Feedforward control to suppress the leading edge bulge in photopolymerization-based additive manufacturing

Purpose – This study aims to examine the feasibility of feedforward actuation of the recoater blade position to alleviate the resin surface nonuniformity while moving over deep-to-shallow transitions of submerged (already cured) geometric features. Design/methodology/approach – A two-dimensional computational fluid dynamics (CFD) model has been...

Protocols for minimizing the leading edge bulge in stereolithography

The leading edge bulge is a known defect in stereolithography with free-surface recoating. It is a resin excess that remains after deposition over a deep-to-shallow topographic transition, the leading edge of the cavity. In this paper, we explore an approach based on changing the gap between the recoating blade and the previously cured layer to...

Influence of the recoating parameters on resin topography in stereolithography

The recoating step in stereolithography (SL) is one of the principal sources of inaccuracies. The liquid layer deposition on top of irregular topography leads to a non-uniform layer thickness which eventually results in a poor quality of the final product. To compensate the unevenness of the underlying geometry, an approach where the recoating...

EUV blank defect and particle inspection with high throughput immersion AFM with 1nm 3D resolution

Inspection of EUV mask substrates and blanks is demanding. We envision this is a good target application for massively parallel Atomic Force Microscopy (AFM). We envision to do a full surface characterization of EUV masks with AFM enabling 1nm true 3D resolution over the entire surface. The limiting factor to do this is in the sensor itself:...

On the surface topography of ultrashort laser pulse treated steel surfaces

This paper concentrates on observations of the surface topography by scanning electron microscopy (SEM) on alloyed and stainless steels samples treated by ultrashort laser pulses with duration of 210 fs and 6.7 ps. Globular-like and jet-like objects were found depending on the various levels of the fluence applied. It is shown that these...

Theoretical investigation of van der Waals forces between solid surfaces at nanoscales

A theoretical investigation of van der Waals forces acting between two solid silicon surfaces at separations from zero to approximately 20 nm is presented. We focused our efforts on the analysis of different factors that can cause deviations from the classical pressure-distance dependence p ∼ 1/D3. It is demonstrated that a layer (oxide or water...

Vegetation and Soil Characteristics in SIR-C data

We compared polarimetric C- and L-band and ground truth data from bare soil, young wheat and mature maize fields of the agricultural test site Flevoland in the Netherlands collected during the SIR-C campaign in April and October 1994. We find that the L-band is more sensitive to the soil roughness than the C-band. In particular L-band HH gives...