By Michael R. Kramer, Bosch Rexroth Corporation.
There is a growing recognition in the extrusion industry of the value of fully committing to the connected future offered by Industry 4.0 (I4.0) technology platforms. These smart, efficient, and highly connected systems provide opportunities for increased productivity and profitability, reduced downtime, lower maintenance costs, improved quality, and increased machine performance.
The aluminum extrusion industry has had to navigate the widely varying performance claims of hydraulic equipment manufacturers, a myriad of electronic control options, and misrepresented or misunderstood attributes of various integrated press control concepts. To truly benefit from the connected future, the industry must fully understand the I4.0 technologies from an engineering perspective to ensure planned production goals are achieved and maintained.
Many highly automated manufacturing segments are already benefitting from aggressive implementation of I4.0 technologies (Figure 1), as well as transforming their production management and business analytical processes to benefit from the data-rich power these digital systems supply. Industrial hydraulics users, such as extruders, can reap the same benefits.
In simple terms, I4.0 connectivity is the connection of people, machines, and objects for the efficient production of goods and services. In extrusion press operations, this calls for hydraulics and controls technology with advanced levels of connectivity.
The key to benefitting from I4.0 is using data to generate results. Savings can be realized throughout the production process—from digital supply chain improvements and more flexible equipment performance to advances in energy management, product quality, predictive maintenance, and more sophisticated use of real-time data.
These broader benefits can be applied to extrusion presses that are upgraded with I4.0 technology. For example, the system can use sensors to monitor the health of a hydraulic pump and automatically notify the maintenance manager prior to failure, allowing for replacement during a scheduled outage rather than catastrophically failing during production.
Use of sensors can also help streamline routine maintenance tasks, such as filter cartridge changes. Rather than simply notifying personnel of the need for a filter change when clogged, the system could anticipate when the change is required, automatically assign the task to a maintenance person, and notify purchasing to restock the filter. In addition, system health and operating status are available in real time from any connected device, anywhere in the world, reducing the need for late-night visits to the plant by maintenance personnel.
Press drive and control systems that are I4.0 enabled will also offer production gains through new, more automated and data-driven capabilities. In an optimized extrusion production system, identifying codes could be laser-etched onto logs, billets, and dies so that the control system automatically adjusts to optimum production parameters every press cycle without operator intervention. Multiple sensors in the container can transmit accurate temperature information in real time throughout the push and communicate with a high-response hydraulic system to continuously adjust extrusion speed to the maximum allowable level. At the press outlet, a machine vision system monitoring extrusion quality will also send data to the control system allowing real-time production optimization to ensure the press is always producing at the maximum possible output, while meeting required quality standards.
Extrusion Press Upgrades
One of the key challenges in implementing I4.0 in extrusion press operations is understanding and defining how the extruder should approach these upgrades. Many operational extrusion presses are really not ready for the connected future. However, if the press frame is sound, a retrofit and upgrade of key press components, such as hydraulics and controls, can extend the life of the press at a lower cost than a new press.
This method can create a more flexible, reliable, long-term manufacturing solution that meets the needs of the extruder, raises press performance levels, and includes the connected hydraulics necessary to gain the benefits of I4.0 operations. When considering a hydraulics and controls systems retrofit, evaluate the following factors to determine the ultimate scope and return of a press retrofit project.
The extruder should consider their current level of extrusion control. How precise is it? What is the scrap rate? How much time and effort does it take to achieve high-quality, low-defect parts consistently? If the output of the press must be scrapped due to unacceptable quality, then it may need better electro-hydraulic controls.
Today’s state-of-the-art PLCs and closed-loop controllers provide much finer accuracy, whether operators are using press velocity or part temperature to manage extrusion throughput. An improved control system provides greatly enhanced precision and automation of the hydraulics circuit, achieving much higher levels of position, velocity, and endpoint control.
PLCs also allow instantaneous adjustments during the extrusion cycle to keep production moving. Increased extrusion precision leads to greater control over butt length, helping to reduce aluminum waste and increasing the number of shapes produced per hour.
Hydraulics Efficiency and Effectiveness
It’s important to fully assess the efficiency and reliability of the hydraulics and controls systems components. For example, many older-generation presses have servo valves to control the hydraulic pumps and the speed of the press. These can be expensive and temperamental, requiring hydraulic fluid that has a dedicated filtration system with finer particulate removal than that of the rest of the system.
