Grinding, as one of the most prominent abrasive processes, is widely applied to obtain high
accuracy and high-quality mechanical, electrical and optical parts. It is one of the core
technologies for many important industries, such as semiconductor, electronics and aerospace
fields.
During the grinding process, workpiece measurement is the key technology which can affect
the accuracy of precision machining. Thus, a new air beam assisted in-process optical form
error measurement method was investigated. Compared with the initial water beam approach,
this method can eliminate the effect generated by the coolant dilution and optical transmittance
through multiple media. Through computational analysis and experimental study, it is found
that the new method can effectively generate a...[
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Grinding, as one of the most prominent abrasive processes, is widely applied to obtain high
accuracy and high-quality mechanical, electrical and optical parts. It is one of the core
technologies for many important industries, such as semiconductor, electronics and aerospace
fields.
During the grinding process, workpiece measurement is the key technology which can affect
the accuracy of precision machining. Thus, a new air beam assisted in-process optical form
error measurement method was investigated. Compared with the initial water beam approach,
this method can eliminate the effect generated by the coolant dilution and optical transmittance
through multiple media. Through computational analysis and experimental study, it is found
that the new method can effectively generate a transparent window to permit the in-process
optical measurement. Research work on the main factors which may affect the transparent
window size A
t and the transparent window size stability e
st has been fully developed. It was
found that table velocity v
t, the air velocity v
a and the air nozzle diameter d
a were the key factors
among those which may influence the two main parameters. To achieve a transparent window
of a suitable size and also to avoid turbulence in the air flow, the air velocity v
a should be correctly selected between 26-32 m/s. An increase in the table velocity vcorrectly selected between 26-32 m/s. An increase in the table velocity v
t causes a reduction in
the transparent region area.
It was well known that machining tool was another critical factor in affecting the machining
precision. In former study, a series of CNT epoxy grinding wheels were fabricated. The
previous results indicated that CNTs could be used as abrasive grains for nano machining.
To further understand this new CNT abrasive tool, CNT grain distribution and spacing in the
epoxy based wheel were simulated by a grain spacing model. Furthermore, preliminary testing
was conducted to investigate the chips generated in machining processing. Both theoretical and
experimental results show that the uncut chip is in the range of nanometer. However, chip
gelling effect due to agglomeration and epoxy melting was found.
Therefore, a new metal based CNT grinding wheel was proposed and studied to improve the
wear-resistance and hardness of the CNT tool. Meanwhile, diamond grain was also considered
to be added in the CNT wheel.
A new co-electroplating method was proposed to be utilized to fabricate this new metal based
CNT/diamond grinding wheel. Through the studies on the fabrication of the electroplated
CNT/Diamond wheel, a preparation procedure and conditions of the plated surface was studied.
It was found that the hardness of the electroplated CNT/Diamond wheel could be controlled by
the thickness of the nickel substrate. The grain spacing and cutting-edge density of the
electroplated CNT/Diamond wheel was affected by particle concentration. And some
electroplated CNT/Diamond wheels were successfully fabricated.
A new Wire EDM system was proposed and developed for shaping and truing electroplated
CNT tools for precision machining. For system design, problems including the 4-axis
workpiece high precision infeed, wire tension control and wheel infeed control should be
considered. A series of Wire EDM experiments were conducted to fabricate the small-scale
wheel body. A machined structure as small as 100um has been obtained. In the Wire EDM
system, a new tension controller is proposed and developed to allow use of ultra thin wire for
small workpieces without wire breakage. This new Wire EDM system will permit possibility
to make complex workpiece profiles quickly and easily.
In conclusion, through the investigation on the new air assisted measurement method, it was
found that the new method can effectively generate a transparent window to permit the in-process
optical measurement. And furthermore, a new nano precision machining tool, which is
CNT grinding wheel, was proposed and studied. A new CNT grain spacing model was
proposed for better understanding of the new wheel. And a new electroplating method was
proposed to manufacture electroplated CNT grinding wheels. Main factors were investigated
for the purpose of performance optimization. Finally, a new Wire EDM system was proposed
and developed for shaping and truing electroplated CNT tools. This will permit possibility to
make complex workpiece profiles quickly and easily. The research in this thesis may pave a
road for further research on CNT applied in precision machining.
Keywords: Air beam, in-process form profile optical measurement, form error, CNT
machining tool, nano machining, CNT wheel, electroplated CNT/Diamond wheel, Wire EDM
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