Manufacturers have much to weigh before making tensile testing a part of the production line process.



The trend in today's manufacturing environment is to move test and inspection equipment as close to the production floor as possible. This migration is not as simple as placing a piece of equipment previously located in a laboratory on the shop floor, hooking up power and hitting the start button. Manufacturers must assess the need for test equipment in the line, consider the effects of a harsher environment and assess operator skills before making such a move.

Environmental test equipment, such as leak testers, is already integrated into manufacturing lines. But what about material test equipment such as tensile testers?

"In the past, I'd say 90% of our machines were going into the laboratory environment, primarily for research and development (R&D) and failure testing. Today that trend is shifting toward use in a manufacturing environment," says Gilbert Bial, product manager for physical measurement at Shimadzu Scientific Instruments (Columbia, MD), a supplier of tensile testing systems.

Chris Giebner, mechanical systems manager for Com-Ten Industries (Pinellas Park, FL), another supplier, reports a 50-50 split between the production floor and the laboratory as the ultimate destination for his company's tabletop tensile testing machines. The low-cost, ease of use and ruggedness of his company's machines make them ideal for the shop floor, he says.

"Most of the machines we sell are for quality control applications close to the (shop) floor," adds Fred Otto, product manager at Instron Corp. (Canton, MA), which also sells tensile testing systems.

Is It Needed?
However, there are myriad challenges in moving tensile testers to a production floor.

"The trend in manufacturing is to streamline manufacturing," says Bial. "Anything not necessary to the process is moved out of the way." And tensile testers can be quite large and cumbersome, he observes.

Otto says that tensile testing is seldom an on-line process. But he adds that Instron does sell some systems for production line use. "They test one part once every five seconds and are in no way a bottleneck to production," says Otto. Such systems often integrate other technologies, such as indexing machines and robotics to address high-volume production requirements. For high-end systems, according to Otto, the tensile testing machine itself can sell for $20,000, and the cost of the entire integrated system can be notably higher, depending on what other technologies, such as robotics, vision or material handling systems, are added. "But not everyone needs, or can afford, a high-volume solution," says Otto.

For those who don't have the pocketbook, the floor space or production needs for high-end tensile testers, Giebner says that tabletop machines such as those sold by Com-Ten can provide a shop-floor tensile testing solution. Giebner concedes that these machines--which must typically be manually loaded--can't match the production rates of some competitive high-end machines on their own. However, he maintains that their ease of use doesn't compromise productivity. "And, the cost of the equipment means a manufacturer can afford more of them to use on his line," says Giebner. Compared to more traditional full-size tensile testing systems, which can start at $20,000, Com-Ten's tabletop machines start at $3,000 for a basic model.

Giebner admits there is a tradeoff in this low-cost solution. Com-Ten has no traveling technicians; the service is done at company headquarters in Florida. Further, the design of the Com-Ten units is fairly standard and stock parts are frequently used, unlike more expensive machines that typically offer more customizable options.

Otto thinks that service and support at the customer site is important. Instron has more than 200 engineers who can do on-site visits to prevent downtime, something that is critical in a production environment, he says. "You have to look at tensile testing in the long term vs. the short term. How long do you want the machine to last?" asks Otto.

Giebner counters that his machines are rugged and can withstand the harshest environment. As for any downtime, Giebner says that the low cost of his machines allows manufacturers to buy additional machines for use as backups.

Chicken Juices
Simply deciding if tensile testing is appropriate for a particular production process and what kind of tester can be used is only the first step in actual implementation. A manufacturing floor is not a laboratory environment, and operators must be certain that a tester can survive in the shop.

Giebner says his company's machines are often subjected to tough environments. "To offset very harsh conditions, we'll do some customization of our testers," he says. One such customization included combating the chicken juices that flowed from patties during compression tests.

In addition to physical contaminants, shop floor testers must deal with temperature variations and conditions that are usually more severe than the laboratory. But it seems as if the innate nature of tensile testing has already accounted for such needs. Most suppliers offer machines with frames built of rigid steel. Besides withstanding temperature extremes, a rigid steel frame ensures that twisting is minimized or nullified and that manufacturers test the material, not the machine.

Despite these solutions to environmental concerns, not all suppliers are convinced the shop floor is best for tensile testers. "Tensile testing is very sensitive to do on the (shop) floor. You can avoid problems by having the equipment isolated in a room next to the production floor," says Bial. "There is a disconnect between R&D, quality control and production," Bial relates. He says the R&D person may be using material resistance as his or her standard of quality, a manufacturing engineer may be using the shape as the standard of quality and the consumer may use a completely different standard. Often the equipment supplier is tasked with making such "translations."

Many agree that the biggest difficulty in moving tensile testing to the production floor is trying to repeat the tests originally done in the laboratory. "It doesn't matter what machine you have in the lab or what you have on the floor, it's a challenge," says Giebner. He says that quality control or manufacturing engineers who were responsible for the test parameters in the lab and are implementing the testers on the floor have fewer of these"If you need to measure peak force on material, you have to make sure the machine is not set to use break force as the measure," says Giebner. In addition to the physical similarities needed between lab and floor tests, a manufacturer needs to be cognizant of different operator techniques.

Operator Friendly
The operator is critical to shop floor testing in another way. "Twenty years ago, most of the people we saw operating these machines were Ph.D.s. There has been a steady trend away from that," says Bial. The person operating today's equipment more often has a high school diploma only; although the person programming the tester likely has an advanced degree. Another challenge is operators who perform varied tasks and to whom tensile testing is simply one more task they may do today and someone else may do tomorrow, sources point out.

"Our challenge is to provide easier-to-use equipment and software. The software is key," says Bial. He notes that Shimadzu's operator software is set up in an "if-then" sequence for operators-- "if" this is happening, "then" take this action.

Otto says Instron has simplified the software user interface on its testers so that a programmer can create a defined checklist of conditions, and only the information the operator needs to know is offered to him or her. "We've made it for the person who has virtually no experience operating the tester," says Otto.

So is there a future for tensile testing on the shop floor? For many manufacturers, who currently outsource such tasks, the answer is still no. Because tensile testers don't actually "produce" parts, they are often the first thing to be put aside when production line constraints are considered, says Bial. Also, any test equipment that may reveal what is being done incorrectly on the line will be the last thing purchased, he says.

Still, having such tensile testing capability in house for production line use is a positive, regardless of the equipment chosen or the process shortcomings that it may reveal, some vendors contend. As Giebner puts it: "It gives [the manufacturer] more control."