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AHP Merkle GmbH
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79288 Gottenheim

phone: +49 7665 4208-0
fax: +49 7665 4208-88


15.04.16 Can cushioning action increase the performance capability of a hydraulic cylinder?

Philipp Santen, our development engineer, explains what underpins linear cushioning and the potential that it is able to release.

AHP Merkle moves. In this sector, that is not a secret. Now we are going one step further, and are directing our attention to an option that has so far attracted little or virtually no attention. Nonetheless, these efforts may be the sprat to catch a mackerel, in the quest to exhaust the performance potential of a hydraulic cylinder. We are optimizing the cushioning action of our hydraulic cylinders and are delivering a solution with our new linear cushioning system that is absolutely new and unique. We wanted to know about this in greater detail and talked to development engineer Philipp Santen about this new linear cushioning.


Mr. Santen, you played a leading role in the development of linear cushioning. What prompted you to optimize the cushioning in hydraulic cylinders?

Customers were calling for hydraulic drives capable of delivering even more performance, and major efforts were being invested to shorten cycle times even further. Our high-quality cylinders have a tremendous power-to-weight ratio. They are capable of moving large masses at high speeds, indeed this is what they are predestined for. However, cushioning action can rapidly become a limiting factor. You see, once a mass has been accelerated, it has to be braked again at its limit position - something that is frequently neglected. If the cushioning limit is exceeded here, the cylinder gets damaged. This shortens the service life of that cylinder and, in the worst case scenario, can even cause complete system failure. With this new form of linear cushioning we can eliminate these limitations. The customer is able to design the cylinder, and therefore also its cushioning capacity, specifically for his intended application. It was our intention to devise a solution that took the mystery out of the great unknown – cushioning action in other words – by turning it into a factor that can be calculated accurately. With this understanding, we have been able to increase the efficiency of the cylinder and of the entire system.


Linear cushioning is an innovation - indeed, it does not yet exist as such. You are promising various things, including greater efficiency and improved function of the cylinder. What is the secret of linear cushioning ?

That's a simple one! The secret lies in how braking action is applied. Linear cushioning achieves almost the fastest possible braking action while also only applying a slight load to the cylinder. The same cushioning work is performed, but in the shortest possible time. This increases performance and therefore also the efficiency of the cylinder!


In which applications can linear cushioning deliver its greatest potential?

I see many possible constellations. Firstly, they can be employed wherever large masses need to be moved quickly. Depending on the size of cylinder, they can weigh a few kilograms or several tons. Secondly, linear cushioning is advisable whenever there is a need to reduce the cycle times in an application. The time savings are achieved through faster movement and shorter braking times. To express that in figures, the benchmark in the past for speeds was between 0.1 to 0.5 meters per second. With the new linear cushioning you can now brake at speeds of up to 1 meter per second reliably. Then, last but not least, the use of linear cushioning on synchronous cylinders seems like a good idea. This assures uniform braking action, i.e. identical cushioning characteristics in all cylinders. Which means that no geometric distortion occurs.


Another advantage of the new type of cushioning is that it requires no adjustment. What does that really mean for the user?

For the user, the great advantage of this is that the cylinder can be calculated on the basis of its application parameters, and then the supplied cylinder simply has to be installed. There is no longer any need for manual cushioning adjustment using the cushioning screw on the cylinder. This not only eliminates any possibility of adjustment errors, but it also saves a lot of time.

And there is another advantage: Because no adjustments are required on the cylinder any more, this increases the level of design freedom. In other words, the cylinder can be installed where it fits best. There is no longer any need to provide access to the adjustment screw on the cylinder.


You mentioned that the cylinder is calculated on the basis of application parameters. What aids and tools do you give to your customers for calculating and configuring these cylinders?

We have described the five steps for the calculation and design configuration of our cylinders in detail, all documented on a step-by-step basis. These instructions can be downloaded in » PDF format.

Also, shortly, an update of our App ahp.cad, will be available too. With the new function ahp.calc it is child's play to define the correct cylinder. All the customer has to do is to stipulate his application parameters and the desired type of cylinder, then ahp.calc performs a calculation and indicates whether the level of cushioning is or is not sufficient. Perhaps interesting in this context also: As part of our training course schedule at the AHP Technikum we offer helpful training courses and workshops. On our Practical Days, linear cushioning is scheduled to be a focal topic.

Whenever the going gets tough, you can depend upon our promise: We are only ever a phone call away and are always delighted to assist you!


From what date is linear cushioning going to be available?

The new cushioning is already available now, but first as a special cylinder. During the current year, we shall be rolling out cushioning damping progressively for all hydraulic cylinders in the HZ series.


How long have you worked with linear cushioning and could you describe to us the development work being conducted at AHP Merkle?

We here at AHP Merkle have been working intensively for the last three years on the cushioning of hydraulic cylinders, simply because practice has shown us that there is a component that can introduce uncertainty into the system. In other words, if this weak area is eliminated, great potential is revealed. Step by step, and in many test set-ups, we have tested this cushioning action and have found a mathematical way to describe the processes involved in cushioning  With this knowledge, we were then able to tackle the mechanical optimization of cushioning action.


Here we are in a very modern test laboratory - your second workplace. What activities do you engage in here?

In the test laboratory, we perform all the tests that arise. That can include the testing of new seal or gasket concepts, or guidance concepts, and it can also include tests of the development status of linear cushioning: All of those tests have been conducted here. Of course, we also test the prototypes of our new cylinders here in this laboratory/ This very robust limit stop test rig is something we designed in-house. Combined with this exceptionally flexible hydraulic device, we are able to deliver enough power to get even large cylinders up to speed. Since we are able to simulate various application situations, we also conduct tests in close collaboration with our customers.


In your opinion, what is the great argument in favor of linear cushioning that will win the day, and will convert into practical applications?

Linear cushioning brings nothing but benefits to the customer. It allows customers to move larger masses faster, and to reduce cycle times. In some applications, for example where large masses have to be moved, or on synchronous cylinders, there is not in my view any viable alternative to linear cushioning.

The usability of this function offers decisive benefits in terms of the selection of a suitable cylinder, and at the commissioning stage. In general operation, linear cushioning makes a contribution towards damage prevention and it extends the service life of the cylinder.


Our cylinders in the HZ series are going to be getting equipped this year with linear cushioning on a rolling basis, and they are identical in terms of their installation dimensions to the previous model. There is therefore no need to make any adjustments. Plug & Play. All of these are arguments in favor of linear cushioning.



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Personal details:

Philipp Santen has been at AHP Merkle since 2012. After training as an automotive mechatronics specialist, he studied mechanical engineering at technical college (FH Offenburg). As a permanent member of our development team, his area of responsibility covers the designing and calculating of new hydraulic cylinders and the optimization of existing units. Philipp Santen is also responsible for producing FEM simulations and calculations. The Finite Element Method (FEM) is used when designing our hydraulic cylinders to test complex components for resistance to thermal and mechanical loads.


Participants on training courses at the AHP Technikum get to know Philipp Santen as a tutor, and benefit from his expert knowledge. In the 'Quality & Know-How' block, he places the emphasis on damage prevention. Ever since his first customer call-out outside the company – a cracked piston rod – it has been clear to him that AHP Merkle needs to raise the awareness of its customers for issues relating to damage prevention.