What is it? Types and Application of Hydraulic Press
About hydraulic press
Before choosing the right hydraulic press type, it is essential to know its working mechanism, types, applications and uses. Here’s all you need to know about a hydraulic press!
What is a Hydraulic Press?
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Hydraulic Presses are devices that use the static pressure of a liquid to produce compressive force. It consists of a mainframe, controls, and a power system. The mechanism helps to structure, dismantle or organize different types of metals, rubber, plastic, and wood.
The working mechanism of a Hydraulic Press
A hydraulic press works on Pascal’s law, according to which coercion changes by applying pressure to a confined liquid. The piston is a pump that ensures the required mechanical force to smaller and larger patches.
The simplest arrangement comprises two pistons of the same size attached by a fluid-filled tube. The fluid inside the cylinder is pushed through the pump and into the second piston. Thus, it produces an equivalent force downwards on both pistons.
Types of Hydraulic Presses
There are various types of Hydraulic Presses with unique traits. Check them out below!
1. H-frame
The H-Frame Hydraulic Press consists of a steel frame, a pump, a press cylinder, and a movable bolster; all put in an “H” shape. It is used for repair and maintenance by the manufacturing units during the arrangement. The simple, rugged design provides easier maintenance and is beneficial for medium and low-volume production purposes.
2. C Frame
A C-frame hydraulic press is a heavy-duty manual or semi-automatic machine with an open frame, moving slabs, and exposed gears. It offers excellent rigidity, high accuracy, pace, and arrangement. Thus, it is perfect for minor operations and requires a limited floor area.
3. Four-Column
Four-Column Hydraulic Presses find their use in oil, gas, chemical, building materials, metallurgical, and other industries. These presses help punch holes and cut slots in metal sheets, pipes, rubber, and steel plates. The single or double-cylinder arrangement depends upon the requirements of the process and the type of material.
4. Horizontal
The horizontal press has a unique hydraulic system that safeguards from overloading and comes with a two-speed technique as a prototype. It is a powerful, valuable machine that is instrumental in many industries. This type of press helps shape workpieces that are longer or shorter than the expected length of a vertical press.
5. Hydraulic Wheel Press
A hydraulic wheel press is suitable for shaping metal into diverse forms. These presses help in rectifying shaft parts and compressing shaft sleeve parts. The aerospace industry uses it to manufacture different parts of airplane bodies and landing gears.
6. Straightening
Straightening Hydraulic Presses help to straighten the bent, twisted, or warped metal parts without the urge to remove them from the assembly. This device helps deform parts with a high-strength steel thickness of around 20 mm. The machine is beneficial as a part of workshops and small repair shops, depending on its type and size.
Applications of a Hydraulic Press
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It operates on high-pressure to produce energy. It is a significant and cost-effective technique to apply pressure on any object. Its applications are below:
Various industries use a hydraulic press, including automotive, military, construction, aerospace, etc.
Metalworking, welding, compacting food items, making instruments, forging, creating aircraft, and more use them.
It is used for commercial and industrial purposes since it can deal with large pressure volumes. Academic setups for training and research purposes also use hydraulic presses.
Hydraulic presses serve in heavy-duty jobs like stamping and creating metal sheets, forging, extracting plastic pipe, and curving oversized diameter tubes.
The manufacturing industries preferably use them for pressing, forming, stamping, and bending metallic articles.
Hydraulic presses also help during the manufacturing of products like food cans, siding on house roofs, and truck beds.
Such presses are efficient tools for molding plastics and metals, and they can punch, shear, or bend materials into the required shapes.
Hydraulic presses are highly useful for workshops for manufacturing purposes.
When should you choose a hydraulic press?
If you seek weight reduction and material conversion, it is better to use a hydraulic press. It has a low initial and production cost and provides a high tonnage capacity. It is a safer option than other industrial presses due to built-in overload protection.
