What is a mould press and how does it work? Moulds, like every part used in the machining industry, have to be manufactured. The discipline responsible for making moulds is known as die and mould making, since it also covers the production of dies. Which machine tool is used for this type of work?
How are moulds made?
Moulds are small parts used in everyday life for very basic tasks, even for making ice. You can also find moulds for baking and, of course, moulds for manufacturing screws, nuts and countless other things around us every day. A mould is a pattern that is filled with a material, usually in liquid form, and then removed to obtain a specific part.
Who makes these moulds, and how? The branch of metalworking in which moulds are manufactured is known as die and mould making. Moulds are not the only items produced: dies are made too, and they are essential for machine tools. The person who carries out this work is called a toolmaker and is an expert in the field.
Moulds can be manufactured using various processes, including casting and forging, two techniques that have been used for this purpose for centuries. However, with the arrival of more sophisticated machine tools and simpler machining processes, it is now possible to use a mould press and much more advanced equipment such as CNC machines.
CNC machines are also ideal for mould making, as they can work in series and produce large quantities.
What is a mould press?
The metalworking industry uses several types of press, but the press used for moulds is the hydraulic press. This machine tool is fitted with a hydraulic cylinder; in other words, it works by means of a fluid that generates a compressive force. In metalworking terms, hydraulic presses use the equivalent of a mechanical lever. You may be surprised to learn that the hydraulic press is also known as the Bramah press, after the inventor who designed it in 1795.
Operating principle of the mould press
The hydraulic press works on Pascal's principle, according to which the pressure in a closed system is constant. One part of the system is a small piston that acts as a pump on a small area. The other part is a larger piston, which produces a correspondingly greater mechanical force. The system is completed by a small-diameter, pressure-resistant pipe that comes into play when the pump is separated from the cylinder.
Uses and types of hydraulic press
The mould press is not only used to make moulds: it is also used for forging, riveting, die cutting, punching, deep drawing and forming metals such as sheet metal. The hydraulic press is extremely useful in metalworking because it can create highly complex shapes; it is also fairly economical and takes up little space.
Moving-table press
Moving-table hydraulic presses can withstand heavy loads and are very powerful, generating from 25 to 200 tonnes of pressure. These presses can be operated with a forklift or a hoist, and the machine head can be raised or lowered to carry out the work.
Moving-frame press
With this type of press, the head can be brought closer to the workpiece. This movement allows the head to focus on the area that needs to be worked.
Air-operated presses
Not every machine shop has an electrical installation large enough to meet the demands of a machine tool. That is why there are hydraulic presses that run on a compressed air connection.
Manual mould press
Manual presses are very easy to use, even though they may seem very basic. They require no power supply and deliver high-precision results.
Parts of the mould press
A hydraulic press, or mould press, basically consists of two cylinders, two pipes and two pistons. Some hydraulic systems use several cylinders, the number depending on the workload; if the press has more than two cylinders, most of them will be small and one will be larger. The fluid is supplied by a pump and a hydraulic accumulator.
The accumulator stores hydraulic pressure in the form of pressurised fluid, which is released when needed. The pump moves the hydraulic fluid to the accumulator continuously so that the pressure remains constant. A mould press can also be fitted with three types of hydraulic pump:
- Vane
- Gear
- Piston
High-performance hydraulic presses usually use piston pumps, because pistons are capable of generating high pressure.