# Review and New Aspects in Combining Multipoint Moulding and Additive Manufacturing
## 2 Vacuum Assisted Multipoint Moulding  
### Definition and Historical Development  
Multipoint moulding (MM) is based on the idea of creating a mould that can be adapted to the part to be produced and thus it is not necessary to produce a mould for each individual part. [PERSON] and [PERSON] [1] define a multipoint mould also called a reconfigurable tool: \"A reconfigurable tool is defined as a machine that can be repeatedly configured by a user for shaping mechanical parts in a manufacturing setting. Although most machines are reconfigurable by virtue of their replaceable cutting bits, dies, moulds, rollers, and the like, the machines [... ] are reconfigurable pin-type tools with a variable surface similar to the popular 3-D pin art or PinPressions(tm) toy, [... ]. To be clear, the machines discussed here are not fixturing devices, nor are they used for secondary cutting or finishing of parts.\" Figure 1 shows the schematic of such a 3D pin art. As shown in Figure 1, the toy consists of a set of needles behind glass. The needles are mounted in two plates with open ends at the back. The image is then created by the movement of the pins, e.g., pressing a hand on the back and thereby creating a three-dimensional image behind the glass. The first known approaches to multipoint moulding date back to a patent of [PERSON][3] from 1862 who developed a device for sheet metal forming with adjustable pins (see Figure 2). After inserting the sheet metal, the pins should be adjusted by hand and thus the shaping should be realised. Figure 2 shows the structure of the device. It consists of a set of pins with rounded heads and a studding which mounts the pins in the backplate and allows the adjustment in the forming process. The raw material is placed on the pinheads and is then pressed against the counter-pins on the other plate to be transformed. Figure 1: Schematic drawing of 3D pin art (based on the work in [2]). The further development of multipoint moulding with the main contribution of the authors is shown in Table 1 in a chronological order. \begin{table}
\begin{tabular}{c c c} \hline \hline
**Authors** & **Year Published** & **Main Contribution** \\ \hline [PERSON] [3] & 1862 & development of multipoint moulding for sheet metal forming \\ \hline [PERSON] and [PERSON] [4] & 1998 & examination of pin shape and matrix structure \\ \hline [PERSON] [5] & 1998 & closed loop automatic adjustment control \\ \hline [PERSON] and [PERSON] [6] & 2000 & implementation of closed-loop automatic adjustment control for hydraulic actuation \\ \hline [PERSON] and [PERSON] [7] & 2000 & separated pins at larger distance and extension as a fixing device on CNC machine tables \\ \hline [PERSON] et al. [8] & 2003 & densely packed pins with interpolation layer and a single vacuum chamber for CFRP parts \\ \hline [PERSON] et al. [9] & 2004 & fully computer-controlled adjustment by a commercial CNC system \\ \hline [PERSON] and [PERSON] [10] & 2006 & forming of very large aluminium sheet metal in several working steps mainly for large spherical objects \\ \hline [PERSON] et al. [11] & 2007 & forming of perforated titanium sheets for individually formed plates for skull reconstruction \\ \hline [PERSON] [12] & 2008 & studies on multipoint moulding in injection moulding with the technical implementation \\ \hline [PERSON] and [PERSON] [13] & 2009 & second vacuum circuit under the interpolation layer for concave shapes \\ \hline [PERSON] and [PERSON] [14] & 2011 & adjustment and configuration for use in injection moulding \\ \hline \hline \end{tabular}
\end{table} 
Table 1: Chronological development of multipoint moulding. Figure 2: Schematic drawing of the first multipoint mould (based on the work in [3]). An actual further development was made by [PERSON] et al. [23] relying on a densely packed pin field with vacuum support to enable forming of concave carbon fibre-reinforced plastic (CFRP) components (see Figure 3). Figure 3 shows that the concept used by [PERSON] et al.