DAILY NEWS Jun 28, 2012 2:15 PM - 0 comments

Production of metal parts with NO hard tooling or press required

Precision photo chemical machining

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By: Hassan Nojoumi, president, Shimifrez Inc., Concord ON
2012-06-28

There’s an alternative method to produce precision parts today – PCM – Photo Chemical Machining also known as chemical blanking. With the fastest response time and lowest photo tooling costs available, PCM is suitable for both prototyping and manufacturing medium / large production quantities of metal parts. Instead of stamping or laser cutting, PCM produces highly accurate and identical components for small and large batches. Chemical etching has no effect on magnetic properties or deformation whether internal stresses or thermal resulting a burr free component.

Virtually all aerospace, medical and electronics devices contain a precision metal part. Shimifrez was established 30 years ago specifically to manufacture high precision chemically etched components. PCM provides precision custom-designed metal parts of any complexity and is very well suited to several applications covering almost every market segment including: medical and micro-electronic devices for which parts like EMI/RFI shielding, sieving and metal grids, nozzle heads and lead frames are required. In general this technology is particularly convenient on thicknesses between 0.01mm up to 1mm (0.0005” to 0.039”), when geometries are very complex, tolerances are very tight and time to prototyping and production is very short.

Process outline

The PCM manufacturing process begins by cleaning the metal and coating it with a light-sensitive resist. The coated sheet is then exposed to ultra violet light through the photo master from both sides, hardening the photo resist where exposure takes place. The unexposed areas are developed away, thereby removing the resist and leaving the metal bare where etching will occur. Etching solution is sprayed under pressure onto the top and bottom surfaces, accurately producing the component by removing the unwanted metal. The resist is then removed to leave burr- and stress free precision components.

Precision Photo Etching

Inexpensive and quickly-produced

Photo tools, used in photo-chemical machining, replace conventional steel tools and dies. Photo tools can be generated in a matter of hours from a customer-supplied CAD drawing or data file. Prototyping cycles can be reduced from weeks to days compared to hard tooling.

Flexible and fast

From initial tooling to finished parts, the entire photo etching cycle can be completed in days. Given a normal backlog, typical lead times for new parts are 2-3 weeks. Often, repeat orders can be processed more quickly. Prototypes orders may be done in several days or even hours.

Consistent tolerances

The photo tool is the foundation of accuracy. A photo tool is like a stencil. Its only working exposure is to light. So there is no tool wear that needs to be monitored. Dimensional tolerances are a function of the thickness of the material. Typically, dimensions can be held to +/- 10% of the thickness of the material.

Complexity made simple

PCM can produce complex parts that would be either impossible or impractical to produce by stamping or laser cutting. The etching process produces parts that are free of burrs and mechanical stress. Investment upfront is very low since the cost of photo tooling is an order or two less than in competing technologies.

Material properties unaffected

Chemical etching imparts no mechanical stresses on metal substrates. Where stamping, punching and die-cutting impart shearing deformation, and laser and water-jet cutting can leave ablative deformation, photo-chemical machining simply dissolves the unneeded metal, leaving a flat and burr-free part.

Materials

Virtually all materials can be etched, although some are etched more easily than others. Etching is basically rapid, controlled corrosion. Thus corrosion-resistant materials are difficult to etch and require extremely corrosive etchants. However, many materials such stainless steels, beryllium copper, nickel alloys and brass, used commonly in manufacturing, can be etched readily by using aqueous solutions comprising ferric chloride.

Precision products

PCM has provided a major, rapid-response service to supply components to the microelectronics, mechanical and electronic engineering industries over the past several decades. The demand has been for thin (< 1mm thick), complex, precision parts at an economic price. Leading examples can be items such as sieves and meshes, shims, washers, optical encoders and filters, EMI/RFI shielding enclosures (folded boxes), belts , sputtering and deposition masks to name a few.

Micro engineering products

PCM is now also used to fabricate components used in micro systems technology and micro electro mechanical systems (MEMS), medical diagnostic equipment and biomedical engineering applications such as body nozzle heads, X-ray light choppers and grids to IC leed frames for semi conductors, gimbals and micro channels are some names to declare.

Aesthetic products

In addition to the above, PCM can provide parts with intrinsic aesthetic value and is much used for the production of jewellery, signage or decorations and name plates. Very often, the etching process is combining with electroplating, anodising or painting processes to give additional colour and difference.

Three-dimensional products

Hand-foldable, etched bend channels are one of the unique features that Shimifrez can incorporate into a RFI/EMI shielding enclosure (board level shielding). Etched bend channels allows users to bend the sidewalls of a shield from a 2D flat part to a 3D finished shield, quickly and precisely. Bend channels can offer the designer several benefits such as the etched bend channels that are typically intended to create 90º right angle bends. They can also be used to create acute angle bends between 0º and 90º.

Or since the enclosure can be formed without the need for any traditional forming tooling, users can typically save hundreds of dollars in tooling and several days of delivery lead time for prototype and production needs. Finally the etched bend channels exhibit a zero inside radii when formed. Designers can save space on a board or the instrument by reducing the clearance necessary between the part and the components within it. This technique has been used successfully in many technical applications

Intricate, thin PCM parts

The resolution of etched parts depends on material thickness and thus the most intricate parts are fabricated from the thinnest materials. Photo etching has been the most general method for micro metal fabrication. This method needs a masking process for the selective removal of material. As this method is based on a chemical reaction, undercuts or overcuts can be generated depending on the density of the chemical material and the duration of etching.

Electroforming

Electroforming is a specialized process Shimifrez uses to produce precision metal parts that are 4 to 5 times more accurate in getting to tight tolerances than chemical etching. Electroforming is a metal forming process that grows metal through the electroplating process. The process creates an electroform piece through electro-deposition of a mandrel in a plating bath (nickel, gold or copper) onto a conductive patterned surface.

The electroformed part can be stripped off the mandrel, once the material is plated in the desired thickness. The electroforming process allows extreme precise duplication of the mandrel. This results in perfect process control, high quality production and very high repeatability. This makes electroforming perfect suitable for low cost production and high volumes.

The highly resolution of the conductive patterned substrate allows advanced geometries, tighter tolerances and higher edge definition. When requirements call for extreme tolerances, electroforming is very effective. Compared to other metal forming processes like laser cutting, photo etching or stamping.

www.shimifrez.com

Photos

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Caption: Shimifrez Fig 1
Shimifrez Fig 2
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Caption: Shimifrez Fig 2
Shimifrez Fig 3
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Caption: Shimifrez Fig 3

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