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The E-Mobility Roadmap: Speeding Up Tool Development With A High-Accuracy CMM

The E-Mobility Roadmap: Speeding Up Tool Development With A High-Accuracy CMM

The time saved on measurements helps MAPAL Dr. Kress KG develop innovative tool solutions even more quickly for trends that will play such a pivotal role in the future. Contributed by Carl Zeiss Pte Ltd.

These days, employees from the development department at MAPAL Dr. Kress KG generally know within an hour if new tools will offer the level of precision their customers require. Instead of having to wait days for a service provider to deliver the measurement results, the company started performing onsite measurements at the beginning of 2018.

With the high-precision coordinate measuring machine (CMM) ZEISS PRISMO ultra, MAPAL inspects the workpieces machined with the new tools it manufactures. The time saved on measurements helps this global company develop innovative tool solutions even more quickly for trends that will play such a pivotal role in the future like e-mobility.

With the high precision coordinate measuring machine ZEISS PRISMO ultra, MAPAL inspects in-house the workpieces machined with the new tools it manufactures and generally gets results within one hour.

How a Workpiece Ensures a Precise Tool

“We need extremely exact measurement results to develop high-precision, innovative tools and tool solutions,” says Dr. Dirk Sellmer, vice president of R&D at MAPAL. For years, the company had an external service provider measure its workpieces and tools. Seller compares MAPAL’s tools to “Lego blocks that are combined to create complex solutions.” To deliver these bespoke products to the customers more quickly, the company invested in an extremely precise CMM from ZEISS.

In January 2018, two employees began working with the ZEISS PRISMO ultra. Almost a year later, Sellmer has reached the conclusion, “The investment has paid off.” The measuring machine provided MAPAL with the necessary precision and was immediately running at full capacity. The two employees from the development department, who alternate between the measuring system and the production machines every two weeks, inspect the department’s tools on the CMM.

Most importantly, however, MAPAL employees measure workpieces that are machined in the development area with the company’s own tools, thereby determining the workpieces’ precision and stability under manufacturing conditions. Precision is on everyone’s mind because most MAPAL tools and tool solutions are used when components need to be machined with a very high level of accuracy.

The stator housing for an electric motor is one example of how MAPAL is successfully meeting its customers’ requirements. The challenge with this cast part is to create the primary, large-diameter borehole that runs through the entire component—all with an accuracy of just a few microns. For perpendicularity, the tolerance is just 30 microns (0.03mm) and, for coaxiality, 50 microns.

The Right Tool for Stator Housings

These are extremely narrow tolerances for such large boreholes. Yet, a closer look at the design of the electric motor illustrates why these stringent requirements are necessary. Take for example the permanent magnet synchronous motor, the most frequently used motor design in new energy vehicles (NEVs). The stator is the stationary component within the motor. Coils or copper wires known as hairpins are attached. These generate a current that creates a rotating magnetic field. The rotor is located within the stator and, thanks to its own constant magnetic field, follows the magnetic field of the stator. The three-phase current of the rotor causes it to rotate in synch with the magnetic field.

The rotor cannot move unless there is a gap between it and the stator. However, the rotor is subject to considerable magnetic resistance, which in turn reduces the magnetic flux density and with it the power of the motor. Thus, designers make this gap as narrow as possible.

To ensure that the manufacturing process does not compromise the component’s design, MAPAL offers its customers a high-precision tool which is also very light for its size.

First, a borehole is made in the cylinder for the stator housing. This means that a tool approximately 30cm long creates a hole in the outer die-cast layer of the housing. Then, the surface is carefully ground down. Tools for the highly precise machining of primary boreholes for stator housings have been part of MAPAL’s product portfolio for one-and-a-half years. And since not all housings are identical, these tools are customised for each customer.

On-site Measurements for Reduced Wait Times

Automotive manufacturers generally provide 10 to 30 housings that MAPAL must then machine with the corresponding tools in its testing area. The measurements performed after multiple rounds of machining serve as the basis for optimising the highly complex tool solutions in line with the customer’s needs.

Before purchasing their own CMM, MAPAL had an external service provider measure its workpieces and tools. However, the company’s measuring expenses rose significantly within the span of just 10 years. MAPAL increasingly manufactures the tools for its customers and takes on pre-series production. Numerous measurements are performed to ensure that the customer has all the information they require. The need for more measurements also increased outlay.

Yet as the company considered whether or not to invest in a CMM, it was not the costs that ultimately tilted the balance, but time.

“We used to have to wait two to three days for measuring results. This is no longer the case,” explains Sellmer. Now, these are generally available within an hour.

Since the employees performing measurements at MAPAL have also received metrology training, there are fewer artefacts. “Since our team also works with the machines used in production, they have a highly developed intuition and know, for example, where contaminants might have impacted the measurement result,” says Sellmer.

Moreover, the components are now clamped in the machining fixtures for measurements and measured on the company’s premises. This reduces potential artefacts caused by removing the workpieces from the fixtures or preclamping them. Another significant benefit for MAPAL is the ability to intermittently perform unplanned measurements, such as with thin-walled components like a stator housing. This way, the company can see how fixturing impacts machining.

