Lost Wax Cast Ring

The Big Picture

• Make a ring model out of wax.• Make a mold around the wax.• Melt out the wax so you have a ring-shaped

hole.• Fill the hole with melted silver scraps (you did save up your scraps, didn’t you?)

Casting is like a taking a cruise……if you’re late, you miss the boat.

Keep up with your work on this unit!

• This is an individual project with an individual grade, but you will be casting as a group. Please do a quality job finishing your tasks on time and don’t let your group down.

• Because of the amount of dry time, cure time, and burnout time required, if you are not ready to tree your ring on the due date, you won’t be casting.

How the pros do it

These videos show the basic steps we’ll be taking. After this will be specifics on how you will design and create your own model.

http://www.youtube.com/watch?v=nbST9SBtBNchttp://www.youtube.com/watch?v=Yyx7RXIy3ng

Hints for working with modeling wax

• Use a coarse file to remove large chunks. Work your way from 80 to 600 grit sandpaper to further smooth and finish your model.

• Modeling wax is really brittle. Don’t press too hard or cut into the wax. Take off a little at a time. Support your ring on a wooden ring mandrel.

Part One:Making the Individual Ring Model

• This portion of the project needs to be complete by the end of the period on ***. You can take home most of the materials to complete the ring model, so if you’re absent, slow, or have a catastrophe, you can still get the model done in time. Absolutely no extensions, no late work, no excuses.

• A really great idea would be to have the ring model done a day or two BEFORE the due date just to be sure. And let your group members know where it is, just in case you happen to be absent on the day it’s due.

Sand sides flat• Sand the flat sides of the ring where it was cut

off the wax cylinder.• Sand with 80 grit until you have the thickness

you want.• Work your way up to 600

grit to smooth your sides.

See me for a whole page of ideas. Keep it simple.

Size ring model

• Try on the green template as a ring. Find the size that is just a bit too tight.

• Using the green template, scribe a circle that is a little smaller than your ring size. This is tricky but quick—come see me if you need help with the scribing and I’ll do it for you.

• Sand with 80 grit on a wooden mandrel until the ring is about ¼ size too small. Be sure to flip ring occasionally so it is even on both sides.

• Work through to 600 grit sandpaper to create the correct size ring model.

Shape the outside

• Decide how you want your ring to look on the outside.

• Do not make a simple band that could be made in 10 minutes with a piece of sheet or wire—instead, do something 3-dimensional that you couldn’t make otherwise.

• File and/or sand until your ring looks the way you want it to.

Thin out the ring shank

• The top of your ring can be quite thick, but the back and sides of your ring need to be a maximum of 8 gauge.

• Use the Brown & Sharpe gauge—your ring shank should fit in the 8 ga space.

Reduce extra weight

• There is a weight limit on your ring, because very large rings are prone to cracking when casting.

• Your individual wax model can be no more than *** grams. Weigh it on the gram scale.

• If your ring is overweight, you’ll need to remove and rework it until it meets the guideline. Ask for help if you’re not sure what to remove.

• Write down your individual ring model weight on your purple casting worksheet (PCW).

Gather your individual silver

• Weigh your silver scraps, using a gram scale. If you’re not sure, bring the scraps to me. If I’m not sure, heat them up till glowing red and pickle them about 5 minutes, then I’ll be able to tell for sure.

• Write the weight of your individual silver scraps on your PCW.

From here on out, everything will be done in groups of five. You can choose your own groups, or I can assign you to one. Write down

your group number and members on your PCW.

Part Two:Making the Group Sprue Tree

Pick up your group supplies

Each group will need• One piece of thin sprue wax (pink, green, or

blue)• One short piece of sticky wax (yellow)• One sprue trunk (pink)• One rubber base• One metal flask• One OLD WAXY X-acto knife

Determine your final group

• If a member of your group is not done with his or her model by the deadline, move on. Unfortunately, because of the complex process, there is no late work in the casting unit. If you wait for someone who wasn’t prepared, your group runs the risk of not being ready to cast and not having any rings at all.

• If you do not finish your ring by the due date, you can still get points for your wax model. You will not get points for casting and finishing, and you will not have a silver ring after the casting process.

• If you are not ready, please let me know so I can condense groups so casting will go more quickly.

Pick up your casting supplies

One per group of each:• Alcohol lamp• Metal pipe section• Rubber base• Red sprue trunk• Green sprue• White sticky wax

Prepare your rubber base• Remove all old tape,

wax, and investment from your rubber base.

• Write your group number on a piece of masking tape and stick it to the side of the rubber base.

• Weigh the base in grams and write the weight down on your PCW.

• Cover your work area with butcher paper

Whittle the end of your sprue trunk

• Use a knife to carve your sprue trunk down so it fits in the rubber base.

• Trunk should not wobble.

• Do not carve to a point.

Insert the sprue trunk

• Slide trunk into base so it doesn’t wobble.

• Trunk should be 1 to 1 ¼ inches high

• Secure trunk with sticky wax.

Attach sprue to your ring• You will attach the sprue at the

back of your ring because it will leave a bump.

• Scratch up the area of the ring where the sprue will be attached.

• Heat sticky wax over alcohol lamp.

• Put sticky wax on your ring• Push the sprue into sticky wax.• Let the connection cool, then test

it to be sure it’s sturdy.

