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Determining the size and location of water lines
Water lines are located at standard distances form each other and from any wall in the mold. The convention is not to locate a waterline within one diameter range on the mold wall.
Deciding mold dimensions based on above conclusions
Based on all the above decisions the approximate mold dimensions can be estimated and rounded off to the nearest catalog number. Considering all the above aspects before even modeling the mold base reduces the cost and time that go into redesigning.
2.4 Formulation of the Problem
Based on issues that require human knowledge/experience, and aspects of mold design that consume time referring to tables, data sheets etc., the problem for developing the application is defined as shown in Figure 2.
Figure 2. Organization of the Mold Design Module.
While most of the input, like the number of cavities, cavity image dimensions, cycle time are based on the client specifications, other input like the plasticizing capacity, shots per minute etc., can be obtained from the machine specifications. The output of the application contains mold dimensions and other information, which clearly helps in selecting the standard mold base from catalogs. Apart from the input and output, the Figure 2 also shows the various modules that produce the final output.
2.5 Framing rules
At this stage, the expert’s knowledge is represented in the form of multiple If-Then statements. The rules may be representations of both qualitative and quantitative knowledge. By qualitative knowledge, we mean deterministic information about a problem that can be solved computationally. By qualitative we mean information that is not deterministic, but merely followed as a rule based on previous cases where the rule has worked. A typical rule is illustrated below:
If Material = “Acetal” And
Runner Length <= 3 And
Runner Length > 0 Then
Runner Diameter =0.062
End If
When framing the rules it is important that we represent the information in a compact way while avoiding redundancy, incompleteness and inconsistency. Decision tables help take care of all the above concerns by checking for redundancy and comprehensive expression of the problem statement. As an example, in the process of selecting an appropriate mold base, the size of mold base depends on the number of cavities and inserts. To ensure that all possible combinations of cavities and inserts have been considered we use a decision table and subsequently use the decision table to frame rules. Table1 shows more than one case where the mold dimensions are the same.
Table 1. Sample Decision Table
Number of cavities(1,2,4) 1 1 1 2 2 2 4 4 4
Number of Inserts(1,2,4) 1 2 4 1 2 4 1 2 4
Mold Dimensions A* * A B * A B C
Case A:
Mold Width = (Insert Width + 2)
Mold Length = (Insert Length + 2)
Mold Thickness = Insert Thickness
Case B:
Mold Width = (2* Insert Width + 3.5)
Mold Length = (Insert Length + 2)
Mold Thickness = Insert Thickness
Case C:
Mold Width = (2*Insert Width + 3.5)
Mold Length = (2* Insert Length+ 3)
Mold Thickness = Insert Thickness
Figure 3. Mold Dimensions for various combinations of Inserts and Cavities
The case where the number of cavities is one and the number of inserts is one has the same mold dimensions as the case where the number of cavities is two and four. The three cases can be reduced to one single rule: