Manufacturers struggling to meet tight tolerances and even tighter lead times can look to a variety of areas to make improvements, from adding more skilled personnel to investing in more advanced ERP solutions and just about everything in between. Increasingly, manufacturers using hydraulic presses have been finding their improvements by updating and replacing various aspects of their equipment.
Breathing new life into an older hydraulic press can be a more cost-effective venture than investing in brand-new equipment and can also be a way to avoid excessive downtime and other issues suffered when integrating a new piece of technology.
For example, is the hydraulic press outfitted with an antiquated control panel? If so, programmable logic controllers (PLCs) can be installed to significantly improve production.
What about the valves, cylinders, motors and pumps? Those, too, can be retrofitted or upgraded for vastly more productive outcomes. Bearings and guide components, safety features and automation are also areas deserving of a fair amount of attention for manufacturers considering hydraulic press improvements.
Timing counts
For some manufacturers, the best time to make improvements to their hydraulic presses was yesterday. For those not yet sure if retrofitting or upgrading components is the right direction to go, Tim Wilson, design engineer at Greenerd Press & Machine Co., advises to consider how reliable and functional the equipment is at present. The answers will vary depending on the technology currently in place, which means there is no one-size-fits-all solution.
“It is not always necessary to upgrade an entire system to gain reliability or added functionality,” Wilson says. “Auxiliary systems and safety items are commonly added to older equipment without a complete rebuild. It is very common to only upgrade a failing PLC and not change any other components. Some customers take advantage of the increased capabilities of a new PLC and later upgrade critical valves and feedback devices to increase accuracy and improve diagnostics.”
Timing the improvements is always going to be a factor, as downtime has to be planned for meticulously. Wilson says that timing greatly depends on the components being upgraded and whether or not they’re in stock. For example, high-response valves can have a lead time of more than 22 weeks. PLCs can be installed to significantly improve production.
“On-site evaluation from a hydraulic press expert can help identify cost-effective areas for refurbishment and provide options for increasing functionality,” he says.
Motors, pumps and valves
Hydraulic press motors have evolved over the last decade-plus. For example, today’s motors offer reduced rotational mass and are constructed with higher quality copper, which means they have improved winding technology. Press users also have more options for motor starters, including soft starters and variable-frequency drive technology.
Both of these allow the motor to ramp to full speed, but the inrush current is decreased. The advantage to this scenario is that the hydraulic press will start the motor when the press is ready to work, and will turn off the motor when movement of the platen is not required. This new approach means that motors run at slower speeds when the press is idle, which allows for accumulators to charge and the oil to cool or be filtered.
Pumps are also stronger and more efficient today. Improvements in seals as well as stronger hoses and couplings have practically eliminated leaks and minimized maintenance. Hydraulic fluids have also improved, as new additives increase their effectiveness. The improvement to motors and pumps also means less noise in the workplace – they simply run quieter.
Most hydraulic presses have the ability to reverse on a pressure setting or position setting. The advancements of proportional directional valves have made it possible to greatly improve a press’ position reversal accuracy. Older presses were designed with small proportional directional valves to achieve the reversal action. However, it is difficult to achieve positional accuracy with old valves.
“When rebuilding a press,” Wilson says, “a faster PLC, more accurate position measurement devices and improved valve control all incrementally increase the control over reversal position, sometimes down to a thousandth of an inch.”
Wilson adds that servo-quality proportional valves have fast response times, even in larger size valves, which can handle the required flow and faster cycle times. Furthermore, proportional valves offer an improved reliability over older servo valves that are sensitive to contamination, which can lead to maintenance issues.
Safety first
While productivity is important, manufacturers are increasingly cognizant of creating a safer work environment. New options for safer hydraulic presses primarily lie in adding safety light curtain circuits. A safety curtain drastically reduces the probability of operator injury. The more popular safety curtains use an infrared LED beam that can detect when a person has put themselves in danger.
Another highly popular safety option for presses are safety relays for anti-tie downs on the press buttons. With both hands required to operate the press, it’s important that they won’t be in the contact area where they can be injured.
Wilson says upgrading to ANSI B11.2-1995 (R2010) while adding safety curtains can allow the press to be run by an auxiliary piece of equipment, such as a feeder or footswitch, which will reduce cycle time. The ANSI standard applies to hydraulic and pneumatic power presses and touches on risk assessment processes, safeguarding, training, responsibility and additional requirements for operation. The latest ANSI B11.2-2013 requires additional safety features including safety catchers on the moving platen and verification of valve position. The additional requirements can reduce the risk of injury to an operator that is frequently loading and unloading parts under the moving platen.
Evaluating upgrades
To determine whether or not they are ready to make an upgrade, and to increase efficiency, manufacturers need to establish their end goals, at which point cost can be more accurately assessed. Establishing a relationship with a reputable press manufacturer can be a great first step as a way to keep informed about what new technologies are available and which of those will work on specific types of presses.
An expert with years of experience will help provide a comprehensive analysis of a manufacturer’s equipment and recommend the appropriate upgrades. Greenerd Press & Machine Co. supplies custom hydraulic press solutions and provides retrofit and rebuild services.
Greenerd suggests taking the following into account to help determine if a retrofit or an upgrade is going to be in the cards:
- Upgrading to the current ANSI B11.2 for safety
- Building in speed control for handling hard-to-form materials and increasing cycle rates
- Adding closed-loop pressure and position control
- Improving accuracy and repeatability
- Integrating automation components, such as robotics and feeders
- Adding the ease-of-use and accuracy of touchscreen controls
Depending on the manufacturer, a bar code reader might even be brought in to improve quality control. This has been a trend in recent years, as more manufacturers are interested in scanning tools for work orders to automatically upload new parameters for a component. And for added safety, a worker’s employee badge can be scanned to ensure they have permission to operate the press.
