The Most Difficult Items
6 months ago
Monday, April 12, 2010
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Docs Instructions
Hello and thank you for using Doc’s casting plaster. We have found that Doc’s can be used for a number of purposes. Like casting cad-cam models, or in situations when casting in three hours will save a sale or satisfy a critical account. These extra uses for Doc’s are easier to use if each has its own instructions. We have made those and enclosed them with this letter. Of course, the original platinum casting instructions are also enclosed. Please do call with any questions you might have.
We are also enclosing information on Outcast 950 palladium, the very latest alternative to brittle or expensive white golds. Doc’s is ideal for casting 950 palladium from any casting grain supplier. If it will cast at all, it will cast in Doc’s.
Sincerely,
Daniel Ballard
National Sales Manager
Technical Support Online-WWW.docscasting.blogspot.com
2009 DOC’s Multi-Purpose Instructions
Before you start
· This investment is ideal for 90% or 95% platinum, 950palladium, white gold with nickel or palladium, and any casting from carving wax, plastic, or any cad-cam model material that presents unusual burnout needs.
· Doc’s (Rapid prototype investment) is very different from regular gold, silver, and common platinum investment powders. Water to powder ratios and recommended working times are different and require your full attention to detail. The liquid to powder ratio is always 25/100 as compared to 40/100 for gypsum bonded investment powders. Doc’s is more forgiving than other investments with similar characteristics but that does not allow you to ignore the standard operating procedures. This investment appears much thicker than investment slurries that you may be used to and there is no need for concern. Doc’s will give you satin smooth castings if you follow the directions.
· Using chilled elixir (binder) will help to slightly extend your working time. You should consider your maximum working time to be 4 minutes and getting finished in as little as 3.5 minutes is even better. Because the working time is shorter, prepare your work and materials so that you can get the steps completed within the time allowed. Going beyond the recommended working time will cause you to have nodules on your castings caused by bubbles that were trapped during the extended investing process.
· As you will see later, 3 burnout schedule variations are recommended. The elixir/binder helps control the stress of the rapid expansion of the investment material
- This material can be used to cast flask less or with a flask. No flask liner is required however when using a steel flask it can make the removal of the material from the flasks after casting much easier. Use rubber sprue bases instead of absorbent material bases that are commonly used for platinum investment.
· Weigh your sprue base first before you attach your waxes and record that weight. After attaching your waxes, reweigh your base and record that weight. You will use this information to calculate the required amount of metal later.
· If you are using this material to simply overcome the defects that you encounter from the use of carving or RP waxes, you can just as well use a normal jewelry burnout cycle in the same oven as your normal daily production flasks.
For Casting Platinum, Palladium, Palladium White Gold, Nickel White Gold or Silver With Injection Wax in Our Flaskless System
*For 1 flask (i.e. plastic type 3 1/4” x 2 3/4” o.d.) and assuming injection wax-Not milled or resin photopolymer models
1. 360 grams weighed from bulk box (all powder should be room temperature-70-75F. Liquid at 50-55F.)
A.) Place liquid in small plastic cake mixing bowl. (Do not use black rubber) Add powder to liquid. Wet powder thoroughly with stir stick. About 10 sec.
· 23 mls. Per 90 grams for bulk only. (92-93 mls for 360 grams).
B.) Use a common portable cake mixer with beaters and mix wetted investment for 60 seconds at high speed, beating the mix vigorously with arm action. (Helps to make slurry more viscous)
C.) Tape a collar around top of bowl (if needed) and place under vacuum and boil for 30 seconds after investment rises and falls. (pound table with fists, or you may need to reduce the vacuum a time or two.)
Note:
(Your vacuum equipment should reach at least 29.5” of vacuum and should do so quickly. If vacuum takes too long to reach boil, try a smaller bell jar. Or your vacuum may be too weak, and maintenance or an upgrade will be needed.