Moreover, it has a simple design, requires less floor space, and makes less noise. It also helps you generate a high amount of pressure. These presses have greater adaptability and a longer lifespan. So, if you wish to increase the strength and rigidity of your project, go for a hydraulic press!
Choosing the Right Press
Press technology — whether mechanical, hydraulic, or servo — plays many roles
Greenerd designed and manufactured this custom, complex double-moving platen deep draw hydraulic press. It’s fully integrated with two six-axis FANUC robots that load/unload, plus prompt the press to perform multiple operations required to produce a heavy-duty, high-pressure cylinder tank. (Provided by Greenerd Press & Machine Co.)
There are choices in presses, which is a good thing. The debate is not which is best, but which one is right for the job at hand. There are tradeoffs in cost, function and quality between the main types of presses one could choose.
It’s a friendly debate, and the cards are on the table for all to see.
Quick Review of Tech
According to Stephanie Price, senior application engineer at Promess Inc, Brighton, Mich., many people in industry don’t fully appreciate the advantages of servo press technology. Conversely, Mike Josefiak, mechanical engineer at Greenerd Press & Machine, Nashua, N.H., makes a good case that a hydraulic press is the best solution for some applications. And Jim Landowski, vice president at Chicago-based Komatsu America Industries LLC, would tell you there are still situations in which a traditional mechanical press is fine.
A mechanical press converts the rotational motion of a flywheel into the linear motion of the ram pressing into the workpiece. As Landowski described it, you can “imagine the circle, with zero at the top and 180 at the bottom. A mechanical press goes from zero through 180 and back to zero, or 360, in one continuous motion.” The stroke has no force at the top and maximum force at the bottom, so “depending on the die, you might start pushing the material at 160 degrees or so. But when it gets to 180, the part is finished, because your slide is going back up.”
As Bob Southwell, executive vice president of AIDA-America, Corp. Dayton, Ohio, explained, most servo presses are versions of the same arrangement, “except that you’re powering a mechanical drive train with a servo motor, versus a fly wheel with a clutch brake mechanism.” A mechanical press has a fixed stroke and a constant speed. But “add a servo motor to it, and now you’re able to program the motion profile. You can slow down, pause, perform rapid restriking, and do various things that were never possible with a standard mechanical press.” There is also a direct drive version (servo motor to ball screw), with better torque characteristics than the servo-mechanical hybrid.
A hydraulic press combines a set of pumps, valves, and hoses to engage the ram with pressurized fluid. While this approach has advantages, they don’t include the kind of motion control covered above. So a servo press offers additional capabilities and solves a number of problems that occur with pure mechanical or hydraulic presses.
New Materials, New Challenges
Landowski observed that the move toward advanced alloys brought on by automotive light-weighting and other factors is driving demand for servo presses. As he put it, “think of steel as a liquid, it has to flow…You don’t work the material, you work with the material.”
Harder materials require fine adjustments to the ram velocity in order “to let the material flow correctly, or else it becomes like taffy and starts to come apart.” For example, he said, forming a cup in a hard alloy might require slowing from 30 to 15 IPM over the course of a 3" (76.2-mm) stroke, at a precise—and perhaps varying—rate of change.
This Komatsu H2FM 400 is producing long parts for train tank cars using a proprietary automation system integrated with the press control. Production speeds and other parameter adjustments on servo presses can be made on demand to compensate for material variances or other variables in real time without stopping the press. (Provided by Komatsu America Industries LLC)
Only a servo control could manage this, given that the adjustments occur in milliseconds.
The main advantage of a servo, Landowski stated, is the flexibility to work with different metals by dialing in the material flow. “That’s why we have people come in to try various options. I can make a good part or a bad part just by changing the velocity of the slide.”
Southwell concurred and reported that these material challenges have resulted in a servo press market share of roughly 80 percent in North American automotive manufacturing. “The high strength and ultra-high strength steels and aluminums are much more challenging to form than the materials of ten to fifteen years ago. And a servo’s ability to adjust the forming profile has proven extremely beneficial to the customer base.”
