- Email: [email protected]
Testing device for electrical car networks
Journal of Materials Processing Technology 164–165 (2005) 1452–1458
Testing device for electrical car networks a , G. Wszołek a,∗ , A. Baier a , G. Ciupka b , O. Winter c ´ J. Swider a Department of Engineering Processes, Automation and Integrated Manufacturing Systems, Faculty of Mechanical Engineering, Silesian University of Technology, Gliwice 44100, Poland b DSE Draexlmaier, Germany c Johannes Kepler University, Linz, Austria
Abstract One of the production steps in DSE Draexlmaier Company (http://www.draexlmaier.de/), which is – besides other activities – a global player in producing electrical car networks is to make a final test of their products after manufacture process. The problem was connected with designing a mechatronic fixing and checking device for plugs of electrical car networks. The available testing device, on hand by DSE Draexlmaier, was completely analysed and simulated. The device should test the air tightness in order to make sure that the electrical isolation is waterproof. Additionally, two electrical connections should be checked during the test. The main aim of this project was to make an improvement of the whole device in order to decrease the production costs and to make it smaller than the existing one. The resulting concepts were modelled in CATIA® V5 and animated with CoCreate OneSpace Designer® 2002 programs. Both assumptions were taken into consideration in the designing process and as the final result solution which serves required expectations and constitutes the basis for the possible future manufacture implementation has been achieved. © 2005 Elsevier B.V. All rights reserved. Keywords: Virtual simulation; Electrical car network; Mechatronic device
1. Introduction One of the many activities of DSE Draexlmaier Company is production of electrical car networks with production sites all over the world. Reputable German car-producing companies were supplied through a long period of time and in the future, the GM group as well. To maintain the high level of their products, the company as everyone else, has to prove the quality at the end of the production line in order that everything works fine. Therefore a testing device was introduced, along with others. 1.1. Development Changing technical demands and the progress in the field of car networks enforce continuing development of the existing testing sites. One step of the production line is shown in Fig. 1. ∗
Corresponding author. E-mail address: [email protected] (G. Wszołek).
0924-0136/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2005.02.163
The plugs and the wires were attached to the mounting platform while sensors observe the process. After connecting all plugs and wires to the network it is attached to the final testing site. 1.2. Testing site During the production in company DSE Draexlmaier, two different kinds of testing sites were used. The older system, with vertical construction is shown in Fig. 2. The advantage of this construction is the improved approachability from the rear to manipulate the testing devices and the connections. Nowadays the construction has changed to a horizontal arrangement. A disadvantage of the old system is the used testing devices itself. Some parts of the fixing device are taking place above of the surface of the testing site. After the test, problems with dismantling the networks can occur and in the worse case, wires could be damaged. The new horizontal system, as shown in Fig. 3, has one disadvantage in comparison to the old one. The
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This configuration allows a simpler attachment to the testing site. One of these new testing devices were the basis for this project. The system used to fix the plug and the other functions were analysed and documented.
2. Description of the testing device Fig. 4 gives an overview of the used parts. Fig. 5 shows the principle of the simplest testing device. The plug is fixed and the electrical connections are tested by appropriate software. Fig. 1. Production step of electrical car networks.
2.1. Testing device for simple plugs If the light of the combined switch is on, then the testing device is ready to use. The plug is put through the front platform into the inlet. As soon as the plug reaches the switching contact, a signal goes to the electro-pneumatic valve and the cylinder presses the closing element, in this case a bar, into the empty space of the inlet and the plug is fixed by the bar. By using the contacts, the control software is able to test the connections. If something is wrong and changes have to be made at the plug, it can be removed by pressing the combined switch button. A signal goes to the valve and the cylinder removes the bar and the plug can then be removed. If everything works correctly and the tests are complete, the power supply will shut off causing the opening of all fixations. Fig. 2. Vertical testing site.
approachability to the inside of the testing site may not ideal, but the advantages far exceed this problem. The testing devices are built in modules, which allow small manipulations without reaching the inside. The new generation of testing devices does not disturb elements above the surface while the horizontal arrangement avoids damages as well. During the production, the network remains in the horizontal position.
Fig. 3. Horizontal testing site.
2.2. Advanced testing device The received testing device is able to cover a function with additional parts, which are not shown in Fig. 5. The car network also supplies some parts that take place in an unfriendly environment like the side mirror motor or some parts in around the engine. To protect the electrical contacts
Fig. 4. Used testing device.
