Think This Process Will Work?

Discussion in 'Investment casting Block method' started by 0maha, Oct 2, 2020.

  1. crazybillybob

    crazybillybob Silver Banner Member

    I don't know what kind of silicone you're using but some tin type silicone doesn't like the sulfur that's in some of the modeling clays. Platinum Silicone seems to do fine.
    But I would test a little bit before I went whole hog and wasted a bunch of $$ because my silicone didn't play nice with my clay.
    I'm pretty sure dave uses the "good Stuff" when it come to silicone....Some of the rest of use don't know any better and start with the "cheap stuff" we learn a few things the hard way.;)
     
  2. rocco

    rocco Silver

    What do you mean by "doesn't like"? I.E. doesn't cure, sets up hard or brittle, etc.
     
  3. 0maha

    0maha Silver

    I'm guessing I'm ok on the "will it cure" front. My first test involved casting a huge block of RTV inside a frame, with the 3D print sitting on a bed of clay. Came out fine, more or less, and that was with a large section of the rubber sitting directly on top of the clay.

    Here's the next question: With a bit of luck, it won't be long until I'm ready to try to make wax molds from this. I saw a video on the R&R site where they melted the wax and brushed on a few layers, then put the two mold halves together and poured in wax to fill up the rest. I'm thinking that looks like a pretty good way to go, unless you guys think otherwise. The stuff they used is called SculptaCast Dragon Wax. Should I start with that, or do you have a different recommendation?
     
  4. Aaron M

    Aaron M Copper

    If you're having to do all that work I don't think it's the same thing. Bedding in clay does help quite a bit, you need to stick 3d prints to the bottom well or they float, but you're thinning and doing what appears to be a lot of work just to get the product to flow in the details. I'll post some pics later, but i 3d print my mold box, top and bottom, it's the only to fly, makes like a lot easier. I also build on a cutting board, so you can "drop" it once or twice to lodge any trapped air, just about an inch or so.

    Moldstar 15 or 30 pours smooth, bubbles rise to the top, pot life is 50 min, cure 4hrs, I leave it over night. At about 45 minutes, run a flame across the surface and it will pop any surface bubbles, but those don't really matter.

    Post some mold box pics later.
     
  5. Aaron M

    Aaron M Copper

    Here are some box pics, Mold 1 are the 2 halves of the box, blue side is the top, it has the support lip. Fill the bottom with clay, rolling pin flat, use an old knife to cut the surface flat and that's your bed. put the part, snap the top to the bottom, it will make that little edge, fill that with clay to seal it., like glazing a window pic 2/3. Then fill it up. I make them as I go, so they are just slightly larger than the part Pic 4. I mold the connection gates, those all have a slight taper so the wax will pull Pic 5. You put those on after the top is poured, flip the box, remove the wax, put in the gates in holes in your part. With this method you can make some elaborate mold boxes, pic 6 is a sloped base box that lines up with lines of the part so it pulls well. It gives yo a lot of flexibility.

    No idea why they would be brushing unless they have some serious detail issues that they are trying to address. Typically, spray a mold release, I use Stoner Release, only use a little. Close the mold and pour. Pour the wax as absolutely as cool as possible, every degree makes a different wax. I have a 3 gallon wax pot on a PID, keeps it 90C plus or minus a degree or two. For me at 88C don't pour and at 92C open the lid and stir a little first to cool the wax. is you are running a spread greater than that, you are not making the same part, you'll notice significant differences. Molds don't give up heat well, so you will need to force cool for any production rate. and AC blowing straight down works well, from one side, you will need to rotate the part like on a lazy susan. If you can't cast wax, don't try brass. :)

    The red wax you are looking at mentions "Slightly tacky once set" that's bad. the green wax, which costs more, of course, has improved properties. The Red wax looks like a base product that you add additives to, so it cost less to begin with, but then you need to know what modifiers to add then the price goes back up.

    I use Westech green reclaimed (cheap) and ad virgin red to get the right feel. After you do it a few times you'll notice the pour off the ladle, whether it's good or not, go to preference and how your mold is setup.

    Good luck.
     

    Attached Files:

    0maha likes this.
  6. Aaron M

    Aaron M Copper

    CrazyBillyBob,

    I make my molds at home typically over the weekend, pour one side on Saturday, flip and the other on Sunday, demold on Monday morning. When I was having problems with the silicone not setting, I would get really pissed off. Lot of cussing. My wife made it a habit leaving early on demold Mondays to avoid me and any possibility of being anywhere in sight if a project went south.

    Thanks
    Aaron
     
    Tobho Mott likes this.
  7. 0maha

    0maha Silver

    That's great stuff, Aaron. Thanks!

    I'm sending a test molding frame to my 3D printer at this very moment.
     
  8. crazybillybob

    crazybillybob Silver Banner Member

    Normally it shows up as not curing. Or it is very sticky.
     
