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Molding plastic
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  dcorb

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Posted: December 13 2008 at 6:34pm | IP Logged Quote dcorb

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  dcorb

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Posted: December 15 2008 at 8:54am | IP Logged Quote dcorb

Work has been keeping me busy and now it is -8 with a wind chill of -30. I doubt I will be doing much work in the shop for a while.

In the mean time I am going to pickup some plaster and clay to play with in the house to see if I can make a mold..  

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  midmichigun

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Posted: December 15 2008 at 12:51pm | IP Logged Quote midmichigun

dcorb,

I am back home. Doing Homework that is... As you know, work wants results... and if I slip down in workload...

I just stopped at NAPA for some Tiger hair. 1qt can was nearly $20.00. I could swear it used to be cheaper!  I saw that they had some long strand there also. However, I opted for what I knew: the short strand. I figure that it would be easier stuffing it into the molds... vs. long stringy stuff.

While the wife is away.... I will play! She hates the smell of autobody stuff, however as noted with your temps... it is getting cold outside.

While looking at the Napa brand filler, it said that it was "waterproof" and fiberglass reinforced. While they gave me a CAS number, they didn't mention the total volumes of components. However, they do state that there is Talc in this stuff.

So I will begin to prep my plaster molds. Hopefully I can post results later this week. I was going to stop off and get some West System epoxy. Going with a solid casting will be good with this stuff.

I also want to start making my "ergo" grip for an AK.

Recently I was looking at the Plastic Dip that you can buy at various stores. Anyone try this? If you get the black and add some sand, it would give you a very positive grip. However I believe this stuff crack over time? Can anyone confirm this.

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  Inabadhood

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Posted: December 15 2008 at 1:12pm | IP Logged Quote Inabadhood

Hey Dcorb,

I hear you on the weather!  A few inches of snow on top of 1/2" of glare ice covered roads S(_)CKED for rush-hour this morning!  It's warming up to our 'HIGH' temp today of -4 Degrees F, but the windchill in St Paul is still around -25 Degrees F, and we're going to have an overnight low of -9 DegF, with windchills close to -40 DegF tonight!!!

YUCK!

My 23 mile commute this morning took me 1 Hr, and 45 Minutes!!! 

Thankfully, work is picking up for me as well around here!  Luckily my 'workshop' is in the basement not too far from the gas fireplace! 

Although it's not as large as yours, Dcorb!

As for these plaster molds, I was wondering, how long does it take for them to dry?  Like a smaller mold, maybe the size of the pistol grip one...  I mean, how long until it FULLY dries?  I'd imagine with our current temps, there'd be serious problems bringing a partially-wet mold out into the cold temps.  Likely resulting in cracking, etc., so how long must you wait until it's fully dried?

Any molding/casting work I do will likely be done outside in my shed, and it's not even REMOTELY warm out there...  With a space heater, it'll get around 40 degrees to keep it just above freezing, but not with this week's temperatures!

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  midmichigun

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Posted: December 15 2008 at 1:58pm | IP Logged Quote midmichigun

inabadhood,

Just checked on my AK pistol grip molds (in plaster) for you. They sound and feel dry. They have been sitting on my wifes dryer for..... 16 days... ish. Remember I have been gone for 11days. The room has a woodstove in it... which is a dry heat. Dimensions for comparison are 5.25 long, 3.25 wide and .75 deep (inches) for each side of the mold. If I wasn't so cheap, I would make the molds BIGGER for more strength... and also reinforce with metal.

However, there is a tipping point where you just go with a better mold material (like metal) if you want ultimate strength.

I would use a plaster mold within a few hours of pouring, it you plan on doing simple stuff, and you are NOT pouring in HOT material. Please note you probably won't have full strength either.

However, it is best to wait to dry. Plaster is nice since if you pour outside, you can bring it in to dry... there are NO smells or harmful agents released.... I just wouldn't breath in the dust when you are making the mold. If you can convince your wife, you could also put the plaster mold in her oven on a low heat setting... or my favorite... above the "vent" burner on our electric stove. Nice gentle heat.. Wife can cook... and my molds dry out. I don't know what would happen if you took the wet mold outside however... never tried it... but you could assume it would crumble or crack?

