Measurement Renishaw's 5-axis scanner delivers faster results

Editor: Lina Klass

The protagonists in the automotive industry are dominated by price and time pressure. Everything that makes the production of parts cheaper and faster, reduces this problem. 5-axis scanning achieves these demands, for example, in powertrain production.

Renishaw's Revo-2 head with advanced roughness sensor type SFP2.
Renishaw's Revo-2 head with advanced roughness sensor type SFP2.
(Source: Renishaw)

The 5-axis inspection on coordinate measuring machines (CMM) can be described as a technical breakthrough. In powertrain production in the automotive industry, which is characterised by fierce competitive pressure, there is a constant search for more efficient solutions. At the same time, attempts are being made to reduce production costs.

5-axis scanning for CMMs to inspect part characteristics is a significant technical breakthrough that has reduced cycle times by 20 to 70% depending on the application. Systems that use 5-axis scanning technology allow for significant savings in the production of complex parts.

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Some 50% time savings are not uncommon when measuring cylinder heads, engine blocks and transmission housings. With the help of a roughness sensor, which enables measurements with the same automated CNC measuring routines, it is also no longer necessary to transfer to another measuring device or to carry out manual testing with hand-held measuring devices.

Faster and more precise scanning

All CMMs with only three linear axes (X, Y and Z) are subject to variable scanning accuracy, which becomes even worse at higher speeds. The reason for this is that the acceleration and deceleration forces noticeably twist the machine structure, which also leads to errors in the measured data. To avoid these errors and to achieve the required accuracy, the scanning speed is kept relatively low. It is usually below 25mm/s.

Renishaw's proprietary Revo 5-axis measuring system is a technique that has radically changed the speed/accuracy conflict: The measuring head has two additional rotary axes which avoid these dynamic errors at high measuring speeds (up to 500mm/s).

This is achieved by using a fast-reacting measuring head to perform, for example, circular scans, while the machine structure remains fixed. When measurement paths require more than two synchronised axes, such as spiral scanning, the X, Y and Z axes can be programmed to move in a vector at constant speed and the head performs the fast scanning movements. In this case, the machine structure runs at a constant speed and the above errors can be avoided.

The Revo system offers five different types of probes, each designed to maximise the benefits of 5-axis motion and continuous positioning. The probes can be changed automatically and there are probes for tactile scanning, touch probes, probes for roughness measurements and non-contact optical probes. All probes are used within a common coordinate reference system and offer the optimal tool for measuring multiple features on a single CMM platform.

Automated roughness measurements

For a few years now, 5-axis scanning has been saving time. New developments now justify the use of 5-axis CMM techniques in powertrain manufacturing, including the enhanced SFP2 roughness sensors for the latest Revo-2 head. With Revo's continuous positioning, all features, including small bores such as valve guides in cylinder heads, can be checked. Due to this additional option, there is no longer any reason to use traditional, hand-held surface tools and roughness measurement now only takes about half the time previously required.

Programme-controlled surface inspection captures the data in the same coordinate reference system as other probes and automatically saves the results for later use. The equipment savings for new lines are around 25% if a 3-axis CMM with manual testing station is replaced by a 5-axis CMM with roughness measurement capability. The 5-axis technology features the latest CMM standard but can also be retrofitted to many older machines.

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As a result, CMMs equipped with Revo require fewer stylus configurations, reducing both tool inventory and cycle times. In most cases, even highly complex powertrain parts can be completely tested with two styli, often only one stylus suffices. This is particularly important as CMMs require a large part of their cycle time for calibration or the exchange of styli.

Two design features of the Revo 5-axis system offer the following possibilities:

  • Unlimited rotary positioning options, so that all angular interventions are programme-controlled and do not depend on changing different stylus configurations with fixed angles.
  • The ability of high-speed scanning with both short and long styli is achieved thanks to tip-sensing probe technology.

These functions allow even the longest stylus needed for the deepest feature to accurately measure features on the surface.

How does tip sensing work?

In tip sensing, the position directly behind the stylus tip is measured with a laser beam directed at a reflector on the stylus. The reflector changes its position as soon as the stylus touches the workpiece and bends slightly. The altered return path of the laser beam is then detected and the exact position of the stylus tip is determined, since the reflector and the stylus ball are close together.

The advantages of a digitally connected machine hall have already caused a lot of enthusiasm in the industry due to the potential of enormous efficiency savings. Ideally, the size and position of the characteristics are automatically monitored and automatic adjustments of the upstream machining processes – based on trends – are carried out. Tolerances should therefore remain within the process limits. The need for fast data acquisition is therefore very important and the fast 5-axis inspection enables a higher number of samples or the implementation of a complete inline inspection.

Renishaw also offers the Revo 5-axis system as a retrofit. In this case, the existing CMM is subjected to intensive testing to assess the condition of its mechanical and electrical components. The company's many years of experience with virtually all CMM models makes it possible to predict a defined increase in system performance as well as to conduct planning for retrofitting measuring devices.

Renishaw offers flexible maintenance and calibration solutions and the ability to regularly check machine accuracy with analysis tools. The retrofitted system is open and the customer remains the owner of his system data files. In this way, the customer is guaranteed the free choice of service providers for the ongoing maintenance and support of his system in the future as well.

This article was first published bywww.maschinenmarkt.vogel.de.

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