High Aspect Ratio Features and Deep Draws

Discussion in 'Lost foam casting' started by Al2O3, Aug 22, 2017.

  1. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    This thread is a condensed version of an AA post at the link below where the unabridged version and contributions of others can be found.


    OK, so we’ve had intersecting tubular plumbing, small unsupported loose sand cores, how about deep aspect ratio features? So I thought I'd start another thread for this subject. Sing along please:

    1.1 Cylinder Parts Fab.jpg

    1.1 Cylinder Parts Fab.jpg

    It’s 2” bore. The fin thickness and spacing are about 0.1” and cylinder itself about 3/16” wall. The fins are 9/16” deep so between a 5:1 and 6:1 aspect ratio, no draft of course.

    Ah heck, it needs a cylinder head too. Same fin dimensions. I just drilled a shallow hole with a forstener bit, ripped the fins on the table saw while the block was square, then sanded it round and rabbited the bottom with a router bit. -It was quick.

    1.3 Cylinder and Head.jpg

    1.4 Head on Cylinder.JPG

    Are ya still with me?

    I made a router jig so finned cylinder foamies are easy to come by now.

    1.5 Jig.jpg

    It is further discussed here


    Here are the resulting patterns. I applied a very thin coat of mud on the jig machined pattern. I just slathered it on and brushed with a small paint brush while it dripped off. This thin, it a couple coats. I poured them all together.

    1.6 Fomies.JPG
    1.7 Fomie Close Up.JPG

    1.8 Thin Mud.JPG

    Here they are sprued up. I think I could have just as easily gated into the side of the head and cast it at an angle like the rest of the parts but decided to use a horn gate on the head to see how well it worked running in blind under the head.

    1.9 Sprued Foamies.JPG

    When I was machining the first larger pattern before I made the jig, I gouged a few of the fins. So I thought it would be a good test part to see if the thin spots filled. So I cast it first. It filled well and was a good part. You can see where the pattern fin was thin and it seem to cast just as the pattern appeared. This one was not coated; just bare foam in coarse sand.

    1.10 Sample Cylinder.jpg

    Seeing how well the sample part poured I just decided to cast the remaining foamies together in the same session. Here they are in my lost foam rig before I slipped the pouring cup on them.

    1.11  Cylinders In Sand.jpg

    …and here they are as cast. They all filled well. The larger cylinder and head were bare foam in sand and the smaller cylinder I cut on the router jig was coated with dry wall mud.

    1.12 Cylinders As Cast.JPG

    Here they are with the sprue and gates removed.

    1.13 Larger Cylinder and Head.JPG

    1.14 Small Cyl.JPG

    1.15 Small Cyinder.JPG

    1.16 Cylinder Group.JPG

    I really didn’t make much effort to improve the foamie’s finish on the smaller cylinder but I did take the time to coat it with several thin layers of drywall mud and must say, it makes for a nice part and think it may modestly help with mold stability. Success came quickly with finned cylinders. Wow, I’m very impressed with the lost foam process.

    Here's a thread of a similar part for a chainsaw cylinder head.



    Attached Files:

    Last edited: Aug 23, 2017
    Red97 and DavidF like this.
  2. PatJ

    PatJ Silver

    That is some really nice foam work.
    Very creative.
  3. HT1

    HT1 Gold Banner Member

    you have exceeded what I thought was possible witth lost foam

    V/r HT1
    DavidF likes this.
  4. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Thanks Pat, much appreciated.

    Me too! -Still learning the art of the possible and re-learning some things I thought weren't possible.


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