by admin | Oct 17, 2018 | Mould Technology Blog 1
Cooling time Theoretically, cooling time is proportional to the square of the heaviest part wall thickness or the power of 1.6 for the largest runner diameter. That is: where the thermal diffusivity of polymer melt is defined as In other words, doubling the wall...
by admin | Oct 17, 2018 | Mould Technology Blog 1
A culprit in shrinkage and warpage problems Residual stress is a process-induced stress, frozen in a molded part. It can be either flow-induced or thermal-induced. Residual stresses affect a part similarly to externally applied stresses. If they are strong enough to...
by admin | Oct 17, 2018 | Mould Technology Blog 1
Unbalanced cooling from the mold wall to its center can cause thermal-induced residual stress. Furthermore, asymmetrical thermal-induced residual stress can occur if the cooling rate of the two surfaces is unbalanced. Such unbalanced cooling will result in an...
by admin | Oct 17, 2018 | Mould Technology Blog 1
Chapter 25-3, Residual stress, china injection mold Home » Mould Technology Blog » News Center » Chapter 25-3, Residual stress, china injection mold FIGURE 5. Variable residual stresses arise and the part deforms as layers of different frozen-in specific volume...
by admin | Oct 17, 2018 | Mould Technology Blog 1
Why do they occur? Shrinkage is inherent in the injection molding process. Shrinkage occurs because the density of polymer varies from the processing temperature to the ambient temperature (see Specific volume (pvT diagram)). During injection molding, the variation in...