Injection molding is a dance between quality, cycle time, and cost. All three are tightly wound together. Experienced tool designers and molding partners will tell you that it’s really tricky to produce round parts. It looks easy but plays hard. This is because residual stresses in the part can make it challenging to hit the specs, which can lead to longer cycle times to let the part cool, which can increase the cost.
Residual stresses can warp round parts (like barbed connectors) after they are released from the mold. This can be offset by exotic materials and longer cooling cycles, but that also drives up cost.
Quality tool engineers can balance melt flow and reduce cycle times with hot runner systems, increase cooling capacity with copper cores and forced air flows, and produce precise round parts with out-of-round tools (what??). Yes, you read that correctly.
Depending on the part design, material flow, and residual stresses, sometimes it takes an out-of-round tool to produce precision round parts like fluid connectors. Molding partners that don’t know this can set themselves and their customers up for a very long and hard journey.