CNC Turning and Milling Differences and How to Choose

CNC Turning and CNC Milling Locations Nationwide

CNC Turning and Milling Specifications and Tolerances / /

Below are the specs and tolerances specific to CNC turning and milling:

• Metal materials +/- 0.005
• Plastic materials +/- 0.008
• Pre-merger CNC machinery chart:

HaasTL 2 Lathe216 x 48HaasSuper Mini Mill116 x 12 x 10

While designing for a CNC turning or CNC milling job, there are several important factors to consider. The desired part’s geometry will affect how it will be positioned in the CNC machine and the amount of time required for set up. If a part is manually repositioned, the accuracy and cost of the project will be affected. The tool used to cut the part may vibrate during operation, resulting in loose tolerances. The workpiece may vibrate during machining due to temperatures and cutting forces, resulting in deformities. The geometry of the tools used during the manufacturing process will also affect how a part is shaped. Additionally, if the cutting tool cannot reach a surface, it cannot be machined, limiting the ability to create hidden internal geometries. For parts with highly complex shapes and internal chambers, the experts at Fathom recommend Direct Metal Laser Sintering (DMLS).

CNC Turning and Milling Materials List / /

Advantages of CNC Turning / /

The CNC turning process offers many advantages. Compared to manufacturing processes operated by hand, CNC turning offers increased production speed, safer operations, higher efficiency, higher quality results, accuracy, and increased cost-effectiveness. For projects that require a quick turnaround, increased quality, and a cylindrical shape, CNC turning is a good match.

Advantages of CNC Milling / /

CNC milling is a versatile manufacturing method with multiple benefits. Compared to manual manufacturing processes, CNC milling offers an increase in precision, lower labor costs, and higher replicability. CNC milling can be used with various materials, including metal and plastic, and may be used as a secondary finishing process.

CNC Finishing Processes / /

Finishing the surface of a part is the last step required during CNC machining. Finishing is used to erase flaws, create added resistance and strength, improve the look of a part, and more. Here are some common finishes for CNC machined parts.

• Bead Blasting: The bead blasting process adds a satin or matte finish to a CNC part. The matte finish is accomplished by using a pressurized air gun to shoot glass beads at a part.
• Powder Coating: After a part has been powder coated, it has a thin protective layer that adds strength and wear-resistance. During the powder coating process, the part is first primed using a chromating or phosphating coat. Next, the part receives a dry powder coating from an electrostatic spray gun. Lastly, the part is cured in an oven.
• Anodizing: After a CNC part has been anodized, it has an oxide layer that increases its density, thickness, and durability. Anodization also makes a part electrically non-conductive. During the anodizing process, the part is placed into an acid electrolyte bath which serves as an anode. A cathode is added to the part, and an electrical current is passed through the acid. Oxygen ions from the electrolyte and atoms from the alloy are combined along the surface of the part.
• Surface Grinding: The surface grinding process is used when a specific size or precision finish is required. Surface grinding removes material by using a high-speed abrasive wheel as a cutting tool.
• Polishing: The polishing technique can improve the dimensions and accuracy of a part while producing a mirror gloss finish. Polishing tools and abrasive materials are used to achieve a smooth surface.
• Passivate: After a CNC machined part has completed the passivation process, its corrosion resistance is improved. Passivation may include spray application, circulation in a chemical solution, gel application, or tank immersion.
• Chemfilm: Chemfilm finishing is a chemical conversion coat that adds corrosion resistance to aluminum substrates, acting as a base for organic coatings. The part is dipped, brushed, or sprayed with the chemfilm layer.
• Vacuum Metallization: The vacuum metallization process results in a mirror-like or decorative uniform finish while also improving thermal, air, light, or water barrier properties. In the vacuum metallization process, the part is placed inside a closed chamber where a metal vapor adheres and coats the part.
• Silkscreen: Screen printing is used to transfer a design or logo to a part. When a part is silk-screened, a mesh is used to apply ink onto the surface, but only to permeable areas that are not covered by a blocking stencil.
• Plating: Plating adds corrosion and abrasion resistance, conductivity, and reflectivity to parts. In the course of electroplating, the part is submerged into an electrolyte bath with the material that will be used for the metal coating. An electrical charge causes the material to transfer to the part, resulting in a uniform metal coating.
• Tumbled: Tumbling or ultrasonic polishing removes any sharp points or edges from a machined part. During the tumbling process, the part is placed inside a barrel along with media, water, and detergent. The barrel tumbles at different speeds depending on the desired finish.
• Painting: Painting may be used to add color, varnish, or ink to a part. Painting methods may include spray painting which uses a device to coat the part.
• As-Milled: As-milled or as-machined products do not require a secondary process. They will still have visible blemishes and may have a rough surface.

Examples of CNC Turned Parts / /

A variety of parts can be used using the CNC turning manufacturing methods, including:

• Valve stems
• Valve bodies
• Spacers
• Shafts
• Shanks
• Pivot rods
• Nozzles
• Pins
• Housings
• Handles
• Driveshafts
• Bolts
• Dowels
• Fasteners

Examples of CNC Milled Parts / /

Many parts can be made using the CNC milling method, including:

• Mold cavities
• Mold bases
• Valves
• Engine houses
• Bone fracture plates
• Shafts
• Reflectors
• Adapters
• Furniture
• Medical parts