# Review and New Aspects in Combining Multipoint Moulding and Additive Manufacturing
## 3 Possible Additive Manufacturing Methods
### Process Discussion
The big disadvantage is the high effort in dealing with the powder and resin residuals. When it comes to other materials the production of sand attachments directly on the vacuum assisted multipoint mould leads to the same problem as with all powder bed processes, although sand models would ensure good temperature stability. The extrusion of concrete already shows clear advantages here since no excess material has to be removed yet the penetration of concrete into the vacuum assisted multipoint mould carries risks. Furthermore, the material cannot be stored ready for processing, but would have either to be mixed in the process or produced in advance of production. Subsequently, the components require a long setting and curing time until the actual component can be manufactured. The high temperature stability would be an advantage too. Paper models would ensure relatively easy processability, but the model must be impregnated before the infiltration of the carbon fibre part starts. Otherwise, the paper absorbs the resin of the component to be infiltrated with and adheres to them. Summarising, there are different possible additive manufacturing methods available for the integrated process of enhanced vacuum assisted multipoint moulding with additive attachments. The fused filament fabrication is clearly the easiest way to implement the process, with just one disadvantage which is the relatively low temperature stability of the attachments. Therefore, only resin systems curing at room temperature can be used for the carbon fibre reinforced plastic parts. Hence, this paper will focus on the combination of vacuum assisted multipoint moulding with attachments produced by fused filament fabrication. Therefore, the next chapter will focus on the different possibilities and difficulties of integrating fused filament fabrication to the vacuum assisted multipoint mould. Discussion of the Process Combination in Enhanced Vacuum Assisted Multipoint Moulding with Additive Attachments  
By default, the fused filament fabrication process is operated with low melting point plastics and therefore has the disadvantage that only material with low curing or forming temperatures can be used for part production. In addition, in most cases a glass plate is used as a construction platform for the fused filament fabrication, which inherits a number of differing properties in comparison to the interpolation layer made of silicone. Moreover, the building platform is usually flat. This means that the curved building ground on the vacuum assisted multipoint mould also represents a deviation from the standard process. According to [PERSON] and [PERSON] [63] the discrete pins of the vacuum assisted multipoint mould cause unevenness in the part despite the interpolation layer (see Figure 4). The degree of unevenness the so-called dimpling essentially depends on the mechanical properties and the thickness of the interpolation layer. However, the use of a thicker interpolation layer results in a significant decrease of the smallest producible structure. Hence, an appropriate middle course must be chosen here. While [PERSON] and [PERSON] [63] detect the occurrence of dimpling in the forming of plastic sheets, [PERSON] et al. [64] show that this effect also occurs during the forming of sheet metal. Similar influencing parameters are determined in each case. According to [PERSON] et al. [65]the compensation of this [PERSON] would either be to make the system significantly more precise and rigid, which would cause high costs. Hence, [PERSON] et al. [65] develop a readjustment of the pins based on a 3D measurement of the surface[PERSON] Therefore, the pins are initially adjusted followed by a three-dimensional scan of the actual shape of the interpolation layer. This actual shape is matched with the CAD model of the part to be produced with a best fit method. Based on this match, the deviations of the individual pins are determined and in the next step the VAMM is adjusted accordingly, thus the form deviations of the VAMM can be reduced.