Wax burnout using high internal heat

Discussion in 'Lost wax casting' started by JBC, Apr 7, 2021.

  1. rocco

    rocco Silver

    All microwave will but how and what matters, most importantly, shape matters, loosely crumple up a piece of aluminum foil and see what happens when you nuke it.
     
  2. JBC

    JBC Copper

    Incoming plasma arc.
    Graphite will heat up like a mutha too and this wax for injecting clears out pretty quickly too.
     
  3. Jason

    Jason Gold

    I nuked a cheeseburger a few years ago in a foil wrapper. When the carousel came to the front, it royally screwed the window in the door. Of course it was a rental house:rolleyes:. Cost me a microwave I didnt get to keep.:mad::mad:
     
  4. rocco

    rocco Silver

    And to add insult to injury, I'll bet your cheeseburger was still cold too.:p
     
    Jason likes this.
  5. JBC

    JBC Copper

    But how did it taste?
     
  6. Jason

    Jason Gold

    Like melted plastic. Burger was cold, wife is pissed and I'm out 300bucks.:rolleyes:
     
    JBC likes this.
  7. JBC

    JBC Copper

    Quick....make her a bronze burger.
     
  8. JBC

    JBC Copper

    (I am still working on getting a kiln for burn-out while working on my microwave approach).
    I microwaved the wax out of two molds and then placed the molds into a toaster oven set to 400F to dry out the mold and raise the mold's temp. Once my metal was ready I used these tongs to move the molds to the vacuum table. Both developed cracks before I poured. Did I handle them both poorly? Pinching too hard with the tongs (mold diameter is maybe twice the diameter of the curved area of the tongs)?

    Little Tongs.jpg

    If these cracks were mostly due to not following the Ultra-Vest burnout process why aren't there more cracks?
    Mold1.jpeg mold2.jpeg

    The results were pretty good on my detailed pieces (the word "Saint" has a texture inside of the letters).
    Saint1.jpeg Saint2.jpeg

    The other casting was affected by the cracked mold. The surface on the bottom of the casting was thicker where the mold had cracked.
    Mold.jpeg
     
  9. Jason

    Jason Gold

    Did you buy that vacuum table at rio?
     
  10. I've never seen investment based molds that weren't contained in steel tubes.

    If your model expands faster than it melts out, it produces outward pressure on the mold. Without a sleeve on the outside there's much less resistance to that outward pressure. That pressure could cause a crack.

    Have you considered either putting the molds in a steel tube (flask) or ramping up the wax melt out temperature more slowly, to reduce the expansion?
     
  11. JBC

    JBC Copper

    Yes I did.
     
  12. JBC

    JBC Copper

    I've been trying a different routine for a few reasons.
    I'm melting my wax out in a microwave which doesn't like metal. The wax melts out easily and has not caused any cracking before but this time I waited to melt the wax out after letting the mold sit for a full 24 hours. It could be that when I've melted out the mold before, more water in the investment helped it get steamed out avoiding damaging the integrity of the mold.

    I plan on melting out the wax today four hours after I invest (as I had been doing) and then leaving the mold out for 24 hours and then get the mold temp up tomorrow before I pour.
    If that works then the steam helped me more than I thought which could have avoided the expansion issues you mentioned.

    I was pretty pleased with how the casting turned out but obviously not good enough.

    I put my flasks in a toaster oven (24 hours after investing), set the temp to 400F, and let it sit for a few hours. I would have thought having to sneak up to 400 wasn't needed. But maybe it is.
     
  13. I've only used R&R Advantage for investment. I just double-checked their instructions to heat to 300F (as quickly as possible) and hold for 1 to 3 hours for water removal.

    Does your investment provider specify 400F? I would think that might cause a lot more steam to come out more quickly.
     