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Fig. 6. Electro-pneumatic scheme in initial state.
Fig. 5. Dismantled visualisation of the testing device.
against dirt and water, there has to be some sealing and a suitable medium has to proof this function. A damper reduces the air pressure from the available pneumatic system to an appropriate level and is connected with the space inside of the plug and second connection reaches a pneumatic-electric sensor. If the pressure reaches a certain level, the sensor gives a signal to the control program that the connection is airtight and consequently watertight. 2.3. Electro-pneumatic diagram To show the function of the system, electro-pneumatic diagram [2] was drawn by using the FLUIDSIM3 program. This software also allows a simulation of electro-pneumatic systems [4,5]. The initial state of the system is shown in Fig. 6. On the left side, the pneumatic system is depicted. The basic function of fixing the plug is provided by the pneumatic cylinder and its valve. The damper controlling the air tightness test was set to 50% during the simulation, as shown in the centre of the left side. The empty space inside of the plug is symbolised by another cylinder. Unfortunately the library of the software did not offer the symbol for a pneumaticelectric sensor. To solve this problem, a differential pressure sensor was used to cover this function. The drawings on the right show the electrical connection of the testing device. The combined switch and light is figuratively represented by the drawing of the lamp and the switch P LOCK. If the testing device is in use, the plug is pressed into the inlet and the switching contact P LOCK is closed by the plug.
The electrical connections are closed and the light indicates the active state. This electrical connection also causes a signal to the valve Y1 and it changes its state and activates the pneumatic cylinder. The bar is fixing the plug inside of the inlet. As mentioned above, the same pressure supply is connected via a damper to the empty space inside of the plug and the pressure increases. If the sealing works properly, the pressure reaches certain level to operate the electro-pneumatic sensor. Simultaneously the control software through the contacts tests the electrical connections. This state of operation was simulated and is shown in Fig. 7. The switch P RELEASE provides the possibility to remove the plug in order to change something. If everything works fine and the control program is finished, all plugs can be removed. By turning off the main source, the cylinder opens the fixation and the system turns back into its initial state, as shown in Fig. 6. The network can be removed by the operator.
Fig. 7. Electro-pneumatic scheme in operating state.
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3.2. Functional requirements If the plug is fixed inside of the inlet, the only additional task to do is attach contacts to test the connections. Three different kinds of inlets are shown in Fig. 8. The air tightness test is solved in the best and cheapest way. Something has to get into the empty space inside of the plug and air is readily available and cheap as well. Other mediums would possibly leave something behind. Therefore this system requires no improvement and remains in place. 3.3. Space requirements Fig. 8. Sample plugs and related inlets.
3. Solution requirements In a complex car network exists many different kinds of plugs, Fig. 8 shows only a few examples. First of all the new solution should be suitable for all different kinds and shapes of plugs. It should be able to fix the plug with or without the air tightness test. The required space for the testing element should be standardised to the size of the front platform in Fig. 5. The available testing device needs twice as much of space, as shown in a later chapter in Fig. 12. 3.1. Universal usage To achieve the aim of universal usage it is not possible to be dependent on the special shape of each plug. Therefore the solutions, which are based on the specific shape, are not taken into account. For example, it would be possible to fix the plug with bigger shapes by using a kind of balloon, which increases its volume inside of the plug. Another concern is to reduce the problem of fixation to a simple requirement: a solid body with one edge has to be fixed somehow, as shown in Fig. 9. The size of the plug does not matter because if it is required, more than one element could be used to fix it. If this goal would we realised, the functional requirements are easy to fulfil.
Fig. 9. Reduction of the fixation problem.
Some plugs were given by the company to get an idea of their variety. Fig. 10 provides a wide range of shapes and sizes. To achieve the aim of universality, the biggest plug with the dimension of 39 mm × 22 mm × 22 mm was chosen. If the new solution can handle this plug every other plug would be no problem to fix. The available square of space to use was 75 mm × 32.5 mm and in comparison to the dimension of the plug, it was pretty obvious that the existing system with a pneumatic cylinder is not able to handle all the different plugs. The upright standing testing device in Fig. 9 was also chosen as a reference to get an idea of the available space. A closer look makes it clear that there is not much space around the plug. As mentioned above, the old testing devices have another disadvantage; the fixation elements are above the surface and could cause trouble or even damage to the network during dismantling. However there is plenty of space underneath the surface except space for the inlet. Approximately 250 mm can used for attaching the required parts to the device which gives a total space of 75 mm × 32.5 mm × 250 mm. 3.4. Dismantling the plug The existing systems do not provide a device for removing the plug from the inlet. At the end of the testing process everything is loose and the operator has to remove the network. This works for plugs shown in Fig. 10 where some parts of the plug are still above the surface while inside of the inlet. If
Fig. 10. Different plugs and two old testing devices.
