Industrial presses apply a controlled force to material or part to complete a process step. They can be powered by many different energy sources and range greatly in size. Many manufacturing facilities use an industrial pressing operation in their process to create, form or assemble a product.
Entire books are written on the topic of industrial presses, so this article will narrow its focus and concentrate on the relatively low-force, precision press machines used to assemble parts. Most assembly presses are made up of a frame, ram and platen. Custom press frame configurations give engineers endless options; however, most standard assembly presses utilize a “C” frame, “H” frame or two-post configuration. Regardless of the frame’s shape and orientation, the ram is the moving element that applies the pressing force, and the frame is a secure mount for the platen that holds the workpiece.
Even in today’s world where plastics and polymers dominate, metalworking remains a vital part of many industries in the U.S. Metals and metal-worked pieces are critical components in many goods, from tiny computer chips and watch gears up to the moulded pieces forming kitchen appliances, and even further to the carefully formed outer structures of cars, aeroplanes and other machines.
In this article, you will learn about what is press and the different types of press machine used in workshops.
Press machine is a metal forming machine tool, which is designed to form or cut metal by applying mechanical force or pressure. With the help of a press machine, you can form metal in any desired shape without removal of chips. The presses are exclusively intended for mass production work.
The main advantage of using these types of machine is that they are the fastest and most efficient way to form any sheet metal into the finished product.
Press primarily represents a specified form of the machine tool. It is essential for performing multiple industrial manufacturing procedures. This machine tool helps in delivering energy through force, which can act over a stroke or distance. One major application is going to be metal forging by the industrial manufacturing unit. The energy is used to close die and forging part within. These machine tools are used for applying force or energy to work in a different manner than drop hammers. Hammers are also part of the machine tool but of a completely different kind. Forging is the only form of the manufacturing process, which employs press.
Below, we’ve outlined the five main types of presses used in industrial settings, their typical usage, and methods that can be utilized to verify the assembly process. Each type of press creates a force in a different manner, and this impacts the application, purchase price, operational cost, precision, safety, and process feedback capabilities.
As the name implies, these industrial press machines are powered by a human operator. They are simple, basic tools, and therefore the purchase price and operational cost of this type of press are low. Manual presses utilize different methods to produce force and linear motion of the ram. A common press for very low-volume assembly work utilizes a self-contained hydraulic system. Pumped via a lever, a hydraulic cylinder slowly extends with high force to press self-guided assemblies together. This system is very slow and takes a lot of effort, so it is typically used only for one-off, high-force processes.
Arbor presses utilize a lever arm or large wheel with a mechanical linkage to move the press ram up and down. The force is amplified by the linkage, which is typically either a rack and pinion or toggle mechanism. Rack and pinion presses amplify the applied force equally throughout the entire ram stroke. Toggle mechanisms start with a lower force and increase the amplification toward the end of the stroke. In all of these variants, the assembly process and speed is controlled entirely by the operator. Press monitoring options are limited but include stroke verification switches, force displays, and also locking mechanisms, which prevent the ram from being raised unless the stroke has been fully completed. Like any hand tool, safe operation of the press is the responsibility of the operator.
These assembly processing machines utilize compressed air as their power source. A standard air cylinder and “two-hand, anti-tie down” control valves are used to initiate the press cycle and move the ram up and down in a safe manner. The maximum force is relatively low and is determined by the cylinder bore size and the pressure of the regulated air source. The press force is consistent throughout the entire ram stroke and cannot be adjusted mid-stroke by the operator.
Advantages of the pneumatic press type are its higher speed, relatively low total cost and reduced operator fatigue. However, the operator cannot “feel” the assembly process, as there is no tactile feedback. With additional control devices and cost, the assembly process can be monitored using stroke position switches, linear transducers, load cells, and part sensing devices. Since air is compressible, unless an additional oil-dampening circuit is employed, the working press stroke may be choppy and vary from part to part. This inconsistency limits the resolution of the process monitoring system; therefore, pneumatic presses are generally not a good choice if precise force/distance signature analysis is a quality requirement.
