Compression Molding
Compression molding is the renovation technique most commonly used for SMC and BMC molding as the big presses can put up large platen sizes, making it ideal for large components ranging from train carriage panels to bath tubs. In high volume processes such as producing parts for automotive applications, SMC charges are normally prepared using an automatic peeling and slitting machine. The SMC is automatically peeled off its carrier film and cut into the appropriate pieces, which can then be stacked and arranged in the predetermined charge pattern. The weight of the charge is checked to ensure that it is within set-up tolerances. Where low to medium volume applications apply, like those found in the electrical industry, then these operations are generally done manually.
The charge is placed in the mold in a set position determined by the features of the mold, scribe lines marked in the tool or laser lines, to ensure a consistent charge placement. For high volume applications, robots are used to accurately place the charge. Handling and carrying of the SMC is normally by needle gripper techniques.
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Generally, the mold is a matched set of forged steel dies that are plated or surface treated to reduce wear. The mold is heated (electric or oil) to 130-170°C. The mold is closed with a fast approach speed followed by a controlled final closure speed. Variable pressure (50-100 bar) profiles can be used during the mold closure phase. Thermoset compounds have the property to flow. Under heat and pressure it is transformed from its leather-like quality to a very low-viscosity liquid. The compound flows to fill the mold cavity. A shear edge zone in the perimeter of the cavity enables air to pass through. The small amount of material that escapes through the sheer edge results in flash. The cure time varies from 30-150 seconds, depending primarily on the thickness of the part and material formulation.
The part is de-molded by internal ejector pins. Larger parts can be handled using manipulators. Flash (normally 0.05 – 0.15mm) is normally removed by hand using abrasive paper although in large series production, robots normally do this job for speed and to ensure consistency in critical tolerances.
The molded part then transfers to a machining center where holes and apertures are cut out or drilled. Often this operation utilizes CNC (computer numerical control) equipment that reads G-code instructions and drives the machine tool. The operating parameters of the CNC can be altered via software load programs. Robot machining centers and 5-axis routing machines are often used. Water jet and laser cutting are also technologies increasingly being utilized by SMC/BMC molding operations.
At Prazastinav we are proud to offer a complete thermoset manufacturing solution. That’s why our services include a thermoset compression moulding facility producing a range of components from large Automotive and Aerospace components to more intricate over moulded products in a range of materials.
Expert Thermoset Solutions
Our thermoset compression department stands alone from our other facilities – we believe in dedicating the right tools and expertise to perform a particular task. Whatever you need, we can deliver by utilising the correct machine from one of the largest ranges of compression presses.
Where other processes are not suitable thermoset compression is a tried-and-tested technique for moulding. Our semi-automatic hand loaded machines are operated by a team of skilled operatives. Our vast experience and multi skilled technicians give Prazastinav Compositech the edge over other companies, that’s allow us to bring to you a component that meets all the needs of its application.
Our range of compression presses allows us to mould small single impression tools, multi-cavity moulds and the larger sized single cavity over-moulded components.
We’re passionate about combining traditional techniques with the latest technology to deliver a cost-effective service you can rely on.
We also offer post moulding and heat treatments operations to suit your particular needs.
High-Strength Thermoset Molding
We offer close tolerance compression molding services to produce low weight and high strength components fabricated from thermoset composite materials. Prazastinav Compositech Pvt Limited ISO 9001:2015 certified mold shop is equipped with an extensive range of up-acting and down-acting compression presses with different tonnage capacities. These compression presses also have top, bottom, and double transfer capabilities.
Ideal for different applications, our thermoset compression molded parts retain their mechanical properties even at elevated temperatures. By thermoset compression molding, we fabricate multi-cavity molds and custom parts according to your specific dimensional requirements. In addition to compression presses, extensive de-flashing equipment enables us to save flash removal cost.