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the aim to fix the reference plug is achieved, the lack of parts above the surface poses a challenge for its removal. 3.5. Results of these requirements The system to test the air tightness is ideal and was taken from the existing system. To meet the other requirements, a cheap, reliable and compact solution to fix all kinds of plugs had to be developed. Additionally, an appropriate device can be employed to improve the process of removing the network.
the flapping bar in order to fix the plug. The plug itself would remove the bar out of the inlet by rotation around the axis. As soon as the fixing edge reaches the same level as the bar the plug would be fixed. A short press on the protrusion on the top right allows the plug to be removed. Very simple solution and low production costs. No energy would be needed to fix the plug. The disadvantage is that every plug would have to be released manually before removing the plug. 4.2. Mechanical solution with energy consumption
4. Solution approach 4.1. Mechanical solution without energy consumption The suggestion for completely automatic opening of the fixations could be argued by the fact that the operator has to touch each plug anyway to remove it from the inlet. The first solution approach is to propose that the operator’s second hand should be used for opening the fixation manually. Another supporting argument is that the person has to brace him or herself against the surface anyway and this hand could be used for another purpose. Only bigger plugs could cause a problem concerning the number of elements because it is not possible to operate more than two in a small distance from each other. For the reference plug, it would be possible to use two fixation elements and operate them with one hand. The simplest solution would be a bar that is pressed by a spring into the inlet and fixes the plug. This idea was already used in the former system to operate the device manually. In the case where the operator must make a manual change, the plug can be removed in this way and at the end of the testing process; the pneumatic is used to open everything. As mentioned above, this solution is unacceptable because of the disruption of elements that are above the surface. The second reason for neglecting this solution is that it is not very easy to manually operate both bars quickly to remove the plug. Since the operator uses both hands to remove the plug and that it is necessary to brace at the testing site opens the possibility to propose a solution of a flapping bar, as shown in Fig. 11. Similar to the linear bar, a spring could operate
Fig. 11. Flap bar.
If the demand for completely automatic opening is more relevant then it is necessary to put energy into the system. The most obvious energy source would be the compressed air, which is available. Referring to the space problem, it is not possible to use the existing solution with the pneumatic cylinder. The testing device for a relatively small plug with air tightness test needs twice the space that is available by following the company requirements as shown in Fig. 12. To reach this aim, it is not possible to use this system in this way and the fixation has to be achieved in a different method. The valve and the cylinder are among the most expensive parts and it would be cost-effective to avoid using them. Before choosing the energy source, it should be clear in which way the force reaches the plug or the fixing element. Again, the limited space is a rigid requirement. As mentioned, the fixation problem can be reduced to fix a solid body with one edge. If no parts are above the surface, it is obvious that the whole plug has to be inserted into the testing device or even lower. The element that fixes the plug must be in the space between surface and the edge. The existing elements deal with this problem by a linear bar as described above. This linear movement has to be powered by a source that is located in a different level than the fixing element. The mechanical construction has to be very solid in order to ensure its function and this leads again to the space problem. Therefore another solution to transform the force is proposed by using a rotating movement to operate the fixing element. This principle is shown in Fig. 13.
Fig. 12. Front platform of the testing device.
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Fig. 13. Force transferring principle.
This configuration creates a space between the closing element and the force source where the parts for the air tightness test can be attached. The two arrows in Fig. 14 show the only place where the fixing element could get in touch with the plug. This leads to a triangular-shaped plane surface for the fixing element, which is in contact with the plug. If this element were accomplished with straight edges, the other kinds of shapes would be fixable with the same element. The second basis question to be considered is the decrease of the costs. A cheap solution is to produce the force for moving the part in at least one direction by a spring. This principle is implemented by using a single acting cylinder. The existing solution needs energy during the whole test to fix the plug, despite the fact that compressed air is cheap. From the energy point of view, it would be better to fix the plug with a spring and insert energy to the system only for releasing the plugs. But the difference between the normally open and normally closed is not very considerably. A simple bevelling of the fixing element should provide the function to remove the element by inserting the plug to the inlet. In the initial state the element is located inside of the inlet powered by a spring. The first realisation of the swivel bar is shown in Fig. 15. The rotating axis is placed in the centre of the plug. The dotted lines show the centre plane. The mentioned triangular shape allows the usage of the same element for all different kinds of plugs; only the position of the rotation axis has to be modified to the certain plug in order to make sure that the right part of the swivel bar is entering the inlet. The second realisation to achieve the normally closed setup is shown in Fig. 16. Similar to the old system, the plug
Fig. 14. Reference plug.
