Mold Design: Pin Gate Frustration
The part that caught my attention this month represents two problems that have plagued molders for as long as I have been in plastics: poorly designed pin gates and an unbalanced runner system.
Mold Design: Living Hinge
This design is simply a modification of a flash gate into a cavity. The web will neck down the first time it is flexed. To ensure a good flex life, the hinge should be flexed several times immediately after being molded, since orientations of the web is what gives it strength.
Plastic Injection Mold Design: Venting
Proper venting of cavities is very important. Inadequate venting can result in gas burns, poor weld line strength and nonfilled parts. Too much venting can result in excessive flash and poor weld lines due to inadequate pressure buildup.
Plastic Injection Mold Design: Cooling and Ejector Pins
Molds must be provided with adequate cooling to take advantage of the faster cooling rates of reinforced compounds. Poor cooling results in rising mold temperatures and longer cycle times. Inadequate heating can result in voids, shorts and poor surface finish. Cooling and heating channels should be located directly in the mold inserts and cores if mold design permits.
Molding Part Design: Free Standing Boss With Four Gussets
Bosses are used in parts that will be assembled. Connect the boss to a wall or rib with a connecting rib as shown in Figure 1. If the distance of the boss from the wall makes a connecting rib impractical, design the boss with gussets as shown in Figure 2.
Injeciton Molding Guidelines: Support Ribs
Sometimes we use support ribs when design a plastic part.
Ribs should follow the proportional thickness guidelines shown below. If the rib is too thick in relation to the part wall, you may experience sinks, voids, warpage, weld lines, and longer cycle times. Position ribs in the line of flow to improve filling and prevent air entrapment.
Injection Molding Guidelines: Boss or Rib
A reinforced or protrusion on a mold part for strength or alignment during assembly or fastening.
Ribs should follow the proportional thickness guidelines shown below. If the rib is too thick in relation to the part wall, you may experience sinks, voids, warpage, weld lines, and longer cycle times. Position ribs in the line of flow to improve filling and prevent air entrapment.
Injection Molding Guidelines: Rib Details
Ribs should follow the proportional thickness guidelines shown below. If the rib is too thick in relation to the part wall, you may experience sinks, voids, warpage, weld lines, and longer cycle times. Position ribs in the line of flow to improve filling and prevent air entrapment.
Plastic Injection Mold Design: Adjoining Walls
The connection point between two molded surfaces are called adjoining walls
Injection Molding Guidelines: Thick to thin Wall Gating
Avoid sudden changes in wall thickness by using transition zones to eliminate stress concentrations and reduce sinks, voids, and warping in the molded part.