Windshield washer fluid canister
Development of the product’s housing, consisting of the container, cap, funnel, and label
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Technologies: injection molding, blow molding
Materials: PE-HD
Planned production volume: >1000 000 szt.
Operating conditions: outdoor, from -30 to 60°C
My role: design engineer
Time spent on the project: 56h.
Project duration: 5 mo.
There was a design concept agreed upon with the client -- essentially, the appearance of the product. It had to be turned into a set of production-ready files, that is, manufacturable 3D models. In particular, it was necessary to design the threaded section
Although the cap and the canister neck use the same thread (in terms of diameter and pitch), their geometry is different due to the manufacturing processes involved. In the canister, the thread is formed by pressing the softened preform against the mold walls with air, while in the cap, it is created by injecting molten material into the mold cavity, followed by unscrewing the threaded section
Threaded caps for containers made by polyethylene blow molding are very often made from the same material -- HDPE, though of a different grade
There are several reasons for this:
First, polyethylene itself is very cheap -- both in terms of raw material and processing
Second, the relatively low surface quality typical of PE is not critical for this type of product -- it’s just packaging
Third, the relatively low mechanical properties of PE make it possible to forcibly "tear" the cap off the core: the material has a low modulus of elasticity and high elongation at break, which allows it to stretch over the height of the thread during demolding and then return to its original shape. This simplifies the tool design (saves money) and shortens the molding cycle (more savings)
In this case, the packaging, in addition to its main function -- storing the product -- also had a presentational role. Formally, that’s always the case: a candy is not only what’s inside but also the wrapper outside. The only difference is how much the manufacturer is willing to invest in that "wrapper" to make their product stand out among competitors. Here, it was decided -- as they said in Pretty Woman -- "We’re going to spend an obscene amount of money" on design (compared to those who don’t spend at all)
When it comes to the container itself, we can only work with geometry -- the surface finish is dictated by the material’s properties -- but with the cap, we have some room to maneuver. And here’s what I was leading up to: the material I chose for the cap was polypropylene
And here’s what I was leading up to: the material I chose for the cap was polypropylene
Parts made of polypropylene look more premium than those made of HDPE: they are stiffer, have sharper geometry (HDPE parts usually appear a bit “blurred”), and, most importantly, they provide a more pronounced gloss. For the funnel, however, these parameters are secondary -- it’s hidden inside, behind the label, and doesn’t influence the customer’s purchase decision. Here, only the cost matters. Therefore, the funnel is molded from injection-grade HDPE
That was the situation at the stage of the product’s engineering design
The next stage -- coordination with the manufacturer -- as usual, brought some rethinking of the previously developed solutions in the context of cost optimization
For instance, the client decided to move the funnel compartment to the other side
Initially, a large combined label was planned, with a semi-transparent tear-off zone above the funnel. Whether it turned out too expensive, or the client got worried that a poorly removed tear-off section would spoil the appearance -- I don’t know. In the end, they decided to make the label smaller and leave the funnel niche open
For the sake of "clean design", the client also decided that the tamper-evident ring -- the part of the cap that breaks off when first opened -- would ruin the whole feng shui. So, the cap type was changed to one where the ring can be completely removed after the first opening
However, the new stepped cap required changes to the neck geometry -- its upper diameter had to match the diameter of the tear-off ring. We redesigned it
The manufacturer said that the embossed logo on the canister wouldn’t just lose sharpness -- it would be completely unreadable. We removed it
All caps with tamper-evident rings can roughly be divided into two types:
— the ring rotates together with the cap but doesn’t move along the unscrewing axis;
— the ring moves along the axis but doesn’t rotate.
The first type looks better before opening (a clean cylindrical shape) but worse afterward -- the collar that breaks the ring off prevents it from being removed, so it stays on the bottle forever
The second type is the opposite: it looks worse before opening (a stepped shape, dictated by the technology -- the retaining lugs can’t overlap the thread projection), but better afterward -- the ring can be easily taken off
Now moldmakers have turned the “bug” of the first type into a “feature” by adding a small connection between the ring and the cap -- supposedly so the cap doesn’t get lost (how did we even live without that?). In reality, to put it politely, it’s annoying — pure pseudo-convenience. But that’s another story
According to the manufacturer, the funnel niche turned out to be too sharp-edged and located in an unfavorable spot -- too close to the largest wall, where the material experiences maximum stretching during blow molding. We rounded it off as much as possible and moved it farther from the handle
For cost reasons, it was finally decided to mold the cap from HDPE as well. This worsened the appearance, but for this type of product, it’s not critical
The graphic design of the label -- which completely negated all the efforts of the industrial designers -- was handled by the client independently, already at the stage of mass filling of the washer fluid
Summary of the work done: based on the design model, I developed a production-ready parts optimized for high-volume manufacturing
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