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Fig. 15. Swivel bar.
Fig. 16. Solution proposal.
has to remove the bar before it is able to enter the inlet. If the plug touches the bar, it starts a rotational movement and it will leave the empty space of the inlet. The centre plane is again symbolised by dotted lines. As soon as the plug reaches its final position, the spring presses the bar into of the inlet, the plug returns to the initial position and the plug is fixed by the swivel bar.
4.3. Construction suggestion of swivel bar The reference plug and two swivel bars to fix it are shown in Fig. 16. If the plug reaches the slanted surface, the swivel bars would move around their rotation axis which is symbolised by the drilling. As mentioned earlier, the plug has to be underneath the surface and this could cause a problem for removing the plug. The simplest solution would be to produce two openings, which allows the operator to grab it. Another way to deal with this problem is to attach a replacement part as shown in Fig. 17. By operating the opening and a little further movement, the slanted surface causes the plug to be lifted leading to better accessibility.
Fig. 17. Swivel bar concept with replacing element.
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5. Possibilities to generate the needed force The proposed solution described in the former chapters solves the space problem by shifting the source to fix or to open in another level. Despite the amount of space necessary for the air tightness test, all available space can be used to generate the force. That means that another technology with lower power density compared to pneumatic could be used. 5.1. Pneumatic The usage of the readily available compressed air would be the easiest way to produce the force. However in addition to the costs of the pneumatic elements, some mechanical parts would also be needed to transfer the force to the top. This leads to higher costs as in the existing testing device and one main aim would not be reached. Regardless of the cost, pneumatic is a reliable technology and almost maintenancefree. • • • •
Compressed air available; Reliable technology; Long, almost maintenance-free operation; Costs.
that is already used to operate the fixing element. However, when heated to above their transition temperature either by a source of heat or by a small electric current, they change to a much harder form and the wire returns to its un-stretched length. The wire shortens with a useable amount of force which can be applied to unlock the plug. FLEXINOL wires are usually used to devise very lightweight, flexible mechanisms but in this application, the low price and less space requirement are more important. Low current consumption and voltages allow easy interface to standard electronics, which also keeps the costs low. 6. Conclusions The combination of a swivel bar and the FLEXINOL wire is the simplest and cheapest solution. The requirement of universal usage and the functional requirements are solved by introducing the solution with the swivel bar. The space problem is generally solved by introducing the principle of force transferring by rotational axle. The implementation of the replacement mechanism would result in lower replacement time, and provide easier work for the operator, thereby increasing the productivity.
5.2. Electromechanic
Acknowledgement
A cheap possibility would be to use electromechanical actuators, as they are used in cars to lock the door automatically. One problem may lay in lowered reliability and additional costs for operation the actuator. However, it would still be a cheap solution.
This work has been conducted as a part of the research project No. 4 T07C 01827 supported by the Committee of Scientific Research in years 2004–2006.
• Lower costs compared to pneumatic; • Maybe less reliability.
References
5.3. Usage of alternative materials Another alternative would be the use of an actuator made of a nickel–titanium alloy. Under the brand name FLEXINOL [3], the company Dynalloy sells these wires in five different diameters. At room temperature, FLEXINOL wires are easily stretched by a small force, which could be done by the spring
[1] [2] [3] [4]
http://www.draexlmaier.de/. Fundamental of Electropneumatic – FESTO Didatic, 2000. http://slow.free.fr/materiaux/flexinol/flexinol.htm. J. Swider, (Redaction) Control and Automation of Technological Process and Mechatronic systems, Silesian University Publishing Company, Gliwice, 2002. [5] J. Swider, G. Wszołek, The methodical collection of laboratory and project tasks of technological process control, in: Pneumatic and Electropneumatic Systems with Logical PLC Control, Silesian University Publishing Company, Gliwice, 2003.
