LEADER
 IN DESIGN

PRESSES

 

Fully pneumatic press powered by a relatively small air cylinder providing substantial travel and a secondary larger air cylinder acting through a high leverage mechanism providing the intensified pressure work stroke. A "Heavy Duty" press well suited for "Tough" applications.

 

Press

 

A Single Choice

For the past thirty years or so, Air over Oil cylinders have been choice for simpler metalworking applications such as bending, shearing, forming, clinching, coining, etc...  Air over Oil cylinders have similarly found their way into some spot welding applications in Automotive Body in White (BIW) where they are used to power robotic Welding Guns. Under either application (Metalforming or Welding), a first stage cylinder is used to provide substantial displacement of the tooling followed by a second stage cylinder actuating a self contained hydraulic pressure booster to provide for the substantially elevated working pressure used to perform the necessary metalworking or spot welding work.

 

Widely accepted, these devices provide a low investment, high efficiency, low noise, modular and compact solution ideal for these types of applications.

 

Although this technology has been near perfected by thirty years of research, development and advancement in sealing and containment methods, two major drawbacks remain from the reliance on hydraulic fluids and oils.

a) Relatively slow operation due to inherent requirement to displace a relatively high viscosity fluid.

b) Eventual depletion of the hydraulic fluid due to escapement into the exhaust air creating need for replenishment.

Slow operation is strictly a throughput problem and notwithstanding, these devices remain practical. Oil escapement is the somewhat more interesting drawback. Manufacturers have overcome this problem using two distinctly different approaches.

 

a) Oversizing the oil chambers of these devices to stretch out the maintenance requirements.

b) Separation of the oil and air, as much as possible, to minimize the loss of hydraulic fluid.

However clever either approach is, regular maintenance and oil refills is still required. Escaping oil, however minute is no other than yet another source of contamination ranging from the "not so bad" to drastic, and must be tolerated.

 

 

A Controls Problem

Bearing in mind that the conventional Air over Oil design is based on alternating occupation of air and oil media of some internal areas of the device with every cycle and with resistance of the hydraulic oil to displacement being proportionate to the product of oil viscosity and the oil displacement velocity2 (mathematical square), if the speed of this type of device is set too high, an oil film slips past the seals which therefore fail to wipe clean the internal surfaces of the device consequently resulting in oils mixing and escaping with air, a phenomenon known in the industry as boundary flow or boundary layer escapement which is typically considered an intolerable leakage necessitating fine speed adjustments, experimentation and substantial slowdowns of the device.

 

 

Yet another difficulty

Yet another controls problem is the shift from high advance speed to a lower speed of engagement of the work. If the decrease in speed is too abrupt (and especially if the tooling carries substantial mass), oil is subject to a negative pressure resulting in cavitation and bubbling negatively affecting the performance of the cylinder. Bad enough! This problem is additionally totally invisible requiring guesswork in adjusting actuation speeds forcing the user to slow down the device substantitally to err on the safe side.

 

In welding applications, the problem is yet more severe. With Air over Oil devices typically actuating a set of Welding Jaws with substantial moment of inertia, collision of the welding caps with the work can only be avoided by unacceptable slowdowns of the first stage cylinder necessitating elaborate pneumatic metering devices to control and nearly stop the air flow to the first stage air cylinder as the welding caps approach the work in order to overcome the momentum of the tooling. Major drawback of this approach is unreliable and/or unpredictable results forcing OEM's to result to other "Totally Pneumatic Cylinder" or "Servo Actuated Gun" solutions.

 

 

Aside from substantial advantages discussed in the following pages of this website and stated in the simplest terms; Our Airtechnix Press suffers NONE of these simply unacceptable drawbacks.