Abstract
The study covers the free linear shrinkage of samples from PLA, HIPS, and ABS filaments used for FDM 3D printing in the ranges of extrusion operating temperatures (t). It was found that the PLA filament features by shrinkage values in the range of 0.2–0.6 % at Δt =200÷220 °С. HIPS filaments (Δt = 220÷240 °С) and ABS filaments (Δt = 240÷270 °С) have a shrinkage of 0.3–0.8 %. Linear shrinkage values must be taken into account when designing mathematical models of the future cast product. The influence of the print density dр (degree of internal structure filling) on the ash residue A when burning out samples obtained from the studied filaments was investigated. It was shown that the A value also increases with an increase in dр (5–15–30 %). The PLA filament has minimum A values (0.19–0.48 %). It was concluded that the PLA filament features the highest processability in the FDM 3D printing of casting patterns for casting into refractory ceramic molds (RCM) in terms of the set of free linear shrinkage and ash residue indicators. Clusters were made by FDM 3D printing from the PLA filament to produce «Nozzle» castings by casting into RCMs. Clusters were used to form RCMs. When burning out the clusters from RCMs, it was found that some RCMs cracked under linear heating. This was due to excessive pressure exerted by the expanding filament when heated to its softening temperature, and pressure exerted by gas emitted during the subsequent filament burn-out. The proportion of cracked RCMs increased with an increase in the heating rate. A stepwise mode of RCM heating combined with RCM calcination was developed in order to prevent cracking. There was no RCM cracking when clusters were removed in the stepwise mode. Experimental «Nozzle» castings were obtained from BrA9ZH3L bronze. The casting quality met the design documentation requirements.
Published Version
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