Making Complex Mold Textures with CNC Milling(horizontal milling machine Amelia)
- source:YESCOM CNC Machining
Benefits of CNC Texturing
There are several key benefits to using CNC milling to create mold textures:
- Accuracy and Consistency - CNC can repeat the same texture pattern with extreme precision, ensuring consistency across all parts produced from the mold. Hand texturing methods can vary slightly between applications.
- Complexity - Intricate textures with tight tolerances, undercuts and high depths of cut can be machined via CNC. These complex geometries may be infeasible with manual engraving.
- Speed - CNC texturing is very rapid compared to hand engraving or EDM texturing, which reduces mold production time.
- Automation - Once the CNC toolpaths are programmed, texturing can be automated. This reduces labor costs compared to manual texturing techniques.
- Versatility - CNC allows flexibility in design. Textures can be modified by simply editing the toolpath program.
Types of Textures Possible with CNC Milling
A wide variety of surface textures can be produced using CNC end mills, ball mills and engraving tools. Here are some examples:
- Stippling - Dense fields of overlapping dots created with a ball end mill. Stipple patterns provide grip and hide mold defects.
- Line patterns - Straight lines or geometric shapes engraved via end mill. Different line widths and depths are possible.
- Wavy patterns - Undulating lines and grooves generated with an engraving tool. Mimics natural patterns like wood grain.
- Prismatic - Diamond shaped cavities produced by point milling. Creates reflective facets on molded parts.
- Sandblast effect - Irregular rough texture resembling a sandblast finish. Made by randomly stippling with an end mill.
- Artistic textures - CNC can mill pictorial artwork, logos, text and other graphic elements into a mold.
- Custom textures - For unique surface designs, custom bitmap images can be converted into CNC toolpaths.
Optimizing Textures for Manufacturability
There are some design considerations when developing custom CNC mold textures:
- Draft angles - Texture geometry should have proper draft angles for demolding plastic parts. Between 2-5 degrees is recommended.
- Smoothness - Gradual transitions between textured and non-textured areas prevents stress concentrations.
- Venting - Channels between textures allowing trapped air to escape from the mold. Prevents defects.
- Directionality - Long linear toolpaths can cause visible machining lines on parts. Radial or contour patterns are preferred.
- Tool selection - Carbide end mills and ball mills are typically used. Higher stepover values increase surface roughness.
- Depth - Shallow textures tend to fill back in with plastic. Etching at least 0.005-0.010” deep is advisable.
- Data density - Higher resolution STL files yield better definition on complex 3D geometries.
Programming Techniques for CNC Texturing
There are two main approaches to programming mold textures with CNC:
1. Direct milling of CAD models
- 3D CAD allows creating complex freeform surface designs.
- STL files are imported directly into CAM software.
- Toolpaths follow topology of CAD geometry.
- Gives high precision on curved surfaces.
- Can be time-intensive for programming.
2. Bitmap image engraving
- Raster design files are converted to G-code toolpaths.
- Each pixel in the raster image is etched into the surface.
- Flexible method for 2D patterns and artwork.
- Texture resolution limited by pixel size.
- Requires effective image isolation and thresholding.
Mold texturing via CNC milling provides limitless options for achieving unique surface finishes on molded and cast parts. By utilizing next-generation CAM software and high performance CNC machines, manufacturers can efficiently develop the textured molds demanded by today's product designers. CNC Milling CNC Machining