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Is flash a measure of quality?


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#21 Don Sikora II

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Posted 29 June 2012 - 10:44 AM

"Flash" on a styrene kit is the result of at least one of two causes: Most think of flash as the result of poorly mated tooling halves, which of course can be true. However, the biggest cause of flash in a plastic model kit, as told to me by a production engineer at AMT Corporation years ago, is improper temperature control. Styrene is very much like pancake syrup in this respect: The hotter you heat it, the thinner the consistency, and not hot enough makes for a much thicker "syrup" of styrene. Too much heat, the styrene gets very thin, and can flow out in the minute clearances between the parts of a mold, resulting in flash. Too little heat, and the plastic may well not flow as it should through all the sprues and injection passages, which results in "short-shot" parts. (Many of use have seen both!).

It is a measure of quality, but more in terms of production quality, rather than a severe defect in the tooling,

Art


I worked in Revell-Monogram Tool Engineering from 1992-2005. I'm not a molder, but have spent plenty of time around molding machines and kit tooling. There are so many possible causes for flash that it's not just a simple answer. Temperature control is one cause, another big one is because of mold filling problems. Getting any mold to run well is an art, and it can depend on how much time/effort the person dialing in the machine is willing/able to put into it. Sometimes filling problems can be worked out in the machine, but lots of times old molds probably didn't run well when they were new. We'd spend a lot of tool room changing stuff like gates and runners to try to get stuff to fill without having a ton of flash. Flash can cause problems with the mold too because chunks of it can get stuck between the mold halves and get "smashed" causing further mold damage/problems.

#22 1930fordpickup

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Posted 29 June 2012 - 01:27 PM

Sometimes it is just about the money, if they fix a mold or take the time to get it to run properly this all adds up to money . That might be one less Million the CEO can take home this year.LOL

#23 Chuck Most

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Posted 29 June 2012 - 02:32 PM

Whether there is a micron of a seam that needs to be smoothed or a quarter inch of paper thin flash, either way there's going to be sanding and I don't see where it changes much when prepping a model.

I don't get it either. A mold seam is a mold seam, no matter how prominent it is. You have to remove it either way. As long as there is no mold misalignment, does it really matter? For the record, I like prominent mold seams, makes them much easier to spot, and thus easy to remove BEFORE you hit the model with that final color or clear coat. B) I'll point out where they are when talking about a kit, but how faint or huge they are doesn't register on my personal 'quality meter'.

Maybe it's the same reason 1:1 car reviewers point out things like wide and inconsistent body panel gaps. It supposedly sends a message about the car's overall quality, though I don't know anyone who ever turned down a car because there was a .005" variance in the hood-to-fender gaps.

#24 Skip

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Posted 29 June 2012 - 07:21 PM

Flash and excessive mold lines are a quality problem. Doesn't really matter where the cause lies, what matters is how much the manufacturer is willing to pass off to the consumer. With today's vastly improved design, manufacturing and molding technology flash is pretty much unacceptable. Especially when one considers that our hobby like it or not isn't growing in numbers by leaps and bounds. With a limited number of hobbiests the manufacturers should be bending over backwards to put out quality kits especially at the today's prices!

#25 mbl4321

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Posted 30 June 2012 - 06:23 AM

I do not agree that a "mold seam is a mold seam". Nicer kits have very light ones that come right off in a few swipes. Older or lower quality kits can wear you out removing some of them. Back to the question, is flash "a" measure of quality? Absolutely. The only one? Certainly not. The most important one? Certainly not.

#26 Lunajammer

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Posted 30 June 2012 - 09:49 AM

I'm very much enjoying this discussion and learning. Thanks for everybody's input.

#27 bbowser

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Posted 30 June 2012 - 10:27 AM

Flash on a new tool, unacceptable. Obviously a quality issue. On a repop from 20 years ago, I'm just happy to get it. On an out-of production for ages Johan (for instance) kit, I'll put in the extra effort. It's all a matter of degree.

#28 charlie8575

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Posted 01 July 2012 - 09:47 PM

I think it's a combination.

Sometimes, there is wear in the molds, and that should be addressed. Sometimes, I think there's impromper clamping, poor injection pressure, the plastic is too hot/too cold/too whatever.

When I got my Hornet, while I was very pleased with the quality of the detail of the parts, I was a bit shocked at the amount of flash and the heavy, heavy mold lines on the body and frame. There were a few warped parts, too. On a brand-new tool, especially with all that re-working, I thought it was a bit disheartening to see. Now, don't get me wrong, I'm having a blast building mine, even with those couple of hiccups, but for that tool to have that kind of problem I thought was poor attention to process control at best, and still more problems with the mold at worst.

I think we can do better as an industry. I think Tamiya, from the couple of their kits I have, also has the best molding quality out of all manufacturers. The Volvo 850 wagon I have, and the Jeep Grand Cherokee, for example, have 0 flash.

The Japanese learned long ago the secrets of quality from two Americans- W. Edwards Demming, and Philip Crosby. Perhaps the rest of the industry should begin to learn from them, too.

Some argue quality costs more. Perhaps a little initially, but it pays for itself in saved defects, repeat customers and your reputation.

Charlie Larkin

#29 Art Anderson

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Posted 02 July 2012 - 03:12 AM

I think it's a combination.

Sometimes, there is wear in the molds, and that should be addressed. Sometimes, I think there's impromper clamping, poor injection pressure, the plastic is too hot/too cold/too whatever.

When I got my Hornet, while I was very pleased with the quality of the detail of the parts, I was a bit shocked at the amount of flash and the heavy, heavy mold lines on the body and frame. There were a few warped parts, too. On a brand-new tool, especially with all that re-working, I thought it was a bit disheartening to see. Now, don't get me wrong, I'm having a blast building mine, even with those couple of hiccups, but for that tool to have that kind of problem I thought was poor attention to process control at best, and still more problems with the mold at worst.

I think we can do better as an industry. I think Tamiya, from the couple of their kits I have, also has the best molding quality out of all manufacturers. The Volvo 850 wagon I have, and the Jeep Grand Cherokee, for example, have 0 flash.

The Japanese learned long ago the secrets of quality from two Americans- W. Edwards Demming, and Philip Crosby. Perhaps the rest of the industry should begin to learn from them, too.

Some argue quality costs more. Perhaps a little initially, but it pays for itself in saved defects, repeat customers and your reputation.

Charlie Larkin


Those heavy mold lines were a serious issue--AND Dave Metzner took the factory to task over that, trust me! The Chinese company who does model kits for Moebius is one that both Dave and I have a lot of experience with--to my mind's eye, the first run of the Hudson Club Coupe was an anomaly. Just opened my production kit of the Convertible (bought off the shelf, not my complimentary kit from Moebius) and the body shell in that kit is El Perfecto! Nary a mold alignment problem--in fact this body shell rivals anything done by any model company, anywhere, any day.

Art

#30 1930fordpickup

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Posted 02 July 2012 - 03:04 PM

Just opened my production kit of the Convertible (bought off the shelf, not my complimentary kit from Moebius) and the body shell in that kit is El Perfecto! Nary a mold alignment problem--in fact this body shell rivals anything done by any model company, anywhere, any day.

Art

Art this is what I would expect from a brand new tool from 2011/2012 to be . The best I have held in my hands .