Top 8 Hydraulic Press Facts You Need to Know

What should you do to keep your hydraulic press running? Know your press&#;when it is working properly or when it needs attention. You can extend press life and maximize your investment by keeping your eyes and ears tuned and by performing these eight preventive

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1. Keep It Cool. A hydraulic press should run cool&#;typically between 120 degrees F and 140 degrees F, and no higher than150 degrees F.

2. Allow No Leaks. Hydraulic press that are in good working condition have no leaks. Check around the ram of the press and the O-ring seals on valve seats and hose end fittings, as well as all hydraulic lines. You should refer to the machine operator manual for the specific type of oil that the manufacturer suggests for your press. While you check seals, be sure that sufficient lubrication is applied wherever necessary.

3. Build Pressure Quickly. A hydraulic press in good working condition takes one-half to one second to build to the maximum required pressure. A pressure buildup of more than two to three seconds may indicate a pump problem. Typically, pressure problems are pump-related; however, occasionally the relief valve may be working too slowly. Perhaps dirt or grit is in the line or the valve is open too wide. Also, if the press&#;s motor is not producing sufficient revolutions per minute (RPM), a drop in pressure could occur.

4. Ensure Smooth Valve Shifts. Valve shifts should be smooth from one speed to another&#;you should not hear any banging noises during speed changes. In fact, any sounds that are not considered normal should be investigated promptly.

5. Check the Electronics. Coils that are located on valves normally have a life cycle of 3 million strokes. Relays normally have a life cycle of 1 million strokes. Replacing the coils before they fail can eliminate or reduce hours of troubleshooting and reduce downtime. Install an hour meter and a nonresettable cycle counter to help maintain accurate records and facilitate maintenance scheduling.

Fix loose wires and fittings and frayed hoses because frayed hoses and incorrectly crimped fittings can cause plumbing failures. Hoses should never touch each other, and fittings should be crimped by an authorized facility to ensure they can withstand the system pressure.

Check the control wiring annually to make sure all connections are tight and that the wiring is in good condition (see Figure 1). Loose wiring should be placed in wire ways or tied with wire ties. All spares or unused wires should be capped off or removed. Dust or dirt should be removed from enclosures.

6. Keep the Oil Clean. Maintaining your press&#;s oil in good condition is a relatively simple way to extend press life. Dirty oil and low oil levels reduce press life rapidly. Dirt and heat are common culprits.

7. Maintain Optimal Oil Temperature. The ideal operating temperature is about 120 degrees F. Either air or a water cooler can help maintain the temperature. Probes are inserted into the oil reservoir and temperature maintained with a thermostat. An air cooler uses a radiator to separate the heat with an electric fan, circulating the air through the cooler.

The radiator should be kept clean, as it tends to collect dirt and dust in the vanes, which inhibits airflow. Attaching a common filter, such as the kind used in heating and air-conditioning units, to the heat exchanger is an inexpensive way to help keep the unit clean (see Figure 2).

Water coolers work similarly except that water instead of air travels through the vanes. The water source could be city water, chillers, or rooftop-mounted exchangers. Running city water through an exchanger could be expensive and will tend to rust the inside of the exchanger. Also, many municipalities discourage the use of city water, depending on local water restrictions and codes.

Rooftop-mounted units tend to collect dust and dirt, which can clog the exchanger and perhaps cause rusting. Placing a filter inline will help remove any fine particles. A water chiller is the best way to dissipate heat because the inlet temperature can be adjusted. Also, antirusting agents can be added to the water. Inspection of all of this equipment should be done yearly.

8. Change Filters. The next step in good maintenance is to perform oil samplings to ascertain when you need to change filters and if they are being changed at proper intervals (see image at top of the page). This should be done at least yearly. The sampling can tell you how many particles of different sizes are in the oil if the oil has water in it, and the lubricity properties. Usually, it is not necessary to change the oil, but certain additives may be needed.

You also can tell from the results if the correct micron level of filtration is being used. Simple hydraulic systems require only code 10 filters, which result in a cleanness level of 20/18/15. More complex systems or those with servo valves require code 03 filters, which have a cleanness level of 16/14/12. Numerous companies can perform this test and maintain the records.

Create a daily (see Daily Checks), monthly, and annual checklist for all the equipment in your shop. This allows you to detect problems early and avoid potentially expensive fixes later.

When to Replace Your Press

Despite following good maintenance practices to prolong the life of a hydraulic press, sometimes it is necessary for you to replace the press to ensure that part production is accurate and consistent. It&#;s important to recognize critical indicators that signal a new press is required:

The press can no longer build up the pressure. Key areas to look into are the pump, press motor, and valves. However, if the pump is faulty, you may be able to replace just the pump.

The frame is cracked. These fractures can be subtle or obvious. A temporary fix is to possibly weld the frame, but ultimately the press will need to be replaced.

