1 Baila Diana, Contributions to Management Swarf High-Speed Machine Tools, UPB,

Abstract: The transition from traditional manufacturing with machine tools and CNC machine tools at high speeds requires modification on the technological concept of steel, machinery, tools and cutting regimes. This paper aims to draw attention to changes in management and management swarf. It also presents some additional tests designed to increase the life of tools used at high speeds.

Key words: traditional machine tools, CNC machine tools and high speed, conical swarf, semi swarf, SIM analysis.

1 Baila Diana, Contributions to management swarf high-speed machine tools, UPB, .

1. INTRODUCTION

Development of manufacturing with high-speed machine tools previously claimed, the development of techno-economic study further the research and management chip.

In general, chip generation and management problems have made ​​practical activities in workshops, which resulted in finding technical solutions and safety, as correct.

In this respect, with the evolution of machine tools have diversified and expanded research objectives, as follows:

-the traditional machine tools (lathes, milling machines) with cutting speeds of 35-70 m/min was used Merchant model to calculate the optimum cutting conditions and chip evacuation recommendations were included in the STAS:

-chip-shape and characteristics;

-how to remove the chip from the workpiece;

-compression chip-evacuation and transportation are provided by the factory.

-the NC machine tools and CNC machining centers at speeds of 60-120 m / min was used Oxley model [7], [10] to calculate the optimum cutting conditions and chip evacuation is included in STAS.

-the high-speed machine tools 150-480 m /min, is used at present, the american way [1] to calculate rough cutting regimes. Household chips are discharged inside the car and involves the following elements:

-detached from the workpiece chips should have taper type IIIB;

-to remove chips from the workpiece is recommended to use 4 way chip clearance with turning chips into each cup to get seated properly so called conical fragment (fig. 1) and compression chip is inside the machine frame.

Chip not detached from the workpiece, due to high speeds necessary to make three additional tests, namely:

-determination of thickness of the resistance of semi-chips;
-analysis of the microstructure of white strip in the middle section cutting;
-finding the diffusion of metallic elements (Cr, Mo, V, Ti) on the lower surface of the chip.

Fig.1. Conical swarf

1. RESEARCH ON THE PROCESSING OF LOW ALLOY STEELS TEMPERED

Programme of work uses a test bench from ENI Tarbes laboratories where they planned the following actions:

2.1. Choice of workpiece material

In the last decade, most research contracts aimed at economic reasons, the use of tempered low alloy steels, which in case of high speed machine tools, provides:

-obtain workpiece with high strength and toughness;
-processing of these components is done with some hard cutting regimes provides hard-schemes:
-workpieces with fine-structure (give up to rectification);

-in the case of precision parts after cutting take electroerosion apply to Ra = 0.2 m.

Consequently, taking into account the provisions of the agreement, a group of steels commonly used in cars with high speeds (table 1), choose low-alloy steel 32CrMoV13 quality and delivered in the form of bar.

Table 1. Tempered low alloy steels

Steel grade

Metallurgical state

Fig.2. General appearance of the CNC lathe

Researching test equipment (fig.2.) is provided as follows:

-normally a lathe's wondering where the gearbox was adapted to achieve cutting speeds between 60-480 m/min;
-were chosen ceramic plates mineral ceramics type TP-200-TNM-160412-M5;
-cooling-medium: air stationary.

-pot type samples (fig. 3) are obtained from steel bar 32Cr MoV13 delivered at dimensions of 100x150mm.

-it uses front turning scheme (fig.4)
-hard cutting regimes are scheduled:
-cutting speed v = 100 m/min;
-cutting thickness t1 = 0.1, 0.2, 0.3 mm;
-cutting width w = 7 mm;
-rake angle =0.

Fig.3. Pot workpieces

Fig.4. General appearance of the CNC lathe

Preparing the way for chip evacuation is taking these measures IIIB in the workspace:

Since adopting the ISO chip clearance mode 4:
-for outside the sample pot;
-advance movement in the opposite direction (fig.5).
By positioning curled cup ensure proper reception cone chips IIIB as shown in fig.6.

Fig.5. Working in the opposite direction of advance movement

Fig.6. Working cup

Results of tests on three samples pot are shown in

Table 2 .

Table 2.

v

2.2. Processing results

When processing the results through two objectives:
-processing results in photomicrography;
-processing of the results obtained with a complex apparatus.

2.2.1. Processing results in photomicrography

To process the results using an optical microscope to Carl Zeiss Jena type MM3 and 38 mm respectively three cylindrical samples, from which:

-fragment is positioned for measurements (fig. 7);

Fig.7. Positioned fragment for measurements

-symbolizes the chip with a plastic paste;
-leave a hole in the center centering cylindrical sample and measurement system.