If the operator has additional tasks, and two-hand controls limit throughput, a light curtain can be utilized as a component of the machine’s safety system. A machine safety assessment, by qualified professionals, is extremely important and should not be overlooked. Not only is compressed air stored energy, if the air source fails, the press ram could fall, which could also cause injury. To prevent a falling load, air-piloted check valves or shaft-locking devices may also be necessary.
Pneumatic Intensified (Air/Oil) Press
These machines are similar to pneumatic presses, and many of the characteristics, advantages, disadvantages, and safety concerns mentioned above hold. They are powered by compressed air; however, the addition of hydraulic oil into the control circuit enhances the capabilities of this press type. Since oil is not compressible, it can be safely intensified to high pressures. The high-pressure oil is smaller in volume than the air that produced it, so the total displacement of the high force stroke is relatively short.
This “power stroke” can, however, be controlled with flow-restricting valves resulting in a smooth, uniform ram motion. Packaged air/oil cylinders often advance the majority of their stroke with low force, and, after contacting the workpiece, they utilize internal fluid passages to shift over to their full-force power stroke automatically.
If the process requires force/distance monitoring or high force over a short distance, an air/oil press may be the best solution. These presses can consume a lot of compressed air, which is a costly form of energy; however, they can be a good, lower-cost solution in many applications.
Hydraulic Assembly Presses
This type of industrial machine utilizes plant electricity, a hydraulic power unit and a hydraulic cylinder to move the press ram. These presses can be purchased in a variety of pressures and a range of sizes as “stand-alone” pre-engineered units. They are ready for use as soon as part-specific tooling is mounted to the ram and platen.
Like the pneumatic press, maximum force is determined by the machine’s cylinder bore size and regulated operating pressures. Unlike an air/oil press, the pressing force is consistent throughout the entire stroke range. Ram speed is limited by the flow and oil volume restrictions of the hydraulic power package and circuit. Operator safety is again a serious concern, and one must be sure to engineer the system utilizing applicable safety-rated switches and sensing devices.
With additional control devices and cost, the assembly process can be monitored using stroke position switches, linear transducers, load cells, and part sensing devices. Since hydraulic oil is not compressible, the entire press stroke will be a smooth motion, which enhances the resolution of the process monitoring system. There are many advantages to this type of press, and many are used in factories around the world. The main disadvantages are the inevitable leaks, noise, smell and significant heat generated by the hydraulic power unit. In addition to the higher initial cost, maintenance costs can also be higher due to the system complexity.
Servo Electric Presses
These industrial processing machines have been around for decades and are continuing to grow in popularity. They are increasingly selected over the other press types in many factories as the cost of servo motors and control electronics has come down significantly in recent years. The initial higher investment is also offset by lower operational and maintenance costs of an all electro-mechanical system.
This type of press utilizes plant electricity, a servo motor/drive unit, and an integrated ball screw actuator to impart linear motion to the press ram. These presses can also be purchased as pre-engineered packages with a wide variety of options. It’s very common to have integrated load cells, linear transducers, external part sensing, and other quality monitoring devices controlling the process, thereby lowering scrap rates and improving quality significantly.
The press software generally offers options to assist with the controls integration of safety devices, HMI display screens, and statistical quality control packages. Another capability, offered by some servo press manufacturers, allows the addition of controlled rotational motion integrated with the linear motion. This is beneficial when the assembly procedure requires the components to be rotated relative to one another during the press stroke to prevent damage.
How Does a Press Work?
The key to a press machine is the plate or die used to reshape the metal from its original form into the desired piece or part. These carefully formed pieces are pressed against the surface of the metal to deform it into the desired shape. Sometimes they are one-sided; the metal is placed on a flat surface, and the forming element descends to push and press it into the desired shape.
