Wax piston sprue extruder?

Discussion in 'Lost wax casting' started by Zapins, May 21, 2018.

  1. Zapins

    Zapins Silver

    Thinking about how easy it would be to make a sprue extruder. A 6 to 7" diameter aluminum tube with about 1/2" thick walls would work for loading wax into, then a 3 ton piston (that extends about 24" or so) could push a plate through the tube against a die and force warm wax out.

    You'd need to line bore the tube and make sure the piston was well fitted, then thread the end of the tube so you can attach different sized dies and you'd be set. Basically 3 parts, piston/plate, tube, threaded die plate. Done.

    Not sure I can line bore with my lathe without a lot of modifications but perhaps a local machine shop can make it for me and thread the end? Might be worth it to avoid the PITA it is to melt/cast my own sprues all the time. Especially since I need very thin sprues for TIG work and then large 1" sprues for casting and everything in between.

    Like this:

     
  2. oldironfarmer

    oldironfarmer Silver Banner Member

    Looks like a couple of hydraulic cylinders would do the job, one for oil pressure and one for wax.
     
  3. Jason

    Jason Silver Banner Member

    Uh yeah... sounds easy in principle. The execution is a bit different. I have sprue showing up tomorrow. I'll pop a photo of it. 5bucks says you'll change your mind. ;)

    Hey zap, why the need for skinny tig filler rod? I buy my bronze filler at airgas and man it's a DEAD RINGER for the bronze I've been pouring. It's not expensive and a pound or two will last you a long long time.

    Meanwhile, watch this for entertainment. It's pretty cool.
     
    Last edited: May 21, 2018
  4. Jason

    Jason Silver Banner Member

    As promised... This is 9lbs of sprue wax. 1/4", 3/8" and 1/2" from Douglas and Sturgess. 77bucks with shipping. That's a lot of wax sprue. They are 24inches long. I could build a machine, but ya gotta pick your battles. If I did, I would build 2 at the same time and give one to a buddy. ;)

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  5. Zapins

    Zapins Silver

    We are buddies right? :)

    I'd be happy to build a machine. I think long term it would add up to make a machine. Those rods are pricey. I use that much sprue material every couple months.
     
  6. Jason

    Jason Silver Banner Member

    Yes good old buddy of mine! :D
    And I thought it was a decent deal. :oops:
     
  7. Zapins

    Zapins Silver

    I might ask at some of the machine shops near me this next month. See how much they would want to bore a 24" tube out and thread the end.

    I doubt I have the skills to do it on my lathe or the time for that matter :(
     
    Jason likes this.
  8. Jason

    Jason Silver Banner Member

    Try to cut a deal for 2 setups. I'll chip in. I have the heater already pictured in the video I posted above. You can find them on Ebay. I think I paid 20bucks. Been awhile, but it wasn't much.
     
  9. Zapins

    Zapins Silver

    Hmm you think a heater would improve the extrusion? I was thinking of making a warmer to batch warm large chunks or wax and put them in warm.

    Probably wouldn't be a bad idea to warm it from outside with that heater.

    Wonder what the actual cutting edge of the die needs to look like? Sharp edges or beveled?
     
  10. Jason

    Jason Silver Banner Member

    You will need some heat on the end of that thing. I would use a sharp edge on the dies. Somewhere on that guys website or YouTube page he had a few details on that was pooper. Take a snoop around. You might finger it out. Did you consider a cheap hydraulic press from HF to do the pushing??
     
  11. Zapins

    Zapins Silver

    Found a 24 inch 3 ton press for about 40 to 50 bucks.

    The expensive part will be the boring and machining.

    It would be easy to use a propane torch to warm the die up if needed? I think the pressure involved will help heat the wax up as it is extruded. I wonder how necessary a heater will be. I don't see one in the video I linked. Seems pretty low tech.

    Not sure how you'd make hollow tubes though. Pretty sure this would be much easier for thin stringers or smaller sprues. The larger sprues would work too but aren't as hard to make the old fashioned way as the thin ones are.

    The material costs are fairly high. Half inch thick walls on a 24 inch length 6.5" diameter tube is about 90 bucks. Then I'm guessing machining costs will be 150 to 200 if they can even bore it. And then a few fittings and the press should be another 50 to 100. So I'm guessing around 400 bucks for one unit.
     
  12. Jason

    Jason Silver Banner Member

    yeah.. makes 77bucks sound cheap.
     
  13. Jason

    Jason Silver Banner Member

    He's got a heater on the end of that thing. Look close, you'll see the wires. the heater looks like a clamp.
     
  14. I was thinking a pot of hot wax with a hole in the bottom and a removable plug to block it that empties into a tank of cold water might work without a press.
     
  15. Zapins

    Zapins Silver

    Hmm. What was the name of the heater you got?

    I'll look into them and see.

    I suppose if I Jerry rigged my lathe and knew what I was doing I could make it myself for the cost of materials. I just know I don't know enough to do that reliably yet. If I had a few months I could figure it out but I'm away from my lathe. Meh.

    What rods do you get for welding? I was concerned that the color would be ever so slightly different with store bought bronze rods and it wouldn't match my everdure sculptures. Even a small difference can ruin a piece.

    Wax floats on water and spreads out when it touches. So you get a thin skin of wax with tons of bubbles rather than a solid rod of wax when poured like that.
     
  16. Jason

    Jason Silver Banner Member

    Here is the label from the sil bronze rod at air gas. Are you still using home made bronze? Budget casting supply is 5.50 a lb and FREE SHIPPING for CMX certified ingots. That's the stuff I use, but I don't buy from them.

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  17. Jason

    Jason Silver Banner Member

  18. oldironfarmer

    oldironfarmer Silver Banner Member


    A hydraulic cylinder is relatively cheap and is already honed to an excellent surface with a nice fitting piston. If you cut a window in one in order to load the wax all you have to do is make your die at the other end and provide some means of retracting the piston. An electric heater would make the wax flow easily and it might be profitable to liquefy the wax for withdrawing the piston. You could even make the wax come out the port of the cylinder and into the die chamber. For small diameters you can machine multiple holes into your die plate and extrude more than one at a time, or two or three sizes.

    You make a hollow tube by supporting the inside disk from the feed side of the die. The extrusion material (wax in this case) has to flow around the supports to get to the die opening.
     
  19. Jason

    Jason Silver Banner Member

    Maybe this will help you. Something strangely satisfying about watching this thing shit candles.
     

  20. I forgot about that, you'd need something with a lower specific gravity than wax's 0.9 that won't dissolve the wax, vegetable oil might work with the same density but then it's all oily. So much for that idea...

    Edit:
    An arbor press in one of the larger sizes would probably be up to the task, especially with a smaller bore cylinder. You could extrude yard long sprues one at a time by hand with a pull of the lever while listening to podcasts and having the occasional beer.
     
    Last edited: May 23, 2018

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