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How To Decide Between Contact & Non-Contact Measurement? measuring technology

How To Decide Between Contact & Non-Contact Measurement? measuring technology

How To Decide Between Contact & Non-Contact Measurement

Making a right choice between tactile and non-tactile measuring technology may be a challenging task.

By Joson Ng

At IMTS, one metrology company mapped out an overview of new opportunities and emerging trends resulting from the integration of measurement technologies with factory automation devices such as industrial robots. Such a combination can be found in production environments in the aerospace and automotive sectors.

In more advanced economies, automation has been increasingly applied to metrology, creating two areas of innovation in this sector. The first application utilises a robot as a carrier for a device to perform an automated inspection measuring technology. The second application employs a metrology device as a method to improve the absolute accuracy of a robotic system, allowing high-precision guidance for automated assembly applications.

While the marriage between metrology and robotics is not exactly unheard-of in this part of the world, the emerging economies in Southeast Asia are still relatively early in the adoption of metrological technology. Question like ‘which technology shall I use to measure my parts efficiently?’ would probably occupy the thought bubbles of most job shop owners or QA managers in this region.

Get In Contact With Accuracy

The Southeast Asia region on a whole has attracted a whole host of foreign investors over the years and with manufacturing very much alive and kicking in countries like Thailand, Indonesia, Vietnam and Malaysia, metrology companies have set up shops here, bringing with them a plethora of metrology solutions, including non-contact measuring equipment.

While owning a CMM is a considerable achievement for a job shop a few years ago, the million-dollar question now is ‘do I use the contact measuring technology or non-contact measurements for this part?’ Although the question is a relatively simple one, the answers, however, are far from simple.

“As a general rule of thumb, if you can measure something by contact (method), it is better and more accurate to do so. However, non-contact measurements have become important, particularly when it comes to small features, those too small to be probed by a measuring technology contact sensor or something that can be deformed by contact (method),” advised Steve Bell, the GM of Renishaw (ASEAN).How To Decide Between Contact & Non-Contact Measurement? measuring technology

“For contact measurement, it is normal for high precision. The tolerance is very high, for example about two to three microns. Non-contact measurement techniques can’t achieve that accuracy, they are about five micron,” said Sugiarto Tan, senior technical support engineer of Wenzel Asia Pacific.

However, he conceded that non-contact measurements do have their merits. He said non-contact methods can be flexible and useful for small items because when using video for measurement, operators can zoom in to have a better view.

Take A Step Back Before Taking The Plunge

The contact and non-contact debate may rage on, dividing opinions but most industry observers would prefer to study the part first before deciding what is the best way forward.

The general questions to ask, according to Anthony Lur, product marketing specialist of Faro, are: 1) what needs to be measured, 2) the type of application, 3) the level of accuracy and precision required, 4) the size of the part, 5) and the scanning speed required.

Adding his views to this issue, Shaun Lim, regional division manager of Carl Zeiss, said: “Before deciding which type of measurement method does the job best, it is important to guide customers in understanding and realising their application requirements and limitations.

In terms of measuring uncertainty, contact measurement using tactile sensors will always be more accurate than non-contact types. Non-contact measurements today come in the form of camera probe sensors, laser sensors or CT technology.

Camera probe sensors are normally deployed in situations where contact tactile sensors have limitations in reach, such as micro-bores, where even the smallest stylus cannot reach. Laser sensors are preferred for capturing point-cloud data on freeform surfaces and typical applications include CAD comparison and reverse engineering.

CT measurement is also technically a non-contact type of measurement, but its key application lies in NDT (non-destructive testing) and internal part analysis such as porosity, assembly, or defect. Non-contact measurements are also recommended for requirements that place speed above accuracy, as non-contact measurements typically capture data much faster than contact tactile probes.”

Sentiments In Southeast Asia

In this region, the contact method is still the preferred way to measure a part although many believe that non-contact methods should not be discounted.

“Although we see an increase in demand for non-contact measurements, the widespread use of contact measurement today will continue to dominate the metrology arena.

measuring technology Many observers feel that contact measurement is still the method of choice in Southeast Asia.

