How Hydraulic Presses Help With the Production Process

Types of Hydraulic Presses

 

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There are various types of custom hydraulic presses available on the market today. However, it is important to understand the difference between each type of hydraulic press, their functionality, and their intended application before deciding which type to purchase. A wide range of industries use customized hydraulic presses for a variety of applications, some of which include compacting in the cosmetic industry, assembly in the automotive industry, forming for electronics, and stamping for the appliance industry. 

• C-frame hydraulic presses, also commonly referred to as gap frame presses, are characterized by their unique frame style, resulting in the formation of a &#;C&#; around the bolster plate. Hydraulic floor model C-frame presses deliver high force while maintaining a small compact footprint. C-frame hydraulic floor presses are typically best suited for applications requiring smaller bed sizes and lower tonnages. 

• A customized 4-post hydraulic press, also commonly known as a 4-column press, can be designed to accommodate a variety if die sizes and are well suited for part manufacturing that requires superior rigidity and precise bed-to-ram parallelism.

  4-Post hydraulic presses

  are advantageous because they are typically more economical than gib-guided presses and allow four-sided access to the working area.

    

• Straight side or column presses are also known as gib-guided presses. Gibs are press components that guide the reciprocating motion of the ram to maintain superior squareness and parallelism throughout the stroke. Gib-guided designs are the frame style of choice for the most demanding applications. 

• The horizontal press is ideally suited to bar, shaft, and plate straightening, and in addition may be fitted with a number of tools to perform such work as bar, angle and channel cut-off, rail/structural contouring & straightening, and numerous other applications where the horizontal configuration and smooth, long stroke hydraulic power are assets.

  Horizontal presses have a unique hydraulic system that protects itself from overloads

  .  

  What to Look for When Purchasing a Hydraulic Press

 

Purchasing capital equipment is an involved process because there is much to consider. Starting with the frame construction, it is important to ensure the custom machine has been fabricated to stand up to years of work. Key interlocked frames are preferable for higher tonnage because they are more durable, allowing for more long-lasting and

reliable use. Custom hydraulic presses come in an array of sizes, each with certain tonnage capacities.

Because hydraulic presses may be application specific, discussing the intended application of each press is important to ensure the machine is appropriately equipped for the job. Items to consider prior to purchase include,

correct tonnage capacity, tool sizing, and whether the process requires level or off

&#;

center loading as the load types may determine which

style press should be purchased for a specific application

.

Additional hydraulic press solution considerations may include:  

• For drawing applications certain processes require cushions or clamps to hold the material at a certain pressure, to control the speed of the material being drawn into a die.  

• Consider whether the customized hydraulic press die has nitrogen springs in it &#; if so, ensure the hydraulic machine can handle the &#;spring back&#; force. 

• Hydraulic press parts availability, meaning

  does the press require off

  &#;

  the

  &#;

  shelf parts or will they need to be special ordered. This is an important factor to consider as downtime hinders shop productivity and ultimately business profitability.  

• Service availability can play a key role in the decision of purchasing a custom hydraulic press solution. Having local technician

  s is helpful for ease of initial set-up and having local availability to train operators and troubleshoot issues that arise. Local service technicians help to eliminate detrimental downtime in shops. 

• If automation is going to be a part of the process, special consideration will need to be made as to what capabilities the system must have and how the product will move through the press.

    

• When purchasing capital equipment, ask questions about warranties and understand what types of services and repairs will be covered by the selling company, and for how long after purchase the warranty will be valid.   

 

Benefits of Utilizing a Custom Hydraulic Press (vs Other Methods) For Production

 

There are many production methods that can be used for metal forming. Hydraulic presses can be used for compacting, assembling, punching, forming, embossing, and drawing.

Customized Hydraulic presses offer versatility in stroke length, die space

,

and pressure capabilities that other production methods such as mechanical presses

cannot.  

• Consistent pressure or force

  :

  Hydraulic presses offer full tonnage available anywhere in the stroke. Mechanical presses, on the other hand, require the operator to calculate where they need to position their parts if they need the full tonnage of the machine.  

