Information Technology Reference
In-Depth Information
4.1 Knowledge acquisition
The most common obstacle in utilization of SPMs in manufacturing industries is
inadequate knowledge of manufacturing engineers and machining specialists with this
technology, and the lack of a solid foundation for technical and economic feasibility
analysis. This is not an easy task and requires engagement of qualified personnel with
reasonable expertise and experience in this field. One needs to do a lot of computations
and use various handbooks and assumptions in order to accomplish this task. In recent
years artificial intelligence techniques have proven to be capable of restoring human's
logic and expertise and efficiently applying this expertise to tackle complicated
engineering problems. For example, KBESs have been used to restore human's logic and
expertise and efficiently applying this expertise to tackle complicated engineering
problems including product design (Myung and Han, 2001), design for assembly (Sanders
et al., 2009), and process planning (Patil and Pande, 2002). Accordingly, a KBES has been
developed in order to capture the knowledge of SPM specialists in a computer program,
and integrate it with a large amount of machining and tooling data restored in the
database. This allows less experienced people to use the system developed in order to
perform a detailed and accurate analysis of SPM utilization for production tasks. A rule-
base has been developed that restores knowledge in the rule-base in the form of if-then
rules. An example rule is presented here:
Rule 121:
if there are multiple holes of the same diameter and on the same plane,
and the minimum centre-to-centre distance is 30 mm,
then a multi-drill head can be used in a combined operation,
else the holes are to be machined in multiple operations.
A number of expertise rules have been developed in order to restore qualitative
information in the rule-base as shown in Figure 11. One group of rules is specific to
determination of workpiece setup such that there is tool access to all machining features
in a single setup if possible. Another group of rules determine proper clamping method
such that workpiece is securely held in place during machining. A group of rules
determine the number of machining stations such that the total number of stations is kept
minimal. Determination of required cutting tools and cutting conditions, and required
machine power are performed by other groups of rules. Some rules are developed for
selection of machining units, sliding units, chassis, and accessories such as multi-drill
heads, angle heads, etc.
As can be seen in Figure 11, the KBES developed in this work is also equipped with a
database. It contains quantitative information of available cutting tools and corresponding
cutting conditions extracted from handbooks, together with characteristics of standard SPM
components. Machining and sliding units restored in the database include CNC units
(CNCmasters), quill units (MONOmasters), small drilling units with flexible power
transmission mechanism (MULTImasters), power units (POWERmasters), and tapping units
(TAPmasters). Table 1 represents characteristics of eight MONOmasters restored in the
database which include designation, maximum drill diameter when used for drilling low
carbon steels, working stroke that determines maximum hole depth, available power and
thrust, spindle speeds, and weight for each unit. Other information restored in the database
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