Parting lines on plastic parts
One has to keep in mind what the plastic mold will look like when designing plastic parts. The green part at right shows an example of good and bad stepped parting line. When looking at the part, it might not be so obvious, but take a look at the mold steel shown below it.
As we see, the mold steel on the one side has a sharp edge to it. That edge will break down quickly, resulting in ugly looking plastic parts.
When people with no experience in designing plastic molds design plastic parts, these kinds of mistakes are very common. Send a part like that to a third world country to have the mold built, and the plastic mold will likely be built exactly as you designed the part, resulting in very poor quality plastic parts.
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