Testing device for electrical car networks a , G. Wszołek a,∗ , A. Baier a , G. Ciupka b , O. Winter c ´ J. Swider a Department of Engineering Processes, Automation and Integrated Manufacturing Systems, Faculty of Mechanical Engineering, Silesian University of Technology, Gliwice 44100, Poland b DSE Draexlmaier, Germany c Johannes Kepler University, Linz, Austria
Abstract One of the production steps in DSE Draexlmaier Company (http://www.draexlmaier.de/), which is – besides other activities – a global player in producing electrical car networks is to make a final test of their products after manufacture process. The problem was connected with designing a mechatronic fixing and checking device for plugs of electrical car networks. The available testing device, on hand by DSE Draexlmaier, was completely analysed and simulated. The device should test the air tightness in order to make sure that the electrical isolation is waterproof. Additionally, two electrical connections should be checked during the test. The main aim of this project was to make an improvement of the whole device in order to decrease the production costs and to make it smaller than the existing one. The resulting concepts were modelled in CATIA® V5 and animated with CoCreate OneSpace Designer® 2002 programs. Both assumptions were taken into consideration in the designing process and as the final result solution which serves required expectations and constitutes the basis for the possible future manufacture implementation has been achieved. © 2005 Elsevier B.V. All rights reserved. Keywords: Virtual simulation; Electrical car network; Mechatronic device
1. Introduction One of the many activities of DSE Draexlmaier Company is production of electrical car networks with production sites all over the world. Reputable German car-producing companies were supplied through a long period of time and in the future, the GM group as well. To maintain the high level of their products, the company as everyone else, has to prove the quality at the end of the production line in order that everything works fine. Therefore a testing device was introduced, along with others. 1.1. Development Changing technical demands and the progress in the field of car networks enforce continuing development of the existing testing sites. One step of the production line is shown in Fig. 1. ∗
Corresponding author. E-mail address: [email protected] (G. Wszołek).
0924-0136/$ – see front matter © 2005 Elsevier B.V. All rights reserved. doi:10.1016/j.jmatprotec.2005.02.163
The plugs and the wires were attached to the mounting platform while sensors observe the process. After connecting all plugs and wires to the network it is attached to the final testing site. 1.2. Testing site During the production in company DSE Draexlmaier, two different kinds of testing sites were used. The older system, with vertical construction is shown in Fig. 2. The advantage of this construction is the improved approachability from the rear to manipulate the testing devices and the connections. Nowadays the construction has changed to a horizontal arrangement. A disadvantage of the old system is the used testing devices itself. Some parts of the fixing device are taking place above of the surface of the testing site. After the test, problems with dismantling the networks can occur and in the worse case, wires could be damaged. The new horizontal system, as shown in Fig. 3, has one disadvantage in comparison to the old one. The
´ J. Swider et al. / Journal of Materials Processing Technology 164–165 (2005) 1452–1458
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This configuration allows a simpler attachment to the testing site. One of these new testing devices were the basis for this project. The system used to fix the plug and the other functions were analysed and documented.
2. Description of the testing device Fig. 4 gives an overview of the used parts. Fig. 5 shows the principle of the simplest testing device. The plug is fixed and the electrical connections are tested by appropriate software. Fig. 1. Production step of electrical car networks.
2.1. Testing device for simple plugs If the light of the combined switch is on, then the testing device is ready to use. The plug is put through the front platform into the inlet. As soon as the plug reaches the switching contact, a signal goes to the electro-pneumatic valve and the cylinder presses the closing element, in this case a bar, into the empty space of the inlet and the plug is fixed by the bar. By using the contacts, the control software is able to test the connections. If something is wrong and changes have to be made at the plug, it can be removed by pressing the combined switch button. A signal goes to the valve and the cylinder removes the bar and the plug can then be removed. If everything works correctly and the tests are complete, the power supply will shut off causing the opening of all fixations. Fig. 2. Vertical testing site.
approachability to the inside of the testing site may not ideal, but the advantages far exceed this problem. The testing devices are built in modules, which allow small manipulations without reaching the inside. The new generation of testing devices does not disturb elements above the surface while the horizontal arrangement avoids damages as well. During the production, the network remains in the horizontal position.
Fig. 3. Horizontal testing site.
2.2. Advanced testing device The received testing device is able to cover a function with additional parts, which are not shown in Fig. 5. The car network also supplies some parts that take place in an unfriendly environment like the side mirror motor or some parts in around the engine. To protect the electrical contacts
Fig. 4. Used testing device.
