Hydropneumatic Presses Improve Quality for Automotive Assembler

Hydraulic presses can generate tons of force. Some can produce more than 200 tons of force. However, hydraulic presses are not very energy-efficient, nor are they suitable for applications, such as medical device assembly, that cannot tolerate contamination from hydraulic fluid. Hydraulic presses are also less accurate than other press technologies. Hard stops are often needed to control ram position.

Hydropneumatic presses combine the speed, efficiency and low cost of pneumatic presses with the high output force of hydraulic presses. A hydropneumatic press consists of a hydraulic cylinder, an air-over-oil intensifier and an oil reservoir. At the start of the cycle, the ram approaches the workpiece at high speed, but low force, under compressed air. Once the ram contacts the workpiece, the intensifier is automatically energized by a directional control valve. At that point, hydraulic power takes over and the full force of the press is applied. At the end of the cycle, the ram retracts rapidly.

Because it uses compressed air as its primary power source, a hydropneumatic press requires less expensive piping systems and components. There’s no need to fill an oil tank with large quantities of expensive hydraulic fluid. Hydropneumatic presses are also lighter, more compact and more energy efficient than pure hydraulic presses.

Servo presses are the most expensive option for high-force applications, but they’re also the most precise and flexible. 

These were the choices faced recently by a major U.S. manufacturer of braking and suspension components. The company contacted Aries Engineering Co. Inc. to increase the quality of its finished products and free up floor space for a new assembly line. 

The OEM was experiencing persistent interruptions of an assembly line consisting of a rotary indexing dial and hydraulic presses. The presses are used to install bearings and studs in a component. The system was unable to monitor and relay actual insertion forces and distances. Additional floor space was also necessary to make room for a new assembly line, so removing the noisy pumps, bulky accumulator tanks, high-heat motors and leaking hydraulic lines associated with the hydraulic presses was essential.

Aries Engineering retrofitted the indexing table, removing all the hydraulic cylinders and replacing them with IntelliCyl hydropneumatic cylinders operated by simple pneumatic valves. Each pressing station now includes an integral linear variable displacement transducer, a load cell, and a HyperView signature analysis monitor. 

The new system actively measures stud and bearing insertion depth by establishing a series of “windows” around two critical points of the press-fit operation: the contact point and the final depth. Only when the correct stack-up height was confirmed would high pressure then activate to press the bearing or stud into the component. This ultimately reduced in-process part non-conformance to near-zero.

For more information on presses, click www.hypercyl.com or visit the company’s booth at The ASSEMBLY Show South, which will be held April 16-17, 2025, at the Music City Center in Nashville, TN.

Aries Engineering is one of several suppliers of presses and riveters exhibiting at the event. Others include Absolute Gauge Technologies, Orbitform, Promess Inc., Schmidt Technology, and Tox Pressotechnik.

Besides motion control technology, you’ll find some 150 suppliers of adhesives, assembly machines, fastening tools, robotics, parts feeders, presses, test and inspection devices, and other technologies. The show is being held in conjunction with The Quality Show South and Adhesives in Action. For more information, visit www.assemblyshowsouth.com.