By: Thomas C. Hansen, President, R&D Products, Inc.

The tangential laser-centrifuge process is ideal for manufacturing small and very detailed parts, such as microchannel cooling devices used as heat sinks for CPUs typically performed in vacuum or clean room environments. Inserts for injection molding dies with tiny channels can also benefit from the tangential machine process by focusing the laser on very small areas to remove metal. Conversely, conventional machining uses very small bits that can easily break while removing material. This technology allows for making deep holes without debris precipitation on the sides of the hole that ablation machining produces.

Tangential machining removes material and can deposit material, such as in 3D printing. Using a spinning mass of material with a pulsed laser, microdroplets directed in a straight line can be deposited on a substrate to build up material layers. Through precise control of the substrate position, complex parts can be formed. Since the laser can pulse in femtoseconds, the material stream can be deposited faster than current 3D printer technology.

Tangential Systems background

Lasers have been used for both cutting and machining. Light from the laser heats the workpiece material, which must be removed. For laser cutting, the molten material, dross, is usually blown from the cut with a jet of air or gas and can spray on surfaces that then require cleaning. In laser machining, the laser pulses are short and powerful. The intense laser light ablates material, which ejects as a vapor plume that condenses and precipitates on surfaces. The vapor can also create byproducts that can be noxious. Thus, removing the heated debris requires additional technologies to mitigate.

The Tangential System (Patent US7933680B2) provides significant advantages by attaching the workpiece to a centrifuge. The laser-heated material is removed instantly by centrifugal force. The released material can fuse to a substrate to form a separate object (using the released material for 3D printing).

Advantages of the Tangential System include:

• High-speed material removal. The Tangential System removes material at more than twice the rate compared to typical high speed CNC machining.
• No tooling. Instead, the material is energized and released by a laser, eliminating the time to change tools.
• Materials to be formed. Lasers can inherently process a vast multitude of materials, including plastics, metals, composites, glass, and minerals. The type of laser can be matched with the material to achieve good energy absorption.
• Shapes and setups. Virtually any shape can be formed using this system as long as the working surface is visible to the laser beam.
• Machine mass and energy. In the Tangential System, all that touches the workpiece are laser beams. Thus, the entire system can be made of lightweight materials.
• Minimal heat affected zone. The centrifuge instantly removes all hot material from the surface. Therefore, heat in the debris has no time to warm the surrounding work.
• Precision. Debris is instantly removed so the new shape can be measured virtually and concurrently with material removal.
• Efficiency. The laser only needs to provide enough energy to release the material, which lowers the energy requirement of the laser. Additionally, some of the energy used to rotate the centrifuge can be retrieved through regenerative braking. The total energy required for material removal is minimized. As a further benefit, the removed material can be concurrently used to manufacture additional forms.
• Cleanliness. The debris is removed from the workpiece in a specific path. The debris material can then be used to form another object or stored for later use. The minimal heat used minimizes noxious gases and byproducts.
• Concurrent subtractive and additive manufacturing. The material released by the laser can be directed to add the hot material to a separate structure.

How Tangential System manufacturing machines work

The Tangential System can perform material removal and addition concurrently. Material removal is performed by attaching a solid workpiece to a centrifuge. When the centrifuge turns, centrifugal force acts on the workpiece and creates radial acceleration, which can be many times the acceleration of gravity. As the centrifuge spins, a laser beam focused on the workpiece adds energy to the bonds that hold the material together. As the bonds are weakened, the heated material is released and travels in a tangential path away from the workpiece. The released material is typically hot and travels at high speed. A substrate placed in the tangential path acts as a target for this material. With each turn of the centrifuge, additional material is added to the substrate in a directed and controlled manner. As a result, formed objects can be created concurrently — first, from the workpiece on the centrifuge as the material is removed and then on the substrate as the material is deposited.

The following image shows the basic components of the machine.

The next image shows the tangential manufacturing process in four steps.

This final image shows configurations that can be made from the basic design.

Applications for Tangential Systems

This manufacturing technique can be used in many applications because of its ability to process any type of solid in an accurate, precise, fast, and efficient manner. The Tangential System provides the technology for material removal rates many times that of traditional technology. This energy-efficient system can effectively process many types of materials and does not require investments in cutting tools or heavy machinery. In conventional machining and laser ablation machining, vibration and the explosive removal of material induce stresses in the workpiece material, changing the material properties and the heat-affected zone. The Tangential System does not have these side effects and can produce detailed features in fragile materials that would otherwise be impossible to manufacture. Advanced additive manufacturing can also be achieved where composite materials are formed in product construction.

Additionally, there is a need for both subtractive and additive manufacturing in space applications. A machine for these tasks must have low mass to enter orbit, and the Tangential System meets such requirements. Further, it provides the flexibility to process a variety of materials and construct composite structures while using minimal energy.

R&D Products, Inc.
rdproducts.com