Fluid Power technology
Fluid Power technology magazine Pneumohydraulic systems TOX-Powerpackage For thirty years, pneumohydraulic systems are a notable alternative solution for applications which are in need of high forces. With improvements in technology, every day they are seen in more applications. In cooperation with TOX Pressotechnik for 25 years, MKD Makine offers this high quality equipment to the benefit of country’s industry. 38 MDA Technologies 1/2015
DRIVE TECHNOLOGIES Pneumohydraulic systems are supplied with pressurised air only. A built in power converter these systems can give you forces which can not be achieved with usual pneumatic equipments. By six bar air, which can be found in almost every workshop, forces like 100 tons or more can easily be achieved. Working with pneumatics brings many advantages. Problems of hydraulic pumps and control equipment are avoided. While electric consumption, noise level, mechanical wearing are avoided, controlling becomes very easy. Hydraulic leakages, sealing elements which are problematic under high pressures, problems like warming and ageing due to heated hydraulic oil are all eliminated. As there is not moving parts in the power converters, oil does not heat, does not wear, does not get dirty as the converters are closed to the atmosphere. In high volume, high speed heavy duty serial production environment, systems continue production without any need for stopping. In comparison with pneumatic systems, air consumption is lower and creates savings in energy costs increases the production speed and eliminates the other elements being affected because of excessive air consumption. The working principle of pneumohydraulic systems is very simple. A plunger with a small cross section area is inserted in an hydraulic cylinder, through a sealing; as the plunger is forced in, the hydraulic piston with a relatively larger area, protrudes with a force multiplied by the ratio of both areas, which is practically 30. That is, the hydraulic cylinder will have 6,000 kN when there is 200 kN behind the plunger. Naturally, the plunger should be inserted 30 times longer than that of hydraulic cylinder. Therefore, the power strokes of pneumohydraulic systems are quite short. But, the total stroke is enough for most of the applications, with the low power approach strokes. TOX-Powerpackage cylinders have three parameters for selection. Force, total stroke and power stroke. 12 tons, 100 mm and 10 mm for instance. This cylinder can give 12 tons of force upto 10 mm, starting where ever necessary within 100 mm of total stroke. Of course, there are much larger or smaller values for these parameters with different models. In TOX-Powerpackage cylinders, power stroke starts where needed automatically, without needing an adjustment. This sophisticated system is a very simple one actually. Therefore it runs without a problem maintenance free. Our popular models have 12 mm power stroke within 100 mm total stroke; however, in the range, there are models with power strokes upto 100 mm and total strokes upto 400 mm. When longer power strokes are required, clinders’ total lengths are too long with larger volumes of converter sections. For such systems, the important advantages like speed and low air consumptions are become less. Therefore, applications which require shorter power strokes like, cutting, punching drawings go very well with TOX- Powerpackage cylinders where hydraulic cylinders may serve better in applications like deep drawings. Suitable applications for TOX-Powerpackage where the users benefit technically, economically, ergonomically are, rivet head stamping, pressing in studs and nuts and, TOX-Clinching and, insertion and stamping and various forging cutting and punching applications. One suitable application is also, clamping. This application is generally done with mechanical or pneumatic actuators. However, TOX-Powerpackage constitutes a very good solution for clamping where high forces are required. A similar application, where Powerpackage is very found very suitable is, closing forms. Closing spot welding electrodes are also an application where the user benefis air saving and better quality of welding when the TOX- Powerpackage is used. In general, provided that a proper model is selected, TOX-Powerpackage offers its user many advantages like, speed, savings, safety, sustainability, lower maintenance costs. With the TOX-Powerpackage, very special applications can be realized. By using an analog transducer and an actuator, a proportional control can be achieved easily. With this, a profiled press force needed for glueing can be implemented very economically; travel control when flaring a pipe end, even under very high forces, is very easy. In TOX-Powerpackage, you have an air cushion behind the hydraulic force. Therefore, you will never have vibration or shock in the applied force. This makes the tools last longer. The hydraulic pressure and the force at the tip of the working rod is linearly related. You can measure and use the force value once you feed the analog input to your PLC from a pressure transducer. Then, you do not need to use a costly and –mostlydifficultly installed load cell. However, for all models, TOX Pressotechnik offers a rod end load cell which can be installed at the end of the working rod very easily. In the same manner, you can also have a built in travel sensor for many models. TOX Pressotechnik offers several control systems and pressing controls for TOX- Powerpackage family. For instance, EPW 400 pressing control system enables you to display pressing force against travel of the piston rod graphically at very small – like MDA Technologies 1/2015 39
