Casting a minature coffee pot

Discussion in 'Die casting' started by Gerald Dinkins, Oct 5, 2021.

  1. To the members: Sometimes we arrive at a place in our lives and wonder how we got there.

    I want to explain. In my younger days I was raised on a chicken farm. It was during that time that farming meant that you got bigger or you got out. A nearby dairy farm was selling out and I took notice that after the sale a large concrete block building was being erected. Later on I found that the building was going to be a machine shop that was being moved from the city to the old farm. I was curious as to what went on in that shop. I visited often. Along with maching there was a casting shop attached that cast brass and aluminum. I was curious, but school activities took my time.

    In my high school years I took two courses in machine shop, then on to a tech school after graduation.

    Earning a living was first in my efforts.

    After retirement I was one of those that had idle hands with little to do.

    I did electrical repair for friends and did remodeling.

    I had sold the farm and moved to a historic place called Old Salem where I bought a house built in 1797.

    I set about to restore the bare walls and floors and make the old house livable without exposing too many modern ideas. You can see inside at Youtube: Christoph Vogler House.

    Anyway, I discovered that Old Salem had a figure that was their motto. It was a huge tin coffee pot.

    One day I met a guy the lived in Asheville NC. His name was Terry. He and I hit it off as he loved machine shop and actually was involved with the local tech college in Asheville. He asked me if I had made anything that I thought could be replicated in the shop.

    Well, I had a small wood lathe and had made several small wooden coffee pots for Christmas ornaments. He asked to see them.
    Now this is where the casting begins.

    He was intrigued with the design and we let it go at the time.

    Not long we were talking on the phone and somehow casting came into the conversation.

    I casually mentioned that I would love to cast those coffee pots in a 2” to 2 ½ inch size.

    I said he could make an aluminum mold on a CNC machine. I told him to tell me what drills and mill tools he needed and I would get them and send them to him.

    Terry and I struggled with getting the right setup.

    Two years passed and the molds were finally complete.

    I made many errors in the casting process. I used jewelry grade pewter. I must have had to remelt so many errors I lost count, but I finally got it right.

    Terry passed due to lung cancer, I miss him.

    All told I made 630+ of the prefect little images.

    If you know anything about pewter you know it comes out of the mold looking like lead or silver in color.

    I had to polish each one for casting burrs and then dip them in an acid coloring solution.
    The first 250 were donated to Old Salem for gifts during a fundraiser.

    I sold some, but most I gave away. I have very few left but I still have five molds.

    That time in my life was rewarding and I enjoyed all of it.
    Last edited: Oct 6, 2021
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    3Dcasting, Tobho Mott and Bldr J like this.
  3. Without knowing the spout and handle are tapered in order that they could be removed from the molds. A tapered mill had to be bought to make this possible.
    I am considering ordering Epoxy resin with pewter color and try casting resin in the alunimum molds.
    That would put them in the ornament market, but I tested the mold and it holds slightly over one teaspoon of water. With a 0ne to 0ne mix of hardner and resin I could almost get two units out of one one ounce of mix. So three ounces of resin and hardner would make five molds I think.
    Last edited: Oct 6, 2021
  4. So, the couriosity got to me.
    I ordered 8 ounces of base and 8 ounces of hardner along with a release spray and gray coloring.
    I mixed about 2 1/2 ounces and set to stir it well. I sprayed the molds and put them together.
    I then slowly poured the mix into the molds.
    I looked for bubbles and shook the molds to try to get any bubbles to come to the top.
    I waited two days for the mix to harden.
    Then I seperated the molds.
    That was when the fun began.
    The molded item would not come out of one side.
    I had to put them into the freezer and wait overnight.
    I still had to turn the 1/2 of the mold onto the open vise and beat the back side with a fiber mallet.
    I finally got the molded item out, but it was not easy.
    Needless to say, there is not going to be any more molding plastic.
  5. Melterskelter

    Melterskelter Gold Banner Member

    So what you had was an adhesion problem or a draft problem? Sounds like a draft problem. Compressed air shot into the seam between mold and plastic might have helped. Also will comment that wax, grease, and oils are reliable release agents for epoxy. I have less confidence in silicone. Not sure what “spray” you used.

  6. I have some fibreglass release wax and they recommend six coats of wax with drying time and polish in between coats.
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    Back when I built boat molds we would wax them several times, but would also use pva for the first few hulls waxing and reapplying the pva each time to season the mold before trying just the wax for release...
  8. I used APEL mold release spray.
    I trusted it as a reccomended spray.
    It did not work for me.
    I also got a surprise in the fact that there was a bubble in each molded item.
    Looking at the finished product in the posted picture the bubble was in the bottom of the pot where it meets the stem at the outter edge.
    I did not try the compressed air idea as I was unaware of that method.
    The silicone item always stuck in one side of the mold.
  9. That explains why my first few items didn't want to come out too easily.
  10. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Wax-PVA-wax is pretty much SOP. I always thought of pva as barrier as opposed to release agent. Epoxies, urethanes, polyesters, etc will bond tenaciously to PVA but will not reduce or penetrate it. The wax on both sides release it. Upon demolding, I always had this PVA afterbirth which was like the thinnest cellophane. The thing I didn't like about it was even with the greatest of care in applying the PVA, the surface finish of a well polished mold would be somewhat diminished.

  11. mytwhyt

    mytwhyt Copper

    Gerald, for a few you might consider injecting wax in the molds and casting some lost wax in investment..
    DavidF: The great thing about building fiberglass boats is you get to paint the boat first, then build the boat on the paint job.. Its much harder the other way around..
  12. Melterskelter

    Melterskelter Gold Banner Member

    I looked up APEL and and see that it is a silicone spray. I think those sprays are great for two-part rubber molds and the like. And I used to use it on a surface I was mixing 5 min epoxy on. But I found that waxing that surface resulted in better release of the residual epoxy than I got with silicone. And I can say for certain that for silicate cores, silicone is a very poor release agent.

    And it is also worth noting that hard plastic molded items are usually forced out of their molds with ejection pins. Might be a reason for that. Good ole Johnson's wax seems to be a very reliable release agent. West systems also suggests "Vaseline, paste wax, shortening, and cooking sprays can be applied to objects to contaminate the surface to keep the epoxy from sticking." They do not suggest silicone spray.

  13. DavidF

    DavidF Administrator Staff Member Banner Member

    Not all pva is equal... we used purple colored pva, not the green stuff. It was thicker leveled better and had a high glassy shine to it when sprayed...
  14. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    I'd like some of that. Can that be bought in small quantities like a quart or gallon?

  15. DavidF

    DavidF Administrator Staff Member Banner Member

    I can't even remember who made it.. that was 18 years ago lol
    We got it in 5 gallon containers..

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