Fundamentals of Spruing Investing Casting

Fundamentals of Spruing,Investing & Casting : 

Fundamentals of Spruing,Investing & Casting PRESENTED BY: Dr. Mubashir Rasheed M.D.S (Student) Operative Dentistry SUPERVISOR: Prof. Dr. Sohail Abbas Khan Head of Operative Department de’Montmorency College of Dentistry Fundamentals of Spruing, Investing & Casting

Outline of Presentation : 

Outline of Presentation Spruing Technique High Heat Casting Investments Investing Technique Melting & Casting Technique Law Of Casting Analyzing Casting Failures Fundamentals of Spruing, Investing & Casting

The Sprue : 

Definition: Its a channel through which molten alloy can reach the mold in an invested ring after the wax has been eliminated. Role of a Sprue: Create a channel to allow the molten wax to escape from the mold. Enable the molten alloy to flow into the mold which was previously occupied by the wax pattern. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips The Sprue Fundamentals of Spruing, Investing & Casting

Sprue Former : 

Sprue Former *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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*Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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Fundamentals of Spruing, Investing & Casting

Sprue Materials : 

Sprue Materials *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Sprue Former Position : 

Sprue Former Position Often a matter of individual judgment, based on the shape & form of the wax pattern. Some prefer placement at; Occlusal surface Proximal wall Just below a nonfunctional cusp Ideal area- point of greatest bulk in pattern. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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Fundamentals of Spruing, Investing & Casting

Significance : 

Significance To avoid distorting thin areas of wax during attachment to the pattern. To permit smooth flow of the alloy. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Sprue former Direction : 

Sprue former Direction The Sprue former should be directed away from any thin or delicate parts of pattern. It should not be attached at a right angle to a broad flat surface. Sprueing should be done at a 45-degree angle to the proximal wall. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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Fundamentals of Spruing, Investing & Casting

: 

Maximum impedance to flow occurs when a Sprue former makes an angle of 90-degree to the pattern *Laboratory Procedures for Full and Partial Dentures by Derek Stanananought Fundamentals of Spruing, Investing & Casting

Significance : 

Significance Since the molten metal may abrade or fracture investment in this area and may result in a casting failure. The entering metal impinges the mold surface at this point (90-degree angle) and creates hot-spot, producing a localized lingering of molten metal after the casting has solidified. Creates shrinkage void, or suck-back porosity. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Sprue Former Length : 

Sprue Former Length The length of the Sprue former depends on the length of the casting ring. Length of the Sprue former should be such that it keeps the wax pattern about 6 to 8 mm away from the casting ring. Sprue former should be no longer than 2 cm. The pattern should be placed as close to the centre of the ring as possible. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips *Laboratory Procedures for Full and Partial Dentures by Derek Stanananought Fundamentals of Spruing, Investing & Casting

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Fundamentals of Spruing, Investing & Casting

Significance : 

Significance Short Sprue Length: The gases cannot be adequately vented to permit the molten alloy to fill the ring completely leading to Back Pressure Porosity. Long Sprue Length: Fracture of investment, as mold will not withstand the impact force of the entering molten alloy. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Sprue former Diameter/Gauge : 

Sprue former Diameter/Gauge Sprue Former should be thicker than the pattern to which it is attached. Since the thin sections solidify and contract first, they will draw molten metal from thicker sections. Diameter 8(3mm),10(2.5mm),12(2mm) gauge Sprue act as a ideal reservoir for these sections. *Laboratory Procedures for Full and Partial Dentures by Derek Stanananought Fundamentals of Spruing, Investing & Casting

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The Crucible, Sprue and the Mould should be considered as being a wedge –shape: 1. correct 2. incorrect *Laboratory Procedures for Full and Partial Dentures by Derek Stanananought Fundamentals of Spruing, Investing & Casting

Significance : 

Significance Failure to cater for this may result in a reduction in density of the casting by the presence of voids called Porosity *Laboratory Procedures for Full and Partial Dentures by Derek Stanananought Fundamentals of Spruing, Investing & Casting

Reservoir And Its Location : 

Reservoir And Its Location Reservoir portion of a Spruing system is a round ball or a bar located 1mm away from the wax pattern. Reservoir should be positioned in the heat centre of the ring.(Alleluia,1980; Ingersoll & Wandling,1986; McLean,1980; Naylor,1986) This permits the reservoir to remain molten for longer and enables it to furnish alloy to the pattern until they complete solidification process *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Reservoirs : 

Reservoirs Round ball reservoir & a bar reservoir also called connector Fundamentals of Spruing, Investing & Casting

Significance : 

Significance Reservoir is the largest mass of any part of the Sprue system & it is present in the heat centre of the ring, it is the last part to solidify. These properties allow continuous feeding of the molten alloy to compensate for Solidification shrinkage & avoid Shrinkage porosity. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Spruing Techniques : 

Spruing Techniques Direct Spruing: The flow of the molten metal is straight(direct) from the casting crucible to pattern area in the ring. Even with the ball reservoir, the Spruing method is still direct. A basic weakness of direct Spruing is the potential for suck-back porosity at the junction of restoration and the Sprue. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Direct Spruing Technique : 

Direct Spruing Technique Fundamentals of Spruing, Investing & Casting

Suck-back porosity : 

Suck-back porosity It can be seen at the junction of restoration and Sprue Fundamentals of Spruing, Investing & Casting

