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Getting rid of injection molding marks

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  • Member since
    October 2016
  • From: Louisiana Gulf South
Getting rid of injection molding marks
Posted by Mrchntmarine on Monday, May 2, 2022 10:14 PM

Ive never been very good at this.....  I have this older kit and would like to get rid of some of the more obviuos marks.  I have to say though that some of them are in hard to get to spots.  With the deck ones - am i making it worse?  1 is what they looked like and 2 is where i am now.   With what i have now at spot 2, will the primer and paint cover the scratches i can still see now?  Its smooth but looks scratched.  If i get them to this point, will it be noticeable after priming and painting?  Tks.

 

 

Keep on building!

  • Member since
    August 2005
  • From: Mansfield, TX
Posted by EdGrune on Tuesday, May 3, 2022 7:58 AM

Were there supposed to be photos attached?   Not seeing them

As to your question, paint does not correct poor surface preparation.   Scratches on the surface will show through paint ... unless you apply the paint too heavily.   Then that is a problem of its own.

Take the time to complete surface preparation before moving on

  • Member since
    October 2019
  • From: New Braunfels, Texas
Posted by Tanker-Builder on Tuesday, May 3, 2022 8:32 AM

Hi!

 Oh, You did a "Tanker-Builder"-LOL. No Photos! No ,Really, all kidding aside. Any Mold marks whether (inside a model) in an important Place and visible or on the outside cannot be hidden with paint at any time. Unless you pour the whole bottle on there! Even on decks, Which does happen, you have to work it out by sanding till it doesn't show ,THEN, sand with continually smaller and finer grits till all scratches and gouges are gone. Then Paint. The primer will cover or fill very infinite scratches and grooves( ones that are hard to see anyway).

     The final step is to sand the paint( primer) till it's glass smooth then check once more and finish coat! Yeah, Coming back to this I know which kit it is.And, Yes they are a pain! What I did with the last one (Remember, I do conversions a lot!) I cut the sharper edges off with my trusty plastic chisel. Then over filled them slightly, with Sprue Glue (White), and did what you are doing now. You are going to be good here. 

  • Member since
    October 2016
  • From: Louisiana Gulf South
Posted by Mrchntmarine on Tuesday, May 3, 2022 9:19 AM

hummm, weird - when i pull up this thread, i see the photo above

 

Keep on building!

  • Member since
    October 2016
  • From: Louisiana Gulf South
Posted by Mrchntmarine on Tuesday, May 3, 2022 9:23 AM

do you see it now?

 

 

 

Keep on building!

  • Member since
    September 2006
  • From: Bethlehem PA
Posted by the Baron on Tuesday, May 3, 2022 9:35 AM

As far as the linked image goes, it looks like it's stored in Google images.  When I click the link in the original post, I'm prompted to log in to Google (I'm currently logged out, on this machine and in this session). 

As far as fixing ejection pin marks goes, yeah, it's tricky.  It's like fixing any other surface mark-you will likely wind up removing surrounding detail.  You need to be prepared to touch that up or even replace the detail as necessary.

If the mark is in a relatively open area, with no surrounding detail (like deck planks), you can sand it away gently.  I have taken a small strip of sandpaper and wrapped it around the end of a pencil, that is, from one side of the end, across the end, and up the other side, and used that to sand the mark away.  I've filled the mark with putty as necessary, too.

I recently tried Perfect Plastic Putty, and it would work very well for this application, since you can apply it and then remove the excess with a wet fingertip.

You can use a chisel, or a knife blade, to scrape the mark away, too.  And if it's a deep mark, you can punch a piece of styrene of appropriate thinness, glue it into the mark, and then sand as necessary.

I haven't bothered looking for ready-made tools for this particular task, but you might want to try a search and see, too, if you're not sure about improvising with the tools you may have at hand.

You can always practice removing the marks on the inside of a model, like the inside of a wing surface, hull, fuselage, car body, etc.  That way, you can find something that works best.

The bigger the government, the smaller the citizen.

 

 

  • Member since
    September 2006
  • From: Bethlehem PA
Posted by the Baron on Tuesday, May 3, 2022 9:52 AM

I forgot to mention that you can put down tape on the surrounding area, if possible, to protect it while you remove the marks.

The bigger the government, the smaller the citizen.

 

 

  • Member since
    May 2009
  • From: Poland
Posted by Pawel on Tuesday, May 3, 2022 10:02 AM

Hello!

I can't see the first photo, but I can see the second one. And I'll tell you: you're almost there! You got rid of the knock-out mark, now you have to get rid of the scratches and that should be easily done with finer sandpaper. There's also this cool tool called glass fibre pen that can get very handy for jobs like this - it can be bought in electronics supply stores.

My procedure is to fill the mark, to make sure it's higher than the surroundings - I take molten sprue or CA for this - and then I sand it if the place has good access or scrape it with my hobby knife if the access is bad. Then I smooth the surface with fine sandpaper or glass fiber. You can also try putting some primer on and sand it again, to be sure the surface is OK.

