OPW Academy

Everything's up for discussion - including us!

We see achieving the utmost in precision as more than just a matter of manufacturing precision measuring equipment. It also demands precise answers to precise questions - and that's where the OPW Academy comes in. This section of our website provides a platform for the regular discussion of current issues in the field of measuring technology.
We don't want this to be a one-way conversation - so please feel free to get in touch! Tell us precisely what you think about our views and let us know exactly what your own thoughts are. We look forward to a lively debate."

Topic for discussion

Standard reference gauges made from original materials
Reflections on a highly demanding technology

Standard reference gauges are a real challenge for manufacturers. Gauge specialist OPW has nevertheless raised the bar even further and offers standard reference gauges made from original materials for special applications ? thus giving its customers valuable additional benefits.

What are standard reference gauges?
Standard reference gauges are precision dummy components used at production facilities. They define all of the key dimensions which are to be produced and/or checked. Precision standard reference gauges are used to set up and test production facilities and also provide a template for the calibration of critical production steps as well as the overall production process. Standard reference gauges are therefore often far simpler than the corresponding original components. On the one hand it is crucial that they accurately reproduce the required calibration and test dimensions ? yet on the other they do not necessarily have to feature all of the functions included in the original component. In some cases it may not be cost-effective to specially manufacture a gauge which reproduces all the dimensions, areas and points of reference that need to be measured. The solution is ?standard reference gauges made from original materials?.

The technology should really be referred to as ?standard reference gauges made from the original workpiece?. This is a challenge even for materials specialists: Gauges are usually built out of steels such as 90MnCrV8 (1.2842) or 16MnCr5 (1.7131) but in this case consist of original materials such as die-cast aluminium. Special thermal treatment ensure that they remain true to dimension for as long as possible. Gauge production involves the use of machining methods ranging from lathing, milling and grinding to honing and lapping. This facilitates the achievement of an extremely high level of accuracy down to a tolerance of just a few micrometres. Conventional industrial materials such as the aforementioned die-cast aluminium appear totally out of place in this context.

Standard reference gauges demand a very high level of production precision. It is for this reason that techniques such as lathing, milling, grinding, honing and lapping are used. Between each processing step gauges are treated using techniques which may include tempering or ageing. Surfaces which will come into contact with probes are hardened in order to prevent them from becoming worn, while gauges themselves are aged in order to ensure that they remain true to dimension for many years to come.

One important argument in favour of standard reference gauges made from original workpieces (i.e. from original materials) is their resistance to temperature ? or rather their ?temperature neutrality?. The reason behind this is that the dimensions of a standard reference gauge only correspond with those of the original component at a specific temperature (generally 20øC). Component and gauge are usually made from different materials with different linear expansion coefficients and therefore respond to heat in different ways. Not so in the case of standard reference gauges made from original workpieces: The steel or carbide measuring points integrated into the workpiece are usually tiny and only lead to a negligible variation in the gauge?s temperature behaviour when compared with the standard component.

Conversation with Bruno Kaupp, Sales Technician at OPW

Mr Kaupp, will standard reference gauges made from original materials replace those made from gauge-quality steel in the medium term?

Bruno Knaupp: No, they certainly won´t. Standard reference gauges made from original materials are a special solution, a real niche product. Thats not going to change.

But it all sounds so simple: take an original component, modify a few surfaces and there´s your gauge.

Bruno Kaupp: On the one hand we need gauge-quality steel inserts for surfaces which are to be measured or used as points of reference ? lower-quality surfaces would become worn and the gauge would soon no longer be true to dimension. On the other hand fitting the inserts is a big challenge for the production department.

So there’s a price tag attached?

Bruno Kaupp: Only if you look at standard reference gauges in isolation. Design, production, fine-tuning: there are naturally a number of costs involved. But once you?ve factored in the additional process insights you stand to gain, not to mention the ease of use that characterizes gauges of this type, then that puts those costs into perspective.

In which scenarios do you recommend customers have their standard reference gauges made from original components?

Bruno Kaupp: One example is if their workpieces feature geometries that are too complex to be cost-effectively reproduced by machining gauge-quality steel. Another is if gauges needs to exhibit specific properties ? for example a particular type of behaviour when exposed to temperature ? which are only present in the original component.

More on standard reference gauges.

Just as components are sometimes turned into one-off gauges we have set up a dedicated website for our standard reference gauges focusing on one key issue: Absolute precision.
To find out more please visit www.einstellmeister.de.

Topic for discussion

The simplicity of measurement
OPW workshop on the future of gauge engineering

OPW has been a manufacturer of precision special gauges for over 60 years - and during that time both production and measuring technology have taken giant leaps forward. 3D measuring machines and optical measuring systems now compete with special gauges and SPC-assisted measuring stations. The OPW Academy aims to engage in critical analysis of these concepts and therefore invited a number of OPW?s experts in this field to take part in a workshop on the topic. The participants were as follows: Mr Leicht (Design Engineer), Mr Brendle (Sales Technician), Mr Kaupp (Sales Technician), Mr Hauser (Design Engineer) and Mr Hildebrandt (Managing Director).