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Fig. 6. Electro-pneumatic scheme in initial state.
Fig. 5. Dismantled visualisation of the testing device.
against dirt and water, there has to be some sealing and a suitable medium has to proof this function. A damper reduces the air pressure from the available pneumatic system to an appropriate level and is connected with the space inside of the plug and second connection reaches a pneumatic-electric sensor. If the pressure reaches a certain level, the sensor gives a signal to the control program that the connection is airtight and consequently watertight. 2.3. Electro-pneumatic diagram To show the function of the system, electro-pneumatic diagram [2] was drawn by using the FLUIDSIM3 program. This software also allows a simulation of electro-pneumatic systems [4,5]. The initial state of the system is shown in Fig. 6. On the left side, the pneumatic system is depicted. The basic function of fixing the plug is provided by the pneumatic cylinder and its valve. The damper controlling the air tightness test was set to 50% during the simulation, as shown in the centre of the left side. The empty space inside of the plug is symbolised by another cylinder. Unfortunately the library of the software did not offer the symbol for a pneumaticelectric sensor. To solve this problem, a differential pressure sensor was used to cover this function. The drawings on the right show the electrical connection of the testing device. The combined switch and light is figuratively represented by the drawing of the lamp and the switch P LOCK. If the testing device is in use, the plug is pressed into the inlet and the switching contact P LOCK is closed by the plug.
The electrical connections are closed and the light indicates the active state. This electrical connection also causes a signal to the valve Y1 and it changes its state and activates the pneumatic cylinder. The bar is fixing the plug inside of the inlet. As mentioned above, the same pressure supply is connected via a damper to the empty space inside of the plug and the pressure increases. If the sealing works properly, the pressure reaches certain level to operate the electro-pneumatic sensor. Simultaneously the control software through the contacts tests the electrical connections. This state of operation was simulated and is shown in Fig. 7. The switch P RELEASE provides the possibility to remove the plug in order to change something. If everything works fine and the control program is finished, all plugs can be removed. By turning off the main source, the cylinder opens the fixation and the system turns back into its initial state, as shown in Fig. 6. The network can be removed by the operator.
Fig. 7. Electro-pneumatic scheme in operating state.
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3.2. Functional requirements If the plug is fixed inside of the inlet, the only additional task to do is attach contacts to test the connections. Three different kinds of inlets are shown in Fig. 8. The air tightness test is solved in the best and cheapest way. Something has to get into the empty space inside of the plug and air is readily available and cheap as well. Other mediums would possibly leave something behind. Therefore this system requires no improvement and remains in place. 3.3. Space requirements Fig. 8. Sample plugs and related inlets.
3. Solution requirements In a complex car network exists many different kinds of plugs, Fig. 8 shows only a few examples. First of all the new solution should be suitable for all different kinds and shapes of plugs. It should be able to fix the plug with or without the air tightness test. The required space for the testing element should be standardised to the size of the front platform in Fig. 5. The available testing device needs twice as much of space, as shown in a later chapter in Fig. 12. 3.1. Universal usage To achieve the aim of universal usage it is not possible to be dependent on the special shape of each plug. Therefore the solutions, which are based on the specific shape, are not taken into account. For example, it would be possible to fix the plug with bigger shapes by using a kind of balloon, which increases its volume inside of the plug. Another concern is to reduce the problem of fixation to a simple requirement: a solid body with one edge has to be fixed somehow, as shown in Fig. 9. The size of the plug does not matter because if it is required, more than one element could be used to fix it. If this goal would we realised, the functional requirements are easy to fulfil.
Fig. 9. Reduction of the fixation problem.
Some plugs were given by the company to get an idea of their variety. Fig. 10 provides a wide range of shapes and sizes. To achieve the aim of universality, the biggest plug with the dimension of 39 mm × 22 mm × 22 mm was chosen. If the new solution can handle this plug every other plug would be no problem to fix. The available square of space to use was 75 mm × 32.5 mm and in comparison to the dimension of the plug, it was pretty obvious that the existing system with a pneumatic cylinder is not able to handle all the different plugs. The upright standing testing device in Fig. 9 was also chosen as a reference to get an idea of the available space. A closer look makes it clear that there is not much space around the plug. As mentioned above, the old testing devices have another disadvantage; the fixation elements are above the surface and could cause trouble or even damage to the network during dismantling. However there is plenty of space underneath the surface except space for the inlet. Approximately 250 mm can used for attaching the required parts to the device which gives a total space of 75 mm × 32.5 mm × 250 mm. 3.4. Dismantling the plug The existing systems do not provide a device for removing the plug from the inlet. At the end of the testing process everything is loose and the operator has to remove the network. This works for plugs shown in Fig. 10 where some parts of the plug are still above the surface while inside of the inlet. If
Fig. 10. Different plugs and two old testing devices.
