| |
| |
 |
| |
The most effective sprues are the type that are flared and round. A "Channel" must be made in the investment that will allow metal to flow easily without restriction. Sprues should be attached to the heaviest section of the piece. When the molten gold solidifies and shrinkage begins, the area can draw from the tree and button and porosity can be prevented. |
| |
| |
 |
| |
The main sprue or tree (trunk) should be at least five times the size of the individual sprues. Size can vary, but by creating an undersized tree, you will choke up and restrict proper flow. Start sprueing at least 20% above the base. Leave a perimeter of approximately 3/4 of an inch between the pieces and the flask (and the top). Inappropriate size sprues and tree can cause casting defects. A "Rule of Thumb" to go by would be that the "pieces cast should be equal in weight to the sprues, tree and button combined." Remember it as the 50-50 rule (pieces=tree+button). |
| |
| |
 |
| |
Separate casts should be made for different sized pieces. Light, medium and heavy pieces should not be placed on the same tree. The recommended flask temperatures will vary up to 500°F between light and heavy pieces. Casting with the incorrect temperature can cause all sorts of defaults. A cool cast of small pieces can cause incompletes. A too hot a cast of large pieces can cause porosity. Always check our "Recommended Flask Temperatures Chart" as listed. |
| |
| |
 |
| |
To allow a proper burn-out, without trapping potential gases, the pieces employed in the tree must be free to melt out cleanly. The sprues, tree and button wax should be of the type with a lower melting temperature. This will allow them to burn-out first and leave a clear channel for the pieces to do the same. Trapped gases can otherwise cause mold erosion and ruin the pieces. |
| |
| |
 |
| |
For a proper Burn-out of wax from the investment flask, all the wax must flow out and be substituted with air.
Heat to at least 1350°F. Make sure you have "Grooves" on the base plate or space under the flasks to allow the wax to flow out.
Elevate the flask 1 - 2 inches if these grooves do not exist in your Burn-out oven. Proper air supply and exhaust are essential
to avoid problems that will arise due to insufficient atmosphere and trapped gases. |
| |
| |
Always follow Burn-out procedures as instructed by the investment manufacturer.
After Burn-out, allow the flask to cool down to the correct "Recommended Flask Temperature". You are now ready to introduce metal into the flask. |
| |
| |
 |
| |
Ross Metals believes that the above data is accurate and reliable. However, they are only recommendations given to you free of charge, and should be employed by you with discretion and risk. Ross Metals assumes no responsibility for difficulties or damages incurred by adhering to this information. |
| |
