nontrad Machining & Thermal Cutting Processes

nontrad machining

processes that remove excess material by techniques involving mechanical, thermal, elec., or chem energy (or combinations of these energies). Do not use a sharp cutting tool in the conventional sense

Importance of Nontrad. Process

Need to machine hard and non-metals with special properties that make them difficult or impossible to machine by conventional methods

Mechanical nontrad. process

mech. erosion of work material by a high velocity stream of abrasives/fluid (or both)

Electrochemical nontrad process

electrochem energy to remove material (reverse of electroplating)

thermal nontrad. process

thermal energy applied to small portion of work surface causing that portion to be fuse and/or vaporized

Ultrasonic Machining (USM)

abrasive particles contained in a slurry are driven at high velocity against work by a tool vibrating at low amplitude and high frequency (20kHz). Tool oscillation is perpendicular to work surface

USM Applications

- Hard, brittle work materials such as ceramics, glass, and carbides

- Also successful on certain metals, such as stainless steel and titanium

- Shapes include non-round holes, holes along a curved axis

- "Coining operations" - pattern on tool is imparted to a flat work surface

Would USM be effective for ductile materials?

Bad, it is intended to microchip small particles, using micro-cracks to remove ductile material tends to deform rather than break.

Does material have to be electrically conductive for USM appl.?

No

Benefits of USM?

a. capable of machining hard / non-conductive materials

Downsides of USM?

Low material removal rate, and tool wear

Water Jet Cutting (WJC) Process

uses high pressure, high velocity stream of water directed at work surface for cutting.

Usually automated by CNC (comp numerical control) / indust. robots to manipulate nozzle along desired trajectory

Water Jet Cutting Use

Used to cut narrow slits in flat stock such as plastic, composites, floor tile, carpet leather and cardboard. (not suitable for brittle material (glass)

water jet cutting (WJC) advantages

no crushing or thermal damage of work surface, min material loss, no environmental pollution, ease of automation

Abrasive Water Jet Cutting (AJWJC)

When WJC is used on metals/hard materials abrasive particles usually are added to jet stream. Such as aluminum oxide, silicon dioxide, and garnet (silcate mineral).

Abrasive Jet Machining (AJM)

high velocity gas stream containing small abrasive particles

abrasive jet machining notes

normally used as a finishing / deburring process rather than cutting process

Abrasive Flow Machining notes

Abrasive particle mixed in viscous polymer/medium are forced to flow through and around part surfaces and edges

what must work material be for electrochemical machining processes?

must be a conductor

Electrochemical machining (ECM)

Material removal by anodic dissolution, using electrode (the tool) in close proximity to work but separated by a rapidly flowing electrolyte

ECM Operation

material is depleted from anode workpiece (positive pole) and transported to cathode tool (negative pole) in an electrolyte bath

what shape does the tool have for ECM ?

tool has complementary / negative shape, and must allow for the work gap

Electrolyte in ECM:

flows rapidly between two poles to carry off depleted material so it does not plate onto cathode

ECM Applications

die sinking

multiple hole drilling

holes that are not round

deburring

Advantages of ECM

little or no tool wear in ECM

surface finishes achieved by ECM are very good

no residual stresses or thermal damage remain on the part surface

Disadvantages of ECM

high specific energy consumption is required for the process

high capital investment is required for the equipment

How can we remove burr inside many holes?

Electrochemical Deburring ECD

Electrochemical Deburring

Adaptation of ECM to remove burrs or sharp corners or on holes in metal parts produced by conventional through-hole drilling

Electrochemical Grinding (ECG)

form of ECM in which grinding wheel with conductive bond material augments anodic dissolution of metal part surface

Applications of Electrochemical Grinding (ECG)

sharpening of carbide tools

grinding of surgical needles and other thin-wall tubes and fragile parts

Advantages of Electrochemical Grinding

Deplating responsible for 95% of metal removal

Because machining is mostly by electrochem. action, grinding wheel wear is extremely low