Integrated system for modeling and manufacturing the cams.

Stanasel, Iulian ; Dragomir, George ; Blaga, Florin 等

1. INTRODUCTION

The cam mechanisms are used for an accurate construction of some complex functions for the motion transmission.

The Kurz profiles ensure a smooth, shock-free variation of the acceleration which determines a decrease in mechanical stress, noise and vibration level, along with an increase in reliability and the improvement of the intake and exhaust processes (Antonescu P., et al., 2000).The Kurz cam is divided into 10 areas. Within the paper the symmetrical profile of the cam was considered, so that the laws determining the tappet upward motion in the four elevation areas are similar to these defining its downward motion.

The upward motion in the first area represents a cosine curve, has the size of a quarter of wave and corresponds to an interval marked as [[PHI].sub.0], (Fig. 1).

It is expressed by the relation:

[h.sub.0] = [h.sub.p.] (1 - cos [pi]/2[[PHI].sub.0] [[alpha].sup.*.sub.0] (1)

The elevation in the second area represents half a sine curve and corresponds to an interval noted with [[PHI].sub.1]. It provides positive acceleration and is expressed by :

[h.sub.1] = [h.sub.p] + [c.sub.11] [[alpha].sub.1.sup.*] - [c.sub.12] sin [pi]/[[PHI].sub.1] [[alpha].sup.*.sub.1] (2)

The upward movement in the third area is a quarter of a sine curve corresponds to an interval marked as [[PHI].sub.2] and enables the transition from positive to negative acceleration.

[FIGURE 1 OMITTED]

The mathematical relation of the tappet movement in this area is the following:

[h.sub.2] = [h.sub.1f] + [c.sub.21] [[alpha].sub.2.sup.*] + [c.sub.22] sin [pi]/[[PHI].sub.2] [[alpha].sup.*.sub.2] (3)

The tappet elevation in the last area corresponds to an interval noted with [[PHI].sub.3] and is defined by a fourth-degree polynom according to the relation:

[h.sub.3] = [h.sub.2f] + [c.sub.31] ([[PHI].sub.3] - [alpha].sub.3.sup.*])2 + [c.sub.33] (4)

In order to determine the [c.sub.jk] values, the determination by differentiation was required of the mathematical functions of the acceleration and speed levels during the tappet elevation.

After applying the minimal conditions which provide the functions continuity at the starting and final moment of the interval, a system of six equations are obtained:

[MATHEMATICAL EXPRESSION NOT REPRODUCIBLE IN ASCII] (5)

where i and fvalues represent the starting and the final moments of the interval.

The cam profiles were determined starting from the valve elevation laws of the distribution system. In ordere to represent these laws a software programme was made up in Matlab. The data offered by this programme were used to calculate the polar and carthesian coordinates and to mark points on the cam profile (Ghinea, M., Firetanu V., 1998).

2 THE MODELING AND MANUFACTURING THE CAM

The cam solid 3D model was designed in SOLID EDGE using the Cartesian coordinates of the points defining its profile, obtained as a result of optimizing the functional performances. In order to use these matrix elements in the SOLID EDGE program, it was required to imput data from Matlab to EXCEL using the "Excel Link"for MATLAB (Stanasel, I., et al. 2008). The acquired matrix is presented in Fig.2. Next step in order to obtain the cam solid model, is to use the "curve by table" comand from the "Part" menu of SOLID EDGE. This command enables the curves spatial representation using their coordinates from EXCEL. In fig 3 are represented the curve that defines the cam profile in Cartesian coordinates and in SOLID EDGE program. The solid model of cam is obtained by usind the "Protrusion" command (fig. 4).

[FIGURE 2 OMITTED]

[FIGURE 3 OMITTED]

In order to realise the CNC programme it is used NX machining from Solid Edge (fig.4). The application can be used only if is is later installed, being not included in Solid Edge.

It is established then the size of semi-manufactured goods it is chosen the tool, it is established the milling method and the programme performs the path of the tool and it simulates the manufacturing (fig.5).

[FIGURE 4 OMITTED]

[FIGURE 5 OMITTED]

[FIGURE 6 OMITTED]

[FIGURE 7 OMITTED]

After post processed, we obtain the CNC programme. This programme is implied on Siemens 840 D equipment of the machine tool which is done the manufacturing on (fig. 6).

In fig. 7 are presented aspects within the manufacturing with the elaborated programme and the unfinished cam in a manufacturing phase.

3. CONCLUSION

Knowing the laws of movements of the cam it can be written a programme that outputs the coordinated points from the cam profile edge with an enough manufacturing precision.

These points can be exported in Excel and then to SE for the purpose of performing the solid model of cam.

By the use of installed NX machine application it is simulated the cam manufacturing; the CNC programme being post processed for equipments specified to machine tools where you prelucrate on.

The paper presents an integrated method Matlab-Excel-Solid Edge-Unigraphics NX for cam design and manufacturing, the way of technique documentation and how was elaborated the manufacturing programme.

The proposed method can be extended.

4. REFERENCES

Antonescu P., et all (2000)., Mechanisms, Editura Printech Bucuresti.

Ghinea, M., Firetanu V., (1998) Matlab, numerical calculus, graphics, applications, ISBN 973-601-275-1, Editura Teora, Bucuresti.

Musca G. (2007) Computer aided design using Solid Edge ISBN 973-37-1172, Editura Junimea Iasi.

Stanasel, I., Blaga, F., S., Stanasel, O., (2008) Integrated system for constructive optimization of recipients mate by sheet metal, Proceedings of the Oradea University CD Rom edition, pp. 1791-1798, ISSN 1583-0691, may 2008 Editura Universitatii din Oradea, Oradea

*** (2004) Sinumerik 840 D Programming Guide