Dr. Sellmer highlights yet another key advantage: the improved communication between engineers and technicians. They can now discuss the results at the measuring machine, rather than relying solely on measurement reports. And this promotes knowledge sharing. “We now achieve our goals significantly faster,” concludes Sellmer.

 

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Why CMMs Are Manufacturing’s Evolutionary Winners

Why CMMs Are Manufacturing’s Evolutionary Winners

The advent of new, high-performance measuring technologies could have posed an existential threat; but instead, the CMM has proven its resilience and remains key to metalworking manufacturers’ long-term strategies. Article by Sea Chia Hui, Hexagon Manufacturing Intelligence.

The DEA TORO CMMs can be employed as metrology stations in the development and engineering departments for supporting industrial design of complex contoured shapes, as well as flexible gages for process control in a shop environment.

For more than 40 years, the accuracy of coordinate measuring machines (CMMs) has guaranteed them a central role in metalworking companies’ quality control processes. The advent of new, high-performance measuring technologies could have posed an existential threat. But instead, the CMM has proven its resilience and remains key to metalworking manufacturers’ long-term strategies. This is because rather than replacing CMMs, new measuring technologies are complementing their strengths as quality control capabilities expand across the production cycle.

Adapting to Accelerated Evolution

A whole gamut of machines from smartphones and cars through to PCs have benefited from rapid technology advances that include lower cost of processing, higher performance software, and faster network connectivity. CMMs are no exception. But what makes CMMs different is their unique robustness and adaptability. A sizeable number of CMMs in use today have been in operation in excess of 20 years, kept up to date by retrofitting software and sensor systems.

At the heart of the CMM’s longevity are its unparalleled accuracy and durability, combined with an ability to be upgraded for new applications and working methods. Unlike many other machines, there is no need to replace a CMM in order to gain access to new functionalities. Manufacturers simply change a CMM’s controllers, software or sensors, while keeping their principal investment intact for years.

Increased Versatility and Cost-Effectiveness

Recent advances in measuring software, sensors and data analysis systems have played a crucial role in transforming the ease-of-use of CMMs, opening them up to new applications while increasing their measurement throughput.

One of the consistent benefits of a CMM has been its ability to provide 2-D touch probe-based measurement of unparalleled accuracy, precision and repeatability. But today’s metalworking companies often want to combine the accuracy of a 2-D probe sensor with the fast 3-D data capture offered by optical sensors.

Contactless measurement, for example, makes sense for sheet metal parts where throughput and speed of measurement are of the essence, or for metal parts on which a probe would leave an undesired mark. And because laser scanners can be used to create solid models from surface profiles, they are the ideal tool for reverse engineering and rapid prototyping.

Improvements in multisensor systems mean CMMs are ideally placed to support both tactile and 3D non-contact measurement. Crucially, manufacturers are able to opt for CMM software and machine controllers that enable seamless transfers between different non-contact or tactile sensors within a single inspection program. This enables a CMM to automatically switch between different sensors to capture a full metrological report even for complex parts.

And because software systems can be programmed to instruct the CMM to automatically change over sensors, multisensor systems can be left to run untended, whether they’re using touch trigger, optical, chromatic white light, laser point, or laser line sensors. The supporting software also makes it easy to create a graphical analysis of the captured CMM measuring data and overlay it on three-dimensional CAD models to compare the real data with the nominal data. This visual representation makes anomalies easy to identify, allowing operators to take decisions quickly on the shop floor.

And since the advent of intuitive software systems and greater levels of automation have made CMMs simpler to operate accurately, their use has been opened up to a wider range of employee skill sets and levels of experience.

Dealing with the Task in Hand

Not every application will need the same software package—much will depend on parts to be inspected and the complexity of their geometry, and the extent to which manufacturers want to analyse captured data and use it to inform their design, engineering, and production processes.

Similar factors shape the choice of a CMM, which is determined by the volumes of the workpieces to be measured, the tolerances required, and the desired throughput speed. Gantry CMMs, for example, continue to be a popular choice in the automotive, shipbuilding, and aerospace industries, because they are designed to accommodate the measurement of very large sheet metal parts. And they can be adapted to meet different accuracy and productivity requirements.

Parts such as aeroblades or car powertrain gears, for example, need to attain very tight tolerances, which requires the use of high precision CMMs. In contrast, the manufacturers of car bodies or aircraft fuselage are likely to seek a CMM optimised for throughput rather than precision.

When it comes to smaller parts, manufacturers in the metalworking industry have a choice of bridge CMMs that again provide differing levels of throughput, accuracy and flexibility, depending on the application need. Manufacturers can also consider gaining productivity benefits by installing CMMs on the shop floor.

As we have seen, the CMM’s versatility is at the root of its ongoing success, offering manufacturers the possibility to closely match a CMM’s measuring capabilities with their application needs. Whether a manufacturer is looking for an entry-level CMM or the most accurate measuring machine on the market, with the right supplier they can be confident of deploying a cost-effective CMM solution that future proofs their business for years to come.

