Combining clamping systems? –

Designing something new and extraordinary is part of the agenda for the designers at EMUGE clamping technology.

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An exciting excursion into the universe of gear manufacturing

"Solid, complex and really ingenious" - this is how our colleague Gerhard, name changed by the editors, sums up the impressions that come to his mind when he is asked about a very specific clamping device. This statement makes us curious and we ask which workpieces are to be fixed with this clamping device. The colleague explains: "The planetary gear carrier is an essential component of an automatic transmission. It carries the planetary gears, which are needed to couple the sun and ring gears." 

Granted: Explaining a gearbox is complicated at first glance. Let us start from the beginning and clarify a legitimate question right away so that not only technicians and engineers are able to understand this technology: Where does the name "planetary gear carrier" come from? 

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We learn: "The name of the components is based on the solar system: The central point of an automatic gearbox is the sun wheel [3], which is orbited by several shafts. These shafts have gear wheels, the so-called planetary gears [2] and the movement is similar to that of planets around a central sun. This structure is surrounded by a ring gear [1]. As the name suggests, the planetary gear carrier carries the planetary wheels [4].“

Back to the gearbox: By changing gears, the interaction of the various gears mentioned above changes and the drive operates in the optimal speed and load range. 

This simple explanation is enough to get us started. However, we will use the precise technical explanations in the rest of the article, our colleague, an expert in clamping technology, will chime in with his explanations. 

You can look forward to an ingenious clamping concept, an impressive design, many advantageous functions and explanations from experts in this area - let's go! 

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Sophisticated clamping concept from two worlds

This clamping device still amazes us and our colleagues even though the implementation was made a couple of years ago. The resonating pride is unmistakable when he talks about this project: "This concept certainly stands out among the ones we implement in clamping technology. In terms of the design, the clamping concept and also the project sequence." We will learn more about this later. 

To begin with, we are particularly interested in the technical challenges that had to be met in this project. Our colleague Gerhard explains: "The requirements for the clamping concept mentioned by the customer were considerable at the beginning of the project. The focus is on a bulky component that is to be clamped with low distortion and fixed with low vibration by means of enormously high torques. Quite demanding for a milling operation with high machining forces!" 

To meet the requirements, our employees have combined the best of two worlds in the clamping concept: "The primary clamping is carried out by a clamping device "typical" for EMUGE-FRANKEN. A diaphragm chuck with visually striking clamping jaws is used. We use a "classic" concept of collet chuck and hydraulically actuated clamping piston for the additional internal clamping."

We are puzzled - another diaphragm chuck? We ask why our colleague opted for this concept. The reason given is: "Considering the fact that the clamping surface on the workpiece is relatively short and the large working space required for the tools, one immediately thinks of the clamping jaws of a diaphragm". At this point, we are happy to refer to the other success stories in which diaphragm chucks are used.

But let's get right back to this clamping device. The impressive size and the unusual design make it necessary for us to let our colleague show us the individual components of the clamping device. "The proverbial solid foundation is a specially designed plate [2], on which the other components are installed. All hydraulic and pneumatic lines, including the external connections, are worked into this plate." We also notice the distinctive hydraulic connections and the mounts for the load bars. The latter are absolutely necessary given the total weight of over 160 kg!

As already mentioned, the external clamping concept forms a diaphragm. The five clamping jaws [3] are screwed to the diaphragm and rest against the workpiece due to its inherent tension.

This torque is massively reinforced by hydraulic pressure. 
The orange slots of the collet [4] are clearly visible through the clamping jaws in the view from above. The alignment unit [1] is located in an exposed position above the two clamping.  

We do not want to focus only on the impressive construction, but also take a look behind the scenes. We ask ourselves why two clamping systems are combined and what the alignment sleeve is needed for. 

Clamping concept to reduce vibrations

Our colleague has the following answer to the first question: "The inherent tension of the diaphragm is already high and provides good holding torques. This clamping concept increases these holding torques enormously via the hydraulic actuation. Theoretically, that would have been enough for the machining process. The collet chuck is, so to speak, the necessary addition to achieve vibration-free clamping in addition to the high holding forces." And that is absolutely necessary: The milling operation started by the operator is characterised by high cutting forces, which primarily cause vibrations and could thus reduce the machining quality. 
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The alignment unit is another highlight that our colleagues have achieved in the design of this clamping device. We are interested in the functions that this striking component has to offer. Our colleague clarifies: "The first function is the insertion lock. It ensures that the workpiece is inserted correctly during manual loading."