Josefiak from Greenerd agreed that servo control has an advantage in response time versus hydraulics, in which the response is dampened, but said he hadn’t “seen many applications where that level of control in the motion profile materially impacts whether or not you make a good product.” But he acknowledged that “restriking is a good example of a servo-only function. Going to the bottom and then re-striking within a fraction of a second is not something you can do with hydraulics.”
If you don’t need to control velocity, Landowski argued, you may not need a servo.
“If you’re making washers, for example, or small rivets or something like that, you’re not going to slow the press down, you’re not going to control velocity. You want to make as many parts as you can, as fast as you can.” That’s where a mechanical press shines, he said. It’s also where hydraulic presses are least appropriate.
Servo Versatility in Assembly
Servo-presses offer immediate and detailed feedback on the process, to include a visual representation on the control monitor. (Provided by Promess)
Southwell added that the ability of a servo press to be easily reprogrammed for different parts is another factor in their success, even in the high-volume automotive world.
“Most press systems are designed to run multiple types of parts. They will run one tool for an hour, change it out and roll in another tool. Virtually no one sets up one press and just runs it…There’s no way they could stay competitive. We sell many systems to the OEMs through the Tier Ones and Tier Twos for large families of different parts or die sets through a single press.”
Servo press versatility goes well beyond easy programming and extends into delicate assembly operations, said Price from Promess.
Sticking with an automotive example, Price pointed to assembling a door hinge. She explained that a servo press offers both high precision and an inherent feedback loop capable of closely monitoring position and force. So, in pressing the hinge together, Promess is also able to gauge the resulting resistance in the joint, such that they can ensure that the door neither swings open too easily nor is too stiff to be uncomfortable for the car’s owner.
This ability to activate a moving part and measure forces in real time also yields the opportunity to loosen part tolerances, thereby lowering component costs. As Price explained, without feedback during assembly, engineers are often forced to design and manufacture to very tight tolerances in order to ensure that parts fit together properly.
“They use the fact that the press went to a certain depth, and based on their tight tolerances, assume that the part was assembled correctly. They have no signature analysis to verify that.”
With a servo press, they could instead loosen the tolerances and watch the data during the assembly process to determine that what they’ve pressed together is actually properly seated. Price said the built-in sensing capabilities of their servo presses has yielded scrap rate reductions of up to 50 percent in some cases.
Price also pointed out that if an application required additional sensing (beyond the feedback from the servo motor), it’s easy to integrate with their systems.
“We have customers using nine to ten different pressure transducers, or position transducers, or external load cells. We can take in all that information to understand what’s going on within the process,” he said. “And we can react to that during the process. And because everything is electrical, it’s very simple to set up. Just plug in a transducer into a digital signal conditioner. The controller can then take in that signal and use it to make a determination.”
Presses, Control and Tradeoffs
Hydraulic presses are not blind in this area. Josefiak said there are motion controllers dedicated to hydraulic systems with “extremely fast scan times that look at the pressure on either side of a hydraulic actuator. And then using fast-acting pressure transducers, we can show the actual force being applied to the work.” One such system updates the force measurement in under a millisecond. In his opinion, applications requiring faster force measurement are “few and far between.”
An airbag part stamped on an AIDA press. AIDA’s Southwell reported that material challenges have resulted in a servo press market share of roughly 80 percent in North American automotive manufacturing. (Provided by AIDA-America Corp.)
According to Southwell, servo presses are much better than hydraulic presses in making complex parts that require a series of dies. Years ago this would have been done by transferring parts by hand from press to press, he explained. But now “the only way to compete” is to mechanically transfer parts from stage to stage within a single press. But “when you use multiple stations to make a part, you have off-center loading, which is very detrimental to a hydraulic drive train.”
Josefiak countered that “off-center loading is detrimental to both mechanical and hydraulic systems. Both handle these off-center loads with appropriate construction and guiding of the steel framework. We have systems using multiple hydraulic cylinders to allow off-center loading much larger than an off-the-shelf servo-mechanical press.”
