Using an Innovative Silicone Tool to Vacuum Form an RC Car Body

[Music] how to make rc car bodies using the  smooth sil 940 and 960 liquid silicone rubber   and the freeform air hd epoxy putty now in today's  video we're going to show you a step-by-step   procedure that we use to go from a original  model to a soft silicone tool that's flexible   two finished rc car bodies that are vacuum formed  over our soft tool here now our project today does   have several goals we're trying to reproduce as  much detail as possible into the vacuum form parts   that we're making we also wanted to show you how  to create a flexible tool for vacuum forming so   it can be easily removed from any undercuts that  the tool itself has and of course we wanted to   show you how you can easily make many vacuum form  pieces of a original as well as using materials   that can withstand the heat from the vacuum  forming procedure we also want to show you   how to create a original mold or master mold that  can be easily used to reproduce new tools or new   molds for production settings now let's just  jump into this project and see how it's done   vacuum forming is a process where a sheet of  plastic is heated to a forming temperature   stretched onto a single surface tool and  forced against the tool by a vacuum this   process can be used to form thermoplastic sheets  into permanent objects conventional techniques of   producing a tool can be costly time-consuming and  labor-intensive using new techniques and materials   will save you time save you money and save your  labor over conventional techniques i originally   created the form or mold the traditional way by  casting it solid out of a heat resistant epoxy   however what i discovered is that the front and  the back end of this mold here or tool create a   undercut that creates a locking between  the vacuum form piece and the rigid tool   you can see that the vacuum form body here fits  so tightly around our model that it was unable to   be removed and when we did remove it we actually  broke it and ripped it apart because of that issue   we're going to be creating a softer silicone skin  that goes over a rigid shell made of a epoxy putty   this will allow us to peel the silicone skin  out of the vacuum form body that we created   without destroying it so potentially what we will  have is a hard shell that's made out of freeform   air ht epoxy putty and a silicone skin that  sits over that that actually houses the detail   of our tool the model i will be using for this  project today is going to be this old rc car body   and i noticed that there are some gaps between  the windows and the main body so i will fill those   with some clay this is sculpex soft oil-based  clay so any cracks where the silicone that we're   going to use to make the mold can seep into and  underneath the model are going to be filled with   the oil based clay because our model is hollow i  will support it with some foam blocks that we're   going to cut and this is regular building  foam that you can get at the hardware store   and i'm simply going to quickly glue them  together in order to super support the overall   shape of the car the model that we're trying to  make the foam is cut with a razor blade to support   the shape that we're trying to mimic the reason  why we need extra support underneath the model   here is that we're already anticipating we're  going to be pouring a large quantity of silicone   over the model and because it's hollow i'm worried  that the weight off the silicone can deform   or collapse the model underneath so that's why  we're going to be using the lightweight yet strong   foam to prop up the model using the sculptex  soft oil based clay we're going to build up a   bed that the model is going to sit on this is our  working surface so to say and i'm simply going to   speed through this so you guys can see how i go  about claying up these models and i'm going to   flatten out the surfaces as much as possible and  then we're going to start to fill in the areas   around the model you can notice that i raised  the model off the working surface and that the   wheel wells and also the underneath of  the model is sloped away from the model   because the vacuum form pieces will be  removed up and over the model we want   to make sure that the edges are sloped away  from the model and we'll have an easier demold   now the mold box can be built around the model  itself and i'm going to simply smooth out some   of that sculptex clay to make this mold as clean  as possible and then again using the hot melt glue   and some melamine boards here we're gonna put this  box together here i'm going to put a plexiglass   window in the front of the mold so that when i'm  pouring the material you guys can actually see   into the mold as mentioned we're going to be using  the smooth seal 940 platinum silicone the reason   why i chose to use this material is because of its  higher durometer this is a 40a durometer silicone   and because of its hardness or stiffness it holds  shape much better than a softer silicone would so   the firmer silicone keeps its shape easier keeps  up its weight easier and won't buckle or deformed   under its own weight this in turn will allow me  to create a mold skin that's what we're going to   create in this mold that's going to keep true to  its original shape and form and again it will not   distort if you take a look at the shore hardness  scale that you can find on our website this will   put things more in perspective as what to expect  from a