Monday, July 26, 2010

Smush Molds Vs Sprue Molds - A WINNER!!!

Havent I had this post before?  Yes...but I'm always thinking.  Especially when I have issues.  And this post about Shrinkage Rate got me thinking...

Some of my pieces are bigger than they should be.  Again, these are silicone molds, not steel.  Pressure can distort your mold and cast.  And some of these pieces being bigger are causing fitting issues.  Whats up?

And then it hit me...Smush molds DO NOT give a true cast.  It may look close, but it will invariably always be bigger.  When there is a 3%-5% shrinkage rate, how is this possible?  With "Smush Molds" you have exactly that.  2 halves of the mold are filled and then smushed together. guess is, you have slightly overfilled the mold cavity.  So when you put the 2 mold halves together you are forcing the mold cavity to try and hold as much of the resin as possible.  And slightly distorting your mold and cast piece.  The "extra" resin get forced into the only available space left...The space in between the mold.  This then separates the mold ever so slightly and keeps the mold from fully being closed and gets added to the cast piece thickness. 

Oh it isnt much...but it can be.  Maybe only .006"...I had one piece that was .033"  thicker.

With a "Sprue Mold", the mold is already together.  The resin isnt "stressed" into any cavities.  There is no real pressure put on the mold so there is much less distortion.  Much like water running into a crack.   And because of this, you WILL then fully be able to notice your 3% Shrinkage Rate.


IT IS IN MY OPINION THAT...While smush molds require less work at the mold stage and are easier to make and use...And that they do allow for parts with greater detail to be made much easier,  SPRUE MOLDS GIVE A TRUER MORE ACCURATE CAST.  

Saturday, July 24, 2010

Shrinkage Rate

What is "Shrinkage Rate? "  Is it important?

Shrinkage rate is the amount a cast will deviate usually in a descending format from the original master.   When you make a cast inevitably it will shrink.  Engineers and scientists and people with lots of signed pieces of paper on their walls have determined that there is roughly  a  3% -5%  Shrinkage Rate for resins.

And I say "POPPYCOCK!!!"   I dispute this based on 1 thing and 1 thing only...imperfection.

Not to be arrogant and not to cause trouble.  Ever here of a joke that goes...what 10 000 lawyers at the bottom of the ocean?  A good start.   Well next in line are Engineers.  Why?  Because 99% of Engineers have never been outside of their office and seen people putting their calculations to work.  In todays imperfect world their is only one constant.  Their is only one thing in life that IS perfect.  Its math.  Numbers are beautiful.  There is no grey.  Only black and white.  Right or wrong.  And you can make numbers do whatever you want them to.  Their only flaw is the people using them.

On paper...ON PAPER...everything looks good.  Paper doesnt have any factors.  No outside influences or interferences.  Paper doesnt have  "variables".    In the real world, there is EVERYTHING fighting against you.  I did construction.  Sheetmetal.  Man...  Everyones blueprints were based on them being the first ones on site.   Well now I have to work around the electricians work or this beam got missed and is in my way...lots of little things.  According to the blueprint everything fit fine.  Um...yeah.

Engineers are the pain in my ass.

The same applies to casting.   You can say there is a 3%-5% shrinkage rate.  Sure.  Based on WHAT?  Is that for 2 tablespoons of mixed resin or 2 cups or 2 gallons?  Whats the temperature outside?  Hows the humidity?  How big is the actual piece you are making?   AND THE BIG QUESTION>>> How much pressure are you putting on the mold halves when casting?  How far above sea level are you if at all?  What method(s) are you using to cast? Smush?  Sprue?

These are soft silicone molds...not steel injection molds.  There is give and play in the mold.  You can squeeze and flatten the mold if too much pressure is used.  The mold can separate and the pieces can ACTUALLY GET BIGGER if not enough pressure is put on the mold halves.  So where is the shrinkage rate then? 

These are important things to consider.   And thats why sometimes the pieces need to be fitted.  Because shrinkage rate is based on perfect conditions.  We live in a imperfect world.

