Toying with die casting

Discussion in 'Die casting' started by DavidF, Oct 20, 2017.

  1. DavidF

    DavidF Administrator Staff Member Banner Member

    Now keep in mind, these are just tests to get an idea of how things will work out if I start die casting in the home foundry.

    What i did was machine a small mold in aluminum and melt some zinc in a handle ladle with a torch and pour it in, then sat a weight on top of it. By no means is this proper die casting. It was simply a test to see how tings would transfer over and to get a better "feel" of things.
    Lets face it, die casting can produce the lowest cost castings however the costs of making a die casting mold can quickly mount not to mention the cost of machinery to produce the castings.
    My objective here is to attempt to produce low cost die castings with a home cnc and a cold chamber die casting machine (that is home built as well) for production of short runs of parts.

    Here is a shot of the mold. It would still require significant polishing to get the correct surface finish and release required..
    20171020_201258_resized.jpg
    and here is a couple of shots of the cast "part??"
    20171020_201551_resized.jpg 20171020_201358_resized.jpg

    Considering the low pressure from the weight the casting did not come out too awfully bad. My first observations are that the mold temp needs to be much higher than what was achievable by sitting the mold on a hot plate and that a bit more pressure would be needed than just sitting a weight on top of the melt.
    The other thing is ejecting the casting from the mold. There was alot of resistance getting the part to release. This could just be from the poor surface finish.
    These initial tests show great promise in my way of thinking (in my crazy way of thinking) and I am looking forward to making progress in this area of the home foundry....
     
    Last edited: Oct 20, 2017
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    well DAMN!! The whole reason I wanted to go the die casting route was for the surface finishes I wanted to achieve prior to plating. I just ran the two castings across the buffer on the lose wheel with some white diamond compound. The results are very appealing and ensure my initial thoughts on the correct avenue this venture.... 20171020_210522_resized.jpg
     
    Mark's castings likes this.
  3. Tobho Mott

    Tobho Mott Silver Banner Member

    Ok, now that is pretty cool... Should be interesting to see where you take this!

    Jeff
     
    Last edited: Oct 21, 2017
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Looks encouraging. Will zinc always be the metal of choice? How far do you plan to take it?.....will they always be open die or will you eventually introduce gate, pressure fed metal, die temp/cooling etc?

    For emblems with flat backs, if you add an ejection feature, what you have might be good enough if you build yourself a little press to apply the squeeze and hill. Not sure how long you'll get away with an aluminum die. Polished or not they may be sticky. There are of course many spray mold releases for permanent mold but will likely reduce surface quality for what you are looking for. Anodize or some plating may greatly extend life or alternatively just require some occasional polishing as the surface finish is degraded by metal contact. How many shots are you looking to get out of a die?

    Best,
    Kelly
     
  5. DavidF

    DavidF Administrator Staff Member Banner Member

    This was just a quick test. Im going to cut a gate into the mold later on today to see if I can get the mold to fill under gravity. I suspect I will have trouble with the melt freezing before it completely fills. That is unless I put a heater cartridge in the mold.
    Later on I will make up a way to inject the metal into the mold under pressure. Waiting on a book to show up on die casting machines.... When I go to make an actual mold i will use something a little more proper like stainless steel or tool steel and they will be real molds with ejectors and all... I doubt that i would ever have to make more than 10 or 20 of any given emblem, but die casting is the only way to get certain designs to come out properly.
     
  6. DavidF

    DavidF Administrator Staff Member Banner Member

    This is an emblem I was recently asked to make. The shrinkage I would get if I took a mold from one and did it as a lost wax casting would be unacceptable, also there is no way to machine those small bars in the center of the casting as a positive, but would be easy to do as a negative in the mold.... These are for a jeep FC 170, odd looking things...
    fc170.jpg
     
  7. DavidF

    DavidF Administrator Staff Member Banner Member

    So I threw it on the mill and cut a gate into the mold. First pour in a hot mold... Yep froze short..
    20171021_141202_resized.jpg

    Second pour, mold hotter than Hades! Oh so close!
    20171021_142908_resized.jpg 20171021_150800_resized.jpg

    I think that with a little more head pressure and a slightly larger vent I would have it. But this was a nothing part just to test out some tool paths and see how the mill could handle it.
     
  8. cactusdreams

    cactusdreams Copper

    Great proof of concept! That's how we figure out stuff we aren't supposed to be able to do at home. And you got the first die casting thread!
     
  9. ESC

    ESC Copper Banner Member

    David, I have used parts like the your emblem to cast two part molds in PoP or investment and poured with a low temp metal. At least you only get that one shrink, and with the two part mold you can sharpen up the detail. I was able to get multiple castings from the mold before it started to break down. I'll try to find the pieces. There not as detailed as you emblem but they are an accurate copy.
    I also made a permanent mold from cast iron for the pistons with pullaway cores that I vacuumed to help with detail. The pistons were aluminum melted in a ladle the way you did and the mold settled at about 500 degrees while in use. I used motor oil as a release and could make about 15 pistons in an hour.

    IMG_20171026_140055.jpg

    pistonmold5.JPG
     
    Last edited: Oct 26, 2017
  10. Jason

    Jason Silver Banner Member

    Yup... Odd looking thing. A wannabe Unimog. There cant be very many of these ugly jeeps left in the
    world. I hope you are making enough money to make it worth your time off that emblem.

    [​IMG]

    Unimog. Yes they still build these today. Ultimate swiss army knife. That curve in the grill pictured below
    is a PTO shaft hookup
    [​IMG]
     
  11. DavidF

    DavidF Administrator Staff Member Banner Member

    Do you have a picture of the piston as cast?? Im assuming that is the piston mold in the second picture?
     
  12. ESC

    ESC Copper Banner Member

    Here are a couple. The first is the casting in the mold. At first I tried a horn gate, but it didn't fill so you can see it plugged off. I then inverted the mold in the fixture with the pull away core handles hanging down and poured directly into the mold. The wrist pin cores were tapered and removed first then the center core was cammed out to release the two semicircular cores that formed the remainder of the interior of the piston skirt. The vacuum passages are the small gooves that start from the hole nearest the hinge pin. Last one is the finished piston on a rod.

    PA220012.JPG pistonmold2.JPG PA220009.JPG
     
    Jason and DavidF like this.
  13. DavidF

    DavidF Administrator Staff Member Banner Member

    now thats friggin cool....
     
  14. PatJ

    PatJ Silver Banner Member

    That is impressive.
     

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