Some Relevant Aspects of Developing a Customized Remote Control System

1 ILIESCU M, 1DUMITRESCU D., 1 VELEA G., 2COMĂNESCU B.

1Manufacturing Department; 1“POLITEHNICA” University of Bucharest, 2OPTOELCTRONICA S.A.

1Splaiul Independenţei no. 313 Street; 2Atomiştilor no. 409 Street ROMANIA

iomi@clicknet.ro; www.pub.ro ; www.optoel.ro

Abstract: - Developing a customized product requires thorough analysis of the problems involved, so that performances and efficiency could be stated. This paper presents the way computer aided technologies, dealing with modeling, simulation (by SolidWorks and Autodesk Inventor) and rapid prototyping (by Ink Jet 3D printing) , were applied and used so as to a check, to determine, to improve and correct the possible design errors of a remote control system’s components. Key-Words: - modeling, simulation, rapid prototyping, 3D printing, model 1. Introduction Customized products do require special attention nowadays, as they have to satisfy customer needs and, meanwhile, be manufactured with optimum characteristics and minimum effort, all resulting in reasonable price. That is why, once an order for a certain product being received, the development team (including designers and manufacturers) must take a thorough look at it and decide to use adequate means in order to determine possible errors and to avoid failures. Computer aided technologies – specially those dealing with design (CAD) - are of great help, as they enable making drawings of product’s component elements, determine the whole assembly and, thus, evidence all eventual miss-fitting. Software aimed for modeling and simulation - such as SolidWorks and Autodesk Inventor – represent the bridge between idea and technology and allow a correct estimation of component element’s behavior while functioning. Once simulation results being optimized and decided that, theoretically, there is no risk of errors and failures, a further step should be taken in product development, meaning rapid prototyping of its most important elements, so called “key elements”. Rapid prototyping is part of additive fabrication technologies. These belong to a group of technologies used for building physical models, prototypes, tooling components, and even finished series production parts—all from 3D computer-aided design (CAD) data, medical scans, or data from 3D scanning systems. [7].

Rapid prototyping represent the automatic construction of physical objects using solid freeform fabrication. Virtual designs are “taken” from computer aided design (CAD) or animation modeling software and transformed into thin, virtual, horizontal cross-sections. Each cross-section is created in physical space, one after the next until the model is finished. So, the virtual model and the physical model correspond almost identically [6], this technique being one of the kind WYSIWYG. – meaning, What You See Is What You Get. Considering, both the way layers are built to create the part, and the initial form of base material, there have been developed many rapid prototyping technologies. Some of them are the following ones: → Selective Laser Sintering (SLS) – for thermoplastics and metal powders; → Fused Deposition Modeling (FDM) - for thermoplastics and eutectic metals; → Stereolithography (SLA) – for photopolymers; → Laminated Object Manufacturing (LOM) – for papers; → Electron Beam Melting (EBM) – for titanium alloys; → 3D Printing (3DP) – for various composites powders. 3D printing, is an ink jet printing that “comes” from the printer and plotter industry This technique utilize ink jet technology to shoot droplets of liquid to a solid compound and form a layer of an rapid prototype model. So, 3D printing is based on the inkjet printing process, where binder is printed on a powder layer to selectively bind powder together for each layer [5].

ADVANCES in VISUALIZATION, IMAGING and SIMULATION

ISSN: 1792-6130 29 ISBN: 978-960-474-246-2

This paper presents some relevant aspects coming out of the application of modeling, simulation and rapid prototyping (3D printing) in the development of a customized product.

2. Customized Product The customized product to be developed is a remote control system, used in a more complex assembly for optical measurements (ex. surface roughness, dimensions and geometric profiles) or for taking video images / pictures of special processes (ex. combustion analysis, temperature field, failures and cracks propagation).

elastic gear

The objective of a photo or video camera has to be remote activated, through a stepper motor, and thus, the system rotating the aperture ring has to be carefully designed and manufactured. The remote control system, was ordered for a certain camera and for special working conditions so, it does represent a customized product. Its schematic representation can be seen in figure 1 (a. - whole view, b. – detail view)

Component elements whose development aspects are presented further, refer to the gear, meaning the elastic element and the wheel (see figure 2). There should be mentioned that instead of the elastic sector, it could have been used a wheel, too, but because of camera’s objective characteristics, the rotational movement is limited to a certain number of degrees (75º), corresponding to diaphragm’s six aperture positions. Some characteristics of the remote system should be the ones: - remote controlled by RS 232 interface; - accuracy : 0,40 ; - speed: programmable from 0.1 till 5000 step/s; - acceleration/deceleration ramps programmable; - communications speed: 9600bps; To rotate the aperture ring with one position it is necessary to choose the number of steps and command. In micro stepping, the number of steps necessary to command the motor must be multiplied by consequence (2/4/8).

wheel

Fig. 2 Gear components

camera

gear a.

camera’s objective

support

stepper electric motor

elastic gear sector

b. gear wheel

Fig. 1 Remote control system scheme

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ISSN: 1792-6130 30 ISBN: 978-960-474-246-2

3. Modeling and Simulation

Two special software were used in order to model and simulate the rotational movement generated by the gear and its component elements behaviour. They were Autodesk Inventor and SolidWorks (mechanical design automation software that takes advantage of the familiar Microsoft® Windows® graphical user interface). As an observation, it should be mentioned that the linear movement of the objective - corelated to its rotational one, in order to ensure the required focal distance - was not simulated. That is because the interest of this study was focused only on the elastic sector – wheel gear. So, the selection of the parts involved in modeling and simulation, as well as their movement trajectories are shown in figure 3. When loading (in gearing) the elastic sector’s teeth and wheell’s teeth are submitted to loading, so that analysis of bending stresses and strains that do occur must be done. The tooth selection and loading for the elastic sector and wheel can be noticed in figure 4 and, respectively, in figure 5, while the generated meshes resulted in 28.068 nodes and 16.522 finite elements – for the elastic element and 27.650 nodes and 15.715 finite elements – for the elastic element.

Fig. 4 Selection of elastic sector’s tooth loading

Fig. 5 Selection of wheel’s tooth loading

Results of displacement distribution, for the studied cases are shown in figure 6. One can notice that there is a too high displacement for the tooth, specially that of the elastic sector which is over-loaded, so re-dimensioning it is necessary. Fig. 3 Parts and trajectories involved in simulation

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ISSN: 1792-6130 31 ISBN: 978-960-474-246-2

Fig. 8 Finite element mesh for the studied system, obtained by Autodesk Inventor

Fig. 6 Tooth displacement distribution – for the

elastic sector and for the wheel

Fig. 9 Stress distribution in gearing teeth Another important aspects that was noticed wile modeling and simulating of the gear component’s bahaviour was the one that the wheel, as initially designed, was too thin and could not stand the bending stress occuring. Results obtained for wheel thickness, when tooth loading (due to gearing) can be seen in figure 7.

An image of the mesh obtained when the whole assembly was modeled by Autodesk Inventor is presented in figure 8 (56.135 nodes and 32.921 finite elements) . It must be mentioned that the simulation results, for both stress and strain distribution fields, were similar to the ones obtained by SoliWorks software, both inidcating that the gearing teeth could not rssist bending, so re-dimensioning should be required. An example for stress distribution can be noticed in figure 9.

4. 3D Printing Further step in developing a product is prototyping. Once the changes in design being made, as result of modeling and simulation, prototypes of product (component elements) are worth to be obtained. The rapid prototypimg technique studied by this paper is 3 D printing, that is [1], [4]: layers of fine powder (plaster or resins) are selectively bonding by “printing” a “liquid (binder)” from the inkjet print-head, in the shape of each cross-section, as determined by the CAD file.