There is also some controversy about applications requiring the use of food-grade oil as a lubricant. Landowski reported that “several customers have switched from hydraulic to servo mechanical presses solely due to cylinders weeping and the slide gibs dripping onto the material. All parts need to be cleaned after they are formed to remove any and all possible contamination. Customers have also told us that cleaning food-grade lubricants is less costly than non-food grade due to FDA or EPA regs.”
Josefiak said they have satisfied both medical and food safety standards on a number of projects “by modifying the sealing in their presses to use food-grade oil in place of standard industrial oils.” Whereas Landowski stated that their standard off-the shelf servo press don’t need any modifications, “just the food-grade oil for the press drive and the slide lube.” One customer “makes rubber stoppers for test tubes. Every stroke of the press delivers 65 to 75 rubber stoppers, and non-food-grade lubricants would invalidate this particular process.”
Hydraulic Conquers Deep-Draw
Two AIDA DSF-S4-20000 2,000-ton servo transfer presses, featuring a 750-mm full stroke length, programmable down to 200 mm, and a max speed of 40 strokes/min programmable down to 1 stroke/min. (Provided by AIDA-America Corp.)
According to Southwell, “the advantage of a hydraulic press is that you have full tonnage or force capability through the entire stroke. So, if it’s a 200-ton press and you have a twelve inch stroke, you can apply 200 tons of pressure all the way through that stroke. With a servo press that has the same mechanical eccentric drive train as the original mechanical press, you have gearing, the crank shaft or a centric shaft, and a center gear drive. There is a tonnage or torque curve, and the force you can apply varies depending on the motor shaft’s angle off the bottom.” This is not the case for direct drive servo presses like those made by Promess, but these systems become very expensive as tonnage increases. Promess tops out at 1 MN (~100 tons) in a single cylinder, for example.
The ability to apply full force through the whole stroke make hydraulic presses perfect for deep-draw applications, and Josefiak went so far as to say it’s “the only option that really makes sense.”
One recent example he cited is a project to produce ”relatively large pressure tanks. We installed an automated system that loads large, flat blanks into a deep draw press that has a working stroke of five feet.” The system has multiple operations, he explained. The first uses a 170 Ton press to draw two halves of the tank. This is followed by an automated punch press and trimming and welding downstream. The key here, said Josefiak, is that such a working stroke “isn’t something that’s easily replicated with a servo press. So deep draw is an area where hydraulics still dominate. And that’s across quite a few industries. It’s more the process than the industry.”
Josefiak said hydraulic also “does very well in situations with a very long cycle time, where we can manage very low power draw in a consistent pressure across the bed area and relatively inexpensively from a capital cost perspective.” Compression molding offers a major example. “Usually, compression molding is going to be a combination of time, temperature and pressure forming a material into a shape,” explained Josefiak. The press would hold a relatively thin material against a positive or negative die form under pressure. “The duration could be as short as five seconds, or as long as two hours. And very often…we’re trying to maintain a constant platten temperature across the working area of anywhere from around 300 to 700 degrees, and trying to control a very consistent pressure across the working area.” That ensures the material being formed is uniform throughout. The technique is used for things like automotive bed liners (including the new composite bed liners) and automotive headliners made with a carpet-like material. Another example he listed is “powder compaction for making aluminum oxide grinding wheels.”
Cost Considerations
Broadly speaking, the capital investment for a servo press exceeds that of either traditional mechanical or hydraulic presses. But there are operating costs and related factors to consider that make this comparison nearly useless. What’s more, not all presses of a given type are equal, even for the same tonnage/torque ratings.