By contrast, the current generation of proportional hydraulic valves offers the same or better functionality, yet are much more tolerant of variations in hydraulic fluid quality. They are also less costly to purchase and repair. Proper filtration is still crucial: using high-efficiency filtration in a retrofit is another important element in helping a system to survive for years, even when using quality fluid. In this example, if the pump control valves are not as rugged as they could be, or require persistent maintenance leading to press downtime, a retrofit incorporating proportional valves will reduce operational costs.
Hydraulic systems can also be simplified, thus becoming easier to operate and maintain, by replacing in-line valve architecture (where multiple circuits are connected “in-line” on a one-to-one basis) with a single hydraulic manifold. This rationalizes the hydraulic design, reduces the leak points and hydraulic maintenance requirements, and also reduces the number of spare parts that must be stocked to keep the press operating.
Another way a press retrofit can improve overall business performance is through evaluating the energy efficiency of press systems. In many older systems, the electric motors driving the hydraulic pumps are often oversized to compensate for inefficiencies downstream in the hydraulics system (leaks, pressure drop-offs, etc.). “Right-sizing” through the use of today’s energy-efficient motors can be combined with a design concept called “energy on demand.” This integrates sophisticated controllers and variable speed pumps with properly sized electric motors to deliver only as much energy as is needed to accomplish the press cycle.
Hydraulic pump efficiency is also worth assessing. All hydraulic pumps utilize a portion of the fluid flowing through them for lubrication. As a result, to generate the required force in a hydraulic motion sequence, more energy needs to be drawn from the electric motor to compensate for this fluid. Less-efficient, older-generation pumps require more lubrication. They also generate higher levels of waste heat, increasing the loads on cooling systems, and can lead to unnecessary energy consumption.
The latest generation of hydraulic pumps are significantly more efficient, requiring less lubrication and placing lower loads on the cooling system. Newer-generation pumps also feature integrated sensors and diagnostic ports to check hydraulic system status (Figure 2), helping plant personnel pinpoint trouble spots within the hydraulics much faster.
Safety for the machine operator and protection for the press itself have become more significant in today’s manufacturing environment. Presses upgraded to connected hydraulics systems can set unique upper limits on pressure for each die in the press to help protect the die (and other press components) from damage. Upgrading to controls with these capabilities can enhance plant safety and lengthen the life of the equipment.
Two other complaints associated with extrusion press hydraulics are fluid leaks and noise. It is often assumed that these issues are inherent to the power and force dynamics that only hydraulics can deliver—even if it means increased maintenance and an unsuitable operating environment due to hydraulic leaks.
But many of these issues arise from outdated or poorly designed hydraulics systems, which may also have been improperly maintained. For example, presses that utilize older in-line valves have far more points where leaks can occur than systems retrofitted with hydraulic manifolds. In addition, poor control system design or older controllers may be introducing high levels of hydraulic “shock” through the press motion cycle, overstressing valves and seals.
Modern I4.0 electrohydraulic controls offer much finer control of the hydraulic axis, minimizing stress on the system, which results in less leaks and fewer broken pipes. To reduce noise, the use of variable frequency drives can lower the time-weighted average noise level in the plant by reducing drive speed when pumps are not required.
Overall Operating Costs
Many press operators incrementally expend time and resources on repeated repairs and maintenance efforts. These include maintaining spare parts inventories, more frequent maintenance cycles, and repair and service contracts with outside hydraulics and controls service providers—all of which can also reduce press availability. Many of these problems can be solved through a retrofit with significantly less cost than the installation of a new press.
For many press operators, a key goal is also to reduce the extrusion press “dead cycle,” or the time when the press is not extruding parts. A hydraulics and controls retrofit has the potential to significantly reduce the extrusion press dead cycle, enabling the press to push more material per hour.
New Life for Extrusion Presses
Preserving and extending the value of existing manufacturing equipment makes fundamental sense; the challenge is to determine which solution offers the most reliable and measurable return on investment. Productivity increases of 10-50% are common and can often justify modernization costs alone, but the added benefits of energy efficiency, improved safety, and reduced maintenance costs provide additional incentives. For any modernization, it makes sense to evaluate all aspects of the existing systems that drive, control, and affect extrusion press performance, uptime, and part quality.
Each extrusion press operation has unique considerations and business requirements. Connected hydraulics offer multiple advantages, especially to extruders with presses equipped with outdated or poorly performing hydraulics and controls, to help upgrade press performance and the efficiency and productivity of their extrusion business.
Editor’s Note: This article first appeared in the April 2023 issue of Light Metal Age. To receive the current issue, please subscribe.