D.) Put high tape collar 3” around top of flask…pour investment down sides of flask quickly and place under vacuum. After start of boil, time for a two (2.5) minute span or more under vacuum. Agitate vacuum table with fists constantly.
E.) Investment will start to thicken under vacuum—resembling the “mud pots” at
F.) Note: Flask should “glaze over” (lose its water on top) within about 3 minutes after set aside. Within 15 minutes, the top will develop a “mottled” look. Leave flask alone for another 15 or 20 minutes. Plastic should feel just warm-not hot. Pull the bottom; push the flask out of plastic breaking off the rim. Scrape smooth only on corners; do not scrape top of flask.
G.) The flask will steam noticeably,--reaching 120F. (If using a steel flask, use flask liner material and follow set times above.) Do not set the flask aside for any great length of time, such as all day or night. Proceed when the flask is ready.
H.) Place flask in cold oven to start. Then, immediately set the oven for 1250F. (If using a small electric kiln this rise should take about 45 minutes.) After reaching 1250 F., start timing for a two hour burnout. (More is not harmful...least can be 1 1/2 hours) (If time is not a factor, start with a cold oven and rise slowly to 1250 Fahrenheit. This helps eliminate cracks in the flask). You may also use any overnight program for casting.
I.) For Platinum-At 2 hour mark, pull flask from oven and place on bench—set an egg timer for 30 minutes. (Walk away) At the 30 minute mark, flask temperature will be between 500F. And 600F. Or...you can turn off the oven and let it settle at 500F for at least an hour. Take from oven directly and cast. (If a large crack should appear, place the flask crack-side down in your cradle. Call us.) See footnotes table for more temperatures.
J.) At the 28 minute mark—place flask in cradle using only gloves. Crucible is loaded with platinum and pulled back from the flask on the arm of the machine. (Keep crucible away from flask during melting—pushing it up to the flask right before you throw it.) Don’t dwell on the melt after the crucible joins the flask. No more than 1 second and then throw it. You should modify your machine to have a full cradle for the flask. Call us.
K.) Torch Notes-Melt is started at 30 minute mark. 35 dwt. of platinum will melt within a minute or so. (Always use the larger Wesgo crucible) Take 5 or 10 seconds to super heat metal—i.e. until a white “halo” appears around the entire pool of metal…a definite white ring. At that time, push the cradle/crucible up the arm to meet the flask. Immediately let the arm go. Don’t wait-have the metal ready before you push the crucible up.
L.) Let casted flask sit for 10 minutes. Break out (both flask and flask less) by whacking out with a hammer. Remove further investment by hammering the button hard—rest of plaster crumbles. (If casting stones—let sit until flask is cold.)
M.) Remove with best available investment remover. Strong lye works well. Hydrofluoric acid is too dangerous for most of us to use. You can use commercial investment breakout chemicals available at casting suppliers.
WAX PREP
For Torch Casting-Waxes should always be set up for “indirect contact” with the molten metal. On top of the cone in the base—put a cross bar of 6 gauge wax wire attached with hot wax across the flask and setup waxes directly on the wire itself. For induction casting use your usual method.
Critical Footnotes
| General casting temperatures in Fahrenheit- |
| Platinum casting grains should be cast at 500F. |
| 950 Palladium Alloys should be cast at 1200F. |
| 10kt-22kt Karated Gold should be cast at about 1000-1100F. |
| Sterling Silver or any Deox Silvers should be cast at about 1000-1100F. |
You can use a steel flask if you wish, be sure to use a liner for ease of flask removal and easier breakout.
Do not allow very humid air or condensation to get into your plaster. If your area gets humid you will get more cracks in the investment.
For ultra high strength burn out at 1600 F.
For larger flasks multiply your powder in grams by .255 and use that number of milliliters of binder.
Alternative Methods That Work With Docs:
Method A: (For larger flasks)
· Program your oven controller for a ramp rate from 4 degrees per minute to a maximum of 7 degrees per minute. This investment material is very resistant to shock so your ramp up speed can be faster than with gypsum-bonded investment.
