There are significant differences between metal prototypes and plastic prototypes in terms of manufacturing processes, precision control, and technological challenges:
1. Production Process: Plastic prototypes predominantly employ SLA or FDM techniques. SLA utilizes liquid photosensitive resin as the raw material, which is cured layer by layer using ultraviolet laser. It requires additional support structures, and after molding, the residual resin needs to be cleaned and the part needs to undergo secondary curing to enhance its performance. FDM involves extruding and stacking molten thermoplastic filaments, which is easy to operate but has low molding efficiency. Metal prototypes often rely on SLS or metal fused deposition processes. SLS uses metal/ceramic powder as the raw material, with high-power laser selective sintering. The un-sintered powder naturally supports the structure without requiring additional structures, and after molding, professional powder cleaning and sandblasting post-processing are necessary. Metal deposition requires inert gas protection, and the process complexity and cost are significantly higher than those of plastic prototypes.
2. Precision Control: In plastic prototypes, SLA achieves a precision of ±0.1mm, with high surface finish (Rz30μm) and low material shrinkage rate (<0.1%), making overall precision easily controllable. FDM has a precision of about ±0.2mm, with noticeable layer lines that require polishing compensation. Metal prototypes achieve a repeatability of ±0.05mm with SLS, but powder sintering shrinkage (about 0.5%-2%) can easily lead to deformation, necessitating preheating of the platform and optimization of scanning path compensation. Metal deposition is greatly affected by melting and cooling shrinkage, making precision control more challenging, and post-processing polishing can easily compromise dimensional accuracy.
3. Technological difficulties: The core issues of plastic prototypes lie in the high brittleness and weak heat resistance (less than 120°C) of SLA resin, as well as the low interlayer bonding strength of FDM, which makes them prone to cracking. The difficulties of metal prototypes mainly center on high equipment costs, the need for specialized dustproof facilities for powder handling, the difficulty in cleaning powder from complex cavities, the tendency for sintering to produce defects such as pores and cracks, and stricter requirements for metal material recycling and environmental protection treatment, which also demand a higher level of professionalism from operators.
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