certain short hardness that relates to   objects in the real world as you can see here the  40a durometer silicone will feel something like a   pencil eraser so quite stiff and easy to hold its  shape now the smooth sill does have a mix ratio of   108 to 10b that means we're going to have to use  an accurate gram scale to dispense the material   it has a working time or pot life of 30 minutes  while the cure takes 24 hours one thing to note   and understand on the technical bulletin is that  the mixed viscosity of the material is quite high   at 35 000 centipoise or cps for short the  material is more likely to trap air bubbles   because of its thick consistency therefore it  is recommended to vacuum the gas the material   to eliminate any air bubbles that may  be trapped from the mixing procedure   because we are mixing a large quantity for  a large mold i will be using two gallon kits   off the smooth cell 940 therefore i will be mixing  the material in a five gallon container in order   to contain all the material especially once we  expose it to vacuum keep in mind when vacuuming   silicones they will expand twice if not more the  original amount that you have in the container   so it's really important to accommodate that when  mixing large quantities of material to understand   how much they will expand and how big of a mixing  container you will need for this application to begin the mixing process both parts a of the  silicone are combined in the 5 gallon mixing   container the reason why i'm not using an gram  scale is because i'm dispensing the entire gallon   kit into the mixing container and the material has  been already weighed out so that if you use the   entire batch the material will have the correct  mixing ratio and then we're going to add the part   b now using a variable speed drill and a turbine  mixer the two components are mixed together   by scraping the sides and scraping  the bottom off the mixing container   make sure to bring up any material from the  bottom up and mix it as thoroughly as possible   once the mixing procedure is complete i'm going to  transfer the material into a second clean mixing   container and here you can clearly see that  at the bottom of the mixing container there's   still some unmixed material the colors have  not blended well and i will upgrade to a   electrical drill mixer here with more power  and then mix the entire batch one more time   scraping the sides and scraping the bottom off  the mixing container the mix material can now   be exposed to vacuum using a vacuum chamber and  one thing you want to keep in mind when working   with materials that you know you have to vacuum is  to keep the working time or pot life in mind does   this material have enough working time for me to  mix and vacuum the gas before it starts to set up   the mixed material is now exposed to 29 inches  of mercury to vacuum the gas air that has been   trapped in the mixing process in the material  and we're going to allow the material a rise and   a fall this is the correct procedure for vacuum  degassing once you see that rise and fall you're   going to allow the material another 90 seconds to  continue to vacuum and pull air out of the mixture   before shutting the machine down and releasing the  air valve allowing air to enter the vacuum chamber   the silicone is now poured into the mold box that  we prepped earlier and we're going to pour in   one spot the lowest part of the mold box and  allow the material to seek its own level that   way it's going to push any kind of air away from  the model and make sure that we don't have any air   bubbles trapped on the surface the material is  now allowed a full cure for 24 hours after full   cure we can go ahead and demold our mold we can  remove the melamine board that we use to make our   mold box and then we're going to slowly remove the  model out of the mold itself you can see that the   glass part of the model popped out easily first  and then slowly i'm going to work that model out   of the mold you can see how stiff that rubber mold  is because we went with a higher durometer rubber   versus a lower thermometer which allows  us to keep the model or the mold nice   and stiff for future reproductions the next  step here is to cover the inside of the mold   and i'm going to use some regular aluminum  foil that you can get at any grocery store   the aluminum foil is basically a barrier  layer that will protect the inside of the mold   using the sculptex soft which is an  oil-based clay that i've already rolled out   in a half inch thickness we can now slice  that into strips to create the silicone skin   from our mold keep in mind that everything that  we create out of the sculptex clay here will   eventually become the silicone skin that we're  going to use over our tool to pull the vacuum   so i'm just going to fast go through this  and show you how i build up that clay inside   again trying to keep the same thickness and then  smooth out some of those walls off the clay up and   you want to keep in mind that these clay walls  that we're building up here cannot cause any   interlocking between the clay so to say and the  plug so all the walls have to be sloped so that   the plug we're creating can come out of our cavity  here with no problem or in the future out of the   silicone skin that we're creating this key here  that will be eventually in the silicone will   allow the silicone skin to find its original  resting place in our rigid tool more easily and then we can proceed to make the actual plug  that's going