Bending tube greener and cleaner

Figure 1
A small amount of gel lubricant exits a tube bending mandrel. This type of lubricant, combined with a precision metering and dispensing system, provides two advantages: minimal waste and easy cleanup.

Green initiatives have been around for quite some time, probably longer than most people realize. Congress passed the Federal Water Pollution Control Act in 1948 and the first Clean Air Act in 1963. These efforts got a further boost when the Environmental Protection Agency was created in 1970. While household recycling of newspapers, aluminum cans, and glass bottles got underway decades ago, other ideas and concepts have taken root more recently in industries such as power generation and building construction. Likewise, green practices have been gaining momentum in manufacturing.

In recent years the notion of green has been accompanied by another concept¸ sustainability. The difference is that green implies that a process or practice has a lower environmental impact than a conventional process, whereas sustainable is where the recycled rubber meets the road, implying that the process can be sustained over the long haul, essentially indefinitely.

Many might think that sustainable means recycling, but it’s much more than that. Other initiatives can be applied at many points along the way, especially at the start of the manufacturing process, where waste minimization can have a big impact. Engineering a process to minimize waste reduces the need for recycling, which is similar to using statistical process control (SPC) to reduce process variation, thereby reducing the need for quality control inspections at the end of the process. SPC builds quality into a product, which is more efficient than inspecting quality into a product. By the same token, minimizing waste builds sustainability into a process.

It’s also important to note that sustainability is compatible with lean manufacturing, which seeks to eliminate all waste in both materials and process steps. Planning for sustainability is the same type of thinking, but it goes a little further, considering where the raw materials come from and where the spent materials end up. It’s a cradle-to-grave concept and seeks to limit resource extraction and disposal.

While lean manufacturing is gaining more and more traction each year, the U.S. economy is still very inefficient. Only 6 percent of materials actually end up in products.¹ Total waste in the U.S., excluding wastewater, exceeds 50 trillion pounds per year.² The standard of living in western Europe is comparable to that of the U.S., yet resource consumption per capita across the Atlantic is about half that of the U.S.

Green Drivers

Unfortunately, many in responsible positions believe that sustainable initiatives provide little or no financial gain. In reality, sustainable processes often post a return on investment in 6 to 12 months, which enables a manufacturer to justify the time and investment. Two big companies that have embraced lean manufacturing wholeheartedly, and reaped many sustainable benefits along the way, are Ford Motor Co. and Toyota Motor Corp. Water consumption alone is worth a look.

Assembling a single passenger car requires about 2,500 gallons of water. Assuming that 15 million vehicles are produced in North America annually, automakers use 37.5 billion gal. of water. Since 2000 Ford has reduced the water consumption for its North American operations by 10.5 billion gal. This is the annual usage of 105,000 average American households. Note that the 2,500-gal. figure is just for the OEM. Pollution Equipment News^® magazine estimates the actual total to be 39,000 gal. when all of the supplier operations are aggregated.

Toyota Motor’s Green Supplier Guidelines, outlined in its 2007 environmental report, states its expectations: Suppliers are to reduce energy use 10 percent, reduce water consumption, and reduce components made from oil.

Part of Ford’s success is based on minimum quantity lubrication (MQL). Rather than applying liberal amounts of lubricant, the company uses equipment that applies a precise film. This has reduced water usage by 280,000 gal. in plants that have adopted the new application technology.³

An additional benefit of MQL is that the right lubricant in the right concentration can improve the coefficient of friction, which reduces tool wear. In the case of mandrel bending, less friction also requires less energy to bend. Applying less lubricant means less ends up on the shop floor, which is a housekeeping benefit and an annual cost reduction.

