Intense global competition
has forced many US manufacturers to examine their current business practices as
well as evaluate how to meet these challenges and remain competitive. Major emphasis has been placed on disruptive
innovation and manufacturing research with recognition of the need to improve
product and process quality, automation, and decrease scrap.
The traditional
manufacturing process is to produce a part on machine, transfer it to the
coordinate measuring machine, check for quality, and make decisions. If the quality is found unacceptable, the
production line is stopped to locate and alleviate the root cause of the
defect. In such Post Production Quality
Control practice, not only is the part inspected scrapped, but also a
considerable amount of work in progress (WIP) is purged. This preventative quality control practice,
which barely manages to satisfy customer quality requirements, is not
sustainable in today’s competitive market place.
As a better solution,
manufacturers have embraced the concept of Post
Process Quality Control utilizing on-machine probing technologies. In this reactive methodology, the part is
measured for quality attributes on the machine itself after completion of a
single/multiple machining process ensuring quality at source. It leads to
lesser WIP scrap and the need for CMM evaluation. However, it still suffers the
drawback of measuring the non-conforming part after it’s produced. Additionally,
this method does not support the philosophy of first part correct. It also
consumes expensive machine time for quality checks (reduced throughput at the
given station) and may require special labor skills to operate the probe and
probing routines.
The goal is
to develop a MTConnect-enabled, autonomous, in-process quality control system
for manufacturing first part correct with integrated user-initiated alarm
management. The proposed In-Process
Quality Control predictive methodology monitors critical, real-time process/machining
parameters, checks them against boundary limits, and then raises alarms/alerts.
The philosophy is fundamentally different from Post Production Quality Control and Post Process Quality Control because we measure and constrain the
in-process machining parameters like power, forces, torque, thermal effects,
vibration level, etc…, which cause quality issues, instead of reacting to the problem
after it has already occurred. The proposed system will ensure zero scrap and
minimum downtime thus boosting the overall equipment effectiveness and process
capability indices. Another major
benefit of the system will be to reduce the number of inspected parts in a
batch of final product which will directly translate into reduced lead time and
inspection cost.
The current alarm management
systems are not customizable and user-initiated. Some problems include too many alarms on display, high alarm rates
(flooding), false alarms, repeating alarms, excess grouping of alarms, no
defined action, and wrong recipient. Also,
the current alarms are based on the equipment health/condition and not process
conformance. The proposed system will eliminate these issues and have
an integrated, user-initiated alarm management system that will notify the user
of real-time faults and process violations.
Lastly, the system will be
MTConnect standard compatible. The current manufacturing systems are
proprietary. Vendors bundle together software and hardware for competitive
purposes. The MTConnect Initiative was started to address the need for a
standard that will help realize a "seamless manufacturing pipeline"
from design to production. The goal of this pipeline approach is to allow for
“universal” capture of data from the machine tool which would transfer this
captured data into other control systems thereby facilitating a seamless method
for managing and analyzing data for process and product optimization. MTConnect
compatibility will ensure industry-wide applications, easier integration, and
commercial viability for the proposed In-Process
Quality Control system.
