The aguirement of the models 3D CAD starting from the real model: the method reserve engineering.

Iancau, Horatiu ; Onetiu, Gheorghe ; Crai, Alina 等

1. INTRODUCTION

Reserve engineering is a copy process. Sometimes, a design without any engineering data but sample model, such as shoes or golf club, must be production (Masashi, 2005). Reserve Engineering can copy 3D data from the sample model. The method reserve engineering consist of obtaining the model CAD 3D (virtual) from the physical model of the part (the real one). The first step to realize this is the measurement of the real part to determine the section of the three plane as a well as all its dimensions with a high precision. The dates that results after the measurement are remade and the with the help of a software package of projection attended by the computer (CAD-Computer Aided Design) a model of 3D of the piese will be obtained. The next step can be the documentary of the part or of the guide mark by making a new mechanical drawing 2D.

2. THE STAGES USED IN THE PROCESS OF PART MEASUREMENT

As we said earlier the first step to obtain the model CAD 3D of the part was the measurement of geometrical precision of this.This has been realised This has been realised through the help of Regional Centre of Industrial Metrology (CERMI), within the framework of The Technical University from ClujNapoca (http://www.cermi.utcluj.ro/cermi.swf). The equipment with the help which has been realized the measurement in coordinates named Eclipse 550, manufactured by the german Company Zeiss (figure 1). This equipment offers a way of working CNC and a space of 550x550 mm in plan X-Y, respectively of 500 mm along the Z axe.Also this machine for measurement in co-ordinates offers the next precision of measurement (in um): [U.sub.1]=2.5+250/L--for measurements for one direction only ; [U.sub.2]=2.9+250/L--for spatial measurements where L is the measured characteristic.

The software package used for measurement is made also by Zeiss Company and has the name of Calypso (figure 2) (www.zeiss.com). This software package is ruled by Windows, giving the advantage of a better way of working on the dimensional analyse of the measure part. It is a software package based on graphic interface which offers intellingent instruments to make measurements more precise and simple as possible. It is also a friendly enviroment for the user but in the same time is an enviroment orientated especially to precise results.

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The stages of the part's measurement as it follows:

* The position of the part on the table and the settle of a sistem of coordinates for the know as 'part zero' in one of the adges of the part.

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* The measurement of all elements situated on plan X-Y, to establish the shape of the part as well as the dimensions of the geometrical elements situated in this plan.

* Reposition of the part on the table in plan Z-Y and the establishment of the coordinate system the same origin in the case of the part in plan X-Y.

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* The determination of the part's elements situated in plan ZY. This was the last step necessary proper measuring, the position of the part in the two succesive plans for the determination of all geometric characteristics of this.

* This step cosist in summing up of all geometric characteristics determinate to the security of obtaining the model CAD 3D.

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3. THE STEPS USED TO OBTAIN THE MODEL 3D

CAD

After the measurement of the part his geometrical characteritics obtained has been made with the help of a software package of projection assisted by the computer. The software package chose is called Pro/Engineer, version Wildfire 3, produced by the PTC Company-Parametric Technologies. This choice is sustained by the fact that Pro/Engineer is a powerfull instrument use frequently by the biggest companies in the world, from differenet fields of activity aeronautic industry, automobiles and others (www.ProEngineering.com).

Pro/Engineer is parametric software package rulled by the parameters or variable dimensions. This leads to the fact that geometry of a model can be changed easily the by the modification of the dimensions. Geometric elemnts which forma model will be interconnected. The modification of dimension of one element will be spread the long chain of elements which is tied up, leadind the interntion of projection. When one element is a reference for another element, through them a relation like parent/child is formed. Any modification brought to the parent element will be reflected on the child elements.

The steps to obtain the model 3D with the help of Pro/Engineer has been the following:

1. The creation of the part. This has been obtained by a operation named "Extrude" through which we obtain an element 3D "extrudand" a plan 2D.

2. The transformation of the part in one type "carcass" by using the function "Shell".

3. The making of the big rectangular cavity by using the comands "Extrude" and "Extruded Cut"-removed from the material.

4. Similar with step 3 creats the rectangular cavity, smaller as the other two big circular cavities and the smaller circular one.

5. The making of the three pins using the commands Extrude, Extruded Cut and Rib. These three commands are available for the making of the three pins. The other two are obtained by a copy along of one direction named Linear Pattern. The ending of the model 3D. The creation of the latest elements-diferents cuts(Extruded Cut) adding material (Extrusions).

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6. A last step of the operation of Reverse Engineering has been made by the mechanical drawing 2D of the model CAD 3D obtained for the realisation of the hysterical piece. The mechanical drawing is associated with the model CAD 3D, therefore if there is a modification of model 3D, is automatically reflected in the mechanical drawing 2D, this always regenerates taking in consideration the last version of the model CAD 3D.

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4. CONCLUSION

In this paper the authors presented the last method of transformation of the physical model 3D CAD by measuring the real piece and then the remaking of the obtained information with the help of a new sofware package assisted by the computer. In essence Pro/Engineer is a strong model--with its help solid models are developed, allowing the user to work in tridimensional space. Reserve engineering digitalized samples to get 3D data. The digitalized 3D data also can be a criterion to check CAD data, product, tooling and mold. Reversed Engineering helps companies to develop ideas, improve quality and ability of product design (Hagiwara, 2003).

5. REFERENCES

Hagiwara, I.,(2003). Curent Status of Reserve Engineering Including Large Scale Point Group Processing and CAD Formation, Tokyo Institute of Tehnology, October; Masashi, E.,(2005). Reserve Engineering and CAE, JSME International Journal, vol.48, no 2;

*** http://www.cermi.utcluj.ro/cermi.swf, Accessed on :2007 05-08

*** http://www.ProEngineering.com, Accessed on :2008-06-11

*** http://www.zeiss.com, Accessed on :2008-06-12