Reading Assignment (Note: Assignment from multiple sub-chapters)
- 19.3 Electrochemical Machining Processes
- 28.8 Free Abrasive Machining Processes
- 31.2 Oxygen Torch Cutting
Free Abrasive Erosion Machining
There are various forms of free abrasive machining
- Abrasives are mixed in a slurry, ultrasonic transducers provide the mechanical agitation to remove the material
- Waterjet cutting (WJC)
- Water at 60,000 psi and 3000 ft/s erode the material
- Abrasive Waterjet Cutting (AWC)
- Abrasives are added to a Waterjet to improve the efficiency
- Abrasive Jet Cutting (AJC)
- Abrasives are mixed in a high velocity air stream at 1000 ft/s
- A nearly limitless number of feature shapes—including round, square, and odd-shaped thru-holes, and cavities of varying depths, as well as OD-ID features—can be machined with high quality and consistency.
- Features ranging in size from 0.008″ up to several inches are possible in small workpieces, wafers, larger substrates, and material blanks.
- Aspect ratios as high as 25-to-1 are possible, depending on the material type and feature size. View the ultrasonic machining 3D animation to learn more about how ultrasonic machining works.
Ultrasonic machining is suitable for machining of hard, brittle materials including:
- CVD Silicon Carbide
- Technical Ceramics
Applications for ultrasonic machining include:
- Tight-tolerance round thru-holes for semiconductor processing equipment components
- Micromachined and micro-structured glass wafers for microelectromechanical systems (MEMS) applications
- High-aspect ratio thru-vias; 25-to-1 aspect ratios are possible in glass and advanced material
Advantages of ultrasonic machining include:
- The process is non-thermal, non-chemical, and non-electrical, leaving the chemical and physical properties of the workpiece unchanged. This low-stress process translates into high reliability for your critical applications.
- Multiple features can be machined at the wafer or substrate level simultaneously, and the process is scalable. Our process is often the highest quality and lowest cost solution.
- Ultrasonic machined features have vertical side walls, enabling you to preserve valuable space for your designs that translate into higher productivity.
- The process integrates well with semiconductor and MEMS processes. Machined features can be aligned to previously patterned, machined, or etched substrates.
Water Jet Machining
Waterjet cutting works by forcing a large volume of water through a small orifice in the nozzle. The constant volume of water traveling through a reduced cross sectional area causes the particles to rapidly accelerate. This accelerated stream leaving the nozzle impacts the material to be cut. The extreme pressure of the accelerated water particles contacts a small area of the work piece. In this small area the work piece develops small cracks due to stream impact. The waterjet washes away the material that “erodes” from the surface of the work piece. The crack caused by the waterjet impact is now exposed to the waterjet. The extreme pressure and impact of particles in the following stream cause the small crack to propagate until the material is cut through.
The two main types of water jet processes are: Waterjets and Abrasive Waterjets
- Versatile – cuts almost any material
- Tolerances – Tolerances tighter than +/- 0.005″ are achievable, especially in thinner materials such as 1″ stainless steel. However, high tolerances come with a price, sometimes up to 500% higher than if the same part had been specified with a tolerance of +/- 0.015″. By being more flexible with tolerances, prices will plummet as cutting speeds increase. Waterjet cutting has the ability to vary tolerances in different locations on a part, ensuring the best pricing and quality.
- Material Thickness – Materials ranging from 10″ stainless steel to 0.010″ acrylics can be cut by waterjet, making it a very versatile tool. Stacking of very thin materials to increase productivity is possible. Kerf ranges from 0.020″ to 0.050″.
- Burr Free cutting
- Common Line Cutting
- Cutting Speeds
- No Heat-Affected Zone (HAZ)
- For certain materials, cutting speed will be much faster with different processes
- Thick parts lose tolerance
- Tapered cutting
Thermal Separating Processes
Laser-Beam Cutting (LBC)
LBC usually uses an assist gas to clear the molten metal out of the kerf and minimize HAZ. Sometime the assist gas combusts with the material.
- Oxygen is used for mild steel. It combines with the Iron and combusts.
- Nitrogen is used with stainless steel and aluminum.
- Argon is used with titanium.
Clean, accurate, square edges are possible.
Kerf as small as .25mm
Types of Lasers
- CO2 & YAG (yttrium aluminium garnet)
- Pulsed – For thin materials. Enables tight corners.
- Continuous – Fastest cutting mode
Can cut nonmetals, including some composites. When cutting composites, uniform thermal characteristics is preferred.
Available on hybrid machines such as CNC Turret Punch Presses
Plasma Arc Cutting (PAC)
Uses superheated stream of electrically ionized gas to melt and remove material.
Can be used on almost any conductive material.
Used to remove burrs and fins by exposing the workpiece to hot corrosive gases for a short period of time
Thermal deburring can remove burrs or fins from almost any material but is especially effective with materials of low thermal conductivity