Critical hydraulic or electrical problems exist. Intermittent operation problems can signify an electrical short or loose wire. Make sure all wires are tight and have ferrules on the wire ends to prevent cross contact with other electrical components. Some older hydraulic presses may have outdated electrical controls or hydraulic components that are no longer available. These two factors could be a reason to consider getting a new hydraulic press rather than upgrading the electrical control or hydraulics package on an old frame that may have performed millions of cycles.

If you ignore any of these warning signs and run the press while it is compromised, a performance likely will be sacrificed&#;increased cycle times, longer downtimes, and decreased part accuracy.

In one case example, a manufacturer was trying to press fit a bearing into a seat but it could not be seated properly on a consistent basis. The bearing outside diameter was oversized and the sleeve inside diameter was undersized. When the parts were run on a new press with consistent results, this helped the manufacturer determine that the old press needed to be replaced.

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Daily Checks

&#;Oil leaks. All hydraulic lines should be checked because a very small leak can turn into a very big mess. Loose fittings should be tightened and wiped clean of the spilled oil. Keeping a press clean will help you locate any new leaks that might develop.

&#;Oil level. If necessary, top it off. To determine the type of oil you should use, refer to the oil tag that is affixed to most machines.

&#;Loose bolts. Some dies cause vibration and shock that can loosen bolts around the tooling area.

&#;Guided platens. Some bushing fittings should have a thin film of lubricant over the rod (see Figure 3). Overlubricating these fittings may result in dirt accumulation and premature bearing wear. Other bushings have a check valve-type fitting with graphite integrated into the bronze. These bushings require very little maintenance. Mobil Viscolite® or a similar oil is best. Never put grease into this type of bearing.

&#;Oil temperature. After the machine has had time to warm to operating temperature, check the oil temperature. Ideally, it is 120 degrees F.

&#;Press ram. It should be moist, but not dripping oil.

&#;Light curtains. Just break the beam while the ram is traveling down. The press should stop immediately. Breaking the beam on the upstroke may not stop the press. Refer to the owner&#;s manual for proper function.

&#;Cleanness. Check to be sure the work area is clean. This helps to ensure a safe work environment and prevent accidents.

About Hydraulic Presses

The use of hydraulic presses over the traditional mechanical press has increased dramatically over the last 30 years. Until recent history, the mechanical press was the common machine for production press work. The mechanical press utilizes a rack and pinion as well as a crankshaft to achieve significant tonnage without an external power source. It wasn&#;t until the early s that hydraulic presses became the more popular option.

Hydraulic Presses utilize hydraulic cylinders, single-direction mechanic actuators, to create compressive force. Invented in by Joseph Bramah, hydraulic systems were conceptualized by studying the movement of fluids through early toilets, which were later replaced by toilets created by Bramah.

Hydraulics depend on Pascal's law, which basically states that when an incompressible fluid is given pressure, the pressure is applied evenly in every direction. This law allows the force generated from compressing a fluid to be utilized in moving mechanics like a piston. It was also discovered that using a smaller piston to pressurize the fluid, through which moves a larger piston, generates greater forces than using two equally-sized pistons. This is called a force multiplier and is crucial when creating a hydraulic system.

Needs

Before seeking out the best prices, you should consider the role a hydraulic press will have in your personal shop or business. Writing a full list of tasks you&#;d like a press to accomplish can provide a better scope of the strength, size, type, model, etc. of press you will need. Be sure to understand what a hydraulic press can do; the range of abilities are extensive. Bending, blanking, drawing, forming, molding, punching, and stamping are just some of abilities of hydraulic presses. Not all machines are capable of these actions and should be taken into consideration.

Tonnage

After considering the uses for your press, the next important question to ask is what tonnage will be required for the jobs.  If you are switching from a mechanical press to a hydraulic press, the tonnage requirements will not change. Do consider, however, when choosing the right hydraulic press, you only need to know the maximum tonnage you will require for any given job. Opposed to a mechanical press, most hydraulic presses can be tuned down to a lower tonnage depending on the task.

The required tonnage to punch material (or the punching force) varies depending on three factors: perimeter of the punch, shear strength of the material, and material thickness. The tonnage can be calculated with the following equation:

Image

Shear strength is a measurement of the force needed to produce a sliding failure on the material along a parallel plane to the direction of the force; punching a hole in paper is an example of paper failing in shear. Shear strength is commonly measured in kilonewtons per square millimeter (kN/mm2) or pounds per square inch (PSI)­. All materials shear fail at different levels of force, so it is important to understand the specifications of the material you are working with. The material specifications also include the thickness of the material being handled.

Though punching is a common use for a hydraulic press, other functions also require specific tonnage in order to be effective. It is encouraged to understand the tonnage requirements for any job you plan to utilize a hydraulic press for.

 

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