Manufacturing Processes

Process Description
Electro-Discharge Machining (EDM) is machining with sparks. The work-piece is held in a jig submerged in a dielectric fluid such as kerosene. A power supply generates rapid electric pulses that create a discharge between the work piece and an electrode (a continuous wire or a shaped graphite form) at the point at which the two are closest. The discharge creates a plasma causing the melting, and probably the vaporisation, of a minute bite of material, slowly eating into the work piece; the debris is swept away by the dielectric fluid. EDM is remarkable for its ability to shape difficult materials (provided they are conductors) and do so with great precision.
Any electrical conductive material can be machined irrespective of hardness.
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Here's a useful table of tolerance and surface roughness achievable with cutting and machining process (collectively termed "material removal processes"

This information has been collated personally by myself from a variety of sources. If you have any suggestions of processes to include in this table please leave a comment and they will be added.
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I first encountered “Rapid Prototyping” or “3D Printing” back in the late 1980's, when I contracted with a Canadian company that offered the service based on a process that used a laser to cure specific regions of a soup of liquid plastic. Very impressive, and so was the price-several thousand dollars to produce a prototype that, in production, should have cost less than a dollar. Most of the costs were the result of converting the 2D mechanical drawings (about the only option back in those days, unless you happened to work for a major aerospace or automotive company) to machine code for controlling the laser.
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Injection molding is one of the most common manufacturing methods to produce thin-wall engineered parts. Development of molds that produce high quality parts is a talent that develops with experience. Due to the time and effort required to develop a good set of tooling, it is not unusual for manufacturers to seek out injection molding machines that will be compatible with their molds, rather than trying to redesign molds to work on specific machines.

Design checklist
As designers of injection molded products you are probably well aware of design best practice. What you may not appreciate is the important contribution a well designed mould tool can make to the new product development process. The wrong decisions taken at the critical early stage of a project will add cost and time to mould tool design, manufacture and maintenance, put pressure on product launch dates, and, of course, adversely affect product manufacture and in-use performance.
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There are limits to the dimensions and tolerances that can be machined along the plane of the metal sheet, since etchants used in the photochemical machining process concurrently etch metals laterally and vertically through the thickness (T) of the sheet.

Because the metal at the surface of a sheet is exposed to etchant longer than the metal at the center of the sheet, the surface of a part etches laterally more than metal at the center. The following planar dimensions are related directly to the thickness of that sheet.

Hole Size/ Slot Width
The smallest hole diameter (D) or slot width that can be produced by the Fotofab process, as a general rule, is 1.2 times the metal thickness. The minimum practical diameter or slot width that can be machined is .005 inch ( 0.13 mm).

Bar Widths
Spacing of metal between the holes and/or slots in a design is not an issue using photochemical machining. However, when a part contains holes and/or slots that are spaced closely together, such as with a fine resolution screen or encoder disc, the width of the metal that remains between them is referred to as the bar width (W).
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Process description
A coherent beam of monochromatic light is focused on the workpiece causing material removal by vaporisation. Machines are generally CAD/CAM compatible, with 3-axis and 5-axis machines being generally available.
Profile creation of sheet metal parts is the most common applications, but it is also possible to drill holes and create blind features in many different types of material.
Gas-assisted laser beam machining is common. The gas type can be oxygen, inert gas, or air, depending on material type and quality requirements.
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Process Description:
Electrical Discharge Wire Cutting (EDWC) involves a continuously spooling conductive wire (the most widely used is brass). A power supply generates rapid electric pulses that create a discharge between the workpiece and electrode (the wire). The discharge causes the melting, and probably the vaporisation, of a minute piece of material, slowly eating into the work piece. Any electrical conductive material can be machined irrespective of hardness. The position of the wire with respect to the workpiece is controlled in the x and y planes usually by CNC. On some machines the wire can be tilted to create tapered parts. An advantage of this process is that no mechanical stresses are created in the workpiece because the wire does not make contact with it.
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