Additional technical details are: "The alignment sleeve has pins that can be extended and retracted. These give the workpiece the correct angular alignment for machining." The movable sleeve also sets the final position during alignment: The alignment unit frees up enough space for the added tools by retracting away from the workpiece. We are amazed and thrilled at the same time!  The clamping device is pressurised hydraulically, sometimes with a considerable 140 bar. Exactly controlled clamping sequences matched to the workpiece are precisely defined by a complex hydraulic circuit. The hydraulic circuit was limited by the number of hydraulic channels available on the machine side - which is not a problem for our technicians! 

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Targeted project process and partnership-based cooperation

The clamping technology of EMUGE-FRANKEN is best suited for clamping concepts where the highest precision is required. The colleague explains that the design at hand is somewhat different: "The goal was not to achieve the highest possible accuracy. As mentioned at the beginning, the customer wants to run a demanding machining operation with great forces that have to be absorbed by a massive clamping concept and high torques." This also has an impact on the machine, which has to be taken into account during the project process. 

In order to classify the diverse requirements and interests appropriately, our colleagues have focused on a productive exchange with our customers. Both the machine manufacturer and the machine operator, i.e. the end customer, were represented at all meetings from the very beginning and they presented their arguments. "The project process was not unusual in this constellation. The consistent and common focus of all those involved was definitely impressive."

Milestones were aligned at short intervals and everyone involved was always up to date. Our colleagues here are not just designers or engineers. It is not uncommon for them to slip into the role of project manager in such projects, who has to maintain an overall view. The performance of our colleagues was definitely well received by our customers and so the project was brought to a conclusion with a final meeting at the Nuremberg Christmas market.

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Overcoming boundaries through interdepartmental cooperation

What makes this concept so special in the end? "Of course, this clamping concept was about more than just clamping and declamping. It was about the coordination of many movement sequences, a complex control system and finally the huge size of the clamping device!" We can only agree with that! In addition, we learn that this project also occupies a special place in our colleague's personal ranking: "This clamping fixture is certainly one of the top 10 impressive and complex clamping devices built in the field of clamping technology. At least in my area". 
An additional interesting fact: The required holding torques could not be easily checked. Neighbouring departments from the company were activated to accelerate the development. "Our internal test workshop supported us and provided the relevant technology. A two-metre-long torque wrench was used. That was impressive to see. Finally the holding torques could be achieved!" 

We learn that this is precisely what makes the design of clamping devices so appealing: "The possibility of implementing our own concepts for ambitious customer requirements and exciting workpieces is what makes EMUGE-FRANKEN clamping technology so special! This also clarifies why our colleagues have been working in the clamping technology department for so long. 

Relevant advantages for our customers.

Of course, this concept offers huge advantages to our customers: "The clamping concept creates the required torques and also clamps the massive workpieces with low vibration." In addition, the end customer can set up this device a total of six times in his machine. This means that he operates three clamping devices in the machining area at the same time and thus significantly increases the number of machined work pieces! In addition, another three clamping devices can be prepared and loaded on a further, swivelled-out machine table. The result: Production times have also been shortened enormously.
The surfaces of the clamping fixtures have been chemically nickel-plated to ensure that the rinsing and cooling fluids do not have a negative effect on them during machining. The so-called DNC coating provides the necessary corrosion protection. We summarise: The implemented clamping concept not only offers a convincing technical solution, but also a significant improvement of the production process.
Attentive visitors to our trade fair stand will be quite familiar with this clamping device. We have exhibited this clamping concept at trade fairs since 2015. We do not always have cranes and other aids at our disposal here in contrast to the industrial application area of the twin clamping device. That's why this clamping device sometimes makes us sweat when setting up the exhibition stand. But the feedback from the visitors is very pleasing, therefore we will probably send this clamping device to exhibitions more often.