Making Very Large Silicone Molds

I made this silicone mold a few years  ago it's 13 by 20 inches or about   30 by 50 centimeters the silicone  is starting to get brittle   and it's time to make a new one it's made  over a hundred parts in this silicone mold   and i'm gonna take you through my process  and show you how to make a two-part large   silicone mold my name is Eric Strebel welcome  to my channel about product design and making so the first thing that i'm going to do  is that i'm going to take the outline of   my vehicle and i'm going to offset that by 10  millimeters to make this seven millimeter wide   seal the seal is seven millimeters in width and  it's laser cut this allows me to have a 360 degree   seal it does two things it aligns the  top and the bottom half of the mold   and it provides a seal to prevent the resin  from coming out of the mold when we put it   inside the mold cavity to make our part i call  this a key seal because it keys the top and the   bottom and half of the mold together and  it provides a seal i'm using three layers   of relatively thick cardboard my laser is  not big enough to cut the seal in one piece   so i have to go and patch the pieces together  once i'm done i shellack it to seal it   so that it will not absorb the silicone and  i select the sides of my mold box as well my mold box is made out of three quarter inch  mdf and i screw it together really well with   drywall screws the last thing you want  is your mold to leak so screw it together   really well i'm also going to use some  corner blocks to reduce the amount of   silicone as this requires a tremendous  amount of silicone for a mold this large let's add the key seal to our mold you can see  i have a center line drawn down the middle of   the floor and we'll flip the key seal over i  know where the middle of that is i've marked   that as well and we'll just glue that in with  a little bit of white glue and add some weights   to keep it all nice and flat let's take  the master part and apply some white glue   around the flat parts of the bottom of this  mold we want to make sure that the white glue   is spread out nice and even here this will prevent  silicone from leaking under the mold and having   any flash to trim off later i have the part marked  in the center and i line it up with my center line   let's add a date and a volume so we  know how much resin to use in the future this mold requires well over five gallons  around 20 liters of silicone i've already   marked out the weight of this container  so that when we place it back on the scale   when it has silicone in it we know how much  it weighs already fill it up to about three   or four liters right here because we want to  allow room for expansion in the degassing tank so it's important to have a container that is at  least twice as large as the silicone volume   you're degassing pull a vacuum and then turn  off the pump and let some of the air come out   when it starts to collapse you can turn the  pump back on and degas the rest of the silicone   in my case it takes about 20 minutes to degas  the silicone fully my vacuum tank is only a   three gallon vacuum tank so i'm gonna have to do  multiple batches of silicone the first silicone   batch i pour over the entire mold and the reason  for this is so that i don't get any seam lines   on my mold that way the next two batches i  will just pour on top of the existing silicone   and it won't get any weird lines in the mold or  any delaminating later on down the line in let's   say six months or nine months from the silicone  so it's important to pour the silicone over the   entire mold to cover it before you put the next  layer on so we'll repeat the process pour out   the next batch of silicone and we're going to end  up needing one more layer here i like to make my   silicone molds plenty thick enough so that they  don't tear or anything and they last a long time once the silicone has cured usually overnight  it's time to take the mold apart and   make some adjustments so that we can start setting  it up for the second half let's remove the key   seal we don't need this anymore it's cardboard  and i just pull it out and it's a throwaway part   i have a little bit of silicone that is seeped  underneath the edge of the master part and i'm   going through here with an exacto and i'm being  very careful and i'm going to trim off that   little bit of silicone that is seeped underneath  the part so we don't want that the next thing we   have to do here is we want to remove any of the  white glue that we used to adhere the master onto   the floor of our mold before and i'm  using a little tool to scrape off that uh   white glue and i'm being real careful to clean  everything up we want to keep the master part   inside the silicone we don't want to disturb  that or take it out of the mold you want to   leave that in there to create a good seal and  a good bond now i'm going to remove the sides   of the mold and i'm going to release them and  we're going to end up dropping the mold straight   down so the silicone and the master are going to  fall straight down onto my table here and this is   going to give me the space that i need to make the  second half of the mold the top part of the mold all right let's reassemble the mold box with the  silicone and the master drop down to the bottom   and you'll see we have a space at the top  where the second half of the silicone mold   will be molded i'm gonna add some little vent  sprues here and these are pieces of cast resin   that i taper at the end by sticking it inside  of a pencil sharpener i'm going to super glue   these in place they need to be strong enough  to resist the flow of the silicone when we   pour the second half of the mold and let's add  the pore sprue into the middle part here as well   last but not least make sure you add  release agent to your silicone because   we're going to be pouring more silicone on  top of this and we don't want it to stick it's time to pour the second part of the mold  and i have to do this in multiple batches as well   just be careful so you don't knock off  any of your sprues or your port event time to disassemble the mold box and take the  mold apart and remove the master so we can   make some parts all right i carefully peel the two  pieces apart and this is why it's important to put   release agent on your first half of the silicone  release agent is not needed anywhere else other   than where there was silicone because silicone  only sticks to silicone i see a lot of people put   release agent on their parts and i don't know why  they do that you just mess up the surface finish   so we've removed the master and we now have  our completed two-part very large silicone mold let's reassemble the mold it goes back together  quite easily you can see where that key seal is   super handy here it aligns and seals the mold i  place a board on the top of it that has some holes   for my vents and my sprue and i add a weight  just to keep everything together to resist the   pressure of the resin that we pour in it we'll  add some straws for the vent areas because we're   going to tip the tool and this allows the resin  to flow into the straws and not all over the mold   and keep things nice and clean so let's slowly  pour the resin into the funnel in the poor hole   i use a vibration tool to vibrate the bubbles out  of the resin while i pour to minimize the amount   of bubbles in my part and then i'm gonna  untip the tool after a few minutes when   the resin has flowed everywhere and we just  let it cure time to demold and take out our   part twist out the funnel and we'll take  the mold apart and we'll have a good part   make sure you give the video a thumbs up and don't  forget to subscribe if you haven't already done so   also don't forget to follow me  on social media i'm on facebook   instagram and twitter links in the description  below and on the channel page rock on click here to check out some of the other design  and making videos that i have that you might enjoy

Channel: Eric Strebel

Views: 143,724

Keywords: Silicone Mold making, resin casting, two part mold making, prototyping, soft tooling, industrial design, product development, product design, vacuum de-gassing, silicone tooling, Large silicone molds, vibration casting

Id: f8P5Ccyz9Zw

Length: 12min 6sec (726 seconds)

Published: Fri Jan 08 2021