Many special processes have been investigated to improve the appearance, densityand mechanical properties of polymer and metal MEX parts. In this section, examples ofprocesses that hold promise for improvement of metal MEX parts will be discussed.During printing, it is commonly known that there are the intrinsic voids betweenthe deposited paths. Additional in situ systems, e.g., magnetic and ultrasonic, can beapplied with the printing head or printing bed to successfully improve the quality of metalMEX parts [199] (magnetic) and polymer FDM parts [200] (ultrasonic). Squeezing by therollers applied with the printing head is also demonstrated to improve the density andmechanical properties of polymer FDM parts [201]. However, the dimensions of the rolledparts needed to be carefully controlled. These systems can be possibly applicable to themeal MEX process to improve the as-printed quality, thus improving mechanical properties.Metal MEX at the as-printed stage is significantly softer than after sintering. Hence,additional surface finishing of the as-printed parts, such as grinding, shot blasting or laserpeening, can be applied to polish the surface [35]. The very high surface quality aftersintering can also be achieved. Furthermore, HIP is still the most effective process to obtainfully dense parts; as discussed in the previous section, HIP can increase the relative densityvery close to 100% and provide tensile properties comparable to those of MIM and itsstandard [81]. It also reduces the build-orientation dependence of the metal MEX parts.