· About 1 hour after investing, put the flask into an oven that is preheated to about 300oF (150oC), with the wax button facing down.
· Ramp directly up to your top burnout temperature of about 1350 oF - 1600oF, depending on the metal you are casting.
· Hold your top temperature for 2 – 4 hours depending on the amount of wax in the flask and the ending top temperature of your flasks. Lower top temps and higher wax content require a longer top temperature dwell times and higher top temperatures and lower wax content require shorter top temperature dwell times.
· It is always a good idea to flip the flasks over around 1200oF in order to allow combustion gases to escape the mold but is not necessary for longer burnouts.
· Your final flask casting temperature will depend on your metal choice and the design of your parts.
· Quenching this material will not cause the investment to break away from your castings. This step is done at the appropriate time to give the maximum benefit to your metal crystal structure. You will then need to break away the investment using a hammer or a high-pressure water blast cabinet.
If you are using this material to simply overcome the defects that you encounter from the use of carving or RP waxes, you can just as well use a normal jewelry burnout cycle in the same oven as your normal daily production flasks.
If you are using this material to simply overcome the defects that you encounter from the use of carving or RP waxes, you can just as well use a normal jewelry burnout cycle in the same oven as your normal daily production flasks.
Method B: (Smaller flasks or small flask-less castings)
Note: Casting flask-less is ideal with this type of material
· Program your oven controller for a ramp rate from 4 degrees per minute to a maximum of 10 degrees per minute. This investment material is very resistant to shock so your ramp up speed can be faster than with gypsum-bonded investment.
· About 1 hour after investing, put the flask into an oven that is preheated to about 300oF (150oC), with the wax button facing down.
· Ramp directly up to your top burnout temperature of about 1350oF - 1600oF, depending on the metal you are burning out. For photopolymer (Invision or resin based) use the 1600 degree peak temperature
· Hold your top temperature for 2 – 8 hours depending on the amount of material in the flask and the ending top temperature of your flasks. Lower top temps and higher wax content require a longer top temperature dwell times and higher top temperatures and lower wax content require shorter top temperature dwell times.
· It is always a good idea to flip the flasks over around 1200oF in order to allow combustion gases to escape the mold but is not necessary for longer burnouts.
· Your final flask casting temperature will vary and depends on the type of metal that you choose and the design of your parts.
Method C: Rapid Results (Smaller flasks or small flask-less castings with no stones)
This is an emergency burnout schedule.
While Doc’s investment is designed to handle the stress, your casting surface may not be as smooth as it will be when using a less aggressive burnout schedule.
Note: Casting flask-less is ideal with this type of material
· Preheat your oven to between 1400oF and 1600oF
· About 1 hour after investing, put the flask into the preheated oven with the wax button facing down.
· When the heavy smoke stops coming out of the exhaust on your oven, flip the flask over with the opening facing up.
· If your oven was preheated to 1600oF then a complete burnout may be possible in as little as 30 minutes. When the flask opening looks clear and free of wax and carbon, you can turn the oven off and wait for it to reach the casting temperature that you are looking for or you can remove the flask from the oven and place it on a fireproof pad on your counter to cool.
o Lower top temps and higher wax content require a longer top temperature dwell times and higher top temperatures and lower wax content require shorter top temperature dwell times.
· Your final flask casting temperature will vary and depends on the type of metal that you choose and the design of your parts.
· The use of an optical pyrometer is ideal for measuring the temperature of the inside of the flasks by pointing it into the pour hole of the flask to take a reading.
· When you have reached your desired casting temperature, load your flask into your casting machine and cast.
· Quenching this material will not cause the investment to break away from your castings. This step is done at the appropriate time to give the maximum benefit to your metal crystal structure. You will then need to break away the investment using a hammer or a high-pressure water blast cabinet.
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