Let’s start with energy consumption. A hydraulic press must maintain pressure in the lines to move the ram on demand, and that means running the pumps through the cycles. That compares unfavorably with a servo press, which uses electricity only when the ram is moving. According to Landowski, that yields a roughly “50 percent power savings with a servo press, depending on the size of the machine.” Price referred to a study by the University of Kassel, which found the servo press to be 90-percent efficient in energy conversion, versus 57 percent for the comparable hydraulic system. Southwell said Honda studied their own systems and published the finding that servo presses delivered a 30-percent savings in actual power consumption.
This Greenerd 1,000-ton hydraulic press is used in a coining operation for forgings. The 1,000-ton press is sized for 110 tons per square foot and features a 30" × 30" bed size. The press is gib-guided to handle off-center loading. A safety light curtain package is also provided. (Provided by Greenerd Press & Machine Co.)
Southwell also indicated that some AIDA presses use a “100-percent capacitor-based energy management system.” This stores the required working energy in capacitors, which are recharged during the non-working part of the stroke. This “vastly reduces the peak load,” he explained, versus a mechanical or hydraulic press, which have a “huge spike when they first engage.” AIDA current draw is “fairly flat. So your actual peak flow might be only 20 to 30 percent of the peak load of mechanical or hydraulic systems. That’s critical, because power companies have to size the electricity they deliver to the customer by the peak load.”
Josefiak countered that in a high-production environment there’s little or no idle time, so “it really doesn’t matter too much” that the hydraulic pumps are running continuously. And “in systems where we have long idle times of 10 minutes or more, we can install a ‘soft start’ motor control that shuts down the motor to conserve energy.” Interestingly, although this option adds only 2 percent to 3 percent of the system cost, Josefiak reported that there has never been a strong demand for it. He added that switching from a fixed displacement pump to a variable displacement pump can also “dramatically lower our idle power consumption.” But that again is an option that has yet to become the norm in the U.S.
With all its pumps, valves, pipes and hoses, hydraulic technology is often dinged for being more complex and more maintenance-intensive than servo-based systems. Price said their servo presses require nothing more than twice-a-year greasing of the ball screws—and even that is being very cautious. Conversely, keep hydraulic lines under high pressure for months, through cycle after cycle, and sooner or later something is bound to leak or a sub-component is bound to fail. The counterargument, said Josefiak, is that “nobody is using NPT fittings anymore. There is a range of metal-to-metal and O-ring style seals, built with better materials, that have done a much better job controlling leakage.” Plus, he said, the individual components are relatively inexpensive and easy to repair, while “doing repairs to a servo system is dramatically more expensive.”
This last point brings us to the topic of correctly sizing the components for the job. It’s true that if you burn out a servo motor in a few years you’re in for a big repair bill. But Price said their systems routinely run for 20 years without any such failures, because they are designed with a safety factor of 2.5×. The drives are sized to run in the continuous current of the servo motor, instead of the peak, so the press can hold the part indefinitely without overheating and failing.
Likewise, the ballscrews will have a dynamic load capacity of 2.5× the force rating of the press. For example, the ballscrew in a Promess 40-kN press has a dynamic load capacity of 134 kN and a static load capacity of 320 kN. Price said such a system can be expected to perform without a failure for 22-plus years when running a job with an average force of 30 kN, with 16 cycles/min over 14 hours/day. Compare that to only 32 weeks for a ballscrew rated at 40 kN dynamic load; even at a rating of 80 kN, the system would last under five years.
Types of Hydraulic Press Explained
Types of Laboratory Press Explained
A laboratory press is a device used to apply pressure to a sample, in order to compress or compact it. Laboratory presses are often employed to study the properties of materials, or to prepare samples for further analysis.
Laboratory presses are typically equipped with a hydraulic system that can generate up to 1,000 pounds per square inch (psi) of pressure. The press can be used to apply pressure to a variety of materials, including powders, sheet materials, and polymer beads.
A hydraulic press uses an oil-filled hydraulic cylinder to generate a compressive force on a moveable piston. The machine works using the principle of Pascal’s law, which states that the pressure exerted on a fluid is transmitted evenly throughout that fluid. The force generated by the press is proportional to the area of the piston, multiplied by the applied pressure. The press consists of a cylinder with a piston inside, and a pump that is used to apply pressure to the oil inside the cylinder.
