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Dealing with the body parts mould/parting lines


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Hello! 

So my main enemy is those lines. I'v always seem to struggle these evil things. But only on body parts. 

So this how I try to deal with them. 

1. mark them down with permanent marker

2. sand down

3. spray some primer

4. cry because now there is shallow mark line what used to be  high line. 

Seems no matter how I sand it, it always shows through primer and other coats. Now I tried to put some putty on that line, but earlier builds I have failed to make this line disappear even with putty. 

Is there anything I can do? 

Pekka 

 

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1 hour ago, roymattblack said:

I remove the mould lines by dragging a sharp blade backwards over them, then a final sand with a sponge nail file block.

Always works for me...

Likewise. A very useful nail file block is one that comes in a set of three from Poundland (provided they're still stocked, I bought mine over a year ago). Four sides, coloured - file, buff, smooth, shine.

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3 minutes ago, MR2Don said:

Likewise. A very useful nail file block is one that comes in a set of three from Poundland (provided they're still stocked, I bought mine over a year ago). Four sides, coloured - file, buff, smooth, shine.

I'm currently sanding some mould lines using sanding sticks, I think the next time I go near a Poundland I'll have a look for those nail file blocks as they sound like a bargain alternative.

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14 minutes ago, johnlambert said:

I'm currently sanding some mould lines using sanding sticks, I think the next time I go near a Poundland I'll have a look for those nail file blocks as they sound like a bargain alternative.

They are great as being sponge, they conform to the shape you are sanding...

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Are you sure that you are sanding enough and that the permanent marker isn’t giving the illusion of shadow under the primer? Or that the seam has only been sanded away from one side ?

 

Just a couple of couple of thoughts . . .

 

Nick

 

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Just to give you an idea of what I managed with sanding sticks on a Tamiya Toyota Celsior (also known as the Lexus LS400).

 

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Typically of Tamiya the mould lines are quite fine, but sometimes these can be the worst to eradicate.

 

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The rear bumper was probably the worst.

 

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Sanding was done with 240, 320 and 400 grit sanding sticks from Albion Alloys.  The grit numbers sound very coarse but are actually quite fine.

 

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After a coat of Tamiya surface primer.

 

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Seems to have been pretty effective.

 

Some kits put up more of a fight, I'm surprised this one seems to have been fixed first time; usually I regard the initial primer coat as almost sacrificial in order to highlight imperfections that aren't visible on the unpainted plastic.

 

 

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8 hours ago, alteregoni said:

I just wander why on earth that ridge type line turns into ditch type of line...? 

I could be completely wrong, but looking at this from an engineering perspective, if you imagine the parts of the moulds coming together there is always likely to be a very small gap between them, and the molten plastic under pressure will find its way into this gap creating the ridge. As for the ditch, if the two parts of the mould aren't perfectly alighned, one would be very slightly lower than the other, and even a fraction of a millimetre would be visible when primered. As you've sanded the high side when you got rid of the ridge, it will be just the low side which is untouched and unless you've sanded the 'high' side down far enough to be level with the 'low' side, the bit of the low side which abuts the ridge will appear as a ditch.

 

As for how to fix it, I can't really add anything to what has already been written, but as John said I tend to consider the first coat of primer as an indicator of which mould lines I've missed.

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1 hour ago, Nick Belbin said:

Are you sure that you are sanding enough and that the permanent marker isn’t giving the illusion of shadow under the primer? Or that the seam has only been sanded away from one side ?

 

Just a couple of couple of thoughts . . .

 

Nick

 

Yes marker was completely sanded of.

But when I read through these replies, I wonder that maybe I'm not so patient. 

Really good notes here, many thanks! I decided to put some putty on those lines, like really pushing it tight to surface. Now that I sanded it down, it really show that there was that "cap", and putty filled that up. At least I hope so, putting some primer on it so let's see result then. 

Pekka 

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The other thing is that when you sand the plastic it will become 'dull' and any unsanded plastic will remain shiny. So if you can still see shiny plastic, it means that you haven't reached it yet: you want to keep sanding lightly until each side of the seam becomes dull.

 

And yes, patience is required - it's quicker in the long term! 😉

 

Nick

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On 9/20/2020 at 11:05 AM, roymattblack said:

I remove the mould lines by dragging a sharp blade backwards over them, then a final sand with a sponge nail file block.

Ditto.

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