• Ability to vary stroke length per part requirements

  :

  Mechanical presses require utilization of the full stroke every time, this can be a time-consuming process

  .

  With a hydraulic press

  ,

  the stroke length can be set to have a partial stroke. More care must be taken when using progressive (moving) dies on a mechanical press than when used on a hydraulic press

  .  

• Freefall system

  :

  The slide on a hydraulic press solution can &#;freefall&#; during the approach, which allows the operator to increase the number of strokes per minute. During &#;freefall&#; the machine&#;s slide

  releases and gravity sends it down to its intended location. By utilizing gravity, and operator can speed up their production 

• For aging machinery that requires updating, it is often less expensive to rebuild or retrofit a hydraulic press as compared to the cost of

  rebuilding a mechanical press

  . 

• Hydraulic presses allow for more customization and have the capacity to handle a range of tonnages. Alternatively, mechanical presses are typically one size per tonnage.  

 

Industries That Most Commonly Utilize Hydraulic Presses

Customizable Hydraulic press solutions are application specific pieces of machinery

.

It is important to understand

what product is being manufactured, what force is required, the process involved in producing the part, and the properties of the material

.

Many industries may use customized hydraulic presses in their production process; some examples include:

the automotive industry may use hydraulic presses for assembling two or more parts together such as bearings, shafts, gear or rear axle assemblies. Assembling applications can also be used in medical, electronics or military industries. Compaction applications may include military munition fuse assemblies, Teflon power for seals, fuel cell and battery compaction. The aerospace industry may use a hydraulic press for a deep draw process. Deep drawing is a forming process that can be used to manufacture fire extinguishers, oil cans, fan housings, and aerospace duct-work. Additional industries that use customized hydraulic presses for their applications include, home appliance manufacturers, businesses in the agriculture industry and energy storage. 

 

As a trusted provider of &#;made in the USA&#; custom hydraulic press solutions

,

offering

standard machines

&

completely customized hydraulic press options

Further reading:
36000t Hydraulic Press: Affordable Purchase Opportunity!

Want more information on Hydraulic press types? Feel free to contact us.

,

MULTIPRESS has 70 years of experience fulfilling customers&#; specific pressing requirements. More information about the company&#;s reliable, precision machinery, and dedication to service can be found at

www.multipress.com

.   

Presses of all types&#;mechanical, pneumatic, servo, and hydraulic&#;have their place and offer unique advantages. However, over the past 50 years, hydraulic presses have trended toward greater utility. Today's hydraulic presses are faster and more reliable than ever, and the technology has gone through significant changes and refinements. Improvements in seals, pumps, hoses, and couplings have nearly eliminated leaks and minimized maintenance.

An examination of hydraulic press technology and the press&#;s anatomy, as well as its benefits, limitations, tips for selection, and automation options, can net the best utility from a press.

Hydraulic Press Anatomy, Types

Press Structure. These are the major components and features of the hydraulic press structure:

1. Cylinder. The cylinder assembly comprises a cylinder, piston, ram, packing, and seals. Piston diameter and oil pressure determine the force (tonnage) that a press can deliver.

2. Frame. The frame is the main structure of the press containing the cylinders and the working surfaces.

3. Stroke Control. Stroke length can be set for any distance within the stroke limits of the cylinder in the stroke control. Adjustments include the top of stroke, pre-slowdown point, and bottom of stroke.

4. Throat Clearance. The distance from the vertical centerline of the ram to the frame member behind the bed is called the throat clearance. This distance determines the maximum piece size that can be positioned with the part centerline under the center of the ram.

4.The distance from the vertical centerline of the ram to the frame member behind the bed is called the throat clearance. This distance determines the maximum piece size that can be positioned with the part centerline under the center of the ram.

5. Daylight. This is the vertical clearance from the top of the bolster to the underside of the ram in its maximum up position. This term is sometimes confused with the mechanical press term shut height. Shut height is the clearance over the bed with the ram fully down. Daylight describes the maximum vertical die capacity of the press.