How a hydraulic press works
What are the different types of hydraulic press?
Laboratory presses are available in a variety of sizes and configurations, including manual or automated operation. Choosing the right hydraulic press for your lab will, unsurprisingly, come down to its intended application – as well as how much time and energy your technicians will expend on using it.
A laboratory press is frequently used in conjunction with a pellet die for compacting powders into solid disks. Other tools and moulds can be used for pressing, bending, or forming thin films.
Manual Hydraulic Press
A manual hydraulic press uses a hand-operated lever to pump the oil and apply load to a sample. A hand-operated valve is used to relieve the pressure and remove the load.
The manual presses manufactured by Specac are available in 15 and 25-tonne maximum load configurations and are ideal for FTIR, KBr and XRF sample preparation.
There are no electronic components in a manual hydraulic press and, as a result, this machine is often cheaper than its automatic counterparts; however, choosing a manual press shouldn’t just come down to the purchase price.
When you consider if a manual hydraulic press will suit your laboratory operations, it’s best to review your workflow. Manual presses require more physical effort to operate than an automatic equivalent – so if your technicians will need to use them often, it can become labour-intensive work.
A manually operated press is also harder to use in a repeatable fashion, with every sample being pressurised to a slightly different load by the operator.
However, for infrequent use, a manual press can be a cost-effective addition to your laboratory set-up.
Automatic Hydraulic Press
An automatic hydraulic press uses an electric motor to drive the pump and electric switches to open and close the relief valve. This means they can be controlled to a high accuracy and repeatability.
Automatic hydraulic presses are often used for industrial XRF applications and other laboratory sample manipulation activities. However, their versatility makes them suitable for small and large-scale manufacturing practices, too – including hot embossing, laminating and melting polymers for thin films.
Unlike the lever on a manual hydraulic press, an automatic press is operated by a button. The general mechanics of the two machines are similar – you set the load you want to be applied, which the pump then fulfils – but the die used in an automatic machine can often press and release via automated actions.
Automatic hydraulic presses often improve the workflow in busy laboratories, as – once the press is programmed – it can operate autonomously, allowing the technician to get to work on other tasks.
Available in 8, 15, 25 and 40 tonne configurations, automated presses aren’t as laborious to operate as a manual counterpart. This makes them suitable for frequent pressing work – as well as often being more accurate and consistent, due to the lack of variable factors during use.
Presses for XRF pellet preparation
Where laboratories are running XRF measurements on a large quantity of samples, it makes sense to have a high-throughput hydraulic press for XRF, specifically adapted to the demands of preparing sample pellets. These presses feature integrated pellet dies and have swifter operations for repeated use. In particular, they focus on automations and mechanical systems for quickly extracting the pellet and leaving the press available for the next sample.
Hydraulic Mini Press
A hydraulic mini press is a small, portable press that uses hydraulic power to produce force. They typically only weigh 4 kilos but are still capable of applying around 2 tons of pressure.
Mini presses are typically used to produce KBr discs for FTIR. As the surface area of these pellets are about 7mm – smaller than the usual 13mm diameter of a regular pellet – this enables an equivalent pressure to be applied, despite the lower tonnage.
Mini presses are often favoured due to their compact size. They’re hand-held, easy to transport and low-cost, making them an accessible choice for pharmaceutical labs, polymer testing labs, undergraduate chemistry labs and many other places where FTIR is commonplace.
Why use Specac for your FTIR and sample preparation equipment?
Specac offer a comprehensive range of sample preparation accessories for FTIR, including presses, pellet dies, high temperature film makers, and consumables such as KBr powder.
Besides these, a variety of other sampling techniques – including single and multiple reflection ATR, DRIFTS, and Specular Reflectance – are available.
Our accessories are customised and calibrated for the user’s needs, so why not contact our experts for a quote?
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