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the aim to fix the reference plug is achieved, the lack of parts above the surface poses a challenge for its removal. 3.5. Results of these requirements The system to test the air tightness is ideal and was taken from the existing system. To meet the other requirements, a cheap, reliable and compact solution to fix all kinds of plugs had to be developed. Additionally, an appropriate device can be employed to improve the process of removing the network.
the flapping bar in order to fix the plug. The plug itself would remove the bar out of the inlet by rotation around the axis. As soon as the fixing edge reaches the same level as the bar the plug would be fixed. A short press on the protrusion on the top right allows the plug to be removed. Very simple solution and low production costs. No energy would be needed to fix the plug. The disadvantage is that every plug would have to be released manually before removing the plug. 4.2. Mechanical solution with energy consumption
4. Solution approach 4.1. Mechanical solution without energy consumption The suggestion for completely automatic opening of the fixations could be argued by the fact that the operator has to touch each plug anyway to remove it from the inlet. The first solution approach is to propose that the operator’s second hand should be used for opening the fixation manually. Another supporting argument is that the person has to brace him or herself against the surface anyway and this hand could be used for another purpose. Only bigger plugs could cause a problem concerning the number of elements because it is not possible to operate more than two in a small distance from each other. For the reference plug, it would be possible to use two fixation elements and operate them with one hand. The simplest solution would be a bar that is pressed by a spring into the inlet and fixes the plug. This idea was already used in the former system to operate the device manually. In the case where the operator must make a manual change, the plug can be removed in this way and at the end of the testing process; the pneumatic is used to open everything. As mentioned above, this solution is unacceptable because of the disruption of elements that are above the surface. The second reason for neglecting this solution is that it is not very easy to manually operate both bars quickly to remove the plug. Since the operator uses both hands to remove the plug and that it is necessary to brace at the testing site opens the possibility to propose a solution of a flapping bar, as shown in Fig. 11. Similar to the linear bar, a spring could operate
Fig. 11. Flap bar.
If the demand for completely automatic opening is more relevant then it is necessary to put energy into the system. The most obvious energy source would be the compressed air, which is available. Referring to the space problem, it is not possible to use the existing solution with the pneumatic cylinder. The testing device for a relatively small plug with air tightness test needs twice the space that is available by following the company requirements as shown in Fig. 12. To reach this aim, it is not possible to use this system in this way and the fixation has to be achieved in a different method. The valve and the cylinder are among the most expensive parts and it would be cost-effective to avoid using them. Before choosing the energy source, it should be clear in which way the force reaches the plug or the fixing element. Again, the limited space is a rigid requirement. As mentioned, the fixation problem can be reduced to fix a solid body with one edge. If no parts are above the surface, it is obvious that the whole plug has to be inserted into the testing device or even lower. The element that fixes the plug must be in the space between surface and the edge. The existing elements deal with this problem by a linear bar as described above. This linear movement has to be powered by a source that is located in a different level than the fixing element. The mechanical construction has to be very solid in order to ensure its function and this leads again to the space problem. Therefore another solution to transform the force is proposed by using a rotating movement to operate the fixing element. This principle is shown in Fig. 13.
Fig. 12. Front platform of the testing device.
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Fig. 13. Force transferring principle.
This configuration creates a space between the closing element and the force source where the parts for the air tightness test can be attached. The two arrows in Fig. 14 show the only place where the fixing element could get in touch with the plug. This leads to a triangular-shaped plane surface for the fixing element, which is in contact with the plug. If this element were accomplished with straight edges, the other kinds of shapes would be fixable with the same element. The second basis question to be considered is the decrease of the costs. A cheap solution is to produce the force for moving the part in at least one direction by a spring. This principle is implemented by using a single acting cylinder. The existing solution needs energy during the whole test to fix the plug, despite the fact that compressed air is cheap. From the energy point of view, it would be better to fix the plug with a spring and insert energy to the system only for releasing the plugs. But the difference between the normally open and normally closed is not very considerably. A simple bevelling of the fixing element should provide the function to remove the element by inserting the plug to the inlet. In the initial state the element is located inside of the inlet powered by a spring. The first realisation of the swivel bar is shown in Fig. 15. The rotating axis is placed in the centre of the plug. The dotted lines show the centre plane. The mentioned triangular shape allows the usage of the same element for all different kinds of plugs; only the position of the rotation axis has to be modified to the certain plug in order to make sure that the right part of the swivel bar is entering the inlet. The second realisation to achieve the normally closed setup is shown in Fig. 16. Similar to the old system, the plug
Fig. 14. Reference plug.
