# A Process Decision-Making Method for Planar Machining of Box-Type Components
## 3 Constructing a Hierarchical Information Model for Process Decision-Making
### Hierarchical Information Representation Model for Machining Process Decision-Making
#### 3.2.4 Process Parameter Layer  
The \"Process Parameters Layer\" represents the lowest level in the hierarchical decision-making model for the machining process of box-type components. This layer primarily functions to generate the blank dimensional parameter information and the process parameters information for the machined surfaces of box parts. The blank dimensional parameter information includes the Dimensional Tolerance Grade (\(DTG\)) and the Machining Allowance Grade (\(MAG\)). The process dimensional parameter information for the machined surfaces consists of the Machining Dimension (\(MD\)), Machining Dimension Tolerance (\(MDT\)), Tolerance Zone Dimension (\(TTS\)), Machining Allowance (\(MA\)), and Total Machining Allowance (\(TMA\)). The blank dimensional parameter information (\(PPP\)) and the process parameter information of the machined surfaces (\(FPP\)) can be represented using conceptual sets, as shown in Equations (3) and (4).  
\[PPP=\{\mathit{DTG},\mathit{MAG}\ \}. \tag{3}\]  
\[FPP=\{\mathit{MD},\mathit{MDT},\mathit{TTS},\mathit{MA},\mathit{TMA}\ \}. \tag{4}\]  
In the machining process of box-type components, there are two scenarios: one where the design reference and the locating reference coincide, and another where they do not. However, in most cases, the references coincide [33]. Therefore, this paper focuses on the scenario where the design reference and the locating reference coincide during the flat machining of the box-type component. As the machined surfaces of box-type parts are processed sequentially from the first operation to the last, the process dimensions for the flat machining of the box-type parts are determined using a reverse calculation method. Specifically, the design dimensions and tolerances from the part drawing are used to iteratively calculate the machining allowances and accuracy for each operation, ultimately determining the blank dimensions [33]. This approach is detailed in Equation (5), which provides the process dimension parameters.  
\[Gy=Gy_{0}+T_{Z}. \tag{5}\]  
In the formula, \"\(Gy_{0}\)\" represents the dimension of the machined surface from the previous operation, \"\(Gy\)\" is the process dimension to be achieved in the current operation, and \"\(T_{Z}\)\" denotes the machining allowance for the current operation.  
\begin{table}
\begin{tabular}{c c c c c c c c c c c} \hline \hline
**Processing** & & & & & & & & & & \\
**Program** & **1** & **2** & **3** & **4** & **5** & **6** & **7** & **8** & **9** & **10** & **11** & **12** \\ \hline \hline \multicolumn{10}{c}{Plane to Plane} \\ \hline CMP1 & & & & & & & & & & & & \(\bullet\) & \(\bullet\) & \\ CMP2 & & & & & & & & \(\bullet\) & \(\bullet\) & \(\bullet\) & \\ CMP4 & & & & & & \(\bullet\) & \(\bullet\) & \(\bullet\) & & & \\ CMP5 & & & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) & & & & \\ CMP8 & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) & & & & & \\ \hline \multicolumn{10}{c}{Axis to Axis (or Plane)} \\ \hline CMP1 & & & & & & & & & & \(\bullet\) & \(\bullet\) & \\ CMP2 & & & & & & & & \(\bullet\) & \(\bullet\) & \\ CMP4 & & & & & \(\bullet\) & \(\bullet\) & \(\bullet\) & & & \\ CMP5 & & & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) & \(\bullet\) & & & \\ \hline \hline \end{tabular}
\end{table}
Table 3: Machining program selection under geometric tolerance constraints (2).