Use of rapid prototyping in renovation of old-timers.

Pahole, I. ; Drstvensek, I. ; Veza, I. 等

Abstract: Rapid prototyping offers a great variety of possibilities depending on geometrical and technological complexity of products. It is possible to make geometrically complex products which cannot be made by conventional manufacturing processes. The products can be made singly, in combination with vacuum casting or in small series. Renovation of old-timers is an important part of the cultural heritage of any nation. In renovation the problems often arise how to secure certain component parts. It happens often that the maker of the exhibit is no more operating. In particular, the exposed parts of vehicles such as mirrors, lights etc. are hard to find because they are subject to breaking. The paper presents a model how a new component can be made on the basis of the minimum preserved data on product (photos, sketches, broken original parts etc.).

Keywords: Rapid prototyping, old-timers, numerical copying, CAD/CAM, digitalization, CNC machine

1. INTRODUCTION

The numerical copying processes ensure also the manufacture on the basis of physical models already made. They are used for renovation and/or reproduction of warn parts.

Often the question arises why to make mechanical models, if the making of the numerical model is simpler. Products are often formed by people disliking the computer work. Even some young people are not in favor of working with computers. (Kataliniae, B., 1990). Thus, some industrial designers and artists prefer to make the model in wood or synthetic material by manual working processes and then to process it numerically (Pahole, I.; Drstvensek, I.; Balie, J. & Mikulan, M., 2003).

2. DESCRIPTION OF MODEL OF NUMERICAL COPYING

Numerical copying is almost of the same age as the technology of numerically controlled machine tools. Figure 2 shows an expanded model of numerical copying.

[FIGURE 1 OMITTED]

The greatest advance, which can be noticed, is in copying of geometrical data and in the manufacture (Pahole, I. & Balic. J. 2003). The advantages of numerical copying can be summarized as follows:

* if necessary, the model can be drawn on the computer and then it can be corrected and modified as required,

* also the NC statements can be graphically checked prior to manufacture,

* characteristic errors of conventional copying systems can be considered in the program which removes them itself and, thus, the response time of the system is shortened,

* data on the product can be transferred to several machines, therefore, several products can be manufactured at a time,

* possible connection of measuring systems to various CAP/CAD systems with which exacting problems, occurring in manufacture of very complicated shapes, are removed.

3. ACQUIERING OF GEOMETRICAL DATA

The procedure of copying geometrical data consists of two key Parts

* 3D digitalization of the real model (product, tool) (figure 1),

* processing of the computer model (CAD processing of surfaces) obtained by 3D digitalization.

Nowadays, several different systems are available for 3D digitalization of real models:

* contact systems,

* contact less systems

[FIGURE 2 OMITTED]

The greatest advantages of this type of the digitalization systems are as follows:

* specially fast process of digitalization,

* the system dimensions are almost not limited upwards,

* the system is transferable,

* accuracies of up to 2 micrometers are reached.

Nowadays, there are a great number of makers of equipment of this type. By suitable knowledge and equipment it is possible to obtain an overall solution in the area of 3D digitalization [5].

4. EVALUATION OF COLLECTED DATA

Evaluation of collected data and their transfer back into the CAD programme tools is an integral part of the reverse engineering. The digitalization itself means nothing if behind the digitalization process the relevant procedures of processing the obtained CAD data are not used. The CAD data are processed by means of computer packages.

The obtained geometrical data are transferred into the CAM module where adequate manufacture technology is specified.

The product can be made:

* by processes of material removal,

* by processes of layered technologies.

5. MANUFACTURE

Processes with removal of material are relatively well known and widely used. Regrettably, because of their disadvantages they do not ensure adequate manufacture of the work piece, for example in case of small radiuses, very thin walls, drilled holes of small diameters and great depths etc.

To a large extent, the layered manufacturing methods avoid or complement those disadvantages. It must be a matter of deciding with respect to the time and cost criterion when the individual technologies must be selected.

Rapid prototyping is an important part of modern designing process. By minimum human interference it changes the virtual models of bodies into physical objects for better visualization and understanding. By reducing the time and the costs of each repetition of the design--manufacture--redesign, it enables the designer to make rapidly the prototypes so that he can discover the design errors earlier and at lower cast (Drstvensek, I., 2003).

[FIGURE 3 OMITTED]

Today, most machines for rapid prototyping make the objects by stacking thin layers of material, one section onto the op of the other. Such process of manufacture usually consists of two steps: short period of manual preparation of the product followed by the relatively long period of automated manufacture of the object. The most widespread RP methods nowadays are:

* Stereolitography (SLA)

* Selective laser sintering (SLS),

* Fused deposition modelling (FDM)

* Laminated object manufacturing (LOM)

* PolyJet

* 3DPrinting.

6. CONCLUSION

As indicated above it can be concluded that the described extended numerical copying system offers many possibilities. A disadvantage of such system is particularly its price. The purchase price of the individual units and appurtenant equipment is often too high and not cost-effective for one company. It is reasonable for various research centres. Those canters can offer services to all those needing such services and, thus, they justify the high costs of purchase of the system. It can be concluded that modernization of the computer equipment and introduction of new processes into manufacture are urgently required to be able to remain competitive on the market. Modern digitalization systems have made the process simple for use and by means of high-capacity computer support the data obtained can be processed, modified and adapted at will. It must be emphasised that the personnel working with that equipment must be suitably qualified and specialized. On the other hand the layer technology processes offer the manufacture possibilities with which the conventional technological processes could not cope.

[FIGURE 4 OMITTED]

7. REFERENCES:

Pahole, I.; Drstvensek, I.; Balie, J. & Mikulan, M (2003). Manufacturing of industrial tools for sheet-metal forming by use of reverse engineering, Proceedings of the 12th International Scientific Conference Achievements in Mechanical & Materials Engineering AMME'2003, DOBRZANSKI, Leszek A. (Le.). Gliwice-Cracow-Zakopane, Poland, 2003. pp. 719-722.

Pahole, I. & Balie. J. Obdelovalni stroji, (2003), Fakulteta za strojnistvo, ISBN 86-435-0522-6, Maribor

Drstvensek, I., Slojevite tehnologije, (2003), Fakulteta za strojnistvo, ISBN 86-435-0616-8, Maribor

Kataliniae, B. (1990). Industrieroboter und Flexible Fertugugssysteme furDrehteile, VDI Verlag, ISBN 3-18-401027-9 Dusseldorf

Pahole, I.; (1996). Using data flow matrix for small and medium-sized enterprises. V: Proceedings of DAAAM- 95, Katalinic, B.(ed.), pp 041-042, ISBN 3-901509-02 , Wienna, oct. 1996, Wienna

Herbertson,T.,(2003), Reverse engineering 4th International Conferenc on Industrial Tool, K. Kuzman, pp 419-422, Bled, Celje, april 2003, Tecos, Celje,2003,