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Fig. 15. Swivel bar.
Fig. 16. Solution proposal.
has to remove the bar before it is able to enter the inlet. If the plug touches the bar, it starts a rotational movement and it will leave the empty space of the inlet. The centre plane is again symbolised by dotted lines. As soon as the plug reaches its final position, the spring presses the bar into of the inlet, the plug returns to the initial position and the plug is fixed by the swivel bar.
4.3. Construction suggestion of swivel bar The reference plug and two swivel bars to fix it are shown in Fig. 16. If the plug reaches the slanted surface, the swivel bars would move around their rotation axis which is symbolised by the drilling. As mentioned earlier, the plug has to be underneath the surface and this could cause a problem for removing the plug. The simplest solution would be to produce two openings, which allows the operator to grab it. Another way to deal with this problem is to attach a replacement part as shown in Fig. 17. By operating the opening and a little further movement, the slanted surface causes the plug to be lifted leading to better accessibility.
Fig. 17. Swivel bar concept with replacing element.
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5. Possibilities to generate the needed force The proposed solution described in the former chapters solves the space problem by shifting the source to fix or to open in another level. Despite the amount of space necessary for the air tightness test, all available space can be used to generate the force. That means that another technology with lower power density compared to pneumatic could be used. 5.1. Pneumatic The usage of the readily available compressed air would be the easiest way to produce the force. However in addition to the costs of the pneumatic elements, some mechanical parts would also be needed to transfer the force to the top. This leads to higher costs as in the existing testing device and one main aim would not be reached. Regardless of the cost, pneumatic is a reliable technology and almost maintenancefree. • • • •
Compressed air available; Reliable technology; Long, almost maintenance-free operation; Costs.
that is already used to operate the fixing element. However, when heated to above their transition temperature either by a source of heat or by a small electric current, they change to a much harder form and the wire returns to its un-stretched length. The wire shortens with a useable amount of force which can be applied to unlock the plug. FLEXINOL wires are usually used to devise very lightweight, flexible mechanisms but in this application, the low price and less space requirement are more important. Low current consumption and voltages allow easy interface to standard electronics, which also keeps the costs low. 6. Conclusions The combination of a swivel bar and the FLEXINOL wire is the simplest and cheapest solution. The requirement of universal usage and the functional requirements are solved by introducing the solution with the swivel bar. The space problem is generally solved by introducing the principle of force transferring by rotational axle. The implementation of the replacement mechanism would result in lower replacement time, and provide easier work for the operator, thereby increasing the productivity.
5.2. Electromechanic
Acknowledgement
A cheap possibility would be to use electromechanical actuators, as they are used in cars to lock the door automatically. One problem may lay in lowered reliability and additional costs for operation the actuator. However, it would still be a cheap solution.
This work has been conducted as a part of the research project No. 4 T07C 01827 supported by the Committee of Scientific Research in years 2004–2006.
• Lower costs compared to pneumatic; • Maybe less reliability.
References
5.3. Usage of alternative materials Another alternative would be the use of an actuator made of a nickel–titanium alloy. Under the brand name FLEXINOL [3], the company Dynalloy sells these wires in five different diameters. At room temperature, FLEXINOL wires are easily stretched by a small force, which could be done by the spring
[1] [2] [3] [4]
http://www.draexlmaier.de/. Fundamental of Electropneumatic – FESTO Didatic, 2000. http://slow.free.fr/materiaux/flexinol/flexinol.htm. J. Swider, (Redaction) Control and Automation of Technological Process and Mechatronic systems, Silesian University Publishing Company, Gliwice, 2002. [5] J. Swider, G. Wszołek, The methodical collection of laboratory and project tasks of technological process control, in: Pneumatic and Electropneumatic Systems with Logical PLC Control, Silesian University Publishing Company, Gliwice, 2003.