Monday, July 19, 2010


What Tools do I use?  The tools I use for casting are quite simple and very cheap.  Most of the stuff I have, I have bought at the Dollar Store.  From exacto knives and blades to gloves and mixing sticks.  But there is always one specialty tool.  And there is here too.  Or at least there is for me.   Yed Micronauts are based on a 5 mm system.  But sometimes there are slight deviations.  Most normally a 3 % shrinkage rate.  I drill all my own holes as opposed to casting them with the exception of the little alignment pins in the torsos.  And I do  this manually.  It get hard if you make to big a hole at once.  So I do it slowly.  I start with a drill thats about .040"  in diameter and worm my way up a few number drill sizes at a time till the hole fits whatever it fits.  I would end up drilling the hole about 30 times or so.  Im wearing half gloves with a leather palm and no fingertips and my fingertips are very sore.  And when I use the smaller drill bits, they used to drill backwards into my palm because they were so small.   I have about 10 of the holes still in my palm.  lol

Dollar short and a Day late.  So I just came home from searching the town.   Mr.  Schultz  showed me exactly what I was looking for.    And I had something.  A ratchet style small tap handle.  Except it couldnt handle drill bits under .125"   I finally found whatI was looking for.  To help me drill my holes and still retain feeling in my fingers.   And its called a jewelers drill.  Various makes and models and sizes I suppose from what I saw.   Capable of holding even a .010" drill bit.  So I was sold.   However I had to haul my ass out of the hobby store real quick when I saw their Hot  Wheels display.  Hot Wheels is now making Monter Bikes...SUHWEET!   

Anyways here is one rendition of this jewellers drill that is a virtual godsend to me.  $13.00  You can get various handles.  Im going to  see how this one feels.  I can always machine down the handle ball.

Thursday, July 1, 2010

Enigma Force

As a change or maybe to showcase, from time to time, Homeworld will switch up pictures on our Cover.  I for the most part only use photos I have taken. 

The current cover for Homeworld is a Robert 'Droid' work I commissioned from him.  It was one of 3 he made and this was the one I chose.  This photo "IS" the main or default photo for Homeworld entitled ENIGMA FORCE.   So after I have showcased something on the cover, this will be the cover after the showcase has run its course.

If you have a photo of something Micronaut/Casting related and would like it showcased, feel free to ask.  If it is suitable I could very well be persuaded to load it up.  :~)

Restoring Rigidity to 3 3/4" Micronauts

I wasnt sure how to title this post.  I want it to get your attention.

Home casting is an imperfect art using imperfect methods to best duplicate injection molded parts that are near flawless.  Unless one is willing to invest in equipment most casting is unavailable or the results will leave you wanting. 

One area that has intimidated me is the legs of the 3 3/4" action figure.  The knee joint is a quirky yet precise mechanism.  There are alot of variables involved in getting the knee joint to not just operate, but hold a pose.  So I pulled out some rivets I had bought a while back when researching rivets for the 3 3/4" action figure.  I took some garbage parts and even tho they didnt align, by grinding the mating surfaces flat and installing a rivet in the knee, I was able to salvage them.  Well I could if I wanted to.  But I wont.  These are just test pieces.

Really, there are so many pieces to the Centaurus figure, it is a difficult figure to replicate.  By installing knee rivets, I have strengthened the knee joint and in fact the whole figure and have made the Centaurus a poseable figure no matter how much I 'play' with it.  I have in fact solved a lot of issues faced by home casting by installing a knee rivet.

These photos are of test pieces.  So they dont really look as good as it can.  But originally these pieces would have been scrapped because of slight fitting issues.  Installing a knee rivet overcame the deficiencies of home casting.  Now that I know I can consistently achieve the results I want, this takes alot of the stress off of me during the casting process.

It takes a bit of work to make sure the resin gets all the way into the little hole in the mold that makes the knee pin. One little tiny air bubble in here and the thigh is now a wasted cast piece because the knee pin collapsed. file it smooth, drill a small hole in the knee for the rivet and install the rivet.  This can even be done to vintage action figures.

Imagine...Repto's knees wont flop.  He'll be able to stand without using his tail.  You will be able to pose your vintage centaurus without using a stand.  You hardly notice it is even there.   

If you are interested in restoring the regidity to any of your figures, please email me at the blogs address    I charge $10.00 US to rivet the 2 knees on a Micronauts style 3 3/4" action figure plus shipping.  $25.00 for 3 or 4 figures.   

I'll post some more pictures in the immediate future of knee rivets in more appealing colored parts so you can get the full effect.