to be made out of the freeform air   ht which is a poxy putty that  has high temperature resistance   so the freeform air ht is a lightweight epoxy  putty that offers high temperature resistant   up to 300 fahrenheit when cured at room  temperature and 400 when cured in a post curing   oven the pot life or working time of the freeform  air will depend based on the thickness that you   apply the material in so for example if you apply  the material at a 1.5 inch thickness the pot life   would be about 90 minutes while the handling time  is three hours that means the full cure will be   achieved in 16 hours the freeform air ht has a  2a to 1b mix ratio by weight or by volume now   this is really important to keep in mind because  if you have used the freeform air in the past   you may remember that the mix ratio  is different from the freeform air ht epoxy putties are very adhesive substances and  a release agent is recommended when applying   the material to non-porous surfaces such as resin  metals glass etc you can use sonide wax available   from smoot-on as well as other designated release  agents the heat resistance off the freeform air ht   with a minimum thickness of half inch or 1.27  centimeters will resist temperatures up to   300 fahrenheit as mentioned in the technical  bulletin i'm going to be using the sonite wax   and we're simply going to apply it directly to  the sculptex oil based clay that we put in here   and once you cover the entire surface  we're gonna allow the sonite wax to dry for   20 to 30 minutes i can now proceed to dispense  the freeform air ht remember this is two parts a   to one part b by volume so i can simply start  dispensing to minimize any chance of cross   contamination between the containers you always  want to make sure to change the gloves between   the dispensing off the part a and the part b  the freeform air hd is a lightweight epoxy putty   to mix the material i'm simply going to start  by folding it on to itself so just like bread   if you're making dough for bread you just continue  to fold it onto itself and you're gonna continue   to mix it that way until you get a unified  color that doesn't show any streaking of the   individual components keep in mind that epoxies  are exothermic materials and keeping a lot of   material in mass will expedite the cure of the  product while flattening out the material into a   thin pancake will prolong the working time of the  material so here you can see once the material is   mixed we can apply it i'm keeping the thickness of  the free-form air as even as possible throughout   the entire buildup we want to keep in mind that  thickness reference guide that's in the technical   bulletin that we looked at earlier and what the  working time with the material will be based on   the material thickness i aim for about one inch  thickness on the model here that we're creating   once the entire model is build up with the desired  thickness you can use a little bit of water from   a spritzer bottle to smooth out the surface off  the freeform air do not over apply the water so   that it sits and pulls inside your model you want  to have just enough to get a wet slippery surface   on your hands so that you can work the texture off  the freeform air to a smoother and slicker surface the freeform air ht is now  allowed a full cure of 16 hours   after full cure we can go ahead and de-mold the  entire build-up we're going to remove the clay   and the free-form air shell that we build inside  a mold once the shell is removed the free-form air   edges are cleaned up of any sharp corners and then  i'm going to drill some venting holes into that   channel key that we created in this shell this is  where the silicone will shoot out as we fill the   cavity between the mold itself and this freeform  air shell this will make sure that that key   is solidly filled with rubber and does  not trap any air bubbles in that area   now before we attach this plug i'm going to use  some ease release 205 this is a release agent   for silicone to silicone application i'm using  the liquid version because i have more uh control   over the application i can see exactly where i'm  applying the release agent keep in mind that you   don't want to over apply the release agent  and have it pool at the bottom of your mold   i'm going to brush in a layer off the east  release 205 and then we're going to allow this   to fully dry for 10 minutes the  wood strips are adhered using some   hot melt glue to the freeform air ht shell that  we created and then using a variable speed drill   with a drill bit i'm going to mark the areas where  we're going to drill all the way through the wood   slats i'm not going to go all the way through  into the silicone here and then once we remove   the shell from the silicone mold and we're going  to drill through the wood completely and then   we're going to use those holes that we drilled  through to secure the shell into the silicone mold   and then use some wood screws to hold this in  place now you have to be very exact when placing   the shell that we created here now into the mold  and securing it you want to have the same distance   all around the shell so that you don't create a  skin a silicone skin that's thicker on one side   and thinner on the other so here we have our setup  that's ready now to be poured with some silicone   the reason why we secured the freeform air hd  shell in the silicone this way is so that it won't   float up as we pour silicone in between the mold  and the free-form air hd shell that we created   the silicone skin that we're creating on this plug  is going to be made out of the smooth sil 960.   