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Fabrication Processes

Forming

Economical forming is determined by volume and tolerances of the final part. Dry pressing to size is the most economical forming method for volumes of 300 pieces or more, which help to justify the initial expense of tooling designed specifically for each part. Injection molding is used for complex parts where dry pressing isn't possible. Isostatic pressing is suited to low volumes and prototype items. Slip casting makes thin-walled uniform shapes possible for low- and medium-volume production, while extrusion is used for high-volume, constant cross-section long-length tubing and rod. 

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Pre-Sinter (Green) Machining

Machining in the pre-sintered, or green, state is often desirable because it allows manufacturing of finished shapes without expensive grinding of sintered material. Green machining is accomplished using conventional CNC lathes and mills. Stock removal can be accomplished 15 times faster in the green state than in the sintered state. Green machining provides parts to tolerances of 0.5 percent to 1.0 percent of their final dimensions. Typical green machined surface finishes range around 32 to 64 microinches.

Grinding/Finishing

Final grinding is done with diamond wheels and costs increase substantially as blueprint tolerances tighten. Part geometry and concentricity/parallelism also affect costs. For example, to improve outside diameter tolerances from +.020" to +.010" can increase the price by 2X. To improve from +.020" to +.002" can increase the price by 4X. Saint-Gobain has the capability to grind to close tolerances on most shapes (.0005"). Typical ground parts hold finishes of 16 or better microinches. When surface finishes are critical to improve friction and wear performance, finishing operations such as lapping and honing can improve surfaces up to 4 microinches. Lapping and polishing can provide surface flatnesses to one helium light band.

Quality Assurance

Our company mission is to maintain the highest level of quality for our customers. Saint-Gobain has state-of-the-art nondestructive evaluation equipment for final quality inspections of internal structures. These include bulk and surface wave ultrasonics, fluorescent dye penetrant, radiography, acoustic emission and photomicrography.