In-line measurement: Assessing the benefits
- October 30, 2011
by Mary Scianna
In most instances, the type of measurement system you use in your manufacturing operation is determined by your production parameters.
Typically, in high production manufacturing environments such as automotive, there is a higher demand for automation and in-line measurement systems.
Yet as competitive pressures continue to increase, many manufacturers beyond just high production first and second tier suppliers are looking at in-line measurement systems that bring real time high tolerance measurement to the workpiece.
"In-line or side line measurement can benefit large and small shops by keeping the part quality verification at or near the machine performing the production,” says Peter Detmers, national sales manager for Mitutoyo Canada, Mississauga, ON.
In-line measurement systems help reduce production down time and scrap, he adds, because these measurement tools allow production staff to get answers on parts quickly. If there's a problem, staff can react quickly and make the necessary process changes.
"In many cases, the inline system is measuring production parts from multiple machines. Since the data is being collected in real time per machine tool, production can analyze the quality of parts by the individual machine and could keep track of changes made to the machine, such as tool changes within the same database. Analyzing the collected data over time can indicate tool wear patterns, and other manufacturing related issues that can help to improve the overall process,” explains Detmers.
In-line measurement systems can include gauges, multi-sensor devices and probes. In-line measurement makes sense for high production volume environments, but it also requires a significant financial investment, says David Chang, applications and support engineer for Renishaw (Canada) Ltd., Mississauga, ON.
"In-line systems are usually best in fully automated environments in a production cell, as an example, where there is no human intervention and you have a robot or some other kind of automatic loading and unloading mechanism to transfer machined parts to an inspection system such as a CMM. One consideration with in-line systems is that they are fixed inspection systems that make more sense for a manufacturing operation that makes a lot of the same part. But it's not an inexpensive solution.”
CMMs for example, are highly accurate, flexible and fully programmable systems, but they're also complex machines that require trained inspectors to run them and need to be calibrated at least annually.
"CMMs are one end of the spectrum that offer accuracy and flexibility and at the other end you have fixed gauges that can range from low cost systems such as micrometers to higher end devices, but they're not as accurate as CMMs. These devices are designed to inspect one particular feature or one particular part, so there is no flexibility and less accuracy,” adds Chang.
Renishaw's solution is the Equator, which Chang says fills the gap between the high end CMMs and fixed gauges. Read about Renishaw`s gauge.
"The Equator offers customers more options for measurement. In the past customers would have to choose between a CMM or a fixed gauge and now the Equator gives them the benefit of both systems in one product',” says Chang.
Renishaw`s Equator reflects an important and growing component now being offered in metrology products; flexibility.
`”Manufacturers have been working to build measuring systems that can be used in a wide variety of shop applications,” explains Mitutoyo`s Detmers. "These systems may have sensors for adjusting measurement values due to temperature changes during operation. They may have more robust controllers or drive systems designed to be used in a variety of shop conditions.”
An example is Mitutoyo`s Mach 3A, an in-line horizontal arm CMM. Read more about this CMM.
Suppliers concur that both in-line and off-line measurement systems offer benefits but manufacturers have to assess the best system for their operation needs.
"In-line systems can assist in reducing the measurement load on the Quality Assurance department and keep manufacturing operationg since the data is close at hand. Production has another tool for keeping the process under control, which of course, reduces scrap and raises productivity. In many companies, where more is being done with less, the movement to in-line measurement is practical as it reduces bottlenecks in QA.”
A paradigm shift
For more than eight years, Jay Elepano, business development manager for large scale measurement at Nikon Metrology, Brighton, MI, worked with another metrology company and was responsible for robotic integration for CMMs, "but these systems, even with robotics, were not true in-line systems; they were near-line measurement and it still meant that the part would have to come off the line for measurement.”
Nikon's solution is its optical CMM combined with an innovative software program called Adaptive Robot Control capable of dynamic compensation.
"This blows away the tenets of old metrology measurement. This system is truly in-line and is essentially, metrology on steroids,” explains Elepano. "Instead of make and measure, if you want to be truly in-line and take an innovative approach, you measure and then make; we're shaking up the entire paradigm of metrology with this technology.
Nikon's technology is actually two technologies that work in tangent - Nikon's K-series optical CMM and the company's Adaptive Robot Control software. The optical MM is equipped with three cameras that track infrared LED strobes and triangulate the position of the strobes so the system knows the position of a part or a probe positioned near the part.
"The three cameras on the optical CMM means I physically surround the part and because I can do that, I can track multiple parts simultaneously and more importantly, I can track moving parts. A CMM can't do that. Our optical CMM is equipped with dynamic compensation for moving parts which allows us to have a truly in-line system.
Top image: Nikon Metrology in-line measuremet.