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Preventing deformation in reprocessed plastic parts requires a strategic alignment of processing conditions with material behavior. Reprocessed resins often exhibit heterogeneous molecular distributions due to repeated heating and cooling events, making them more prone to uneven shrinkage and internal stresses that lead to warpage.

Start by ensuring consistent material preparation. Drying recycled resin thoroughly before processing is critical because residual humidity triggers internal bubbling and inconsistent solidification. Use a desiccant dryer and follow the supplier’s recommended drying time and temperature. Trace levels of water can lead to major quality deviations in reprocessed parts.

Fine-tune thermal and mechanical process variables. Decreasing melt viscosity can help reduce thermal degradation and تولید کننده گرانول بازیافتی minimize internal stresses. However, an excessively cool melt can cause short shots and flow marks. Find the sweet spot where the material flows adequately without overheating. Slowing down the injection speed can also help minimize molecular orientation and flow-induced strain.

Packing pressure control is critical. Insufficient pressure leads to non-uniform density distribution, while Overpacking can trap stress within the polymer matrix. Apply multi-stage pressure ramps. Validate uniformity via real-time cavity feedback.

The cooling stage dictates final part geometry. Non-uniform thermal gradients lead to warping, which is the main contributor to dimensional instability. Design the cooling channels to provide uniform temperature distribution across the mold. Minimize rib and boss thickness variations, as these retain heat and induce localized contraction. Use conformal cooling channels if possible, and Synchronize inlet.

Design for symmetric filling. Position gates to equalize flow paths. Employ gated runners to equalize pressure drop. Eliminate unbalanced wall thicknesses, or Integrate stiffening features to resist deformation.

Ejection and cooling protocols affect final shape. Maintain part in cavity until fully solidified. Rapid ejection while the part is still warm can cause mechanical warping. In some cases, annealing the parts after molding can relieve residual stresses. This involves heating the parts to a temperature just below the glass transition point and holding them there for a controlled time before slow cooling.

Testing and data collection are essential. Track warpage measurements across multiple production runs. Correlate them with process settings. Small adjustments in temperature, pressure, or cooling time can have a dramatic improvement. By comparing recycled vs. virgin behavior across controlled experiments, you can achieve consistent dimensional accuracy.