Hope it helps - have a nice day

PaweĊ‚

All comments and critique welcomed. Thanks for your honest opinions!

www.vietnam.net.pl

  • Member since
    January 2020
Posted by Space Ranger on Tuesday, May 3, 2022 10:05 AM

Punch disks from thin sheet styrene to fill the circles as much as possible and glue them in the ejection pin marks. Fill any remaining gaps with putty - not a water-based putty, but a solvent-based putty which will adhere better to the plastic. When all is dry, sand flush with the surrounding plastic.

  • Member since
    October 2016
  • From: Louisiana Gulf South
Posted by Mrchntmarine on Tuesday, May 3, 2022 11:20 AM

Thanks all.  Reason im asking is that ive never been good at this and found a thread or 2 the other day that read that small areas like the one i have - the tiny scuffing would be filled by primer as to be not visible.  Just checking before i do too many more....  

 

Keep on building!

  • Member since
    September 2012
Posted by GMorrison on Tuesday, May 3, 2022 11:26 AM

Put some primer on and see what happens. I would think that a few coats with micro mesh sanding in between would do the job, and yes it would be worthwhile.

Looks like the Hawaiian Pilot.

 

Bill

 Modeling is an excuse to buy books.

 

  • Member since
    October 2016
  • From: Louisiana Gulf South
Posted by Mrchntmarine on Tuesday, May 3, 2022 11:50 AM

Yes - Hawaiian Pilot. I chickened out on cutting up the hull. haha. cant visualize how i would make adjustment to make the rudder work.  Im thinking when im really looking for something to do, ill get a test kit to practice on for that.  I like the idea of the fiber brush. Some of these injection marks are in hard to reach places.  Heck, up towards the bow the was this huge stub sticking up - about the size of a pencil eraseer - haha.  Had to disect it into 4 pieces to get it off.

 

Keep on building!

  • Member since
    October 2019
  • From: New Braunfels, Texas
Posted by Tanker-Builder on Tuesday, May 3, 2022 11:58 AM

Hi Again!

  Oh Boy! That kit is showing it's age for sure. I would just do what you can .Question, why would you want to cut on the hull? The molded waterline is close to her ballast waterline. Don't even try to make a working Rudder, It's not worth the trouble!

  • Member since
    March 2003
  • From: Towson MD
Posted by gregbale on Tuesday, May 3, 2022 1:19 PM

The Baron's suggestion for wrapping sandpaper around a pencil eraser is a great one.

You could also use a small dowel, the head of a mid-size nail, or even a length of large-diameter sprue, and super-glue a small disc of sandpaper at the end...makes a great home-made tool for those sink-marks and similar flaws, easy to take care of small spots and can work into 'tight' areas without harming surrounding detail.

Greg

George Lewis:

"Every time you correct me on my grammar I love you a little fewer."
 
  • Member since
    July 2003
  • From: Building models on my kitchen counter top~somewhere in North Carolina
Posted by disastermaster on Tuesday, May 3, 2022 2:27 PM

Here's my "hi tech" fix using a paper punch with your choice of sandpaper.

The picture should be self explanatory.

 

On the kitchen counter top in North Carolina

  • Member since
    April 2020
Posted by Eaglecash867 on Tuesday, May 3, 2022 5:09 PM

Mrchntmarine
Ive never been very good at this.....  I have this older kit and would like to get rid of some of the more obviuos marks.  I have to say though that some of them are in hard to get to spots.  With the deck ones - am i making it worse?  1 is what they looked like and 2 is where i am now.   With what i have now at spot 2, will the primer and paint cover the scratches i can still see now?  Its smooth but looks scratched.  If i get them to this point, will it be noticeable after priming and painting?  Tks.

Mrchntmarine, what are you using to fill the pin marks before sanding?  You should fill them first instead of trying to just sand them out.  You'll make depressions in your deck surface by just sanding. 

I fill pin marks the same way I fill seams.  Just fill the pin mark with a large enough dab of super glue to fill the whole pin mark (I use Gorilla with the light blue cap) and let the glue cure for a few hours.  After it cures, I use a black sharpie to scribble on the glue blob and just a tiny bit of the surrounding plastic.  The black sharpie serves as a gauge for sanding the super glue flush with the surrounding plastic.  Then wet sand those spots until all of the black sharpie is gone.  Keep in mind that you'll still be able to see the pin mark when the black sharpie is all gone, but that's only because the super glue is translucent.  When you put primer on that spot, you won't be able to tell there was ever a pin mark there.  For the areas you're pointing to in your photo, using sanding sticks should work well.  Alpha Abrasives used to make them, and they came in a pack of assorted grits.  The sanding sticks are about 3/8" wide with wet/dry sandpaper on both sides of a high-density foam core.  Looks like Flex-I-File has taken over that line, so you should still be able to get them.  I find that I mostly just use the yellow and red sanding sticks to get a nice, smooth surface...and the yellow is aggressive enough to level the cured super glue without leaving deep scratches and does minimal damage to surrounding detail if you accidentally hit a raised detail like a rivet or something.

If you prime and find that you can see a tiny void or something in the filled pin mark, the great thing about the super glue method is that you can use it again to dab into that little void.  You can do that right on the primer, because the glue will dissolve and combine with the primer to essentially make another nice, solid, little plastic patch that can then be sharpied and sanded smooth.

"You can have my illegal fireworks when you pry them from my cold, dead fingers...which are...over there somewhere."

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