be integrated into the surface texture.
- Enhanced grip - Rough textures like diamond plate patterns provide extra grip for handling the part. This is especially useful on hand tools, grips, and foot pedals.
- Hide machining marks - Consistent surface textures like bead blasting can conceal the small imperfections left by the machining process.
- Improved paint adhesion - Textured surfaces provide more surface area for paints and coatings to mechanically adhere to.
- Functional purposes - Textures like ribs and bumps can serve functional purposes like improving heat dissipation, reducing slippage, and hiding scratches.
- Simulate materials - Wood, leather, stone, and other natural material textures can be simulated through CNC texturing.
- Branding - Part textures can evoke a company's brand image. A mechanic's tool might feature a coarse, gritty texture while a tech product could have a fine, precision texture.
Popular Texturing Methods for CNC
There are several common ways to add texture using CNC machining:
Milling Textures
Like milling any feature, surface textures can be machined through movement of the cutting tool. By adjusting toolpath parameters, different patterns can be cut into the material surface. The tool must be smaller than the smallest detail in the texture pattern. Typical texturing tools have ball end or tapered shapes in miniature sizes.
Some patterns like horizontal or vertical stripes are straightforward to program by controlling the stepover distance between passes. More complex textures require CAM programming software to convert an image file into toolpaths. Any image can be pixelated and machined into the surface using small stepovers and shallow passes.
EDM Texturing
Electrical discharge machining (EDM) is commonly used to burn very fine texture details into a surface, especially with graphite electrodes. Wire EDM can produce high resolution textures by closely spacing the wire runs. Sinker EDM can also texture surfaces through shaping the graphite electrode and burning the pattern into the workpiece.
Laser Texturing
Lasers can alter surface properties without physical contact with the part. By controlling the heat input and travel of the laser, various metallic and polymer surfaces can be textured. Laser texturing works through melting the material surface and altering its morphology. The resolution of patterns depends on laser precision and optics.
Media Blasting
Abrasive media blasting provides a simple way to add uniform surface texture. By impacting the part surface with grit particles, the resulting peening action work hardens and indents the material. Media like aluminum oxide, glass beads, walnut shells, and others can be used for controlled abrasion. Blasting produces matte, non-reflective finishes.
Chemical Texturing
Controlled chemical etching opens up another option for producing textures, especially on metals. Submerging parts in acids or bases will produce controlled pitting and grain formation. This works through localized material removal influenced by composition, crystal structure, masking, exposure time, and concentration of etchants.
Applications of CNC Texturing
CNC texturing has broad applications across many industries. Here are some examples:
- Vehicle interiors - Leather, wood, carbon fiber, and other simulations for dashboards, upholstery, trim pieces and more
- Consumer products - Rubberized grips on tools and sporting equipment, textured panels and buttons on electronics
- Medical - Textured additive manufacturing implants with bio-mimicking surface Porosity for bone ingrowth
- Robotics - Non-slip tread patterns on wheeled robots for traction
- Mold texturing - Patterned mold surfaces to impart textures to cast or molded parts
- Aerospace - Turbine blade coatings with texture to improve heat transfer
- Architecture - Custom decorative wood grain and stone finishes
- Art and sculpture - Intricate artistic textures for decorative metal, wood, and stone pieces
When designing parts for CNC machining, surface texture should not be overlooked. The versatility of CNC lends itself to replicating almost any texture, allowing customization for appealing aesthetics, branding, ergonomics, and functionality. CNC texturing enhances products by adding both visual and tactile interest compared to uniform machined finishes. With some craft in CAM programming and toolpath generation, CNC machines can mimic everything from a smooth leather grain to a rough cast iron surface. CNC Milling CNC Machining