As an aside, I got a FREE electric oven for my workshop... as in a full size baking oven. That way I can powdercoat and make all sorts of crazy things without trashing the wifes oven. Can also boil water... etc... If size was a problem, I would have looked into one of the smaller "broiler" ovens.

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  Inabadhood

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Posted: December 15 2008 at 2:21pm | IP Logged Quote Inabadhood

Cool!  Thanks for the great info!

I think I might be able to convince the wife into letting me do some of the mold stuff indoors now instead...  She is always apprehensive to agree to let me do any of my 'hobby projects' inside the house!

I wouldn't DARE doing something like parkerizing indoors, and I generally know what can be done indoors, and what cannot! 

As for the mold stuff, I wasn't sure about the plaster dust indoors, etc...  I wasn't sure, but I didn't think it would be too harmful though...  Now, some of my other 'experiments' that I've done over time have REALLY made my wife question my sanity!!!



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  Stomper

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Posted: December 18 2008 at 11:12pm | IP Logged Quote Stomper

Hey Folks,

I actually do a lot of casting in resins and rubbers to make replica movie props... I'm fairly well known in the world's Star Wars circles for my work by all the "geeks" (literally around the world) that are into that particular genre.

 

I use stuff called Smooth-Cast 325 from: http://www.smooth-on.com/ 

You can tint it to just about whatever color you want and is TOUGH STUFF when you cure it according to the directions!

 

Here is an example of my work...

The real scope is on top... NO paint, that's the tinted color:

 

Here's a couple "scratch built pattern" Sterling SMG grips and end caps I made and casted:

A Stormtrooper Blaster I made based on a Sterling SMG:

 

 

 

 

And a Biker Scout blaster I made by molding an old Kenner Toy from the 80's...

 

this one is in Smooth-Cast 325 (no paint):

 

I also make stuff cast in Rubber...

 

The rubber stuff, and silicon molding materials I get on eBay from "Aeromarine Products": http://stores.ebay.com/AeroMarine-Products_W0QQssPageNameZst rkQ3amefsQ3amesstQQtZkm

 

 

Hope that helps!!

 



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  Inabadhood

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Posted: December 18 2008 at 11:48pm | IP Logged Quote Inabadhood

WOW!!!

That's some NICE looking stuff!

Great to see you're a member here...  I'm sure we could all learn a LOT from your experience in this too!

I love the Sterling work!  Looks great! 

(It all does, but I've always had a soft spot for the Sterling)

What are your strongest particular interests in gun building?  Are there any particular guns or homebuilt ideas we might be able to help you out with as well?

I love this place because everybody contributes somewhat to the knowledge base here, and we all benefit from it.  Welcome, and thanks for sharing some of your beautiful work!  I hope to see more of your stuff soon!

-inabadhood

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  gundoctor

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Posted: December 19 2008 at 12:12am | IP Logged Quote gundoctor

Excellent work.  I have some of the smooth-on resin to play with and it looks great in your hands.
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  Stomper

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Posted: December 19 2008 at 9:43pm | IP Logged Quote Stomper

Thanks guys... sorry for the STUPID typos... I can't edit my posts!!

Since you asked... I already learned about the home-brew parkerization in that awesome tutorial you posted... can't WAIT to get that going!!  I have a bunch of 20-round M-14 magazines that I'm going to convert to work in my .308 Galil... they're nice quality Taiwanese knock-offs, but they're blued... and REAL combat weapons/parts are parkerized IMHO.... LOL!  I also just scored a nice spot welder, and I plan to add the front and rear catches to them (after I fab them up) so I want to parkerize them when I'm done...  I'm also wanting to accuire a COMPLETE folding stock assembly for my Galil... then there's the M4A3 carbine I'm building a piece at a time... anyway, I don't want to hijack this thread any further!!  Looking forward to learning and contributing to these forums!!  

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  gundoctor

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Posted: December 19 2008 at 10:14pm | IP Logged Quote gundoctor

Stomper,

I have a question about mold making.

I am building some patterns and plan on making my initial molds out of some Shore A 50 urethane and parts out of a custom Shore D urethane.  Concerning internal features of the mold like fire control group area and magwell, I was considering making these out of aluminum.  By using a rigid aluminum shell for the molds, and making these internal mold pieces of aluminum where they are firmly held by the mold shell (by pins etc), I was hoping to get better parts and mold life.  My plan would be to reuse the aluminum  mold parts after the original mold urethane is no longer usuable, simply pouring new urethane in.   Do you think this type of "hybrid mold" is feasible?  I hope to eventually go to silicone molds (still hybrid I think) but am using the urethane for molds until I get the hang of it because it is cheaper.