    Jason likes this.
  14. JBC

    JBC Copper

    Ah....good question lol.
    This was interesting - "Do not allow flasks to stand at room temperature for more than 10 minutes." I went over by a day lol.

    upload_2021-5-4_11-53-4.png

    Since I don't have a kiln to raise the temps according to the R&R schedule for my investment, I'll try my red-neck success-proof method again and see what happens. The cracks could have been (wishful thinking) due to drying out too much in this 80F+ degree weather in California while sitting for 24 hours.

    I'll try this today;
    Invest and then 4 hours later place in my toaster oven preheated to 300F
    3 hours later pour.

    I'll post results tonight.

    Thanks David.
    I look forward to getting a kiln so I can do this as intended.

    jbc
     
    Jason likes this.
  15. Jason

    Jason Gold

    Get or build a kiln and these problems will go away.
    I applaud you trying something new with the microwave route, but it is what it is. R&R has burn out schedules for your investment, follow them.

    Ebay sells cheap kiln elements and if you promise not to electrocute yourself, we can tell you how to put it together. I can build a 2000degree kiln for a quarter the price rio charged you for that vacuum table.
     
  16. JBC

    JBC Copper

    I have your offer from earlier in this thread pinned and will be taking you up on that hopefully by the 2nd half of this month when I come back from So. Cal.

    The cost of the Vac-table was painful but I have so many rabbit holes to chase as it is so I decided to ignore that one and bite the bullet. I almost made one using the pictures you were showing from an older thread. The cost of the plastic dome made my boot pucker! So I just bought it and put a check mark in that box.
    If the Vac-pump goes out I'll replace it with a quality one Harbor Freight sells.
    The parts for my plastic injector are now all here (don't know if I've said anything in here about it) and that's next on my list.
    The cheap temp gauge I made that uses my voltmeter worked well last night....but my little forge wouldn't show the correct temp and stopped heating a second time after replacing their PID (from them) = sad face.
    I got it to work but having to babysit the temp progress, wasn't on my "want" list for an induction forge.
     
  17. JBC

    JBC Copper

    OK.
    Heating a mold (3.75" Diam / 4" tall mold) at 300F for two hours for water removal does not remove all of the water (the last picture shows the spewed metal). I'm going to check the amount of time to dry out the mold by weighing the mold prior to pouring to help set a target for any sized mold.
    Obviously the larger the mold the more drying will be required.
    Image.jpeg Image.jpeg Image-1.jpeg Image-2.jpeg


    The crack shown here didn't show up till I started pouring so I'm (mostly) fine with that. I will be wrapping my mold before I dry it completely to help resist cracking.
    Image-3.jpeg
     
  18. rocco

    rocco Silver

    There are two forms of water in any type of plaster, free water which is basically just water that's soaked into the plaster and chemically bound water, water that's chemically reacted with the other components in the plaster, 300f would remove all of the free water but only some of the chemically bound water. If you look at that burnout schedule, the chemically bound water is removed during the "thermal transition" phase of the burnout.
     
  19. JBC

    JBC Copper

    Good to know, thank you. I'd love to know how much water weight I'd shoot for to eliminate steam but not over-dry the mold.

    Two days ago I let my molds sit for 24 hours to dry out so steam didn't ruin my results (Like yesterday's). That worked pretty well but I felt the molds dried out too much after 24 hours as they cracked prior to the pour. The level of detail was pretty damn good. They were much better than I expected.
    I can honestly tell you I'd much rather have a burnout kiln to set and forget but till I do I'm going to continue.

    The whole point of all of this is to shorten the time it takes to create and eliminate some costs (burnout kiln).

    I'm out of wax models so after I make more I'll start investing tomorrow morning and share my modified procedure and show more pics.

    If you or anyone else has any knowledge on % of water weight the mold has left at the end of a normal burnout schedule I can target my mold's weight prior to the pour.
    (I'm sure it's a lot different due to the calcification process the higher temps produce but more data is more data).
     
  20. Jason

    Jason Gold

    You must be getting investment either cheap or free! Good thing you're not pouring gold or silver.
     

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