Beckwood Hydraulic Press
A hydraulic press is a press machine that uses hydraulic pressure, or fluid pressure, in order to exert force on an object. This Blog discusses hydraulic press applications, industry news and terms while breaking down issues in manufacturing and new hydraulic press technology.
The hydraulic press continues to be the press of choice for today’s modern manufacturers. The advantages of the hydraulic press versus mechanical presses is being realized and utilized by more and more manufacturers.
Today’s modern hydraulic presses provide; Performance, Reliability, and Unlimited Capability in almost any application. Stamping, Punching, Blanking, Drawing, Bending… All standard press designs and circuits can be configured to match even the most non-standard press requirements.
Allen Bradley Controls
A hydraulic press is powered by a hydraulic pump to a hydraulic cylinder or cylinders that drive the slide. Hydraulic presses allow for job parameters such as travel distance, force and return position to be easily configured for a variety of jobs within a single press.
Various levels of sophistication are available from simple mechanical switches to digitally programmable control. This flexibility yields a hydraulic press’s greatest advantage.
Full Tonnage Throughout The Stroke - The hydraulic press has the ability to deliver full pressing force anywhere in the range of stroke, unlike mechanical presses which can only develop full force at close to bottom of stroke. This significantly adds to the inherent flexibility of hydraulic presses.
- Customization - Whereas most mechanical presses are offered in standardized bed size and tonnage relationships, it is easy to design the hydraulic press to meet the customers’ specific requirements. Users that require large bed sizes but little tonnage can get just that. Conversely, customers that require high tonnage be applied to a small work area, can get a machine that is designed to handle point loading and reduced deflection for the concentrated load.
- Flexibility - With a hydraulic press, you are able to adjust tonnage and maximize cycle time for each job. You can be more efficient with your application by eliminating excessive ram movement, changing pressure and/or varying or maintaining ram speeds throughout the cycle. This can maximize cycle time when you customize the options for each job.
- Dedicated or Multi-Functional - The hydraulic presses can be designed to any level of sophistication. Whether the need be a simple dedicated cell press or a fully integrated multi-purpose system, hydraulics are cost effective and easily modified for the task at hand. Their flexibility is further enhanced by additional stroke capability for simplifying die changes and reducing set-up time. Multiple dies with varying shut heights can be run efficiently in a single press.
- Lower Up Front Costs / Fast ROI - In regard to presses, hydraulic presses are the most simple in basic design and often utilize standardized, proven hydraulic components that are readily available. The basic components to mechanical presses, such as crankshafts, clutch and brake systems, etc…, are expensive and often custom built components which serve to add machine cost. hydraulic presses are often much less expensive up-front and in long term operation.
- No Design Limitations - The principles of hydraulic force allow for creative engineering. Presses can be designed for traditional down-acting, up-acting, side-acting and multi-action operation. Power systems can be placed above, below or remote from the press and force actuators. Large bed presses can be designed for low tonnage applications and small bed presses can be designed for high tonnage requirements.
- Over-Pressure Protection - The incorporation of hydraulic relief valves into hydraulic circuits provide built-in overload protection. A press’ force cannot exceed the pressure that it is allowed to build, thereby limiting the maximum pressure attainable controls maximum force.
- Unlimited Control Options - The hydraulic press can be controlled in a variety of ways ranging from basic relays to more sophisticated PLC or PC control systems. Operator interfaces can be added to press systems to facilitate ease of job set by storing individual job parameters for each die. Presses can be controlled for precise pressure and position; including pressure holding, speed control and dynamic adjustments to realtime operating variances. Ram force and speed can be controlled in any direction with various levels of precision.
- Condensed Footprint - Hydraulics allow for generation of high pressure over small surface area. This ability reduces the overall structure required for support of the force actuators. When compared to mechanical presses, hydraulic presses consume almost 50% less space for the same tonnage capability. This size advantage results in lower manufacturing costs and a faster return on investment by requiring less long term overhead expense.
- Part Accuracy - A hydraulic press’s control over forces and motions empowers the press to provide greater overall quality of a manufactured part than many other types of presses. Control of lateral slide movement caused by off-center or unbalanced loads helps achieve tight tolerances and improves part quality.
Below is a list of important terms associated with hydraulic presses:
- Stroke - The amount of possible ram travel. Stroke is the total distance the ram can travel, from full extension to full retraction.
- Shut Height - The distance between the bed and ram bolsters when the press is fully extended. This is also known as ‘Closed Height.’
- Daylight - The distance between the bed and ram bolsters when the ram is fully retracted. Naturally, this results in the following equation: Daylight = Stroke + Shut Height
- Bolster - Plate that serves as the working surface for the bed and ram. The plate is typically bolted to the bed and ram substructures and can be machined with a variety of workholding features such as; t-slots, drilled & tapped holes, lift rails for quick die change systems, etc…
- Bed Height - The distance from the bottom of the hydraulic press structure to the working height, or top of the bed bolster.
- Stroke Control - The ram travel of the press may be controlled in a variety of ways. Most hydraulic presses are standard with Adjustable Retract Limit Switches to limit the retract distance of the ram (also know as the Up Limit Position). This can shorten cycle times by only utilizing the required stroke for part loading and unloading. Other adjustable limits may include: Slow Down Limit for deceleration from Fast Speed to Slow Speed; Bottom Stop Position and/or Bottom Stop Pressure, etc..
- Method of Return - By Pressure: The press may be designed to return on pressure. This method utilizes a pressure sending device which is adjustable and is set to determine the desired maximum pressure to be achieved by the ram. Once this pressure is achieved, the ram typically completes the cycle by returning to the pre-determined home, or up-limit position. By Position: The press may be designed to return on position. This method utilizes either a position sensing device or a limit or proximity switch that can be set to signal that the desired ram extension position has been achieved. By both Pressure & Position: This method allows the operator to select the desired method of return. For manual systems, a Pressure/Position keyswitch is provided for selecting the deisred return method. For programmable systems, the return method is programmed into the HMI.
- Dwell - Hydraulic presses are capable of maintaining force on the work for extended periods of time. This is typically accomplished by using pressure lock valves or variable volume piston pumps that are remotely controlled for precise holding pressures. Dwell cycles are typically employed for applications which require a set or curing time for the material in question, such as molding & compacting applications.
- Heated Platens - Hydraulic presses can be equipped with heated platens which utilize electric rods, steam, hot oil, water, or other heating methods for achieving the desired working temperature. These systems usually require thermal breaks between the heated platens and the hydraulic press structure. Also, depending on the working temperature, the hydraulic action of the press is often configured in an up-acting manner, allowing the hydraulic components to be placed near the bottom of the press system and away from the rising heat. Platens can be set to achieve and maintain a working temperature, or can be designed to increase and decrease temperature over time depending on the requirements of the part being manufactured.
- Bed Cushion - A bed cushion is a commonly required for draw tooling and is a system that applies resistance when pushed upon. This resistance can be dynamic or statically controlled throughout the stroke. Bed cushions have a “pusher pin plate” that is located just beneath the bed bolster. The bed bolster is provided with multiple through holes where “pusher pins” are inserted. These pins are used by the tooling to generate resistive force as the hydraulic press ram pushes down. The cushion can also be configured for multiple control zones for on-the-fly dynamic control.