My parts are also going to be hybrids.  I am building the patterns so that I can use some metall inserts in the lower I am modeling.

I am taking my time on this but excited about making my first pours.  I scored a 10cfm vacuum pump that will pull 15 microns and an incubator type oven (can set any temp from 0-100c) that will allow me to use heat cured urethanes.

Doc
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  dcorb

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Posted: December 20 2008 at 1:59pm | IP Logged Quote dcorb

Stomper

Your work is fantastic!

This is getting very interesting now!

Once my work schedule frees up next month I am going to get started.

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  weaponeer

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Posted: December 20 2008 at 4:44pm | IP Logged Quote weaponeer

I do like where this is heading...
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  dcorb

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Posted: December 20 2008 at 6:47pm | IP Logged Quote dcorb

Did a little surfing in the star wars forums

http://www.tk560.com/phpBB2/viewforum.php?f=21

Tip on clay:

There are different types of clays. There are water clays and then there are oil based clays, and then there are clays with sulphur in them. Since you mentioned you want to use silicone to mold the sculpture then you should stick to sulphur free clays. Sulphur inhibits the curing of a good many different types of silicone. There are some silicones that are not affected but it's best not to have to worry about it.

So that leaves either water based clay or an oil/wax based clay.

Oil/Wax based clays come in multiple hardnesses and can vary on how they work with tools and get smoothed out. There are several different fine clays that are sulpher free. I'd not recomend Prima Plastilina, even though it is sulphur free it can be hard to get very smooth.

Other then clean clay Chavant makes a very nice sulpher free clay also which I heard is nice to work with.

Water based clays are really easy to work with allow for quick blocking out of shapes and take details nicely. The bad side is that you need them to be fairly thick, kept moist and they do shrink and can crack.

There is a special water based clay called WED (EM-217). It has some very nice properties to it and is what most of the mask making and special effects companies use if water based clays are called for. It is specially formulated and contains a percentage of glycerin instead of water which reduces the shrinkage and allows it to retain moisture better. DEpending on your area you might be able to get some locally. Wed clay is only made by the Laguna Clay Company. If it's not made by them it is not WED.
http://www.lagunaclay.com/

I've known people to keep WED sculptures for months by covering them with a plastic bag and spraying them with a light mist every other day or so depending ont he tempature and climate. WED is relative cheap to buy in bulk, but expensive to ship.

I've molded a few sculptures and will feel free to insert opinions in that aspect when you are ready to hear them also.

PS NEVER use plaster of paris unless it's to make something for breaking.

================================================

Tip on concrete:

Don't use concrete at all. Use cement. Concrete has rocks and cement does not. If you use cement just simply use S-Type masonry cement. It's easily found at any hardware store that sells cement or concrete. S-Type masonry cement is a mixture of portland cement, lime and sand. It comes in 60 to 90 pound bags and is usually under $5.00 a bag. To make your molds as hard as possible use as little water as possible. Look for a liquid concrete / cement hardener additive where you purchase your cement. Use this instead of water. Your mold will be way harder than a cement / water mixture.

Some hardware stores carry hydrolic cement. It has all the above ingredients of the masonry mix including a powder form of the hardener additive. The only thing is that you still have to add water. If you can't find the liquid hardener you may try using this type of cement.

To help in getting surface bubbles out use on of those cheapo type black sponge brushes with the handle. Once you have the form you want dip the brush "TIP" in water and go over the surface to smooth everything out how you want. A regular type brush will leave surface marks like a broom stroked concrete slab. Don't apply to much water at one time to the sponge.

If you make your cement mold on a table or wood use cheap plastic (grocery store bag) underneath the cement. It will be easier to remove without sicking and chipping your mold edges.

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  Stomper

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Posted: December 21 2008 at 8:17pm | IP Logged Quote Stomper

gundoctor wrote:
Stomper,

I have a question about mold making.

