Refurbishing servo-drive triaxis transfer systems cost-effectively

The latest system controls architecture is PLC-based and uses a range of HMIs, such as large, high-resolution monitors.

So, you invested in a transfer system a decade or so back. The system still works. The framing is solid. But although the bones are strong, the flesh is failing and the mind is gone!

Some parts of your transfer system are outdated or failing, and you cannot get replacements for them. Your control system was fine when you bought it, but you know that more advanced systems are out there today. You’d like to take advantage of the latest technologies in drive control, performance, system diagnostics, and energy savings.

So how can you upgrade your servo-driven transfer system? What new technologies can you access, and which capabilities can you gain by doing so?

Many manufacturers are taking advantage of opportunities to refurbish their transfer systems by upgrading the controls, drive trains, and bearings while reusing their frames, in keeping with reuse sustainability goals and cost-saving initiatives.

Controls

When servo-drive technology was first incorporated into triaxis press transfer systems, direct current (DC) motors were used. DC servomotors now are virtually obsolete in the tri-axis transfer industry domestically. Original equipment manufacturers (OEMs) no longer support those installations. They have discontinued direct replacement of motors and motor components and are no longer investing in the development of the associated communications infrastructure.

In addition, the human-machine interface (HMI) subsystems comprise input screens and microcomputers. Microcomputer operating systems have a very short life span, becoming obsolete rapidly.

Alternating current (AC) motors are now the U.S. standard, providing performance at a reduced price. The current AC motors are dimensionally smaller and totally enclosed. They are not vulnerable to contaminants that are inherent in the stamping press environment. In addition, they do not require special cooling provisions. The associated infrastructure is expansive.

The latest system controls architecture is PLC-based and uses a range of HMIs, such as large, high-resolution monitors. PLC software is commonly used in the North American stamping market. As such, many stampers use it to control existing plant systems and are familiar with its programming language. An HMI typically is exposed and susceptible to damage, so modern HMIs are designed to operate independently of the PLC so that a damaged HMI will not result in a system shutdown.

Drive components are critical to the transfer system’s performance. Today a range of drive components are available, allowing stamping companies to perfectly match the application specifications and requirements. The new components provide significant improvements in acceleration/deceleration performance and torque ratings for use in triaxis, transfer, and torque motion control.

The new controls architectures are multilevel, torque; setup, single-cycle; and full-speed motion control. These three levels allow a stamper to set up tooling and dial in the part path with virtually no finger tooling damage. In addition, an automated homing routine, using the torque motion control, is available, which simplifies the homing process and substantially reduces the time to complete it.

Whirlpool Ohio refurbishes its transfer systems

Encoders provide press data for a servo-driven triaxis transfer system. They can include a single smart-quadrant encoder, which provides directional, velocity, and distance press data. This provides a much tighter tolerance to the press motion. This advances earlier encoder technology that could detect direction only by reading the increasing or decreasing values, making it difficult to synchronize the actual press direction.

Bearings

If a system is operating in a repeatable manner, performing to specification, and being well-maintained, do stampers still need to consider changing or upgrading the linear bearings? The answer is yes. They really need to consider all of the potential failure points, especially if exact replacements are not readily available.

Linear bearing designs have evolved, and industry standards have changed. When product changes occur, it is common for bearing manufacturers to continue to offer both the new and previous designs for a period of time. At some point, though, the previous designs must be discontinued because of the increased costs of manufacturing and inventory. Therefore, as transfer systems are updated, the linear bearings are commonly updated also, bringing the transfer’s linear bearing mounting points up to current industry standards. This provides for a platform that is compatible with new industry standards and linear bearings that are readily available as replacements, if or when required.