Sometimes these dies are two-sided. In most of these cases, sheet metal is stretched across the surface of the bottom die, and the top die comes down to shape the sheet metal into the three-dimensional space defined by the gaps between the top plate and the bottom. Carving these dies and plates is often initially done by hand, especially for intricate pieces and parts.
Industries Using Press Machines
Press machines are critical components of many manufacturing industries. This type of machinery produces essential metal pieces that make up many of the end products in today’s markets. For example, a die forging press can be used to make high-strength materials out of metallic alloys for petrochemical industries that make tanks, piping and other machinery to manage chemical reactions. They are also used in transportation industries, aerospace applications and nuclear power applications.
On the other end of applications, press machines can be used to make small parts, such as screws, nuts, washers, nails and other small hardware accessories. The advantage of using a die impact press for these applications is the regularity. Assuming all inputs are correct, these presses produce identical pieces and parts every time. Punch presses are also used to punch pieces from flat sheet metal or from other pre-formed metal parts to create, for example, the pieces used to assemble a motor or a pump.
Training to Operate a Press Machine?
As with any heavy machinery, training is required to use a press machine. There are many hazards that an operator faces on the job. These machines use incredibly high pressures and forces to deform metal as needed. The pressures can cause extreme injury or even death to an operator.
With hydraulic or pneumatic presses, liquids or gases are contained under high heat or pressure. There is a risk of injury if parts of the press fail and spray fluids onto the operator. There may be other hazards depending on the materials, metals, and fluids used to create the parts. In most cases, industries are well-informed and provide general safety training to address all of these potential hazards.
Operational training is also required. Many modern press machines are controlled digitally, which gives the operator some distance from the process. However, manual input is often needed. In most cases, this involves the loading or unloading of the required dies that form a particular part or manual adjustments necessary to make sure they align correctly at the start of the process. Manual input can also involve the loading of the raw material metal or unloading of the finished product, although this process is often automated. In most modern plants, this equipment is automated, and operators only need to interfere for troubleshooting purposes.
More about the main machine
The Press Machines are mainly used in sheet metal fabrication, and metal extrusion processes and these are described to be primary machine tool. Mechanical and hydraulic presses are mainly added during formation of sheet metal. Presses are designed to be used in manufacturing multiple plastic parts. Some of the machining operations can further need the use of presses, such as in broaching.
Varying in size and force
These presses tools are designed to vary in the amount of force implied and size. The energy produced is often used to work on processes, which are in need of tremendous force. Some examples are large plastic deformation task of the sizable metallic piece. Depending on the type of machine used, there will be a difference in nature and method of delivering energy.
Vertical presses are available
You will come across vertical presses, as a type of machine. Here, the force vector is up and down, quite relative to the gravity. In some of the cases, these types are utilized in a horizontal manner. Here, the force is delivered in a perpendicular path to the direction of gravitational force. In case the force is exerted horizontally, vertically or in intermediate angle, then the working principles are same.
Two types are available
In generic terms, Press Machines are available in two major types; mechanical presses and hydraulic presses. Depending on the manufacturing procedure, the machine press type varies. The first consideration has to be the basic process of such a press tool. For example, the one used for extrusion will have different general requirements when compared to the tool, used for pressing sheet metalworking.
The next factor to consider is the press capacity needed. The required capacity is related to the size of the work stock and the process type.
Other primary factors to consider
Stroke length, over which the press is going to deliver force, is another factor to consider while choosing a machine. This needs to be related to the basic process type, which has been employed. Going through these initial considerations will provide you with a general idea on the type of presses available and required for your job. The specified factors of such manufacturing procedure need to be weighed for determining best press tool. Other than the hydraulic and mechanical press, you can even consider checking out the functionality of crank press. Go through the detailed functionality first before planning to invest money on one.
Presses are machines which apply pressure to a workpiece to change its shape and form. Used for a multitude of fabrication processes—e.g., die-cutting, forging and stamping—these machines can be used for processing a variety of materials (generally metal) across a wide range of industries.