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Thursday, July 31, 2014

The Future of Advanced Automation in Precision Machining

As manufacturers push for tighter tolerances, smaller components, and faster turnaround, advanced automation continues to have widespread applications in an increasing number of industries. Automation not only increases part repeatability in micro and ultra-precision machining processes, it significantly reduces the labor required to produce a part. Eliminating labor costs reduces per-piece costs, especially in higher volume applications, and insulates the customer against future price volatility due to the labor market.

Credit: Arnold Machine

Credit: Arnold Machine

The future of advanced automation continues to evolve. As technology is developed to meet manufacturer’s demands, customers continue to push the limits of machining speed and precision, leading to a continuous cycle of innovation in the field of precision machining automation.

Automation solutions entail a number of electronic and mechanical devices. One aspect of advanced automation systems, and perhaps the most obvious, is the electronic motion controller. Electronic motion controllers determine the velocity and position of the mechanical device, commonly a linear actuator or an electric motor. The first electronic motion controllers were built using cumbersome proprietary programming software unique to each machine manufacturer.

As the need for system integration in the development of automated manufacturing cells grew, PLC controllers gained favor. This technology allowed users to program controls based on more common code and provided reliable and real-time control over machining processes.

As older technology becomes obsolete and requires replacement, the development of PC-based controls continues to grow. Prior issues with determinism prevented widespread use of PC-based controls. Time lags prevented controls from expediently responding to the real-time machining environment.

Exact knowledge of position and other machining variables is essential to achieving precise, accurate results. These timing issues have largely been resolved by isolating the control architecture from the PC operating system. In addition, traditional PC hardware often suffered premature failure in the manufacturing environment. This was initially subverted by isolating the PC from the shop floor, making usability an issue. Today, several rugged PC options specifically designed for use in harsh environments are widely available.

These improvements have led to widespread acceptance of PC-based motion control systems. PC-based controls are versatile, intuitive, and allow users to develop custom automated systems based on common platforms using off-the-shelf hardware. By employing PC-based controllers, user interfaces can be made consistent across all machinery and work cells. This provides advantages in operator training and eliminates costly programming errors.

PC-based controls can be integrated with data recording and machine monitoring software, which provides the necessary information used in statistical process control applications. This seamless integration of control and monitoring leads to reduced downtime on the plant floor and increased reproducibility in machined parts.

Complex components, especially those used in the aerospace, medical, and defense industries, often require long milling cycles. Advances in material technology have led to an increase in tooling life and allow machinists to increase machining speed. However, higher machining speed presents additional synchronicity challenges for motion controllers.

Credit: Arnold Machine

Credit: Arnold Machine

Recent advances in controls have introduced algorithms capable of compensating for errors and improving accuracy in high-speed, multi-axis machining applications. This combination of increased tooling quality and improved synchronicity allows for faster cycle times in many automated machining applications, allowing manufacturers to increase machining capacity without purchasing new metal-cutting equipment.

An equally critical aspect of advanced automation systems is the mechanical element, especially the linear actuator mechanism. While electronic control devices typically receive the most attention in developing automation solutions, they are limited by the ability of the mechanical mechanism to respond to the controls. Machining parameters such as loading, orientation, and machining speed must be considered in the selection of a linear actuator. The actuator must be able to smoothly translate the workpiece in order to achieve high levels of precision promised by the electronic motion controller.

Most modern precision machining equipment uses a ball screw linear motion system. Ball screws are capable of handling large axial loads, while maintaining precision positioning requirements, and have very little internal friction, which leads to high machining efficiency. The ISO 3408-1:2006 standard designates Class 3, 5, and 7 accuracy classes for ball screws.

Ground screws have traditionally been used for ultra-precision applications, but machining advances have led to improved precision in rolled screws. Rolled ball screws are typically relegated to Class 3 and 5 designations. This level of accuracy covers most applications and provides a more economical alternative to ground screws.

The base of the linear actuator typically consists of an aluminum or steel frame. Aluminum extrusions provide a cost-effective solution to light- to medium-duty machining, while steel is generally required for higher load applications.

Previously, a major drawback of automation was the limitation it placed on equipment capabilities. This confined most automation applications to high-volume processes. Increased software usability and hardware versatility have opened up automation applications to lower-volume production as well as part families.

Using a combination of part feeders, automated machining centers, gantry robots, and pallet loading systems, manufacturers are often able to automate the entire machining process from raw material to palletized part. Many part families can be produced by using the same raw material, especially in turning applications, making bar feeders a valuable component of automated machining systems. Advanced manufacturing systems are capable of producing different variations of the same part with no appreciable changeover time, meaning parts such as small medical devices can be produced in varying quantities without a loss in efficiency.

Advanced automation solutions provide users with the ability to machine micro and ultra-precision components with maximum reproducibility and minimal labor. Programming for automation equipment continues to become more user-friendly, allowing for widespread system integration of entire processing lines across multiple machining platforms. Advances in the field of electronic motion controllers, combined with increased precision in the mechanical components used to align and translate the workpiece, have resulted in unprecedented degrees of accuracy and very fine surface finishes.

The savings in labor and reduced processing times make these technologies extremely cost-effective, often providing a very short ROI period. Increased cost effectiveness and usability in advanced automation make these technologies widely applicable to a number of manufacturing industries, as market demand continues to push the envelope in the innovation of advanced precision machining solutions.

 

Zach Arnold is president of Arnold Machine Inc., a provider of automation systems and manufacturing services based in Tiffin, Ohio. Arnold Machine serves the automotive, appliance, and heavy-equipment industries with custom sheet metal fabrication, precision CNC machining, and engineering services. It builds automation equipment that includes spray machines, conveyor systems, and pick-and-place machinery. For more, visit www.arnoldmachine.com.

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Comments

  1. Thanks for this great article. We are a small job shop that specializes in precision plastic machining. We just added some bar feeders to a few of our CNC turning centers. It made a great difference in our work flow. We plan to add more in the near future. Thanks for your informative articles.

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