When the heald frame height is excessively high, beating-up will occur at the upper section or even the top edge of the reed air guide part, resulting in fabric cracking and holes on the cloth surface.
When the heald frame height is too low, the upper layer of warp yarns will turn slack, leading to indistinct shed and reduced shed opening angle, which may cause more frequent weft stops.

How to Set the Heald Frame Height of Water-Jet Looms
The core principle for adjusting heald frame height is to keep the fabric fell within the air guide section of the reed, so as to prevent fabric holes. Three shed types are available for height adjustment: clear shed, semi-clear shed and unclear shed, which shall be selected according to the warp density of fabrics.
For high-density fabrics and yarns with poor hairiness performance, semi-clear shed or unclear shed is generally adopted. This allows more layers of warp yarns to separate and alleviates warp adhesion.
For twill fabrics and fabrics with complex weaves, the heald frames for selvedge yarns and ground weave are arranged at front and rear positions respectively. During setting, ensure the selvedge warp yarns will not become overly slack by adjusting heald frame height, so as to reduce weft stop faults.