Is flash a measure of quality?

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Posted · Report post

For years we read a line in almost every kit review that said, "...There was 'x amount' of flash." In some threads here, I see recurring references to how good or bad a kit is because of how much or little flash there is.

Does flash really matter? 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. Only once have I found flash so thick it made a solid piece out of part of a sprue sheet and muddled the detail of smaller parts. Maybe it's my age, but I think removing a blade of flash is just part of building and I don't use it as a noteworthy measure of a kit's quality. Registration is something else though. Thoughts?

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Posted · Report post

I think a kit with or without flash can still be good quality, but a kit without a lot of flash does add quality in my opinion.

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Posted · Report post

In my opinion, amount of Mold Flash is not a measure of quality. I think the most important thing in Model Kit is, how much parts there are and how well detailed are them. For me it usually doesn't matter, if there's some mold flash, because always there are mold lines what need to be removed too. Sometimes, yes, Mold Flash is very difficult to remove, that times mold flash really does matter. (for example little tie rods etc on front axles.)

What I think are the most important measures of quality.

1. How well detailed the parts are.

2. How Much parts does the kit include.

3. Parts fit nicely to each other.

4. Mold Lines and Mold Flash.

Maybe other people think different way than I do, but this is my opinion. ;)

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Posted · Report post

There's nothing more frustrating than having to re-engineer just about every kit part because of all the flash. To me, excess flash does say "poor quality."

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Posted · Report post

Maybe it's my age, but I think removing a blade of flash is just part of building and I don't use it as a noteworthy measure of a kit's quality. Registration is something else though. Thoughts?

If by registration you mean how well the mold halves or sliding mold sections align with each other, then that can definitely affect the amount of flash which is produced, not to mention the size of the molding seams. Excessive flash is usually taken to be a sign of the molds getting worn out and not mating as well as they used to, and later JO-HAN kits are often cited for this infraction, fair or not.

I don't see flash as a huge issue, and have never come across flash so bad that it discouraged me from building the kit.

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Posted · Report post

I think a kit with or without flash can still be good quality, but a kit without a lot of flash does add quality in my opinion.

Since my mantra is "less is more" I would have to completely agree. I just wouldn't poo-poo a kit for it the way I occasionally see on some threads.

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Posted · Report post

IMHO Flash says something about the time and effort that the company took is creating their molds. Flash is simply a result of the missmatch of the two halves of the mold and excess plastic seeping between the halfs. The fit of these molds has a direct impact on the fit of the parts. If the molds are waring out or warped, then the parts they make are fractionally off and will not fit as well. In todays world of CAD/CAM mold making they should fit togeather very well. If they don't the designer or the mold cutter didn't do their job properly. It is a bit like looking at the panel fit on a real car as an indicator of the manufacturers commitment to a quality build. Can you have a quality well fitting model with a little flash? Sure, I suppose it is possible, but a sloppy fitting mold is likely to produce sloppy fitting parts.

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Posted · Report post

A certain amount of flash is expected but when it completely distorts or webs together small pieces it does discourage me from building a kit.

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Posted · Report post

39chev4dr.jpg

Too much flash for me. Oh, wait, it's a resin body.

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Posted · Report post

"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

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Posted · Report post

"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

That being the case, why is it some kits have more of a propensity toward this issue ?

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Posted · Report post

stop whining about flash you bunch of sissies :D . Its nothing a sandpaper/blade couldnt fix, and...

There's nothing more frustrating than having to re-engineer just about every kit part because of all the flash. To me, excess flash does say "poor quality."

... if you dont like doing some preparation work with the kit why dont you buy a die cast completed model instead. Re-engineering is part of the hobby.

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Posted (edited) · Report post

Mold wear doesn't really affect flash that much. Warpage does, though. Really old tooling like the older Jo-Han stuff was made differently than today's molds because of the advent of CAD/CAM techniques. The old molds are made up of many pieces fitted, pinned and shimmed together. Over time corrosion sets in and starts pushing the pieces apart and warping the unit. The flash seeps out between the two main mold halves. Newer tooling is made from a solid block and is water cooled most often and really wouldn't warp.

How often do you see flash on new tooling versus old tooling?

Edited by Modelmartin

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Posted · Report post

stop whining about flash you bunch of sissies :D . Its nothing a sandpaper/blade couldnt fix, and...

... if you dont like doing some preparation work with the kit why dont you buy a die cast completed model instead. Re-engineering is part of the hobby.

They have flash on diecasts! They just paint over it!

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Posted · Report post

stop whining about flash you bunch of sissies :D . Its nothing a sandpaper/blade couldnt fix, and...

... if you dont like doing some preparation work with the kit why dont you buy a die cast completed model instead. Re-engineering is part of the hobby.

It's part of the hobby only because of lousy quality control by the manufacturers. And that was the original question: whether flash was a measure of quality (or lack of quality). And the answer is yes, flash is a reflection on a kit's quality (or lack of).

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Posted · Report post

I prefer flash over sink marks anyday

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Posted · Report post

Flash is a non issue for me because I sand every part any way. For me, it's no different than removing a mold line. Flash on a styrene kit is nothing compared to flash you'll get on a resin kit. Even then,it's nothing that a file and sandpaper won't take care of. What qualifies as low quality to me is inaccurate bodies that I have to fix to make them look right.

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Posted · Report post

Wait, I'm confused now after reading the last comment. Whats the difference between flash and moldline? (non-native-english speaker here)

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Posted · Report post

It's part of the hobby only because of lousy quality control by the manufacturers. And that was the original question: whether flash was a measure of quality (or lack of quality). And the answer is yes, flash is a reflection on a kit's quality (or lack of).

Dont worry I was joking anyway.

But I myself still dont see any issue on the flash/moldlines. I bet manufactures have thought about it and it might not be as simple as we think to prevent the flash when producing a kit. Remember they have to produce it in large numbers and machines get worn out in time. Plus if you want to stay in business you cant invest in ultra-ultra-space-fiction-quality technology if you dont have huge profits.

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Posted · Report post

Wait, I'm confused now after reading the last comment. Whats the difference between flash and moldline? (non-native-english speaker here)

Sort of the same thing, but flash is bigger-it's that thin sheet of plastic that sticks out from some parts.

This is flash:

moldingflash.jpg

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Posted · Report post

"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.

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Posted · Report post

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

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Posted · Report post

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.

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Posted · Report post

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!

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Posted · Report post

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.

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