6. Bed. The bed is the flat, stationary machined surface that supports the bolster and dies.

7. Bolster. This is a plate or structure mounted on the bed that the tooling is mounted and attached to. Most hydraulic presses are constructed so that the bolster is removable.

8. Dual Palm Button Controls. This is a common method of actuating hydraulic presses. Both buttons must be depressed at the same time to bring the ram down, requiring the operator to use both hands. Control circuits include nonrepeat and anti-tiedown features.

9. Work Height. The distance from the floor to the top of the bolster is the work height.

Type of Frames. Many of these hydraulic frame types are common with mechanical press frames:

• Bench. Compact and economical, a bench press is fast and easy to set up. It is used in a range of jobs, from single-cycle operations to automated cell components. Generally, its tonnage capacity is from 3 to 50.

• C-frame. An open-gap, C-frame press is built for long service in multishift industrial production applications in 10- to 500-ton capacities. It is called a C-frame because of its C shape. This type of frame tends to &#;yawn.&#; Applications that cannot withstand this yawning characteristic should be moved to another style of press, such as a four-post or straight-side (see lead image).

• Four-post. This heavy-duty production press is built for continuous operation. It uses four heavy-duty, large-diameter, shouldered columns to tie the frame together. These large-diameter columns precision-guide the moving platen or press slide. This ensures exceptionally consistent upper and lower die alignment, minimizes deflection, and eliminates "lean-back." Any deflection that does occur in this style of press is straight up and down. It also enables loading of the press from any of the four sides, permitting easy integration into production lines and manufacturing cells.

• Straight-side. Designed to meet the most demanding application requirements, a straight-side press has a superior frame construction. Generally, the press is built with a crown, slide, and bed weldment that is bolted, welded, or tie-rodded to large slabs of steel, called side plates. Unlike a four-post construction in which the frame is built entirely of the four columns, a straight-side press is supported by the two steel slab side plates and tie rods to reduce the amount of stretch in the frame under load. Heavy-duty blanking typically requires the tie-rodded construction to withstand the severe shock at material breakthrough. The press can run at high speeds and is capable of millions of cycles per year.

• Gib-guided. A gib-guided press is designed to counter the effects of off-center loading. Rigid steel frames with gib-guided slides maintain parallelism under severe loading conditions.

• Air-over-oil. An air-over-oil press has a four-post construction. It applies force in a vise-like grip for seconds, minutes, or hours, maintaining tonnage for nearly any length of time with the help of an air compressor. It is used mainly for lamination work. It is also suitable for applications that require a force on the product for long periods of time. It is not suitable for typical stamping applications as it has a single-acting cylinder and not conducive for applications that require any pullout/stripping tonnage. It is also upacting, which usually is not very useful for most conventional applications. With a low initial price and minimal operating costs, this press has the force of a conventional hydraulic press at a fraction of the cost.

• Custom. When a standard press design does not adequately meet your needs, a press tailored to your application may be in order.

Hydraulic Press Common Terms and Features

Being familiar with these terms will enhance your understanding of a hydraulic press:

• Blank Holder: A controlled force to hold the edges of the blank in a deep-drawing operation, similar to a die cushion.

• Die Cushion: A hydraulic or air cylinder positioned below the bolster and bed, providing uniform blank holding in deep drawing. Cushions also strip finished parts from the punch or die.

• Distance Reversal Switch: An adjustable limit switch to set the depth of stroke at which the ram reverses.

• Dwell Timer: An adjustable timer to set the length of dwell at the bottom of the stroke. The timer may be used for other functions such as timing a sequence of press movements.

• Heat Exchanger: A device attached to the oil reservoir to circulate water or air to keep oil at the proper operating temperature.

• Knockout: A device that strips the part from the punch or die.

• Platen: A plate, sometimes heated, attached to a moving or stationary press member.

• Pressure Reversal Switch: An adjustable switch to set the pressure at which the ram reverses.

Hydraulic Press Advantages

• Time Savings During Setup, Changeovers. Because the full power of a hydraulic press can be delivered at any point in the stroke, there is no need to determine the exact location of maximum tonnage.

