## 2 Experimental Methodology
### DSC-Derived DPM Results  
All DSC samples were tested using a Perkin Elmer DSC8500 (PerkinElmer, Waltham, MA, USA). Two samples from each of the three test builds were obtained by collecting 5-10 mg of part shavings from the centre of the density blocks. Sampling from the centre of the block is essential to avoid the inclusion of unmelted particles from the surface of the part. These particles can adhere to the part surface during the application of \"finish\" layers, which are included in order to assist the cooling process. The process we describe in this paper cannot distinguish between unmelted particle cores within the part and these surface particles; the inclusion of the surface would, therefore, disproportionately affect the results, leading to inaccurate calculations of the DPM.  
While a value of MCM crystallinity for LS Nylon-12 from the literature could have been used (25%), it was deemed important to identify a corresponding value for HSS Nylon-12, as the introduction of RAM into the parts and the differing cooling profiles between machines could produce different resultant crystallinities. To obtain this value, a new build with the same layout as Figure 3 was carried out in HSS, with the aim of producing a fully melted sample. For this build, the sinter speed was reduced to 100 mm/s, and only 20 preheat layers were deposited prior to RAM deposition, ensuring that parts could be obtained prior to overheating and subsequent build failure. Whilst not fully representative of a standard HSS build, this was found to produce the closest approximation of the peak temperatures and cooling profile compared to a number of other methods attempted. The parts produced from this build were, otherwise, post-processed and prepared for DSC testing in line with other samples. In addition to the part samples, approximately 10 mg of virgin PA2200 was tested, from which the core crystallinity was determined and compared with the literature values (47%).  
The prepared samples were subjected to the heating and cooling profile shown in Table 3. The Perkin Elmer Pyris software (version 11) was then used to calculate the melt enthalpy of each sample by drawing a baseline under any melt peaks and calculating the area between the baseline and the curve, as demonstrated in Figure 4. The MCM, core, and total (sample) crystallinities were then calculated using melt enthalpies from the relevant DSC traces and Equation (3), taking the melt enthalpy of a 100% crystalline Nylon-12 sample to be 209.3 J/g, as obtained in [14]. The DPM values for each sample were then  
\begin{table}
\begin{tabular}{c c c} \hline
**Parameter** & **Value** & **Units** \\ \hline Part Bed Temperature & 160 & \({}^{\circ}\)C \\ \hline Recoating Speed & 70 & mm/s \\ \hline Lamp Power & 2 & kW \\ \hline Ink Density & 3 & Drops per Dot (DPD) \\ \hline Layer Thickness & 100 & \(\upmu\)m \\ \hline Blank “Preheat” Layers & 100 & - \\ \hline Blank “Finish” Layers & 10 & - \\ \hline Part Removal Temperature & 50 & \({}^{\circ}\)C \\ \hline \end{tabular}
\end{table}
Table 2: HSS machine parameters.  
calculated using Equation (1) in Section 1.2, with average values and standard deviations calculated for each data point.  
\[Crystallinity\left(\%\right)=\frac{Melt\ enthalpy\ of\ sample\ \left(\frac{l}{S} \right)}{Melt\ enthalpy\ of\ 100\%\ crystalline\ sample\ \left(\frac{l}{S} \right)}\times 100 \tag{3}\]