I am building some patterns and plan on making my initial molds out of some Shore A 50 urethane and parts out of a custom Shore D urethane.  Concerning internal features of the mold like fire control group area and magwell, I was considering making these out of aluminum.  By using a rigid aluminum shell for the molds, and making these internal mold pieces of aluminum where they are firmly held by the mold shell (by pins etc), I was hoping to get better parts and mold life.  My plan would be to reuse the aluminum  mold parts after the original mold urethane is no longer usable, simply pouring new urethane in.   Do you think this type of "hybrid mold" is feasible?  I hope to eventually go to silicone molds (still hybrid I think) but am using the urethane for molds until I get the hang of it because it is cheaper.

My parts are also going to be hybrids.  I am building the patterns so that I can use some metal inserts in the lower I am modeling.

I am taking my time on this but excited about making my first pours.  I scored a 10cfm vacuum pump that will pull 15 microns and an incubator type oven (can set any temp from 0-100c) that will allow me to use heat cured urethanes.

Doc

 

Hey Doc,

Sorry for the late reply!!  Although I have this topic marked as "watched" I still don't get any email notices... I'll have to tinker with my account settings and see what the dealio is...

As for your question... it's better if I could see photos of what you are intending to do, but let's just "assume" you are trying to mold an AR-15 lower... You can use just about any material you want to make the molds with, but when you have internal details you need to capture you DEFINITELY want to use something that is flexible and has some give to it so you can "shake/flex" your master pattern out of it. 

The main reason I would suggest using a good RTV silicon instead of the urethane stuff is silicon is "slippery" and very few things will stick/bond to it.  This stuff is an art-form on the same calibre as gunsmithing and machining, it takes time, pratice, and RESEARCH.  It's not really possible to "teach" this stuff "from the hip" in a forum post, so the best advice I can give you is to go to a few prop-building websites and read, read, read!  There are tutorials glalore (some written by me) with progress photos showing you the visual details (ALWAYS the best way to learn).

As for www.tk560.com I have been good friends with the owner of that websight for a few years now.  His name is Jim (lives in Texas) and is all too talented and always willing to help out those looking to learn.  Although the website started out as a showcase for making your own Stormtrooper armor and Star Wars props, it has grown beyond just "Star Wars" stuff.  The great thing about all of this is that you can take the priciples and techniques used to make "nerd stuff" and apply them to making totally awesome weapons systems that nobody has ever seen before!

 

Here is a list of a few websites that will help you all out (I go by "Stomper" or "Stomper63" on every forum I'm on):

www.tk560.com (main website)

http://www.tk560.com/phpBB2/index.php (website forums)

http://www.imperial-fleet.com/BBC/community/

http://diyprops.forumotion.com/forum.htm (this is a new forum, but has a few usefull ideas)

www.smooth-on.com (I really can't stress enough how good this site is for ideas and materials!)

 

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  Inabadhood

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Posted: December 22 2008 at 11:01am | IP Logged Quote Inabadhood

WOW!  Great info & Links!!! 
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  Stomper

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Posted: December 27 2008 at 2:46pm | IP Logged Quote Stomper

Here is another link to a fantastic tutorial that illustrates making two-part silicon molds... you can EASILY apply the shown techniques to making replica firearms parts!!

  http://www.paint-sculpt.com/tutorials/mold-making-tutorial/m old-making-tutorial-overview.html

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Posted: December 27 2008 at 10:24pm | IP Logged Quote dcorb

Stomper wrote:

Here is another link to a fantastic tutorial that illustrates making two-part silicon molds... you can EASILY apply the shown techniques to making replica firearms parts!!

  http://www.paint-sculpt.com/tutorials/mold-making-tutorial/m old-making-tutorial-overview.html

That is a great tutorial. I think I might be able to make a mold after all.

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  midmichigun

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Posted: January 01 2009 at 6:45pm | IP Logged Quote midmichigun

Ladies and Gentlemen,

I have been off the forum some time. Couldn't get into the forum with my Home Computer, so I tried my laptop. Also lots of home problems (water/ power/ furnace).

Anyone been trying any mold making and plastic casting?

Stomper has provided us some good references and tips...

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  Stomper

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Posted: January 01 2009 at 6:53pm | IP Logged Quote Stomper

Well... I have been making castings for the last few days like a maniac trying to get caught up with my backlog... but I suppose that doesn't count towards your question... LOL ;) 

Sorry to here of the tribulations... if'n you were close to me here in Oregon I'd come have a look at your furnce for you... since that is my full-time job... fixin' HVAC-R stuff.

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