• Flexibility for a Range of Applications. One hydraulic press can do many jobs within its tonnage range, including high-volume production. Common applications are deep draws, shell reductions, urethane bulging, forming, blanking, piercing, staking, punching, straightening, assembly, and press fits. They are also used for powdered metal forming, abrasive wheel forming, bonding, broaching, ball sizing, plastic and rubber compression, and transfer molding. A press fit is used for pushing a bearing onto a shaft without any mechanical fasteners to keep it in place. Typically, the hole in the bearing is several thousandths of an inch smaller than the diameter of the shaft that it is pressed onto, allowing for a nonmoving or rotating press fit.

Also, programmable logic controllers (PLCs) and other electronic-based controls have improved a hydraulic press&#;s speed and flexibility. With new computer interfaces and monitoring, hydraulic presses can be used in advanced computer-integrated manufacturing systems.

• Built-in Overload Protection. This eliminates worries about overloading or breaking the press or smashing a die. When a hydraulic press reaches its set pressure, that's all the pressure there is. The relief valve opens at that limit and there is no danger of overload.

The built-in overload protection applies to the tools too. If they are built to withstand a certain load, there is no danger of damaging them because of overloading. Tools can be sized to withstand the load of a particular job, not a particular press. The pressure of the press can be set to suit the job. The lack of impact, shock, and vibration promotes longer tool life.

• Lower Operating Costs, Increased Uptime. Hydraulic presses are relatively simple with just a few moving parts, and these are fully lubricated in a flow of pressurized oil. Breakdowns are infrequent, but when they do occur, they usually are minor. Typical routine maintenance items include replacements of packing, solenoid coils, and occasionally a valve. Not only are these parts inexpensive, but they are also easily replaced without having to disassemble the entire machine.

• Larger Capacities for Minimal Cost. Compared to a typical mechanical press, it is easier and less expensive to buy certain kinds of capacity in a hydraulic press with common stroke lengths of 12, 18, and 24 in., and it easily can be equipped with extra stroke length. Open gap (daylight) can be added as well for a minimal cost. Similarly, hydraulic presses can be built with larger table areas and beds, or smaller beds than are standard. The press tonnage doesn't dictate what the bed size will be.

• Great Control. With a hydraulic press, the ram force, direction, speed, release of force, and duration of pressure dwell can all be adjusted to fit a particular job.

• Low Noise Level. Few moving parts and the absence of a flywheel equate to an overall low noise level. Because each phase of the ram movement can be controlled, noise levels also can be controlled. A hydraulic ram can be programmed to pass through the work slowly and quietly.

• Safety. Because ram movements can be controlled, it&#;s easy to make movements safe. Non-tiedown, anti-repeat, and dual-palm button controls are used to enhance safety. The interlocking of guards, as well as other safety devices, is relatively easy because of the nature of a hydraulic press control system.

Hydraulic Press Limitations

• No hydraulic press today is as fast as the fastest mechanical press. If speed is the sole requirement and the material feed stroke is relatively short, a mechanical press remains the best choice.

• Stroke depth is a key factor to consider. If a limit switch is used to determine the bottom, the stroke depth is not likely to be controlled much closer than 0.020 in. Many hydraulic presses can be set to reverse at a preselected pressure, which usually results in uniform parts.

• Generally, if absolute stroke depth accuracy is required, "kiss" blocks must be provided in the tooling. However, some hydraulic presses are now available with an accurate built-in method of limiting the downstroke. New closed-loop servo-hydraulic systems dramatically improve stroke depth control, guaranteeing consistent, repeatable results. In many applications, this system eliminates the need for kiss blocks

• A hydraulic press requires some external or auxiliary power to feed stock. The feeder must have its own power and be integrated with the press control system. However, an increasing selection of self-powered feeding systems are available as roll feeds, hitch feeds, and air feeds.

• Both mechanical and hydraulic presses experience shock after breakthrough during blanking. But the hydraulics of a hydraulic press also must be isolated from the shock associated with decompression. If the hydraulic system does not contain an antishock feature, this shock can affect the lines and fittings.

Which Type of Hydraulic Press Is Best for My Application?

