1) Feasibility : if the part would have been made in one piece, this would involve a silicone mold or a rotomolding or blow molding because of the rounded and wavy shapes. Silicone cannot handle heavy production cadence, rotomodling takes too much time, blow molding cannot make strong thick parts.
a - We can see on each end of the biggest part, the square section is complete and integrates clips : it purposely is for good strength when clipsing each end to the other parts around. We can also see that in those 2 square sections, there is a parting line : meaning the mold is made of 1 bottom cavity that shapes the complete bottom end to end, then 2 sliders that slide out on each side shaped like a square, then 1 top cavity that shapes the inside of this big part. All the 3 movements made by the mold clearly shows how the draft angles are designed and we can see round marks that are in fact mold ejectors to confirm the direction of ejection.
b- The smaller part is made the same way, without the 2 square sliders. We can see the round marks and confirm the direction of ejection.
2) Cost : even if it's 2 parts, it's most likely to be injected in the same mold with 2 channels. As there is low chances to order only one part and not the other for spare parts. Blow molding could have worked but maybe this part requires the be strong or is designed to handle constraints we don't expect.
3) Versatility : the smaller part maybe has different versions to match different situations (several engine bays, additional air intake with a hole or a tube etc...)
Conclusion : there is
always a good reason behind a design that looks questionnable. The cost is almost always the principal point to then take decisions on the other aspects like feasibility, materials, accessibility while maintenance etc..
I work on plastic molding pretty much all year long
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Topic: Why is this duct 2 piece? (Read 2362 times)