OPW has been a manufacturer of precision special gauges for over 60 years. Let?s take a look back at the last two decades: What have been the most significant developments in the field of production technology?

Leicht: There's no doubt about it - tolerances in terms of shape and positioning have become considerably more demanding. There used to be a lot more right angles, even linear dimensions and diameters were simpler.
Brendle: Globalization has had more of an effect on manufacturing than it might seem at first glance. Customers now demand a higher degree of interchangeability. Its a particular challenge in terms of servicing and support, especially in the field of gauge engineering where components have traditionally been paired together.
Leicht:And that´s just the tip of the iceberg. Our gauges are now used around the world, which means theyre exposed to a variety of climatic conditions. China is just one example. The demands placed on materials have gone up and up.

How has measuring technology changed during the same period?

Kaupp:The amount of measurements carried out is now far greater than it used to be. One factor is the increasing complexity of component geometries; another is that there is now much more emphasis on quality than there used to be.
Brendle: Greater quality awareness is also closely linked to demand for more documentation. Not only do our customers now document and archive much more data than they used to, but they also require us to provide far more comprehensive documentation of our products. Certificates of measurement system analysis are now almost the norm rather than the exception.
Leicht: There is certainly more measurement these days, and that applies to both products and individual steps in the production process. In the past it was often the case that only the finished product was measured. Now statistical process control often sees components measured after every sub-process in order to identify any issues at an early stage. It?s an approach driven by cost awareness and the desire to minimize waste.

Have gauges themselves changed?

Leicht: Mounts have become more sophisticated. We now buy in an increasing number of the precision guides we used to essentially all manufacture in-house.
Kaupp: Gauges still tend to feature classical dial gauges in scenarios where speed and robustness are important. That said, an increasing number of our devices are fitted with inductive data transmitters. Martin Leicht was absolutely right when he said that tolerances in terms of shape and positioning have become far more demanding. Electronic data transmitters and SPC-assisted evaluation are now absolutely vital even if you simply want to ensure the proper evaluation of the data gathered.

3D measuring machines and optical measuring systems have always offered a range of electronic data evaluation options - it´s part of their DNA, so to speak. Is it only a matter of time before special gauges are phased out?

Kaupp: With all this talk about advances in the field of production technology weve failed to mention the pressure of rising costs. This is where special gauges are particularly attractive, as even unskilled workers find them easy to use. Another advantage is that they offer a simplicity of measurement which has remained unaffected despite the ever-increasing demands placed on the measuring process as a whole.
Leicht: Gauges are highly available. A 3D measuring machine or optical measuring system, on the other hand, almost inevitably leads to bottlenecks. Their design generally means that they have to be installed in a separate measuring room. That prevents inline measurement, which in turn leads to delays. By the time the results are available another 10 or 12 components - cylinder heads, let´s say - might have been produced. What if the results of the measurement of the first component show it to be a reject?
Hauser: Take a look at optical systems - they quickly arrive at the limits of their capabilities. Theyre great for measuring contours, but what about measuring depths?

Topic for discussion

The renaissance of a technology: Pneumatic measurement

Pneumatic measurement has been rediscovered at OPW over the last few years. The reason behind this is the many benefits the technology offers when compared with conventional measuring technology. Its ability to combine a variety of measuring technologies enables OPW to provide enhanced measuring solutions.

Pneumatic measurement is based on the principle of back pressure. Compressed air is used to determine the back pressure created in the supply hose leading to the test specimen. The difference in pressure measured is then compared against the dimensions of a reference workpiece.

The method is characterized by a high level of measuring accuracy, consistent repeat accuracy (<0.2 æm) and speed of use. This makes it ideal for serial inspections and tests characterized by minimal tolerances. Pneumatic measuring equipment is based on highly robust, low-wear components requiring limited maintenance despite long periods in operation. This non-contact measuring technique can be used to measure all materials which allow back pressure to be created. The fact that the measuring air cleans the workpiece means that pneumatic measuring technology can also be used in dirty environments without risking any loss in measuring accuracy. What is more, pneumatic measuring equipment is relatively small and therefore needs hardly any space to carry out its measuring tasks. The highly compact measuring devices have no moving parts and facilitate the measurement of both spacing and shape tolerance. They are easy to use and therefore allow not only rapid changes from one workpiece to the next but also the option to repeat measurements as many times as is necessary. Electronic data processing is almost always possible even though electronic systems are not required in order to carry out the measurement itself. This means that measurements can also be carried out in wet or humid environments.

Another advantage is that the standard reference gauge is not subject to wear even if measurements involve frequent calibration. This means that even though initial procurement costs may be higher they are offset by lower oncosts."


Einstellmeister von OPW sorgen für hundertprozentig sichere Serienproduktion.


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Chief Representative Mr Yan Lusong
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Phone: +86 10 / 87 22 72 48