Diamond turning technology is an optical parts processing technology promoted and applied by American scientific research institutions since the 1980s. The products created by this technology have excellent surface quality and high accuracy, So, many optical components in the optical system rely on diamond turning to create high-quality ultra-precision parts. However, Do you know how diamond turning works? Today, in this Article, we will share a complete guide with you about this technology.
What Is Diamond Turning?
Diamond turning, also referred to as single point diamond turning(SPDT), is a high-precision turning process performed on a CNC lathe, Using a diamond-tipped cutting tool to remove the material from Workpieces. The diamond-tipped cutting tool has a single point contact with the workpiece due to its small radius, this is where single-point diamond turning comes from.
How does Diamond Turning Tool Work?
To achieve diamond turning, a Precision Diamond Lathe Tool will be used. it incorporates natural diamonds at the cutting tips or edges which have extreme hardness and sharpness. The radius of the diamond cutting edge can generally reach 100nm, and some can even reach 10-30nm. The diamond cutting tip passes through the workpiece at high speed, grinding the material to achieve a polished effect and precise dimensions, this is different from the traditional metal cutting tools that rely on the material’s shear strength.
Diamond Turning Machine
A Single point diamond ultra-precision lathe is the first condition to achieve ultra-precision cutting, and the overall accuracy for positioning a tool can achieve 100 nanometers. This is affected by the machine bed, spindle guide rail, control system, and other components. the diamond turning machines in the market cover from 2-axis to 5-axis. With a 5-axis diamond turning machine, manufacturers can have more flexibility to produce freeform surfaces which may not be achievable using a 2-axis machine. below is a picture to show the axis of a 5-axis machine.
Steps for the Diamond Turning Process
The diamond turning process is similar to the traditional turning process but uses a diamond-tipped cutting tool for the final stage of fine turning.
Step 1: Prepare the CAD model
you can get the 2D or 3D CAD model from your clients or you can create the CAD model with CAD software.
Step 2: Programming
Use CAM(Computer Aided Manufacturing) software to translate CAD models into G-codes which can be read by the CNC machine. the program will contain instructions for the machine such as the cutting path, tool speed, and cutting depth.
Step 3: Set up the machine
Fix the diamond tool and workpiece properly. use a gauge to make sure the workpiece is placed at the center of the spindle to ensure that the rotation axis is the same as the spindle.
Step 4: Start rough turning
Let the machine run according to the CNC program, and Use a traditional cutting tool to cut the workpiece roughly to get the shape of the part. leave 0.5mm thickness for the next fine turning step.
Step 5: Start fine turning
After the rough turning finish, change the cutter to a proper diamond cutting tool, and continue to run the program until the process ends.
Step 6: Quality check
Once the process is complete, take off the part from the spindle. then use a standard interferometer to measure the surface shape and an interferometric microscope to test the roughness of the surface.
if the Quality of the part is not ok, then adjust the program and repeat the steps to machining again until all the dimensions are ok.
Tips for Diamond Turning
- 1. Use a cooling liquid to cool the contact point when cutting metal. if cutting plastic, then use air to avoid damage to the plastic part.
- 2. Control the room temperature at 20°C±0.5°C, and control the part temperature at 20°C±0.05°C by spraying constant temperature liquid.
- 3. Make sure the diamond turning machine is far from vibration and noise effects which could lead to a bad result.
- 4. Make sure the working room achieves at least the 10000 level of cleanliness to reduce the dust effect.
Diamond Turning Methods
Traditional turning
Diamond turning can work the same as a traditional turning process to produce rotationally symmetric parts with a diamond cutting tool but with higher accuracy.
Off-axis turning
Off-axis turning is a method where a workpiece is asymmetrically mounted to the spindle. Diamond turning can work off-axis to produce optic parts whose rotational center is not coincident with the center of the part.
Fly-cutting
Sometimes, Diamond turning lather can allow reversing the position of the workpiece and tool to fly-cutting flat or elliptical surfaces. The tool is mounted to the spindle and the workpiece is mounted to the slide.
Freeform machining
A 5-axis Diamond turning lathe can create freeform surfaces with no rotational axis through the freeform machining process. The milling process usually does this kind of surface, however, diamond turning can create parts with ultra-precision freeform surfaces.
Benefits of Diamond Turning
High Precision
Diamond turning can make parts with ultra-precision, and Surface roughness can reach 4 nm RMS.
Material Versatility
A wide range of materials including metals, plastics, and ceramics can be machined by diamond turning. here are common materials for the diamond turning process:
- Metals: copper, aluminum, nickel, and brass
- plastics: like Acrylic(PMMA), polystyrene (PS), and optical polyester (OKP4).
- Infrared materials like silicon and chalcogenide glass.
Cost-Effective
Diamond turning optic parts can lead to cost savings without tooling needs when prototyping in small batches.
Efficiency and Speed
Diamond turning can make the optic components in weeks to save time make the tooling.
Applications of single point diamond turning
Infrared optical aspherical mirror
Diamond turning technology can be applied to the mass production of the aspherical mirror of infrared optical materials (germanium, zinc sulfide, zinc selenide, lithium fluoride, barium fluoride, calcium fluoride), which can achieve surface shape accuracy less than 0.2μm and roughness less than 0.02μm.
Optical lens mold core
Diamond turning can be used to manufacture aspherical metal molds and die cores, which can be used to produce optical aspherical lenses in digital cameras.
Off-axis aspherical mirror
Off-axis aspherical mirror is a kind of optical mirror whose optical axis and mechanical axis do not coincide. The off-axis aspherical lens can be produced by off-axis diamond turning technology.
Freeform mirror
Aspherical copper and aluminum mirrors turned by diamond lathes will be widely used in imaging, display, laser coupling, and other photoelectric systems.
Conclusion:
Diamond turning is great for creating various kinds of optic components. Kusla, As a diamond turning service supplier, offers customed nanoscale optic parts including flat, spherical, aspheric, freeform, and other core optical components. Welcome to contact us if you have any questions about this process or want custom optic parts.
FAQ
Can diamond turning work on Polycarbonate material?
Yes, however, it is not a good choice due to polycarbonate is soft, and there will be burrs that need a secondary polishing process.
Does diamond turning need a secondary polishing process?
No, Diamond turning can create a mirror-like surface with a surface roughness level of less than 10nm.
