Volumes of production
Dry-bag presses are typically automated from the powder-filling to the part-removal stage, but this is a low-volume production method used to produce parts in their thousands rather than tens of thousands.
Unit price vs. capital investment
Tooling can be expensive for large production runs, although existing tooling can be customized for short-batch production.
Speed
This depends on the particular process—for example, in the wet-bag method the rubber mold is removed from the liquid after each cycle and refilled. The dry-bag method, however, has the bag as an integral part of the mold so it does not need to be removed, but is reused to form multiple parts.
Surface
Depends on the component. Simple forms will not need any further finishing.
Types/complexity of shape
The wet and dry methods are suited to different complexities of shapes. The wetbag method is used for complex components because of the flexible mold, which allows for easy removal of the component. It allows complex shapes to be produced, including undercuts and re-entrant angles such as collars and threads. The dry-bag presses are suited to simple shapes that can be easily removed from the molds.
Scale
The wet-bag method is suited to large shapes, while the dry-bag presses are suited to smaller components.
Tolerances
±1/100 inch or 2 percent, whichever is greater.
Relevant materials
Advanced ceramics and other refractory materials, titanium alloys, and tool steels.
Typical products
The process is suited to products that are used in harsh, aggressive environments, such as cutting tools, advanced ceramic components including carbides, and refractory components. Other applications for pressed ceramics and metals include automotive cylinder-liners for aircraft and marine gas turbine components, corrosion-resistant components for petrochemical equipment and nuclear reactors, and medical implants. However, the most common product that is made by CIP is the spark plug.
Similar methods
Hot isostatic pressing (HIP) (p.170). It is also possible to use injection molding for ceramics.
Sustainability issues
Cold isostatic pressing consumes far less energy than its hot-forming counterpart because heat is not used in either the wet or the dry method. Its high productivity level is energy efficient and it requires minimal maintenance and replacement parts. Pressure and decompression help to decrease the forming of internal stresses and cracks, thus minimizing wastage through faulty parts.
Further information
www.dynacer.com
www.mpif.org
Compression Molding
Product |
electrical plug |
Materials |
phenol-formaldehyde plastic, also known as phenolic or Bakelite |
A ubiquitous product that is an invaluable part of everyday life, but the process that lies behind it is frequently undervalued.
This process can be pressed into service for forming several different materials. On the one hand, it is used for producing ceramics, and on the other, it can be used to mold thermoset plastics (it was the original method for forming Bakelite), as well as fiber-based plastic composites.
To understand the basic principle of compression molding, just think of children jamming their fists into lumps of dough to create imprints.
The elaborated industrial process uses granules as a starting point rather than solid material, and heated molds to replace the fist. The two-part male and female molds can be used to process anything from thick, solid shapes to thin-walled containers.
– Ideal for forming thermoset plastics.
– Ideal for producing parts that require large, thick-walled, solid sections.
– Allows for variable sections and wall thicknesses.
– Limited in terms of complexity of shapes, but good for producing flat shapes such as dinner plates.