Many observers feel that contact measurement is still the method of choice in Southeast Asia.

Due to the rapid development of higher precision products, contact measurement will continue to play an important role in quality metrology. Non-contact measurement will continue to develop its own niche where contact measurement is limited,” said Mr Lim.

Many observers feel that contact measurement is still the method of choice in Southeast Asia.

Mr Lur agrees. He said: “Across Asia, contact measurement is still generally more prevalent in the application as it is easier to perform point-to-point measurements. Laser scanning technology, however, is excellent for acquiring quick and accurate measurements of many data points at once, which is especially useful for larger parts. These data points (also known as a point cloud) require further processing, and this makes the process slightly more complex, often requiring a longer training duration.”

He added that in the portable CMM articulated arm segment, non-contact measurements are acquired via a Laser Line Probe (LLP) attached to the end of it. The accessory introduces an additional joint to the device, which adds one more level of mechanical error to the final reading’s accuracy. Compared to a six-axis arm that performs only contact measurements, the measurements acquired by the LLP will be a slightly lower inaccuracy.

Having said that, he conceded that the choice between contact and non-contact measurement still depends on application suitability, and one is not necessarily always better than the other. “Implementing non-contact measurement methods when it is not required might not be the most efficient or effective, as it would not be optimised for the customer’s needs,” he said.

Combination Machines

Some observers feel that combination machines may be a better option. When asked if he agrees if contact method is the dominant method in Southeast Asia, Kirk Teng Tian of HTT Vietnam Technology and Trading Company (agent for OGP) said: “No, they use both. Most (companies that) we see use both.” He went on to say combination machines will go on and take more market place in the future.

Echoing his point is Candy Ong, the MD of Blum Production Metrology. She said: “I fully support multitasking machines. Multitasking machines can enhance performance and automatically reduce human error.” She made this interesting point based on the argument that there is a shortage of skilled workers in the region and companies will try to make up on that shortfall by introducing more versatile machines.

Metrology measuring technology solutions providers in this region have an important role to play as they are the bridge between the users and the advanced technologies imported from Europe and the US

Metrology solutions providers in this region have an important role to play as they are the bridge between the users and the advanced technologies imported from Europe and the US.

Mr Lim concurs. He said: “Measuring systems with both contact and non-contact sensors will continue its popularity as companies are diversifying their product portfolio which results in a higher mix of applications. Instead of having two separate systems, a single system that has both functions gives the best return in terms of cost-performance ratio.”

Taking the argument of combination machines further is Stefan Ruh, global product line manager vision of Hexagon Metrology. “More often, a combination of the two is the best solution, which is where we go to a ‘multisensor system’ incorporating both contact and non-contact sensors. This enables the customer to check application features in the best possible way.

In the future, we will certainly see more multisensor systems. More customers are choosing combination machines because they provide the best value. Through investment in a single frame, you get multiple sensor opportunities and of course more application types. Software synergy between the different sensors means no additional training is required. You also save workspace compared to running multiple machines, as well as the time you would normally spend moving parts between them,” he said.

Metrology solutions providers in this region have an important role to play as they are the bridge between the users and the advanced technologies imported from Europe and the US.

Spreading The Word

With the adoption of non-contact and combination machines measuring technology on the rise, the salient point is how the knowledge of these technologies can keep up with the pace of adoption.

Metrology solutions measuring technology providers in this region have an important role to play as they are the bridge between the users and the advanced technologies imported from Europe and the US.

“When you talk about non-contact measurement, we are talking about more complex machines. The concept in Southeast Asia is still a little bit unclear as people always think of non-contact measurements for high precision,” said Ms Ong.

Referring Southeast Asia to a region that is in the “educational stage” in terms of understanding metrology and what non-contact measurement can bring to the table, she said: “We educate to sell the concept of total cost savings and we have to try to bring the (knowledge of operators from) entry-level to the middle level.”

Educate to improve knowledge — this is an important point and perhaps the key to using metrology equipment to achieve maximum results because the truth is, there is no one-size-fits-all solution in the world of metrology. Know-hows and the sharpness of minds are perhaps the best way to accurately determine the dimensions of a part.

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