  9. Aaron M

    Aaron M Copper

    Absolutely correct, everything will 'look' great, and then you pull the mold box, still good, separate the halves and blue goo comes out of the creamy center, about 1/8" or less around the entire part. Exceptionally frustrating.
     
  10. 0maha

    0maha Silver

    Didn't want to leave the impression that I am a "one and done" guy...

    ...Spent the last week working and refining and I think getting things ready. At the moment, I'm waiting for everything to cure so I can split my first "this one should work" mold.

    We'll see in a few more hours.

    [​IMG]
     
  11. Aaron M

    Aaron M Copper

    Good Luck, we've been there.
     
    0maha likes this.
  12. Jammer

    Jammer Silver Banner Member

    I had the platinum stuff and it wouldn't set up. I had sprayed the pattern with paint and it reacted to it. Contacted Freeman Supply and they said "Sorry about your Luck". The instructions only mentioned sulfur base clays. I went to Poly-Tek and got Polyurethane based and it worked great and was much cheaper. The even sent me some free passes to a convention in Nashville. My wife and I went and it was really fun, even though it was mainly concrete related. Free food and lots of free samples and it was next to the Grand Ol' Opery. :D
     
  13. 0maha

    0maha Silver

    More or less, success!

    I've got a few things I'll massage on this process as it goes, but this is the first time one has come out essentially the way I wanted it.

    Next step is to get some wax and see if I can use this to cast a proper wax mold. We'll see...

    [​IMG]
     
  14. crazybillybob

    crazybillybob Silver Banner Member

    remember. You can adjust the Waxes after they come out. You're going to need to clean up the split lines etc. any way. A little cleanup on the wax is a lot less grinding that when it's cast in metal.
     
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  15. Aaron M

    Aaron M Copper

    That looks good. It looks fairly insulated, so it's going to be a slow cooling mold, but as long as that's ok with you it's a good deal.

    Get mold release spray, it will make the pull out better. I use Stoner (amazon) but there are others that should be fine. Make sure it's compatible with your material.

    Good Luck
     
    0maha likes this.
  16. 0maha

    0maha Silver

    Already learned that particular lesson the hard way. My first test I was way too light on the spray, and the 3D print tore half the rubber out of the mold when I removed it. Been laying that stuff down crazy thick ever since. Actually, on my first test making the back half of the mold, in my excitement I forgot the spray. Not good. That rubber sticks like crazy to my prints without the release agent.

    With that experience in hand, I'm planning on a good dose of the stuff when I start applying wax to this, no doubt about that.

    Current challenge/refinement is modifying the solution for getting a water tight seal between the 3D print and the heavy plastic backer, as well as between the MDF frame and the backer. I started out by rolling a rope of plasticine clay and using that to make the seal. Sort of/kind of works, but the problem is even if I put the whole thing on the floor and stand on it, the clay is stiff enough that it never fully squishes down. I'm left with roughly a 1/16" layer of clay, which screws up my seam lines. Plus, the clay is proving to be less than 100% waterproof. It doesn't stick hard enough to either the plastic or the print, and I'm getting leakage.

    Tried a test overnight where I replaced the clay with ordinary silicone sealant. Solved the "wont fully squish down" and "not 100% waterproof" problems, but peeling off the plastic sheet was brutal, particularly on the seal with the MDF frame. Got it off, and didn't destroy anything in the process, but it was tough. Pretty much pulled the surface layer off of the MDF. I've got a tube of "peelable" caulk coming from Amazon tomorrow. Never knew about that stuff. Apparently it is used by people with older houses to seal their leaky windows shut over the winter, then they peel it off in the spring. Crazy. Anyway, hoping that is the solution here.

    Wax is on order, so God willing I'll be moving on to that step of the process next week.
     
  17. crazybillybob

    crazybillybob Silver Banner Member

    You can do the silicone on one side. Put some plastic wrap over the other. Squeeze it tight... Let it set. Remove the plastic film coat the silicone with release agent. cover it with plastic wrap. coat the wood side with silicone. Squeeze it tight ... Let it set. Peel off the plastic. Now you have a none stick sealing surface.
     
  18. 0maha

    0maha Silver

    Turns out the peelable caulk works a charm! Really, couldn't have worked out better. It gives me a perfect, water-tight seal, and it comes right off when I need it to.
     
  19. 0maha

    0maha Silver

    Gotta say I'm pretty amazed at how much detail this process can handle. This closeup represents an area about 3" square.

    [​IMG]
     
    Jason likes this.
  20. Jason

    Jason Gold

    Moldstar looks to work pretty well. I've only been running rebound stuff because it hangs well to vertical stuff. And it's cheap too. I do either fiberass or PoP for a mother mold.

    Omaha, did you sort out a vacuum table yet? I took a bunch of pictures of mine for those that want to build one on the cheap. It's in this sub section.

    The issue with the pot you found on fleabay is you can only degas your investment. You still need to pull a vac on the flask when pouring in metal. If you are clever, you can use a flat surface with a hole in it and rest the flask over it with some silicone. This is where solid flasks make more sense than ones with holes. just my 2c.
     
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