Possibility for Replicating Mechanoscopic Surface Marks in the Hybrid Vacuum-Pressure Casting Process

Abstract

Vacuum-pressure casting technology allows small batches of components to be manufactured from polymer materials, mainly from thermosetting plastics such as polyurethane and epoxy resins. Apart from being very simple, the process is also advantageous in that it offers a very accurately reproduced geometrical structure of the surfaces of master patterns used in mold manufacturing. This article presents the results of analyses performed for the process of replicating mechanoscopic marks with the use of three vacuum casting variants, including a hybrid vacuum-pressure casting process developed in particular for the replication purposes. The main research objective was to analyze and evaluate the influence of the parameters of the individual process variants on the quality of the obtained cast parts and on the replication accuracy without introducing additional artifacts on their surfaces. The article discusses the individual stages of the process and provides an analysis of their parameters. The replicas were evaluated for their porosity and reproduction quality with the use of CT methods and comparative photographs obtained from a light microscope.

Industrial‐scale vacuum casting with silicone molds: A review

“…Some exemplary applications of vacuum casting (VC): (a) Preparation of the master pattern (housing of a shaver) with adhesive tape as parting line; (b) cutting of the parting line and demolding the master pattern; (c) resin filled silicone mold; (d) two‐component casting seen inside the mold (images a–d provided and used with permission by z‐prototypenbau GmbH at www.z-prototyping.com); (e) bending guidance for stainless steel pipes 3D printed by fused deposition modeling as master pattern; (f, g) carbon fiber reinforced PUR casting (h) under mechanical load when bending a stainless steel pipe [9]; (i) CNC milled impeller as master pattern, (j) silicone mold cavity, and castings made with PUR resins based on (k) MDI and (l) H 12 MDI [9]; (m) shark skin master pattern, (n) mold made from epoxy resin, and (o) replica cast from silicone ((m–o) adapted from Reference [71] with permission from Elsevier); (p) scanning electron micrographs of Ag‐coated microspike electrodes produced by VC (adapted from Reference [72] with permission from Elsevier); (q) tensile bar with casting frame as master pattern 3D printed by PolyJet (left), silicone mold (middle), and casting made with MDI‐based PUR resin (right) (adapted from Reference [73]); (r.a) composite photo of a ghost toy figure as master pattern 3D printed by fused deposition modeling (left), stereolithography (middle), and selective laser sintering (right) with different surface topographies and (r.b) superimposed 3D scans of the stereolithography master pattern and the casting made of MDI‐based PUR‐resin (adapted from Reference [9]); (s) comparative micrographs of a cartridge case (left) and its PUR replica (right) produced in VC (adapted from Reference [74]); (t) scanning electron micrograph of a microgear produced by VC of PUR (adapted from Reference [75] with permission from Elsevier).…”

“…To investigate the mechanical properties of the thermoset parts, conventional tensile bars were used as master models in various studies [14,73,81]. Frankiewicz et al [74] used VC of EP to produce replicas of mechanoscopic marks on cartridge cases and bullets left by firearms for forensic investigations (Figure 3s). Ng et al [72] utilized VC for the mass‐production of disposable microneedles arrays for electroencephalography electrodes from PUR, EP, and carbon‐filled EP, which were subsequently metalized (Figure 3p).…”

Characterizations of Polymer Gears Fabricated by Differential Pressure Vacuum Casting and Fused Deposition Modeling

“…It was found that process parameters played an important role in eliminating air bubbles on the surface of the resin parts. Frankiewicz et al [ 14 ] demonstrated the results of analyses performed for the process of replicating mechanoscopic marks with the use of three vacuum-casting variants, including a hybrid vacuum-pressure casting process developed in particular for the purposes of replication. It was found that the proposed method not only allowed the tool preparation to be simplified and shortened, but also caused the entire process time to be shortened from 10 to 1.5 h.…”