Gate position adjustment
Based on flow balance: If a single gate causes melt flow distance to be too long, pressure loss to be too large, or filling time to be too long, consider increasing number of gates. At the same time, gate size should be determined based on the overall flow demand of melt and flow shared by each gate. For example, for large flat plastic parts, if a single gate is difficult to achieve fast filling, gates can be added on both sides of plastic part or at a central symmetrical position, appropriate size of each gate can be determined based on filling analysis to ensure that melt fills cavity evenly and quickly.

 

Avoid defects: If gate size is too large, it may cause melt ejection, resulting in defects such as ripples and silver streaks on the surface of plastic part; if size is too small, it will increase melt flow resistance, resulting in stagnation or under-injection. According to Moldflow's analysis of melt flow velocity and pressure, gate size is reasonably adjusted to allow melt to enter cavity at a steady speed.
Optimize number and size of gates
Based on filling mode: Moldflow can show filling order and flow path of melt in cavity. If filling imbalance is found, such as slow filling in some areas or risk of short shots, gate position can be moved to difficult filling area. For example, for a plastic part with a long and thin cantilever structure, if melt has difficulty reaching end of cantilever, gate can be set close to cantilever, or a gate can be added at root of cantilever to improve filling situation.
Consider weld line position: Weld line will affect appearance and mechanical properties of plastic part. By analyzing weld line position, gate is set where melt front can converge at a suitable angle and speed to reduce visibility and adverse effects of weld line. For example, for transparent plastic parts with high appearance requirements, to avoid obvious weld lines on visible surface, gate can be adjusted to make melt converge in a non-critical area.

Runner shape design
Size determination: According to requirements of melt flow and flow velocity, combined with Moldflow's analysis of pressure and flow velocity, adjust runner size. Increasing runner diameter can reduce flow velocity and pressure loss of melt, but will increase material consumption and cooling time. Therefore, it is necessary to comprehensively consider and find appropriate runner size to ensure that melt can flow smoothly from main channel to each cavity.

 

Layout adjustment (for multi-cavity molds): For multi-cavity molds, runner layout should ensure that each cavity can be filled simultaneously and evenly. Using a balanced runner layout, by accurately calculating runner length and diameter, time and pressure of melt reaching each cavity are basically same, avoiding differences in plastic part quality caused by unbalanced filling. For example, in injection molding of small plastic parts with multiple cavities in one mold, length and diameter of runner branches can be adjusted to make filling of each cavity close to same.
Optimization of runner size and layout
Pressure loss consideration: From pressure distribution analysis results of Moldflow, we can see pressure loss in runner. Pressure loss of a circular runner is relatively small. If space permits, try to use a circular runner. For hot runner system, heating uniformity of runner and retention of material must also be considered. Selecting a suitable hot runner structure, such as a needle valve hot runner, can effectively control flow of melt, opening and closing of gate to improve filling effect.
Fiber orientation effect (for fiber reinforced plastics): If injection molding material is fiber reinforced plastic, shape of runner will affect orientation of fiber in melt. For example, using a specially designed runner, such as a runner with a spiral structure, can better disperse and orient fiber in melt, thereby improving mechanical properties of plastic part.

Optimization of cooling channel layout
Cooling time control: According to cooling time predicted by Moldflow, adjust cooling channel size and cooling medium flow rate. If cooling time is too long, if mold structure allows, cooling channel diameter can be increased or cooling medium flow rate can be increased. However, it should be noted that excessive flow may cause pressure changes in mold and affect stability of cooling effect. For example, for high-speed injection molds with short cooling time requirements, diameter of cooling channel can be appropriately increased, and appropriate cooling medium flow rate can be used to improve cooling efficiency.
Temperature distribution uniformity: Moldflow's cooling analysis results show temperature distribution of mold. If mold temperature is uneven, it will cause uneven cooling of plastic part, resulting in warping deformation, inconsistent surface gloss and other problems. According to temperature distribution results, cooling channels are arranged in areas with higher temperatures, or density of cooling channels in these areas is increased. For example, for plastic parts with thick wall parts, heat accumulation is more in thick wall, cooling channel should be closer to thick wall area to accelerate cooling and reduce warping deformation caused by wall thickness differences.

 

Cooling channel size and cooling medium flow adjustment
Consider distance between cooling channel and cavity: If cooling channel is too close to cavity surface, surface temperature of plastic part will be too low, resulting in cold marks; if distance is too far, cooling efficiency will be low. Generally speaking, this distance is usually between 10 and 25 mm, but specific value should be determined according to factors such as plastic part material, wall thickness and mold structure. By analyzing cooling effect, adjust distance between cooling pipe and cavity to achieve the best cooling effect.

Uniform wall thickness design
Melt flow stability: In areas where wall thickness changes, use of a gradual transition method can make melt flow more stable. For example, when transitioning from a thick-walled part to a thin-walled part, setting a gradual transition area can avoid sudden acceleration or deceleration of melt flow, reducing surface quality problems and stress concentration caused by flow changes.
Stress concentration relief: Wall thickness design of gradual transition helps to relieve stress concentration caused by sudden changes in wall thickness. This is especially important for plastic parts that are subjected to large external forces or have high requirements for mechanical properties, can improve strength and service life of plastic parts.
Gradual transition of wall thickness (for areas with wall thickness changes)
Reducing warpage: Warpage analysis results show that uneven wall thickness is one of main causes of warpage of plastic parts. Try to make wall thickness of plastic part uniform and avoid too sudden transition between thick-walled and thin-walled areas. For example, for plastic parts with ribs, pay attention to difference between ribs and main wall thickness. Cooling shrinkage can be made more uniform and warping deformation can be reduced by adjusting rib thickness or setting a gradual transition area between the two.
Control shrinkage difference: Shrinkage analysis shows that different wall thicknesses will lead to different shrinkage rates. In order to control shrinkage differences and reduce surface defects such as shrinkage marks, wall thickness should be kept consistent as much as possible. If wall thickness variation cannot be avoided, shrinkage can be balanced by hollowing out thick wall part or adopting other structural designs.

Ejector position selection
Consider shape and material properties of plastic part: Determine ejection method according to shape, size and material properties of plastic part. Push rod ejection is suitable for plastic parts of various shapes and can be flexibly arranged in a suitable position; push plate ejection is suitable for large, flat or thin-walled plastic parts, which can provide uniform ejection force and reduce plastic part deformation; push tube ejection is suitable for plastic parts with internal hole structures. For example, for round plastic parts with center holes, push-tube ejection may be a better choice, which can effectively protect internal structure and appearance of plastic parts during ejection process
Ejection method determination
Based on residual stress and deformation analysis: Combined with Moldflow's analysis of residual stress and plastic part deformation, choose to set ejection mechanism at a location with small residual stress and less prone to deformation. For example, for thin-walled and complex-shaped plastic parts, avoid ejecting in the thinnest or stress-concentrated area of plastic part, and choose to set ejection device near thicker wall support structure or reinforcement ribs.