Standard & Custom

Press Leaders

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Presses are ubiquitous in both manufacturing and laboratory environments; finding use in a range of processes, including compression molding, transfer molding and vacuum press applications. In this article we take a look at the different uses of presses in research and manufacturing, and explore some of the different industries in which they are used.

Machine presses – more commonly known as just “presses” – are widespread in virtually every niche of manufacturing. The methodologies associated with presses vary almost as much as their applications, but all share one thing in common: presses allow us to manufacture components via the application of pressure. Presses can be used to form any number of materials – primarily rubber and plastics – in processes such as molding, overmolding, laminating and extrusion. Thanks to their unprecedented versatility as a manufacturing tool, presses are responsible for the high-throughput production of a huge number and variety of common items including oil seals, pc boards, aerospace parts, molded cable ends and test plaques. As well as producing these finished products in a single process, presses are commonly used to perform crucial steps in multi-stage in manufacturing processes; such as coil encapsulation.

Despite being a true workhorse of manufacturing and industry, customized precision hydraulic and pneumatic presses are frequently found in the laboratory too. Production of the lead frames used to mount microchips, for example, requires the use of presses with sub-micron accuracy. Heated presses have been used to produce next-generation aerospace components from carbon-fiber-reinforced plastics.1 Presses have even found applications in tissue engineering, where they have provided an effective way of producing cellular scaffolds on which to grow tissues for transplantation.2

Presses are typically either benchtop or floor standing devices, and can be built to a huge range of specifications of force and precision. While standard presses meet the needs of most manufacturing applications, more demanding use cases often require custom press solution capable of applying extremely high forces or moving in extremely precise increments.

Let’s take a look at three of the most common types of processes which are performed by presses: compression molding, transfer molding, and vacuum press applications.

Compression Molding
One of the simplest molding techniques, compression molding is the name given to the process whereby a bulk material is placed in a mold cavity, and compressed so that it fills the mold in a press. Depending on the material, the workpiece can be preheated before pressing, or heated during pressing using heated platens. Compression molding confers a number of advantages: not least it is one of the cheapest molding processes to carry out, and can be used to produce relatively large and fairly intricate components. Compression molding can be used to mold fiberglass, plastics and metals, and is typically used to produce flat or moderately curved components.

Transfer Molding
Transfer molding, or “compression transfer molding”, is a process where material is forced into a mold via the application of pressure by a press. Forcing bulk material into the mold in this manner can result in higher dimensional tolerances, but requires higher pressures than compression molding.3 The requirement for the material to flow into the mold means that transfer molding is typically used for the production of components from resins, to form thermoset products. Transfer molding is versatile enough for applications in aerospace, construction, electronics and sports equipment manufacture.4

Vacuum Press Applications
The term “vacuum press” refers to any machine press where the workpiece is held in an evacuated environment during pressing. Carrying out pressing in a vacuum can yield faster production, higher quality results and reduced waste material. The application of a vacuum can remove heated gases and trapped air from the equation, thus reducing the type of defects that can occur with compression or transfer molding. For this reason, vacuum presses are typically used for manufacturing products where a high level of precision is required.

Hydraulic and Pneumatic Presses for Manufacturing and Laboratory Work
Wabash MPI is a manufacturer and global distributor of standard and custom pneumatic and hydraulic presses for the aerospace, medical, automotive, energy industries among many others. Wabash MPI produce a full range of presses to suit any application in manufacturing, including presses for compression molding, transfer molding and vacuum press applications. A range of accessories can augment the capabilities of their presses, including large or heated platens and vacuum shrouds. Wabash MPI also provides a range of field services including new equipment start-up, preventative maintenance and calibration of equipment. Their sister company Carver produces precision hydraulic and pneumatic presses exclusively for the laboratory. Having been producing presses for over 100 years, their range of benchtop and floor-standing presses are designed with precision at the forefront. They are also world-leaders in the design and production of custom presses and accessories to suit the most demanding applications.

References and Further Reading: 1. Wulfsberg, J. et al. Combination of carbon fibre sheet moulding compound and prepreg compression moulding in aerospace industry. in Procedia Engineering 81, 1601–1607 (Elsevier Ltd, 2014). 2. Hou, Q., Grijpma, D. W. & Feijen, J. Porous polymeric structures for tissue engineering prepared by a coagulation, compression moulding and salt leaching technique. Biomaterials 24, 1937–1947 (2003). 3. Ornaghi, H. L., Bolner, A. S., Fiorio, R., Zattera, A. J. & Amico, S. C. Mechanical and dynamic mechanical analysis of hybrid composites molded by resin transfer molding. J. Appl. Polym. Sci. 118, 887–896 (2010). 4. Resin Transfer Moulding - K. Potter - Google Books. Available here. (Accessed: 1st November 2019)