[Elecraft] Concentric knobs??

[hb9ari]

Hi Vic,

Thank you for this "demonstration".
In my case, for little enclosures used
with optical encoders, for delivery
delay reasons, the factory don't execute
the post molding process, (some heating
with a well defined temp=f(time) profile.
The contract or shrink (tnx to Terry, K4RX)
was not done before assembly.
Between 1 or 2 months after, ~75%
of the enclosure were broken...

My best 73,
Rudi, HB9ARI

On 24.06.2011 18:02, Vic K2VCO wrote:
> This happened more than 30 years ago so I can tell the story. I worked at a kibbutz
> factory in Israel where we made plastic faucets by injection molding. The correct
> adjustment of the temperature profile of the molding cycle was critical to many
> characteristics of the finished parts.
>
> Our engineer was going to Germany to demonstrate some products, so we carefully tested his
> samples so that he would not be embarrassed in front of the quality-conscious Germans.
>
> At the demonstration, he turned the knob on the hot-water side of the faucet: snap. Then
> he tried the cold-water side: snap. Both stems broke off neatly inside the faucet!
>
> The German engineers were not amused. Ultimately we learned how to adjust the molding
> machines properly!
>
> On 6/24/2011 7:12 AM, hb9ari wrote:
>> Hello Guy,
>>
>> I think that you have found the good explanation!
>>
>> May be some of these knobs don't get a correct or sufficient  pre-aging (?)
>> procedure before leaving the factory; at my QRL pro, we get this kind
>> of problem with molded plastic enclosure breaking some time after
>> they were bee assembled.
>>
>> In French, we are speaking of "retrait" but i don't find
>> the correct translation!
>>
>> My best 73,
>> Rudi, HB9ARI