the smootcil 960 has a mix ratio of 108 to 10b by  weight so we do have to use an accurate gram scale   the working time or pot life of the material is  45 minutes while a full cure takes 16 hours really   important to keep in mind that this material has  extremely low shrinkage as well as a high heat   deflection of 450 fahrenheit which will be very  useful because we will be exposing this to direct   heating elements while silicones don't stick to  many substrates it is important to apply a release   agent when using silicone to silicone applications  because they will adhere to the same kind of   silicone that they're made out of so ease release  205 was used for the release agent application   because the smooth sill 960 has a high viscosity  of 30 000 cps we will use the silicone thinner   to bring that viscosity down and help the  material flow into the cavity that we created   furthermore by using the silicone thinner the  silicone will de-air faster when vacuum degassed   the mixed rubber will flow better into  the mold itself the cavity that we created   while the silicone thinner will ultimately  lower the shore hardness or the durometer   of the silicone it'll be very small proportion  because it is a 60a durometer so we will not see   a huge impact on the durometer furthermore  the pot life of the silicone is increased   by adding the silicone thinner and will depend on  the quantity of the silicone thinner that you're   adding the disadvantage of using silicone thinner  is that the ultimate tear strength is reduced in   proportion to the silicone thinner amount that is  used this will not be a problem for our project   here because as you will see the silicone  stain that we're creating will be still very   bendable and stretchable for our application as  mentioned the percentage of the silicone thinner   is added to the total weight of the part a and the  part b of the rubber system it is not recommended   to exceed 10 percent by weight of the total system  combined make sure that you follow the technical   and for the silicone thinner down to its  detail the part a is first dispensed and   then the silicone thinner is added to the part a  and pre-mixed thoroughly before adding the part b   of course make sure to use a accurate gram  scale when dispensing the smooth sil 960   as well as the silicone thinner additive make  sure to pre-mix the silicone thinner thoroughly   into the part a by scraping the sides and  scraping the bottom just like you would do   if mixing the a and b together once the  silicone thinner is combined with the part a   we can go ahead and dispense the correct  amount of the part b of the smooth sill 960.   once the part b is dispensed we can go  ahead and mix the components thoroughly   together by scraping the sides and scraping  the bottom off the container and then i'm going   to transfer the mixture into a second clean  mixing container this is a double mix technique   so we mix in one container transfer into a second  one now everything that was at the bottom of the   container ends at the top and we mix it one more  time by scraping the sides and scraping the bottom   the silicone should have a uniform color  and no streaking should be visible of the   individual components the material  is now placed into a vacuum chamber   and exposed to 29 inches of mercury to vacuum  the gas any air bubbles that were introduced   into the material from the mixing procedure  we're going to allow the material a full rise   and then you can see here i'm going to break that  and allow it to fall and it's going to continue to   bubble up and that is the action of actually  removing the air out of the mixture and once   you see that rise and fall we're going to  continue to vacuum for another 90 seconds   before removing the silicone from the vacuum  chamber the smooth sill now can be poured   into the cavity that we created between the  silicone mold and the freeform air hd plug   and because we added the silicone  thinner the material flows quite nicely   and i'm going to plug those air vent when i  see that the silicone is rising out of them   i use a little bit of the sculptex soft  clay to plug those up again once i see   that the silicone is coming out the rest of  the silicone is now poured into the cavity   the material is now allowed a full cure of  16 hours before proceeding onto the d-molding   after a full cure we can go ahead and de-mold the  silicone that we poured um we're going to start by   removing the screws and those wood slats that we  glued onto the freeform air tool that we made the   shell and then we can simply demold the shell  first the freeform air and then the silicone   is peeled out as well and you can see how flexible  that is even a 60 durometer can be flexible enough   to be peeled out here's our finished silicone  sleeve that will be used for the vacuum forming   application and again here you can see  how bendable and stretchy that material is to create the vacuum on the model itself we still  do need to punch air holes into the model itself   so i'm going to be using these brass tubes that i  have these are telescoping tubes in many different   sizes you can buy them in different shapes as  well hardware stores will have them for this   model size i ended up using about a millimeter to  two millimeters punch hole that gave me enough air   circulation through the entire build up in order  to get good quality pulls off our