**5. Concluding remarks**

**Figure 10.** Schematic illustrating the events occurring when measuring shrinkage due to UV-curing. (a) at first the rheometer plate establishes a baseline by applying a prescribed axial force (0.1 N). As the sample is cured it shrinks (b) causing a decrease in the force, and subsequently the rheometer moves axially until the prescribed force is re-established

For Example TA Instruments Discovery Hybrid Series rheometers, which can measure both tensile and compressive

The shrinkage of the material can also be measured by exploiting the rheometer's<sup>6</sup>

movement, and the upper plate geometry can be adjusted to move in-line with the shrinkage that occurs with cross-linking. As **Figure 10** demonstrates, a minimum compressive force is

axial

(c). Such movements allow the simultaneous measurement of the gap decrease(Δh).

6

forces up to 50 N.

56 Polymer Rheology

The chapter has demonstrated the necessity and utility of rheological characterisation techniques for polymer-based additive manufacturing, irrespective of the technique. For fused deposition modelling, rheologically characterisation are performed to obtain the true shear rate at the nozzle wall, the ideal viscosity for material flow, the critical buckling stress, extrudate swelling and sintering characteristics. For stereolithography, a contrasting AM technique, rheology is a requisite for ensuring the resin possesses the ideal viscosity, as well as attaining information regarding the curing characteristics and mechanical properties of the cured resin.