Microphotographs obtained by consulting with hard cutting regimes in table 2, we can determine the characteristics of the chips from chip geometry of fig. 8, namely:

Fig.8.Geometry chip

-t2-chip thickness is calculated using the formula:

-chip-thickness resistance is on the lower t2 chips and are measured directly, knowing the scale of magnification photomicrography (fig. 9).

Fig.9. Photomicrography

Basically, the objective of the consultation paper aimed at three photomicrography made ​​for t1 = 0.1, 0.2, 0.3 mm and obtaining t2 values ​​in table 2 (fig.10. a, ​​b, c). With these results demonstrate that there is a linear dependence between the advance work using (t1) and the resistance of the chip thickness (t2). The degree of segmentation of chips (Gs) is measured on a peak period T by identifying deep hole h1 and h2. It uses the formula:

Fig.10.Microstructure with different chip advances

Finally, the characteristic features of the chips allow us to note the following:

-thickness of chip resistance (t2) should represent an indication that detached fragment of the piece is right in the cup reception coils (fig. 6). Any fragment breaks minimum thickness t2 = 12 m to stop driving the car, which must be kept fully closed during operation;

-chip-level segmentation (Gs) highlights the instability of the operating regimes of cutting hard and is an indicator for evaluating the workability of the steel cutting study.

2.2.2.Processing of the results obtained with complex equipment

The management can be demanding two more additional analysis:
1-white middle-width strip characterization chips conical IIIB;
2-identification of metal-broadcast on the lower surface of the chip.

Characterization of white middle band width chips:
-Chips in the middle white band width corresponds to the secondary shear zone at the interface tool-fragment. In this area the large amount of heat determines the chip surface but also deep changes in phase austenite/martensite.

-Interferometer is used to analyze Cr anticathode each other as positioned. To see in depth the structure, the lower surface of the chip is polished electrochemically, as follows: Cr-anticathode initially be scheduled for a depth of 6 m where noted:
-Fe austenite existing in the 111 plane angle of 65
-Fe martensite present in the 110 plane at the angle of 68.

-At depths greater austenite disappears almost completely highlighting excessive hardness of the strip of white conical fragment IIIB.
Given the dependence between hardness and strength, hardness white band offers safe technology that will not break chip cone, even if chip thickness t2 resistance is small.

2.2.3.Identifying running on the lower surface of the metal chips
It’s used semi chips obtained by cutting a tough regime: v = 100 m /min, t1 = 0.2mm and pleasant mineral ceramics TNM-TP-200-160412-M5.
After crossing the interface tool-fragment in the presence of oxygen in the air, freshly detached fragment is finding an oxide layer of Fe, Cr, Mo, V, Ti.

SIMS depth analysis on chips made ​​using reverse mechanism, the underlying oxidation process, as follows:
To interface of chip at a distance of 0.1 mm from the edge tool, breathe a jet of oxygen, under certain conditions:
-adjustable pressure-controlled;
-pressure-stabilized;
-at certain times-blasting.

This near-interface layers of oxygen, metal ions cause excitement Fe+, Cr+, Mo+, V+, Ti+, and excitation of ions in the form of oscillations is recorded on a diagram (fig.11)
Processing the results show the following:
elements of the charge-steel (Cr, V, Mo) is in large quantities on the surface of the tool-fragment interface and decrease with depth;

Ti-derived chemical element of the tool material and decreases in concentration, with depth.
Basically, the elements Cr, Mo, V, Ti strongly emphasizes the tool wear in particular crater on the surface of the recess.
Finally, knowledge of the elements Cr, Mo, V, Ti allows taking measures that:
-use another type of plate cutting;
correcting the chemical composition of the cast-steel 32 Cr MoV13.

Fig.11. Depth profile SIMS realized in fragment

1. CONCLUSION

The traditional machine tools with NC machine tools, management of special chips not allowing it to raise a lot of types of chips, according to STAS.

In contrast, the high-speed machine tools, the problems are complicated because:

-the frame is required in the management of the car chip;

-tough regime to accommodate the claims cutting conditions for obtaining a cone chips IIIB;

-during processing, workspace is locked and an accidental breaking of the chip would interfere with proper operation of the machine;

-further analysis shows that it can take steps to increase the lifetime of the tool, even with some tough cutting conditions.

REFERENCES

[1] ALTINTAS Y: Manufacturing automation, Cambridge University Press, 2000;

[2] LE CALVEZ C: Etude des aspects thermiques et métallurgiques de la coupe orthogonale d’un acier au carbone. Thèse. Centre de Paris, 1995.

1 Baila Diana, Contributions to management swarf high-speed machine tools, UPB, .