model here these air holes are punched in very specific  places where we want the the detail of our   model to show up in the vacuum forming that  we're going to be doing so any detail any   corners here are going to be punched with  a hole including the lights and any kind of   recesses so you can see here in the lights and the  corners i have punched holes all around now with a   sharp tool i'm going to mark the form underneath  the freeform air shell that we created i'm going   to punch these holes basically to mark where  we need to drill holes into the freeform air   remember we need a complete pass from the  silicone through the shell here to the   vacuum that is being created in the machine that  we're going to be using for the vacuum forming   so i'm going to go around and all those markings  that we created and i'm just going to check a   couple of times make sure that we have all of the  corners covered and this is what the freeform air   shell now looks like underneath it has all these  holes that we created for the vacuum itself   if you find that a specific area is just  not getting enough detail you can always add   some more vent holes down the line once you  start pulling the first vacuum form examples   off the tool you created the tool is now placed  into the vacuum forming machine starting with the   inner shell that we created and then the silicone  skin we can then lower the tool and the plastic   sheet is inserted that we're going to form over  the tool it's trapped in place and the heating   element is slid over the plastic sheet to warm up  once the sheet is heated up the heating elements   are slid back and the tool itself is raised  into the plastic sheet and exposed to vacuum the freshly vacuum formed material is allowed  a moment to cool down before being removed   from the vacuum form machine and here you  can see that by first removing the core   that's rigid we're now able to remove the silicone  skin out of our vacuum formed object much easier   without destroying the vacuum form object that  we just created the model is now trimmed out   following the seam lines on the model the edges  are sanded using a sanding disc to clean up any   sharp corners and tighten our cut closer to the  model and line it up to the seam lines that are   created in these vacuum form pieces the vacuum  form body is now fitted over the chassis of the   rc car to make the alignments for the body posts  that will be carrying the shell on the chassis   the body of the model is washed masked up and  then painted on the inside of the vacuum formed   model so we're going to paint the inside  with the masking for the windows in place   and we're going to apply several layers off  the paint so make sure you don't spray paint   all at once but rather do several layers of thin  application allowing each layer in between to dry   there are many different paint types  that are available for this application   and of course many different designs that you  can make i'm keeping it here very simple just   masking off the windows and the rest  of the body gets painted in one color   i use the tamiya color for polycarbonate spray  paint for this application again make sure to   use the appropriate paint when painting  this type of plastic for rc car bodies   once the paint is dry the rc car body can now  be mounted to any type of chassis of your liking   i'm putting the rc car body that we created  over a dune buggy chassis so that we can take   our model out and ride it in the dirt and rocks  and here you can see the end result of our project   the car body mounted to the chassis and ready for  a test drive we want to give our special thanks to   formak perfectly formed vacuum machines that  made this video possible and let you guys   know that we use the vacuum form model  508 dt to vacuum form the rc car bodies   that we used here now if you got inspired  by this project and you like to give your   own projects a go and need some material you can  visit any one of our distributors around the world   so and there you have it a step-by-step procedure  that i use to create this vacuum form tool that   deals with difficult undercuts on the original  model now let's take a look at our project goals   we were able to reproduce most of the detail  in the vacuum form pieces as well as create a   flexible tool that is easier to remove from  the undercuts in those vacuum form parts   now we showed you how to easily make  many vacuum form pieces from the tool   as well as how to use the correct materials that  will withstand the heat from the vacuum forming   procedure repetitively finally we showed you  how to make a mold that you can use to easily   reproduce new tools for a production setting  now if you have an idea about what we should   do next please let us know down in the comments  below if you like this video hit the thumbs up   button to keep up with our latest mold making  casting and other videos remember to subscribe

Channel: Smooth-On

Views: 200,162

Keywords: 3d printing, casting, diy, do it yourself (hobby), how to, hpi racing, instructional, making molds, mold making, moldmaking, radio-controlled car (ranked item), rc car, rc cars, remote control, remote control car, smooth on, smooth on mold making, smooth-on, smoothon, tutorial, vacuum form, vacuum form foam, vacuum former, vacuum former uses, vacuum forming, vacuum forming car parts, vacuum forming machine dental, vacuum forming products, vacuum forming rc body

Id: s_S3FPshecM

Length: 34min 30sec (2070 seconds)

Published: Thu Jul 08 2021