Sand casting n

Download Sand casting n

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  • 1. Sand casting
  • 2. Outline Requirements to sand Types of sand Advantages of sand casting Disadvantages of sand casting Steps for Sand Casting
  • 3. Sand casting is a good option, if you already have a part. And youcan draw a parting line on the part so that the both halves can bepulled from the sand without distorting the sand.
  • 4. Requirements to sand Ability to retain mold shape during packing and pouring. High temperature stability. Permeability for the gases liberated from the mold and solidifying metal. Collapsibility - ability of the sand to be shake out.
  • 5. Types of sand Green sand. petro bound sand Sodium silicate bonded sand.
  • 6. Advantages of sand casting Low cost of mold materials and equipment. Large casting dimensions may be obtained. Wide variety of metals and alloys (ferrous and non-ferrous) may be cast(including high melting point metals).
  • 7. Disadvantages of sand casting Rough surface. Poor dimensional accuracy. High machining tolerances. Coarse Grain structure. Limited wall thickness: not higher than 0.1-0.2 (2.5-5 mm).
  • 8. Steps for Sand Casting :-
  • 9. 1Place your part/s on the molding board. Sprinklethem with parting dust. Simple Backing Soda workswell as parting dust and its cheap.
  • 10. 2Place a frame, called the "drag" around thepart/s, then start adding your sand, beingsure to tamp it in well around the parts,especially when there are fine details.
  • 11. 3Once the "drag" is full, level the sand withthe top of the frame using the other boardor "bottom board" that will also beused to cover the drag. Then hold ontoboth boards and turn the flask over so the"bottom board" really is on the bottom.
  • 12. 4Remove the molding board.
  • 13. 5Use a knife or blade to excavate the sandaround the part/s just until you can safelylift the part from the sand without disturbingthe remaining sand.
  • 14. 6Add a "sprue" or the hole through whichyour molten metal will be poured. I amusing a pipe to mold the sprue. Firstpushing one end into the sand to remove acore and form a hole that is a little deeperthat the bottom of the part/s. Then addparting dust.
  • 15. 7Place the pipe back in place to from thesprue. Paper towel rollers work well if youdont have a piece of pipe. Then set on thetop frame or the "cope". Latch the frame inplace if you have latches.
  • 16. 8Add more sand and again gently tamp it in aroundthe part as well as the pipe to from the sprue.There are special tools for this, almost anythingincluding your fingers works well. A blunt 5 poundbock of steel make a good ram for packing frames.Larger frame will need to be more tightly packed.
  • 17. 9Flatten off the sand level the the top edge of theframe or "cope" and also form a funnel cup aroundthe pipe that is forming the sprue. This will giveyou a bit larger target when you pour the moltenmetal. Be sure to leave some sand between thefunnel opening and the wood frame.
  • 18. 10Gently remove the pipe that was formingthe sprue. Then place the "molding board"on top.
  • 19. 11Unlatch the frames and carefully lift off thetop frame or "cope" and set it on itsside. You should be able to rest it on itstop, but less movement is better.
  • 20. 12Using a couple of knife blades, delicatelylift the part/s from the bottom frame or"drag". Be careful to lift the part/s straightup so as not the disturb the sand.
  • 21. 13Using a knife or blade carve out the "gating" systemthat will allow the metal to flow into the part and theair to flow out. The "gates" connect the sprue to thepart a little above the bottom of the sprue. Thevents are very small channels that run from thesmallest section of the part to the edge for cope.
  • 22. 14Time to melt some aluminum.
  • 23. 15Pour the flask with molten aluminum. Dontpour too slowly or the aluminum will hardentoo quickly in the gate, coking the part off.
  • 24. 16After 5 minutes the flask can be opened forinspection.
  • 25. 17Final Parts next to original after the beingbrushed off.
  • 26. Any questions ??