Open-gap presses provide easy access from three sides. Four-column presses ensure even pressure distribution. Straight-side presses offer the rigidity required for off-center loading in progressive die applications. One important thing to keep in mind is that the more critical the work and the more demanding the tolerances, the greater the reserve tonnage capacity should be.

Once the basics are determined, the next consideration is to select options. Most hydraulic press builders offer an array of accessories such as:

• Distance reversal limit switches.

• Pressure reversal hydraulic switches.

• Automatic (continuous) cycling.

• Dwell timers.

• Sliding bolsters and rotary index tables.

• Die cushions.

• Ejection cylinders or knockouts.

• Electronic light curtains and other safety devices.

• Touchscreen controls.

• Servo system feedback for precise, consistent, repeatable stroke control.

Note that the hydraulic circuit for a press is determined mainly by the application. In long-stroke applications such as deep-drawing, a dual-pump circuit with regeneration is typical. This allows the press ram to move quickly down to the work and out of the work while enabling a smooth draw speed.

However, when you are stamping on a hydraulic press, it is best to minimize how many valves you use during what is typically a very short stroke. Most presses used for stamping employ only a single hydraulic pump because of the short stroke required. This setup allows for fewer &#;valve shifts,&#; which reduces cycle time for a complete stroke and allows for many more strokes per minute.

Quality can vary greatly from press to press. Some light-duty presses are capable of "spanking" the work momentarily and reversing, and there are heavy-duty machines designed for general-purpose metalworking applications.

A few constructive points can be used to compare one machine with another:

Frame: Look at frame construction&#;rigidity, bolster thickness, dimensional capacity, and other factors. Cylinder: What diameter is it? How is it constructed? Who makes it? How serviceable is it? Maximum system pressure: At what PSI does the press develop full tonnage? The most common range for industrial presses is 1,000 to 3,000 PSI. Horsepower: The duration, length, and speed of the pressing stroke determine the horsepower required. Compare horsepower ratings.

Speed: Determine the speed each hydraulic press offers.

Designing the Press: Selection Tips

Press Tonnage. The tonnage required to do a job and the formulas to determine it is the same for hydraulic presses and mechanical presses. The tooling usually is interchangeable. There may be certain applications such as deep drawing in which the full power stroke characteristic of a hydraulic press reduces the tonnage, but there are no known instances of a hydraulic press requiring more tonnage.

Selecting press tonnage in the typical pressroom often is little more than guesswork.

For example, if a job is successful on a 100-ton mechanical press, tonnage tends to stay the same for the life of that job. The job may never have been tried at 75 or 50 tons. With a hydraulic press, however, you can adjust tonnage quickly and easily, tuning the press to precisely the right tonnage for each specific job.

How the Press Affects the Job. In most cases, the effect of stroke is the same on both hydraulic and mechanical presses. However, drop hammers and some mechanical presses seem to do a better job on soft jewelry pieces and impact jobs. The coining action seems sharper if the impact is there.

In deep drawing, however, the full power stroke of a hydraulic press produces significantly better results.

Automation Considerations

There are many ways and reasons to automate a hydraulic press, from simple to the very complex. Because press functionality is at the core of automation, it is advantageous to partner with a press manufacturer that is also an authorized system integrator and has a long history of providing integrated press automation systems for a range of applications.

Automation may be integrated during an initial press installation, or it can be added to an existing press setup. For the latter, most of the time automation is added not because the press is running slowly, but as a result of many other factors, some of them surprising:

• Parts demand has increased beyond the capacity or capability of manual labor to keep up.

• Personnel resources in the geographic area are not adequate or available.

• Press operators are required in other areas of the facility.

• It&#;s more cost-effective to automate an underutilized press than to purchase another new or used press.

• More consistent product quality and quantity are needed.

• Parts may have sharp edges, be high in temperature, be delicate, or are difficult to handle.

The challenge is to identify the &#;right size&#; for the automation system to address production needs for today and the future, while keeping within the project budget. As such, tailoring automation offerings to fit a range of applications is important. This includes everything from basic press automation (such as electrically integrating a material feeder to the press) to large multipress, multirobot autonomous working cells.

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