Flow Leaders and Deflectors Flow Leaders and Deflectors

Flow Leaders and Deflectors

Flow Leaders and Deflectors § Subtle changes in nominal wall thickness – Designed to control the flow front § Flow leaders – Thicker parts of the cavity – Increases the flow front velocity – Yellow arrow § Flow deflectors – Thinner parts of the cavity – Decreased flow front velocity – Red arrow

Why Use Flow Leaders and Deflectors § Balance flows § Move weld lines

Advantages and Disadvantages § Flow Leader – Advantages § Reduce shear stress § After tool is cut flow leader can be added by removing steel – Disadvantages § Add material volume § Possible increase in cycle time § Flow Deflector – Advantage § Reduce material volume – Disadvantage § Possible reduction in structural integrity

Thickness Changes § Leaders/deflectors thickness changes – Should be less than a 25% change from nominal wall § Thickness transition – Should be smooth and gradual – Reality midplane is a step – Fusion & 3 D can model a bevel transition Bad Better Best

Setting the Thickness § Midplane – Easy to change thickness property of selected elements § Fusion – Can set thickness like midplane – Can only use for flow to test flow leader/deflector – Must re-translate with revised thicknesses if going on to cool and warp § 3 D – Test as Fusion model if possible – Otherwise must re-translate

Model Preparation § Use layers to set up flow leader/deflector – Select elements whose thickness is to be changed – Assign them to a new layer – Rename the layer § Possibly align nodes to create a smooth transition

Practice - Window Cover Model § Design Criteria – – Gate location fixed Weld line to be moved to upper right corner of window Move by adding flow deflector Material § Lanxess Lustran ABS 450 C – Molding conditions § Mold temperature 60ºC § Melt temperature 250ºC § Injection time 2. 5 s

Changing Thickness § Select the elements that need to be changed – Flow deflector layer § Assign Properties from the Edit menu – Select an existing property or – Create a new one

Window Cover § Run three analyses – Nominal wall – 1. 9 mm flow deflector – 1. 27 mm flow deflector Nominal Wall § Compare results – – Fill time Weld line Flow front temperature Frozen layer thickness 1. 9 mm th 1. 27 mm th

Window Cover § Flow front temperature – At weld lines – Option for weld line results – Help determines quality

Window Cover § Frozen Layer Fraction in flow deflector – Thinner the wall thickness the higher the frozen layer Nominal Wall 1. 9 mm 1. 27 mm

QUESTIONS