On-line Thickness Measurement Of Oxide Layer In ELID Grinding

ELID grinding is widely used as an ultra-precision processing technology for hard and brittle materials because it continuously dresses a metal matrix bonded abrasive grinding tool through electrolysis. Successful application of ELID technique requires proper control of all material and process parameters. A key issue is to keep the balance between effective dressing rate and wear rate of abrasive diamond particles. Thus, to get reliable ELID grinding process, repeatable high quality finish surface and less subsurface damage, it is very important to keep 'the thickness of oxidation layer at appropriate level. Therefore it is necessary to measure the thickness of oxide layer in real time and then to control the electrolytic condition to keep the thickness of oxide layer in appropriate level.In this thesis, the varying characteristics of oxide layer in ELID grinding process are investigated. After wheel preparation, electrolytic pre-dressing of the wheel is carried out. Because the surface of a newly turned wheel has high conductivity, the electrolysis process occurs actively. In dynamic grinding stage, Oxidation layer cover the surface of the grinding wheel, locate in between grinding wheel and work-piece, contact with work-piece directly, just so, the thickness can be decreased duo to reaction of work-piece, then Electrolysis recovery, the thickness increased again, in brief this is a self-circulation process.Based on the analysis of formation and variation characteristics of oxide layer in ELID grinding, a new measurement principle and method for oxide layer measurement in ELID grinding was proposed. The thickness of the oxide layer was obtained based on measurement both outside surface and inner surface of the oxide layer by laser sensor and eddy current sensor. An overall measurement scheme which based on virtual instrument technology and industrial computer is chosen, and a fine-tuning work frame is designed which installed sensors, thus, constructed a hardware platform.Based on Lab VIEW and NI DAQ card, a computer system that detection the state of the oxide layer has been set up. And preliminary experiment confirmed that this method is feasible. And the experiments that on-line detection the thickness of oxide layer in pre-dressing states has been down. Results show that by using laser sensor and eddy current sensor can estimate oxidation film thickness.