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injection molding issues fix?


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#1 Brian_B

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Posted 30 August 2012 - 12:16 AM

hello all,

I have not touched a model in years. Starting my first one tomorrow. I need your help.

I tried to take pictures of this..but I can't get the issues to show up on camera. :rolleyes:

I have been through MrObsessive's tutorial many times.

http://www.modelcars...eling 101&st=0

I do not see anything in his tutorial that describes what I have.

These are all down the sides, on the roof and trunk on mine. Its bad. The model is one of the older AMT 49 fords...cast in gray (not the later white). Yes..a lot of flash to remove too. :(

I cannot feel them with my thumbnail, but there is some sort of imperfection where the plastic flowed together in the injection molding process.

Can anyone explain what to do here?

I know that sort of thing will ghost through the paint. Anything and everything shows on the 1:1 cars I have painted.

thank you in advance.

Edited by Brian_B, 30 August 2012 - 01:43 AM.


#2 Mike Kucaba

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Posted 30 August 2012 - 04:41 AM

Short of actually seeing it,you may need a new body. I'd scuff the body with 0000 steel wool and shoot a coat of primer and see how bad it is after that.

#3 Brian_B

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Posted 30 August 2012 - 05:06 AM

Short of actually seeing it,you may need a new body. I'd scuff the body with 0000 steel wool and shoot a coat of primer and see how bad it is after that.


thank you. My first kit since i was a kid..and the body is screwed. :(

#4 Fat Brian

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Posted 30 August 2012 - 09:01 AM

As long as you can't feel an imperfection it should be okay, I agree that the best thing to do is shoot some primer and see what happens.

#5 Guest_G Holding_*

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Posted 30 August 2012 - 09:49 AM

WHOA BRIAN !!! Don't think the "body is screwed" First I don't think you have an issue....shoot a coat of primer on...I like grey so I can see imperfections...Ghosting only occurs with hot lacquers, and those marks are just in the plastic, not on it. You can use a barrier as Bill describes..he uses future / pledge .So don't worry, grab your kit and start havin fun...IF you screw it up..good learning, grab another and make it better than the last.

#6 Brian_B

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Posted 31 August 2012 - 09:32 AM

Thanks guys. I got tied up and didn't get to play with the body. This is not a great picture, but maybe you can sort of see it in the middle of this door.


I am trying to set up a folding table now to get started cleaning up some of the major parts to get started.

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#7 Mike Kucaba

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Posted 31 August 2012 - 11:05 AM

That is not a disaster. Clean the body real well with some soap & warm water and scrub with a brush and some abrasive cleanser,then prime lightly and continue with the build. Don't forget to wash all the parts too.

#8 Guest_G Holding_*

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Posted 31 August 2012 - 11:29 AM

As Mike said...paint that puppy!

#9 Brian_B

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Posted 31 August 2012 - 12:23 PM

Thanks guys.

I have been cleaning flash, mold lines, and the little nibs (don't know what they are called) off of parts tonight. I will definitely clean everything up and use soft scrub and brush on it before primer.

I will have to wait until these storms (from the gulf all way up here) blow over to go outside and prime.

I started gluing up the engine tonight.

#10 Art Anderson

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Posted 01 September 2012 - 06:56 AM

What you may be seeing is the "flow" pattern of the molten plastic into the molds during the injection molding process. Styrene plastic is heated to the consistency of warm pancake syrup, then injected into the molds under tremendous pressure (upwards of 100-tons or more) and then the molds are cooled by circulating cold water through a water jacket which is quite similar to the water jacket in your car's engine. This solidifies the molten styrene so that when the mold is opened, and the parts ejected out, they are solid plastic parts. However, all the stresses pressed into those cavities of the mold will be present in the resulting parts, and upon painting with certain types of paints (lacquers, for example), those stresses tend to be "relieved" at least a bit, showing up as a pattern of "frosting", even severe crazing on the surface of the model part (body shell). Sometimes, those flow lines, especially on the largest surfaces of any model car kit (the body shell) can be visible, even felt at least slightly, but they can be dealt with almost always.

Art