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TEST & MEASUREMENT Measuring with speed and precision

Jan 23, 2019

Scanning, inspection, analysis and quality control can easily be performed by head and probe systems. Newer technology has allowed for high performance analysis of Coordinate Measuring Machines (CMM), along with a reduction of time and capital. The article takes a deeper look into one such probe system and how it has benefitted through investment.

A Madrid, Spain-based precision engineering business, Mecanizados Escribano, specialising in complex parts for aerospace and defence applications, has invested in a Renishaw REVO® five-axis measuring head and probe system. The change has resulted in a reduction in inspection time by as much as a factor of 5, ensuring quality control and inspection keep up with its high-productivity CNC machine tools.

It’s true that in many ways, making things is getting easier, least as far as the technology is concerned. For example, machine tools are simpler to program and operate, rapid prototyping means that product development is faster and cheaper than ever, and user-friendly CAD software may even negate the need for physical prototypes entirely. All of this assumes that what you are actually making or trying to make is relatively uncomplicated. It’s a different matter, however, if you are building complex multi-million dollar aerospace systems, such as, those engineered by Mecanizados Escribano.

Maintaining the highest standards

“When we buy a machine tool, we specify all the options,” says Juan A Humanes, Company Project Manager, adding, “But, having the best machines is only part of the equation. Our customers demand very rigorous part inspection, which means there’s always the chance that the metrology department can become a bottleneck, especially when the parts are complex and machined to very tight tolerances.”

He continues, “Depending on what the customer requests, we inspect between 10% and 100% of machined parts. The Renishaw REVO system, recently fitted to a Metris CMM, measures nonprismatic surfaces very quickly, many of which would be difficult or impossible to measure with touch trigger systems. In some cases, such as a complex avionics chassis for the Typhoon, the REVO has increased our inspection throughput by a factor of 5; typically, up to 80% reduction in time per part.”

Features of the REVO five-axis system

The key attribute of the REVO five-axis head is its ability to overcome the limitations of three-axis scanning methods, where any attempt to rapidly move the large mass of a CMM results in inertial errors caused by accelerations and decelerations. Therefore, the only possible way to maintain acceptable accuracy in three-axis scanning has been at the expense of measuring speed. However, REVO uses synchronised head and machine motion when scanning, rapidly following changes in part geometry, without introducing its own dynamic errors. The CMM is able to move at a constant velocity whilst measurements are being taken, without impacting accuracy.

REVO also benefits CMM users with infinite head positioning and innovative tip-sensing probe technology, which further improves measurement accuracy by sensing close to the measured surface. This combination of speed, flexibility and accuracy has proven to give exceptional performance in a wide range of scanning measurement applications, including circle, helix, sweep and gasket scanning. Plus, if required, rapid single-touch routines.

Expanding to meet increased demand

Any visitor lucky enough to tour the Escribano factory can see the size and significance of the investment required for such production. Humanes reveals it to be between €1 million and €1.5 million a year, and most of the company’s CNC machines are top-end, Japanese or Swiss-built multi-pallet and multi-axis: Makino, Matsuura, Mazak; Sodick wire EDMs and CNC precision grinders from Jung. All of them are the latest models, meticulously maintained and configured to minimise set-up and non-machining time, mostly using Renishaw OMP40 spindle-mounted touch probes and NC4 non-contact laser tool setting systems.

Escribano has outgrown its current building and has designed and built a new facility, where it will relocate in the next few weeks. Until then, the two small rooms adjacent to the main workshop that house the company’s inspection equipment will remain crowded. In the larger of the two rooms, three DEA Global Advance Co-ordinate Measuring Machines (CMMs), with Renishaw probes, check samples of parts for everything, from thermal imaging cameras to components destined for the Joint Strike Fighter. Alongside the main metrology lab is a smaller room housing the company’s largest CMM: a Metris LKV CMM, equipped with the Renishaw REVO five-axis measuring head and probe system; part of a recent investment in inspection equipment that totalled around €300,000.

For most precision engineering businesses, the Metris and Renishaw REVO combination would be enough to cater for their metrology needs. But Escribano isn’t your typical workshop and its customers are somewhat more demanding, leading to further investments in other advanced metrology systems, such as, a white light interferometer microscope for measuring roughness and a contact profile meter capable of assessing the size and texture of a part’s surface.

Sophisticated expertise and technology

The Madrid-based company is a rarity—privately owned engineering workshops with the expertise and the technology to deliver components and systems for such sophisticated applications are few and far between. No one at Escribano can or will talk about its customers or their products, but Humanes is happy to discuss what the company is equipped to do and how it does it.

“We specialise in machining complex, 5-axis parts in aircraft-grade aluminium, stainless steel, nickel alloys, copper and titanium,” he says and goes on, “The only way to be good at this kind of work is to make the necessary investments in technology and people. Our customers can choose between some of the best equipped suppliers in the world, so we have to make sure that we can deliver exactly what they want and whenever they want it.”

A large proportion of Escribano’s production is for the US defence sector, which probably has more small, privately-owned precision engineering companies than any other country on earth. So the question is: why would a US defence contractor choose to outsource some of its most complicated, quality-critical parts to a company in Spain, instead of one closer to home?

Humanes says, “Some people might assume that we win business because Spanish labour costs are lower than they would be at a similar, US company. But they would be wrong. If that were the case, the work would simply migrate to Asia. The truth is that we are competitive because we invest in the best technology and we train people to high levels. We don’t just benchmark ourselves with competitors in Spain or Europe but aspire to be the best in the world.”

General precision engineering may, thanks to the technology, be getting easier, but Escribano’s willingness to meet almost any standard of engineering precision means that even during the worst recession in living memory – and the Spanish economy is suffering the effects as acutely as any country – this familyowned company is still busy 20 hours a day.

Maintaining highest standards

Head and probe systems are effective ways of performing quality checks. The REVO five-axis system maintains the highest standards by synchronising head and machine motion, maintaining accuracy and reducing the time taken on each part. The investment and diligence put in by Mecanizados Escribano has also ensured that the product will develop further using the latest technology and precision.

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  • Head and probe systems are effective ways of performing quality checks

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