Figure 2
When a thin-viscosity lubricant is used, gravity takes over (top right). In addition to creating a housekeeping task, this produces a slipping hazard that can be remediated with mats (bottom left). Minimum quantity lubrication eliminates both problems by applying a precisely metered amount of lubricant to create a thin film on the parts and tooling

A low-viscosity liquid can be problematic. The tube needs lubricant at every point of its circumference—all 360 degrees—but in the few seconds between applying the lubricant and putting the tube into the bender, the lubricant can start to run. The area at the top (12 o’clock position) might have too little, and the area at the bottom (6 o’clock position) might end up with too much. Attempting to fix this by overapplying the lubricant to the tubing or to the tooling doesn’t help much (see Figure 1).

It’s important to remember that liquids never stop moving. Even when the finished tube is removed from the bender and placed into a parts bin or placed on a rack, the liquid lubricant begins a new journey, ending up wherever gravity takes it. This usually means the bottom of a parts bin or onto the floor. It then creates a housekeeping task and a slip hazard (see Figure 2). Abrupt accelerations and decelerations during bending can even cause thin liquids to fly off the end of the tube, causing an even bigger mess.

MQL efficiencies are best achieved by using an automated application system that pumps the lubricant through the hollow tool rod, delivering it down the length of the rod to the mandrel links at the required amount for each specific bend. The same pump, combined with manifold valves, can deliver a small, controlled amount of lubricant to the wiper die when required.

Matching the Lubricant to the Application System

Bending tube or pipe requires boundary lubrication, a condition in which the pressure between the surfaces of the tooling and workpiece is extreme, potentially causing some amount of metal-to-metal contact. A lubricant for this type of application should be somewhat immobile so it doesn’t end up on the floor, and it should contain extreme-pressure additives that maintain a microlayer of space between the tool and the tube. This space gives the tube a cushion to ride on and in many cases can prevent the frictional microwelds that cause tool wear. The three types of boundary lubricant are oils, pastes, and gels.

Oils are among the oldest lubricants and can contain ingredients that increase viscosity, or ability to cling. The oil can be put into an inverse emulsion stage with water that gives the product a white creamy consistency. The lubricity of the oil and the increased viscosity determine the amount of boundary protection it provides.

Grease-like or pigmented paste products have been used for decades. They became popular during World War II when oil was in short supply. They usually have an animal or vegetable fat base and additional components, such as calcium, clay, or other low-cost powders.

Gel is the third and newest category. Gel-type bending lubricants were invented with MQL in mind. They use water-based polymers to create the needed boundary. The product has the consistency of ice cream or hair gel. The product stays put and has very good lubricity and temperature control

because of the water content and lack of oil. Because gels are water-based, they tend to be compatible with downstream manufacturing operations such as welding. When removal is necessary, often a plain water wash is sufficient. They perform best when applied in a microlayer, which is in keeping with MQL.

Getting Started

MQL doesn’t have to be complicated. It requires equipment that can dispense an accurately metered quantity at the right time and a compatible lubricant. If your company has a large number of bending cells, it might be challenging to switch all of them over at once, so keep in mind that going green is a journey, not a discrete project. It can start in just one shop area and spread. Your program can start out as light green and progress to a deeper, darker green as your sustainability program evolves.

Also, keep in mind that a sustainability program provides more than just external benefits. Proof is available that when companies focus on more than just profits, they not only do good, they do better. A study over an 11-year period demonstrated “stakeholder-balanced companies show four times the sales growth and eight times the employment growth of companies that focus solely on shareholders.”⁴

Notes:

1. National Academy of Sciences, Technology and Environment (Washington, D.C.: National Academies, 1989).

2. Paul Hawken, Amory Lovins, and L. Hunter Lovins, Natural Capitalism: Creating the New Industrial Revolution (New York: Little, Brown, 1999), p. 52.

3. PR Newswire, “Ford Reduces Water and Oil Use in Plants Globally with Expansion of Near-Dry Machining Technology,” 10-16-2013.

4. Sarah Roberts, Justin Keeble, David Brown, The Business Case for Corporate Citizenship (Cambridge, U.K.: Arthur D. Little, 2002).