Fighting Product Fatigue in the Factory

On the plant floor, parts wear out. Motors and drives wear out. The whole range of machinery eventually wears down from near-constant use. In the past, companies dealt with product fatigue by setting up strict maintenance and replacement schedules that required downtime. The idea was to replace the part before it broke or began to lose its efficiency and dependability. That has changed as part maintenance has evolved from preventive maintenance to predictive maintenance and finally to condition-based maintenance.

The idea of condition-based maintenance is to replace the part based on its useful life rather than replacing it on a schedule that calls for replacement whether the part was nearing its end of life or not. Condition-based monitoring lets the plant engineer -- or that machine owner -- watch the part and determine its condition continually. Only when it shows signs of wear is it replaced. As an analogy, why replace your oil at 3,000 miles when it might perform up to specification for 6,000? The answer is you don't know when it begins to lose its effectiveness. If you did, you might not replace your oil until it reached 6,000 miles. Condition monitoring lets you know when the machine or part is nearing its useful end.

Parts manufacturers, machine builders, and control vendors now have the tools to monitor the condition of the machinery and parts. Because of this, the whole notion of when to shut down the plant for routine maintenance has changed. "The condition-based monitoring tools are used by the end user (the control team at the plant) and also the machine builder," Ryan Legg, product manager for Siemens, told Design News. "These tools monitor a wide range of machinery parts: the controller, the control drive motors, the complete system for the control of a machine tool, plus the machine tool itself. You can take a proactive approach in looking at the condition of your machine. Then you can maintain the health of the machine rather than waiting for the machine to go down."

Multiple views of the machine
The monitoring helps plant operators see whether the machine is working properly, which prevents unplanned shutdowns. Sometimes that involves checking wear on the part; sometimes that means checking the machine for efficiency. "We have a software suite that is made up of modules designed to help plants increase their production capabilities," said Legg. "We approach different monitoring efforts with different modules. One module is for conditional-based monitoring. That's called Analyze My Condition."

As well as checking the machine's condition, the suite includes a module that makes sure the machine and its parts are performing optimally. "We have Analyze My Performance, which measures the actual performance of the machine to determine whether it's operating at full efficiency," said Legg. There is also a module designed to grab data from a machine and to make sure the data is being recorded properly. "Access My Machine lets you access the backup data and do automatic backup. If you lose memory in the control tool, you have automatic backup at different intervals," said Legg.

The long-distance close-up
One of the major advantages of condition monitoring is that it doesn't have to be done on site. Like many other new technologies for the plant, condition monitoring puts the intelligence in the hands of the experts, leaving the plant operators to concentrate on operations rather than maintenance. Automation vendors often put the actual monitoring in the hands of the machine builders so they can take full ownership of the machine's health on the ground. "Our OEM (original machine manufacturer) customers use the Access My Machine and Analyze My Condition for remote diagnostics or trouble shooting of their machines," said Legg. "This lets them view the machine remotely rather than sending a technician on site. They proactively monitor the machine's condition to increase uptime."

Siemens finds that OEMs are often in the best position in the production chain to deploy condition monitoring. They know the machine, including its tolerances and its potential failure points. "We work with our OEMs because they like to have control of the machine since they built it," said Legg. "Technically speaking we could offer remote monitoring of the equipment, but practically the OEMs like to run it themselves. Our program is pretty flexible. It is set up different ways for different OEMs."