Attach largest ring to your trunk

• Pinch the sprue of the largest ring to ½”.

• Attach ring to top of trunk with sticky wax.

• Hold in place until the sticky wax is cool.

Be sure the top of the

top ring is at least ½ inch lower than the top of your flask.

Attach next two rings to trunk

• The next two rings should be attached parallel to the top ring on opposite sides of the trunk.

• Notice the angled cut on the end of the sprue.

• Be sure you have a minimum of ½ inch clearance between the side of the flask and the side rings.

• If not, remove the rings, shorten the sprues, and reattach them at a steeper angle.

Minimum ½ inch

Attach last two rings to trunk• The final two rings should

be attached below and perpendicular to the other rings.

• When the flask is placed over, they need to be at least ½” away from the sides of the flask. They need to be very secure.

Find group sprue weight

• Weigh your entire group sprue tree, including the rubber base but not including the flask. Write this number down on your PCW.

• Complete the *** section of the PCW individually, then check your answers with your group. Inaccurate calculations may cause your group to destroy its rings.

Turn in your group sprue tree

• If a member of your group is not done by the deadline, move on without him or her. Unfortunately, because of the complex process, there is no late work in the casting unit.

• Bring the entire group sprue tree, minus the metal flask, so that your models can be checked and graded before they are cast.

Part 3:Investing

• Investing means to make a mold around your ring models and sprues. This needs to be done quickly and accurately in order for your castings to turn out.

• When your group is called, bring everyone from the group up. You will watch the group before you, then will begin when it’s your turn.

• After your group has invested, someone from your group needs to stay behind and help the next group.

Insert flask into base

• Do this carefully. If any rings fall of during the process, don’t feel bad—they probably would have fallen off in a later step, but you wouldn’t have known until it was too late. Consider it a blessing. But put them on more securely.

Mix investment

• Add water to the investment until it’s the consistency of pancake batter.

• You want as few air bubbles as possible. Don’t whip the mixture.

• Put the investment into the vacuum chamber to debubble for 2 minutes.

The vacuum chamber

• This machine reduces atmospheric pressure within the bell jar. Bubbles within the investment enlarge, then float to the top.

• No, it is not an anti-gravity chamber.• Do not touch the bell jar during operation—it

is under tremendous pressure and could implode.

Fill the flask with investment

• Pour down the side of the flask over the garbage can.

• Watch rings carefully to see that they don’t float to the top.

• Fill to about ½ inch from the top.• Put back into vacuum chamber to debubble 2

more minutes.

Clean up and help the next group

• Scrape extra investment into garbage. DO NOT REUSE IT!

• Wash rubber bowl and spatula.• Someone from your group needs to stay

behind and help the next group mix their investment.

Part 4:Casting

How to Behave on Casting Day• Casting is potentially very dangerous and requires 100% of my

concentration to keep everyone safe.• Successful casting requires that every step be perfectly timed.

My being distracted may result in the group’s rings not casting properly.

• I will not babysit on casting day. Be responsible adults. If your past behavior suggests you may not be able to do that without my constant supervision, I will arrange for you to be somewhere else on casting day.

• If I am holding a lit torch, and you are not in the group that I am currently casting, don’t come ask me for help, passes, or anything like that. I apologize now for being rude or ignoring you when you do.

Appropriate Casting Attire

Proper safety attire is imperative for casting. On casting day, you need to wear the following:

• Closed-toe shoes• Long, non-synthetic pants (jeans good, polyester sweats bad)• Long-sleeved non-synthetic shirt (cotton sweatshirt good,

football jersey bad)You will be supplied with gloves, glasses, and/or a face shield as

necessary.If you are not dressed appropriately on casting day, you will not

be able to cast and will not earn points for the casting process.

Choose jobs• The Flasker: Removes 1300 degree flask from kiln, flip over and place on casting

table. Being tall and/or having large strong hands is pretty important for this job.

• The Pourer: Hold the crucible of molten silver and pour it into the hole in the flask—quickly and with good aim. Working well under pressure is helpful for this job.

• The Dunker: After pouring, dunk hot flask into cold water, causing thermal shock to crack investment and release rings. Having large hands is helpful but not required for this job.

• The Opener: Open and close the kiln door. Also responsible for removing rings from sprue trunk, and cleaning and returning sprue silver and blue sprue cutters without being asked. Being responsible and trustworthy would be helpful in this job.

• The Chicken: Far away from heat and pressure, turn on the vacuum pump when instructed. Also responsible for cleaning, drying, and returning the flask and rubber base. This is a great job for someone who forgot to wear the appropriate casting attire.

Casting

• I will go through this with your group before you cast. You will need to come watch the group before you. You will also do a dress rehearsal while your silver is melting so you all know where to stand and move. Be sure to speak up if you don’t understand, because once we take your flask out of the kiln, any hesitation could destroy your rings.

Finishing your ring

• Pickle ring for about 15 minutes. Use a toothbrush to remove any remaining investment. Opener—also clean the silver sprue trunk this way before returning it to me.

• File off the sprue button. Use a coarse file until the button is almost flat, then a smooth file, then work though the sandpapers.

• File and sand off any warts your ring may have.• Buff your ring on the big blue buffers. Use Tripoli first

then red rouge.