Ergonomic design best practices

ControlDesign.com

Keywords: ergonomics, operator safety, machine performance, machine control, machine design and control design

Contributing Editor Loren Shaum reports on the best practices he found for taking ergonomics into consideration in machine control design for operator safety and overall machine performance.

By Loren Shaum, Contributing Editor

We’ve seen for some time now that industrial machine builders must create machines that produce more in less time. This increase in automation often speeds up the pace of work and at times can make work more hazardous to operators.

On the other hand, there still are many jobs done manually, involving heavy physical strain. One of the results of manual work, as well as the increase in automation, is that more workers are suffering from various physical issues. As a consequence, the notion of ergonomics comes in to play more in thoughtful machine design.

If you Google ergonomics, basically we find that it’s the study of work in relation to the environment in which it’s performed by those who perform it. Ergo­nomic correctness attempts to determine how the workplace can be designed and adapted to the worker to prevent a variety of health problems and still increase efficiency. So, to comply with today’s ergonomic sensibilities, machine builders must find a way to make the machine operation fit the worker, instead of forcing the worker to conform to the machine.

Ergonomic design issues that machine builders must confront include:

• Operator interface height
• Operator control access
• Safety considerations (safety mats, light curtains, emergency stop operator access, etc.)
• Visibility
• Maintainability

All of this has to be included and still not jeopardize machine performance or output quality—challenging requirements in a highly competitive global market. You’ll see that the line between what we call operator safety and what we call ergonomics often is a blurry one.

Ergonomically Designed Machines
A machine builder touting ergonomic design is injection molding machine builder Cincinnati Milacron in Lebanon, Ohio. Milacron’s new Mosaic control for injection molding machines consists of a 15-in. TFT touchscreen display with keyboard mounted on a swing arm (See Figure 1 below). The package is sealed to IP65, and includes user-friendly software for five-stage extrusion profiling including graphic setup, a 10-stage injection profile, and 10-stage pack and hold with real-time graphical updates.

	FIGURE 1:  SWING TIME
	The operator display for a Cincinnati Milacron injection molding machines consists of a 15-in. TFT touchscreen with keyboard mounted on a swing arm. Milacron says it handled setup ergonomic issues with screens for data, operator buttons for machine movements, and user-friendly wizards.

Claiming it to be a setup person’s dream, Milacron says it handled setup ergonomics with screens for data, operator buttons for machine movements and user-friendly wizards. “The setup screens complement the ease-of-use with programming wizards based on input from injection setup specialists around the world, making the controls almost human-proof,” claims Mike Litten, manager of controls development at Milacron.

Meanwhile, Minster Machine Co. in Minster, Ohio, manufactures machines, integrated systems and services for the material-forming industry. Minster’s products include mechanical presses ranging from 16-ton, open-back stationary presses to 1,650 ton progressive-die, straight-side presses.

The company designs its own control system using A-B PLCs for equipment monitoring and relay-based controls for the presses’ critical clutch operation, where redundant and monitored schemes are employed. Russ Bensman, staff engineer at Minster, emphasizes that within the ANSI B11 series of Machine Tool standards, Minster references ANSI B11-Technical Report TR1 Ergonomic Guidelines for the Design Installation and Use of Machine Tools in the design of their press and equipment controls.

"The main control panel and pendant stations attached on the press and accessory equipment are located (See Figure 2 below) such that there still is high visibility to the work area, and they’re easy-to-use and relatively consistent from machine-to machine,” stresses Bensman. The ANSI guideline is available from the Association for Manufacturing Technology (AMT).

A machine builder similar to Minster is Pacific Press Technologies, Mt. Carmel, Ill. It has a history with hydraulic press technology for the metal-fabrication industry, including press brakes, plate shears, and hydraulic presses. Ergonomic considerations fit directly into every Pacific Press machine control design, while still assuring machine safety because many of the machines operate on individual cycles.

A good example of a completely safe, ergonomically-correct solution is a press cell Pacific supplied to Homac Manufacturing, Ormond Beach, Fla., a producer of electrical transmission connectors for utilities and contractors. To stay competitive, Homac realized its presses were too inefficient and hard to use and maintain. Improved efficiency without sacrificing operator safety and health entered into the analysis.