Steven Robert Hayashi

Acoustic tool break detection system and method

Substantial cutting condition changes that occur gradually, as opposed to the more usual sudden large change, are detected by setting upper and lower cutting noise mean level thresholds. When the mean cutting noise exceeds the upper threshold or stays below the lower threshold for a preset number of signal samples, a tool break alarm is generated. Techniques are given to reduce false alarms at the start and end of the cut and on runout on initial rough surface cuts. The system comprises an accelerometer or other sensor whose signal is preprocessed to attenuate lower frequency machinery noise and detect the signal energy in a band below 100 KHz, then sampled, and the digitized signal samples analyzed by pattern recognition logic.

Process competition in the micromachining of brittle components

In this paper, after reviewing some of the industrial applications of laser micromachining, we focus on the challenging task of dicing a brittle and/or toxic material with random access capability. Results of wire dicing, OD/ID saw dicing, waterjet dicing, Synova Microjet dicing, direct laser dicing and GE liquid-assisted-hollow-fiber laser dicing are compared. Liquid assisted laser dicing showed more advantages in this competition for dicing Cadmium Zinc Telluride (CZT), which is a critical material for detectors. This is a typical case in the industrial applications of laser micromachining—laser technology must compete against other processes. Applications of laser micromachining have expanded quickly in industry in recent years, and we are entering the era of high-speed laser micromachining.In this paper, after reviewing some of the industrial applications of laser micromachining, we focus on the challenging task of dicing a brittle and/or toxic material with random access capability. Results of wire dicing, OD/ID saw dicing, waterjet dicing, Synova Microjet dicing, direct laser dicing and GE liquid-assisted-hollow-fiber laser dicing are compared. Liquid assisted laser dicing showed more advantages in this competition for dicing Cadmium Zinc Telluride (CZT), which is a critical material for detectors. This is a typical case in the industrial applications of laser micromachining—laser technology must compete against other processes. Applications of laser micromachining have expanded quickly in industry in recent years, and we are entering the era of high-speed laser micromachining.

CZT sub-surface damage assessment using electrical leakage measurements

Electrical measurements of sidewall leakage are used to quantify the degree of sub-surface damage created by cutting CZT. High leakage is found at freshly cut surfaces but not at control surfaces. Dramatic reduction of leakage is demonstrated by subsequent polishing of cut sidewall surfaces to a point matching the control surfaces. CZT parts were cut using outer-diameter saw (OD), wire saw and laser machining methods. An important practical finding is that laser machined surfaces can achieve low leakage performance by the appropriate surface processing, in spite of large initial subsurface damage level. This is of interest, because the laser method provides a random-access cutting capability, whereas wire saw and OD cutting is restricted to linear directional cuts. A comparison of roughness and surface morphology imply differences in the otherwise unseen sub-surface damage that are characteristic of the machining process methods. Leakage measurements with step-wise polishing trials are used to test the depth to which cutting damage extends into the crystal.