Fig. 7 Stress analysis results for the wheel thickness when gear loading

The prototypes were obtained on a ZPrinter 310

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ISSN: 1792-6130 32 ISBN: 978-960-474-246-2

Plus machine [3], [2] and, as consequence, the materials used were : ZP 131 powder (material to be bond by printing); Zb 60 – binder solution and Z-Max – a high strength epoxy (materials used for making the prototype hard enough to be handled and, if necessary, further machined). The printing machine software enables (based on CAD parts drawings) preliminary calculi of important process parameters, such as: models’ height (15 mm); layer thickness (0.1016 mm); number of layers (147); estimated build time (25 minutes); estimated binder usage (10,6 ml); total volume of models (19.47 cm3), etc.

One important element is to establish the position, within the printing machine’s enceinte, of the prototypes to be obtained, so that their easy and correct extraction to be possible. For the studied case, the position is the one presented in figure 10. Images taken while the printing prototyping process is on, can be noticed in figure 11, from both computer screen and machine’s enceinte.

Fig. 12 Extraction and cleaning of prototypes

Once the prototyping process over, after some time (about 30-50 minutes) necessary for cooling of the machine enceinte powder, the prototypes were carefully extracted and then, cleaned off the remaining powder – see figure 12. After that, they were heated into an electric oven (for complete dry) and impregnated by the resin (for hardness), the elastic sector and wheel prototypes being noticed in figure 13. Fig. 10 Machine’s enceinte prototypes’ position

Fig. 13 Prototypes of elastic sector and wheel Fig. 11 Prototyping process phase

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ISSN: 1792-6130 33 ISBN: 978-960-474-246-2

Once all the other parts of the remote control system being prototyped, all the assembly could be “put together” and see if the component elements fit together and the system works right.

So, it was noticed that the gearing was right, meaning the wheel and the elastic gear sector rotated the same angle and there was not too high clearance between their corresponding tooth.

Some other thing that was noticed, was that the elastic sector did not fit the camera’s objective too well. It involved that:

- when the sector was tighten on the objective (to avoid slipper when rotational way changes), then the objective could move no more;

- when the sector was large enough on the objective (to allow movement), when changing the rotational way, there was a free rotation (for a few angles) of the sector, without the objective’s rotation.

So, some adjustments to the inner diameter of the elastic sector had to be done.

An image of the gearing elements – a variant that already exists and the variant proposed by the customized remote control system studied, can be seen in figure 14.

5. Conclusion A customized remote control system was proposed and studied, some of the most important elements in its correct functioning being the gear, meaning elastic sector – wheel. By modelling and simulation there was evidence the need for re-dimensioning, so that the elastic sector’s teeth and the wheel’s thickness could resist to the loading generated when working (gearing). By rapid prototyping, the situation was much “closer” to real working condition and, thus, the need for adjusting the inner cylindrical part of the elastic sector, so that to correct fit the camera’s objective, was evidenced. . Further research, by modelling and simulation, and further use of other (than ink-jet printing) rapid prototyping technique, could be done if several changes in component parts should be required. References: [1] Iliescu M., Nuţu E., Georgescu L., “Finite Element Method Simulation and Rapid Prototyping”, 8th WSEAS International Conference (POWER '08), pag. 257-262, ISSN 1790-5117, Venice, Italy, November 21-23, 2008.

[2] Iliescu M., Comănescu B., Nuţu E., “Rapid Prototyping Use in Manufacturing components of a Medical Laser device”, 2nd WSEAS International Conference on Additive Technologies ICAT 2008, DAAAM Specialized Conference, ISBN 3-901509–72-0, Ptuj, Slovenia, September, 2008 [3] Z CORPORATION, Available from:

http://www.zcorp.com/Products/3D-Printers Accessed: 2010-03.

existing

[4] 3D Printing, http://en.wikipedia.org/wiki/3D_prototyping

studied / proposed Accessed: 2010-03.

[5] Ink Jet Printing, Available from: http://www. Rapid Prototyping Inkjet.html Accessed: 2010-03. [6] Rapid Prototyping, Available from:

http://en.wikipedia.org/wiki/Rapid_prototyping Accessed: 2010-03.

[7]http://wohlersassociates.com/additive- fabrication.html Fig. 14 Gearing elements Accessed: 2010-03.

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ISSN: 1792-6130 34 ISBN: 978-960-474-246-2