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 Post subject: Re: Dr. Evil changed?
PostPosted: 24 Mar 2015, 20:00 
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Judging from the photos of how rubber is made that used to be on the Yinhe website, I can guess at what happened. To make topsheets they use a mold that has two surfaces - a top that is smooth and a bottom with holes (which accomodate the rubber that becomes the pips). The label strip is incorporated into the top or bottom (depending on whether they're making inverted or pips-out topsheets). Each mold (at Yinhe) makes two topsheets attached to each other. The rubber compound is masticated between rollers to mix it up thoroughly with whatever goes into it (including the sulfur which vulcanizes it), and then a rolled sheet of this compound is put between the two halves of the mold and then a stack of molds is put into a heated press (the one at Yinhe used hoses feeding steam into the stack). In the press the compound flows under pressure into all the recesses, this makes the pips and the label strip, and the space between the top and bottom halves of the mold defines the thickness of the basesheet. Obviously, something changed - either the molds were assembled wrong, or they used the wrong tops, or the wrong spacers were used, OR someone decided to change the design of Dr. Evil and ordered the change (achieved by making the change to the molds/spacers/whatever). One wonders how consistent the whole process is when it comes to repeatability, from mold to mold and from production run to production run.

Hmm.. Presports is just down the road. Maybe I should go get a couple sheets of Dr. Evil... Yikes, only one sheet in stock! Oh wait, only one sheet of black but 12 of red available.

Iskandar


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 Post subject: Re: Dr. Evil changed?
PostPosted: 25 Mar 2015, 09:54 
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iskandar taib wrote:
Judging from the photos of how rubber is made that used to be on the Yinhe website, I can guess at what happened. To make topsheets they use a mold that has two surfaces - a top that is smooth and a bottom with holes (which accomodate the rubber that becomes the pips). The label strip is incorporated into the top or bottom (depending on whether they're making inverted or pips-out topsheets). Each mold (at Yinhe) makes two topsheets attached to each other. The rubber compound is masticated between rollers to mix it up thoroughly with whatever goes into it (including the sulfur which vulcanizes it), and then a rolled sheet of this compound is put between the two halves of the mold and then a stack of molds is put into a heated press (the one at Yinhe used hoses feeding steam into the stack). In the press the compound flows under pressure into all the recesses, this makes the pips and the label strip, and the space between the top and bottom halves of the mold defines the thickness of the basesheet. Obviously, something changed - either the molds were assembled wrong, or they used the wrong tops, or the wrong spacers were used, OR someone decided to change the design of Dr. Evil and ordered the change (achieved by making the change to the molds/spacers/whatever). One wonders how consistent the whole process is when it comes to repeatability, from mold to mold and from production run to production run.

Hmm.. Presports is just down the road. Maybe I should go get a couple sheets of Dr. Evil... Yikes, only one sheet in stock! Oh wait, only one sheet of black but 12 of red available.

Iskandar


Using the wrong mold would mean that they then compounded the problem by either not noticing that their run of Rubber X didn't come out as Rubber X but came out as Dr. Evil or that they noticed and then decided to package it as Dr. Evil anyway. It seems more likely to me that somebody simply mixed up a wrong batch of rubber compound.

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 Post subject: Re: Dr. Evil changed?
PostPosted: 25 Mar 2015, 11:41 
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The wrong compound wouldn't have resulted in thinner base sheets but would have resulted in a softer or harder sheet.

The ID strips would be on the pips side, so they can't make a mistake there, but the bottom (flat) side might've gotten swapped with another (pips out) rubber. Long pips sheets generally have thinner base sheet thicknesses, the flat side might've gotten switched with one of those, if the spacer is built into the bottom half of the mold. It's possible they have maybe two or three sets of flat sides in use to make several different sheets and whoever was making rubber that week used the wrong set.

Molds also do wear out, and need to be replaced/refurbished. There's a mold story I heard concerning a very different product (model airplane propellers for competition) where the re-cutting of a mold (using a CNC mill running the very same file) resulted in enough of a change to the final product that they had to change the rules so that ONLY the newer props could be used in that particular class (the old ones were not allowed after that). It might be they had to replace/repair the Dr. Evil mould and something went wrong. They eventually corrected it but not before completing one production run.

Iskandar


Last edited by iskandar taib on 25 Mar 2015, 11:47, edited 1 time in total.

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 Post subject: Re: Dr. Evil changed?
PostPosted: 25 Mar 2015, 11:46 
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iskandar taib wrote:
The ID strips would be on the pips side, so they can't make a mistake there, but the bottom (flat) side might've gotten swapped with another (pips out) rubber. Long pips sheets generally have thinner base sheet thicknesses, the base might've gotten switched with one of those, if the spacer is built into the bottom half of the mold.

Molds also do wear out, and need to be replaced/refurbished. There's a mold story I know concerning a very different product (model airplane propellers for competition) where the re-cutting of a mold (using a CNC mill running the very same file) resulted in enough of a change to the final product that they had to change the rules so that ONLY the newer props could be used in that particular class.

Iskandar


This short pips rubber has a fairly thick base quite unlike some of the paper thin base sheets I've seen with some long pips rubbers.

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