Automotive Water Neck

Discussion in 'Lost foam casting' started by Al2O3, Sep 26, 2017.

  1. Al2O3

    Al2O3 Administrator Staff Member

    This thread and casting were sort of the genesis of my lost foam casting journey.

    Over the last couple days I completed another batch of these water necks which prompted me to review the related threads here on the forum and when I read this one, I thought wow, I’ve changed quite a few things even since this thread. I’ve made a lot of these water necks over the last five years and it’s easily my most reproduced casting. Collectively, these process refinements have improved the quality and produced very high first pass success rates on this and more complicated castings.

    When the above thread was posted I was still using a “Kush Cup” (short straight section of muffler pipe or soup can) and expendable foil sprue for a pouring cup. I haven’t used those for years.

    They were certainly better than no pouring cup at all but I realized much more tranquil pours and surprising degree of improvement when I started using reusable offset pouring basins as discussed here.

    I was still using non-setting drywall mud (joint compound) for a refractory coating and applying with a brush. These days I use a commercial refractory coating and dip coat. The biggest advantage of dip coating is speed and uniformity of coating discussed here. I’m often asked about the commercial coating. I do like the commercial refractory coating for reasons discussed in the second link, but for most hobbyists, I think comparable results can be achieved with non-setting drywall joint compound, brushed or dipped.

    I have since built dedicated molding rigs to vibratory pack and process molds. They are both faster and more effective at packing, and also serve as a means to filter and store sand.

    As in the thread above, I use A356 ingot because I’ve found when bought in quantity to only be marginally more expensive than having to buy recycled auto parts, and I know exactly what I have. I use a resistive electric furnace which has benefits for aluminum. It’s well sealed, the atmosphere starts out as air and becomes oxygen depleted. How depleted I don’t know. With the combination of the two, I stopped degassing the melt and have almost no dross and good dense hermetic castings. Lost Foam typically needs an additional 100F-150F than conventional sand casting. I pour at 1400F-1450F.

    Because I’m tooled to do so and it’s fast, I still use my pin router to make the tubular sections for these parts but use my cnc router to make all the other little bits in nested batches because it’s faster. These days I also almost exclusively use the cnc router for foam pattern making now. It’s more accurate and much safer than having my hands in the vicinity of cutters and enables unlimited pattern complexity.

    I use wax for detailing patterns but as sparingly as possible and strive to keep the pattern as near pure foam as possible. I use a wax formulated especially for lost foam casting that exhibits the same melting vaporization temperature as XPS foam. It’s available from Freemen Manufacturing and applied with heated fillet tools.

    Wax is much denser than foam and the lower the mass to be evaporated by the molten metal, the better.

    For more on my lost foam casting learnings see this thread:

    Tops and dtsh like this.
  2. ESC

    ESC Silver

    Cleaning the shop today and look what turned up. From the date on your original postings this was in 2017. Time flies, I think we were still on AA. As I remember we didn't see any point in casting the logo'd sample since the the plain piece turned out so well.

    Tops and Tobho Mott like this.
  3. Al2O3

    Al2O3 Administrator Staff Member

    So true. Yep, I completed my furnace build and did the first home melt in May 2016, commenced to build other foundry equipment and experimenting with lost foam over the Winter, and though I was still frequently seeing fold flaws, I was so amazed the process actually worked and such shapes could be cast in unbound sand, in April 2017, I sent you, DavidF and another member foam patterns to play around with. Consequently, I never built the muller or molding bench.

    Fast forward five years and here we are, still at it....Monday's bounty.......13 pours through ten 100-lb flasks and a noticeable back ache LoL!

    5-23-2022 Bounty.jpg

    BattyZ, Tobho Mott and Tops like this.
  4. BattyZ

    BattyZ Silver Banner Member

    Now, this is a nice production run! Kudos!

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