THE INTERNATIONAL CONFERENCE OF THE CARPATHIAN EURO-REGION SPECIALISTS IN INDUSTRIAL SYSTEMS

7th EDITION

DIAGNOSTIC OF CUTTING EDGE DURING MACHINING

Jiri KRATOCHVIL, Robert CEP Department of Machining and Assembly, Faculty of Mechanical Engineering, VSB-TU

Ostrava, 17. listopadu 15/2172, 708 33OSTRAVA, Czech Republic, jiri.kratochvil@vsb.cz

Lenka OCENASOVA Department of Machining and Automation, Faculty of Mechanical Engineering, Zilina University, Univerzitna 1, 010 26 ZILINA, Slovakia, lenka.ocenasova@fstroj.uniza.sk

Abstract: Diagnostic of cutting edge serves to full using of cutting material tool life, damage detection, tool life and production of quality cutting surface. There to do exist many methods, using of many resources. Achieve of faithful tool wear diagnostic would take a turn directly at production of machine tool with low price costs. This paper shows diagnostic of tool wear during machining. Key words: machining, tool wear, diagnostic, cutting edge 1. TOOL WEAR

Reason for this research is lay on flexible manufacturing system and adaptable machine tool control. At present time is tool life calculating by Taylor formula (1) to optimal limit of flank tool wear. Tool life calculating by this equation is unfortunately roughly and workpiece has not the same parameters like testing material for determination of material constants. Inserts are changing before end of tool life for quality surface very often.

-m

cTn v. CT [min] (1)

Tn – tool life [min] vc – cutting speed [m.min-1] CT – constant [-] m – exponent [-] Diagnostic of tool wear situation during machining will be enable reporting ultimate

status, stopping machining and change tool insert. We would prevent bigger tool wear by reason of inhomogeneous material and follow cutting insert broken with workpiece surface damage.

Tool wear we can measuring by these methods: – direct

– indirect

Direct methods During measuring of tool wear size by direct methods we battle with many problems.

One of most important is inaccessibleness of wear areas to measuring instruments. Hence we can not use these methods during machining mostly [1].

Between direct methods we can class:

1. weight method (specific), 2. method of radioactive isotopes, 3. micrometric method, 4. optical method (shadow), 5. method of striking impedance layer, 6. pneumatic method.

Indirect methods Indirect methods using some of notes, which are characteristic at tool wear process

and do during cutting. All these methods are somewhere [2, 3]. Belong to [1, 2, 3, 4]:

1. creation of sheen strip on surface, 2. increase of tool forces, 3. increase of cutting achievement, 4. increase of cutting temperature, 5. creation of vibration, 6. creation of undesirable sound, 7. change of color and form of chip, 8. changed of workpiece sizes, 9. downgrade of surface roughness, 10. acoustic emission.

During machining we can use these methods:

Pneumatic method is relatively reliable and simple. Measuring of cutting tool insert decrease is vertical or radial to cutting areas. Measuring principle is on fig. 1.

Fig.1 Principle of pneumatic method

Value xm is determinations for air pressure measured for calibration curve of measuring instrument.

Optical method appears like hopeful, but at practical using can be very problematic [1]. Method is found to light reflection, which fall to cutting edge. Characteristic of reflection light depends to tool wear condition [4]. This method is relatively easy and can be used at milling and grinding.

Measuring with using cutting forces and torsion moment using fact with increasing

tool wear is increases cutting resistance too. Principle of cutting forces and torsion moments measuring are deformation measuring at machine tool – cutting tool – workpiece – fixture system during machining. Both values we can measure by dynamometers and torsion moment at spindle too.

Measuring by vibrations consists in machine tool vibrations and cutting tool wear

correlation. There are registered and evaluate ultrasonic stress waves at acoustic emission

measuring. These waves are information wearing about processes in chip root. Acoustic emission signal is suitable for monitoring of cutting tool status in ultrasonic area. Advantage of ultrasonic range is elimination of environmental influence and proper oscillation, which lies in acoustic signal [4].

Decreasing or increasing of electric resistance can by tool wear measured by striking

impedance layer. It is in principle doing of electrical circuit on tool shoulder. Disadvantage of this method is sensor influenced by chip departure, temperature changing and cooling medium [4].

This method will be enlarged at next papers. Department of Machining and Assembly have got special cutting inserts (fig. 2) from Saint Gobain Advanced Ceramics Turnov. We have special tool holder (fig. 3) and instrument for electric resistance measuring (fig. 4) with PC connection possibility.

Fig. 2. Cutting insert with impedance strike layer

Fig. 3. Tool holder with electrical contacts

Fig. 4. Instrument for electrical resistance measuring Material of these inserts is Silicon Nitride based ceramic KS6000, which has these

application areas: High speed and high feed rate machining of cast iron. Suitable for roughing with coolant. Suitable for high speed milling of cast iron, such as cylinder blocks.

Fig. 5. Classification of KS6000 tool material

Conclusions: Tool wear research by striking impedance layer will contribution for cutting tool economy especially at companies with unmanned machine tool centers. Tool wear determinations at these machine tools have cardinal important for continuous three-shift operation. References:

1. NESLUŠAN, M.; TUREK, S.; BRYCHTA, J.; ČEP, R.; TABAČEK, M. Experimentálne metódy v trieskovom obrábaní, Vydavatelstvo ŽU EDIS Žilina: Žilina 2007. 343s. ISBN 978-80-8070-7011-8.

2. JURKO, J. Opotrebenie rezných nástrojov, Prešov, 2005, ISBN 80-8073-255-8. 3. POPEOVÁ. Monitorovanie opotrebenia rezných nastrojov, Vydavatelstvo ŽU EDIS

Žilina: Žilina 2001 ISBN80-7100-700-5. 4. VASILKO, K.; HRUBÝ, J.; LIPTÁK, J. Technológia obrábania a montáže.ALFA

Bratislava 1988, 1991. 496s. ISBN 80-05-00807-4. 5. http://americas.kyocera.com/KICC/ceratip/grades_ceramic.html.