Seeking help with Sprue and Vents

Discussion in 'Lost PLA casting' started by John Gaertner, Sep 28, 2021.

  1. John Gaertner

    John Gaertner Silver

    Hello Forum, So I have several of these aluminum oil strainer bodies 3D printed with PolyCast. I would appreciate any constructive suggestions on best shape and location for making my sprue and vents. I am attaching a jpeg with the hopes some of you will help. Thanks.
    Pitcairn-Oil-Strainer-3 view.JPG
     
  2. DavidF

    DavidF Administrator Staff Member Banner Member

    Are you using block or shell??

    I'm thinking you'll probably have to Gate into the back of the bracket, then run a vent up off where the drain plug is. Basically casting it upside down... hope you printed a hole where the drain plug goes.... ;)
     
  3. John Gaertner

    John Gaertner Silver

    I am using shell investment. Thanks for asking. Should have included that detail! The drain plug is open on the 3D prints.
     
  4. John Gaertner

    John Gaertner Silver

    Here is a picture of my ideas for the sprue and vents. The vents do not have to be this involved, I do not think? I just drew them as round lofts.
    Can anyone help with whether the vents should be at the top of the pink colored boss's edge to insure no trapped air? Is there any kind of rule
    for the size of the sprue compared to the part?
     

    Attached Files:

    Last edited: Sep 29, 2021
  5. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    Think I'd be inclined to only vent the top. Could be a couple soda straw size contacts and could tie them off to the sprue for strength. Leaving the drain hole open might make it a little easier to dip/shell or invest. You may want to decrease the contact area of sprue keeping it attached at very bottom of mounting flange. This will be aluminum right?

    Best,
    Kelly
     
  6. John Gaertner

    John Gaertner Silver

    Hello Kelley, Thank you for your suggestions and taking a look at this. Yes, aluminum casting, dip investment using SuspendaSlurry. Will redo this sprue per your suggestion. You feel there is no need to vent the individual bosses? John
     
  7. Al2O3

    Al2O3 Administrator Staff Member Banner Member

    If it's a nicely controlled and tranquil fill from bottom up I wouldn't see why those features would need to be vented. Having the optimal melt and shell temp along with insuring debris-free shell will probably be more critical.

    Best,
    Kelly
     
  8. John Gaertner

    John Gaertner Silver

    OK, Great. I have always kept my burned out shells in my PID controlled oven until right before the aluminum charge is ready. So been pretty happy with the results.
    This is the largest part I have tried to make. Thanks, John
     
  9. John Gaertner

    John Gaertner Silver

    Last question for the group, I hope. I redesigned the sprue which I am going to try to 3D printing this weekend in 2 halves. Do the pink boss ends in my picture need to be closed or can I leave them open? The pink area is extra to the parts requirements but I want to be able to CNC machine each boss flat before CNC threading them for their oil line connections. I will vent the top portion using convention wax round rods as has been suggested. Thanks! John Gaertner
     

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  10. John Gaertner

    John Gaertner Silver

    I got my patterns' sprue's installed. I will fill the end with wax before I start doing the slip investment process. I will install the round rods of wax vents closer to investing time. I received my 60 Lbs pail of Suspend-A-Slurry earlier this week.
     

    Attached Files:

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