 

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Renishaw Encoders Support The Latest DUKIN CMM Design

Renishaw Encoders Support The Latest DUKIN CMM Design

The co-ordinate measuring machine (CMM) has become an indispensable tool in the process control regimes of modern production lines. Whether in-line or off-line, CMMs provide the most accurate measurements of parts ranging from turbine blades to engine piston rings.

This case study explores how DUKIN designs CMMs that minimise measurement errors through robust mechanical design and position feedback and how the recent expansion of the DUKIN product range to cover a variety of different accuracy and capacity requirements has been supported by Renishaw.

Background

DUKIN Co., Ltd., based in Korea, designs and manufactures a wide range of coordinate measurement machines (CMMs) that meet standard to ultra-high precision levels of metrology requirements in the electronics, automotive, aerospace and other industries.

These CMMs are used to capture three-dimensional measurement data on high precision, machined components such as car engine cylinders and aircraft engine blades as part of a quality control process.

The CMMs integrate either Renishaw optical or laser encoder systems to meet varying metrology challenges.

Linear position encoders are used in conjunction with Renishaw contact and vision probing systems to measure discrete points on a workpiece. This data is then used to ensure that parts meet predetermined tolerances.

Challenge

Manufacturers require CMMs that achieve high performance and system stability, which is affected by temperature fluctuations and greatly impacts overall accuracy. The instability in linear position measurements taken on the gantry axis affects inspection throughput and measurement accuracy.

Even when deploying Renishaw’s high speed 5-axis systems, which synchronise the movement of the 3 axes of the CMM and the 2 axes of the measuring head to inspect the part, the stability of the linear position measurements is important.

Solution

DUKIN uses Renishaw’s PH20 and REVO 5-axis probe systems on their CMMs with the understanding that robust CMM design is essential to realise the full performance potential of these measurement systems.

System designers at DUKIN deploy robust design principles and use high quality materials and components to minimise the amount of measurement error. These mechanical design approaches are applied in conjunction with software that compensate for errors caused by thermal expansion.

A combination of statistical and theoretical modelling and accurate live measurements of position and acceleration are used for force feed-forward control of the CMM’s motor driven axes.

For example, in a CMM bridge design; the X-axis (along the bridge) is driven along two guideways in the Y-axis direction where each shoulder of the bridge is driven by a linear system equipped with a separate servo motor.

To prevent a torque moment in the Z-axis direction and thereby distortion of the bridge structure, force feed-forward control is applied by the controller. This depends on the detected position of the measurement head as it moves along the X-axis guideway and the setpoint acceleration along the Y-axis.

Alternatively, comparison of the accelerations of the Y-axis guideways may provide additional feedback control of the bridge moment. Dependable, high-accuracy, position encoders are vital for these complex control regimes to work. A combination of a priori data and position and acceleration feedback in the X-, Y- and Z- axis directions are used to give the highest-levels of metrology performance.

Results

Renishaw encoders and scales are used across the full range of CMMs offered by DUKIN and the TONiC incremental encoder system with RTLC linear scale is installed on DUKIN’s gantry and bridge-type models.

RTLC is a low profile stainless steel tape scale featuring a 20 µm pitch. It is accurate to ±5 µm/m and may be ordered in lengths of up to 10 m. Any thermal expansion of RTLC scale is independent of the substrate as it is suspended in a carrier track, which maintains an air gap underneath the scale. As temperature changes occur in the CMM operating environment, the RTLC scale does not follow the same degree of deformation as the granite base. Thermal compensation is therefore greatly simplified – particularly in temperature controlled environments with the encoder scales and workpiece(s) in thermal equilibrium.

TONiC’s dynamic signal processing gives improved signal stability with ultra-low Sub-Divisional Error of typically <±30 nm to help realize superior motion control performance.

Regarding the role of Reinshaw’s innovations in DUKIN’s product lines, DUKIN Technical Manager, Tae Young Ku, has emphasized the important contribution of Renishaw’s encoder products by stating that: “We offer a wide range of CMM product lines, including standard, high precision and ultra-high precision models, depending on the type of position feedback. We have adopted Renishaw’s TONiC encoder series and the ultra-high precision RLE interferometry laser encoder system. The high-performance TONiC encoder is the most widely used and has been integrated into our CHAMP, HERO and VICTOR CMMs.”

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An Insight Into The Utilisation Of Measurement Sensors In Manufacturing Processes

An Insight Into The Utilisation Of Measurement Sensors In Manufacturing Processes

Manufactured parts need to be measured to ensure they meet the original design intent. Modern manufacturing techniques allow complex parts to be designed with numerous critical dimensions. A key element in precision metrology is having the right measurement tool for the job. Modern measurement machines use a variety of sensors to collect measurement data. Metrology software analyzes the measurement data, and through numerical and graphical reports, allows the user to make confident decisions about the part design and manufacturing processes. By Terry Herbeck, Vice-President of Asian Operations at OGP

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