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2. Indirect Spruing: Molten alloy does not flow directly from the casting crucible into the pattern area, instead the alloy takes a circuitous (indirect) route. The connector (or runner) bar is often used to which the wax pattern Sprue formers area attached. Indirect Spruing offers advantages such as greater reliability & predictability in casting plus enhanced control of solidification shrinkage *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Indirect Spruing Technique : 

Indirect Spruing Technique The Connector bar is often referred to as a “reservoir” bar Fundamentals of Spruing, Investing & Casting

High-heat Casting Investments : 

High-heat Casting Investments The high melting ranges of metal ceramic alloys exceed the upper limits of the Gypsum-bonded investments. Phosphate-bonded casting Investments Silica-bonded casting Investments *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Phosphate-bonded Casting Investments : 

Phosphate-bonded Casting Investments Carbon-containing Gray-black color because of the presence of carbon even after burnout. Require a special liquid colloidal silica instead of distilled water. Generally recommended for gold-based metal ceramic alloys. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Noncarbon-containing White color before and after mixing. Used with nickel- and cobalt-base casting alloys, as well as palladium-based noble metal alloys. Because these alloy systems are capable of dissolving available carbon to produce carbides and/or porosity (due to carbon inclusions) Fundamentals of Spruing, Investing & Casting

Main Constituents of phosphate-bonded Investment : 

Main Constituents of phosphate-bonded Investment Binder: Magnesium Oxide (basic) & Mono- ammonium Phosphate (acid) Filler: Silica (quartz/Cristabolite or mixture of both) Binder: It hold other ingredients together. Provide rigidity. Filler: Provides refractory during heating. Regulate thermal expansion. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Investment-Casting Alloy Interaction : 

Investment-Casting Alloy Interaction Variations can occur in the performance of alloys with different investments (Barreto et al,1980; Hinman et al,1985). Nodule formation and fins may occur more frequently with one brand of investment but not with other. Therefore, it is prudent to conduct laboratory tests for adverse alloy-investment interaction before making a large purchase of a new product (Naylor,1990). *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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Rough casting with multiple nodules may be caused by a less-than-ideal alloy-investment pairing *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Casting Ring Liners : 

Casting Ring Liners Asbestos Ring Liner: Traditional material for lining casting rings until it was learned that it posed a potential health risk to dental laboratory technicians (Davis,1987; palmer et al,1961; Priest & Horner, 1980). Asbestos fiber bundles were found to produce hazardous-size respirable particles capable of causing lung disease. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Asbestos liner (original magnification x 500) : 

Asbestos liner (original magnification x 500) *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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Non-asbestos Ring Liners: Ceramic (aluminum silicate) Cellulose (paper) Ceramic-cellulose combination Safety of the ceramic ring liners remains uncertain, because aluminum silicate also appears capable of producing hazardous-size respirable particles (Naylor et al,1987). *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Casting Ring Lined by a Liner : 

Casting Ring Lined by a Liner Fundamentals of Spruing, Investing & Casting

Purpose of Casting Ring Liner : 

Purpose of Casting Ring Liner Ringer liner is he most commonly used technique to provide investment expansion. To ensure uniform expansion , liner is cut to fit the inside diameter of the casting ring with no overlap. Thickness of the liner should not be less than approximately 1mm. Place the liner somewhat short of the ends of the ring, 3mm, tends to produce a more uniform expansion, therefore less chance for distortion of the wax pattern & mold. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Ring liner short of the ends of the ring about 3mm : 

Ring liner short of the ends of the ring about 3mm Fundamentals of Spruing, Investing & Casting

Investing Technique : 

Investing Technique The wax pattern cleaned of any debris, grease or oil. Wax pattern cleaner or diluted synthetic detergent. Thin film of cleaner on pattern reduces surface tension of wax better “wetting” of investment. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Wax pattern cleaner being applied with a camel hair brush : 

Wax pattern cleaner being applied with a camel hair brush Fundamentals of Spruing, Investing & Casting

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2. Investment mixing Hand mixing Vacuum mixing Advantages Amount of porosity in the investment is reduced Texture of the surface casting is smoother with better detail reproduction Compressive strength of investment is increased *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Vacuum power mixer : 

Vacuum power mixer Fundamentals of Spruing, Investing & Casting

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3. Investment material pouring Casting ring is filled up to its rim. Allow the investment to set for about 1 hour. Crucible former is carefully removed. If burnout procedure does not immediately follow investing, place ring in humidor. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Investment material being poured after vacuum mixing : 

Investment material being poured after vacuum mixing Fundamentals of Spruing, Investing & Casting

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4. Wax elimination & heating Invested ring is placed in a room temperature furnace. Phosphate-bonded investments----temperature range----700 to 870*C Temperature rate of rise for the burnout furnace is 10*C/min *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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It is advisable to begin the burnout procedure while the mould is still wet. Water trapped in the pores of the investment reduces the absorption of wax. As the water vaporizes it flushes wax from the mold. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Melting & Casting Technique : 

Melting & Casting Technique Melting & Casting requires Heat source to melt the alloy Casting force, to drive the alloy into the mould Fundamentals of Spruing, Investing & Casting

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Fundamentals of Spruing, Investing & Casting

Casting Torch Selection : 

Casting Torch Selection Two type of torch tips: Multi-orifice Single-orifice Multi-orifice tip is widely used for metal ceramic alloys. Main advantage is distribution of heat over wide area for uniform heating of the alloy. Single-orifice tip concentrate more heat in one area. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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*Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Choice of Fuels : 

Choice of Fuels Three fuel sources are used for Casting Torch Acetylene Natural Gas Propane *Dental Laboratory manual, 1982 Fundamentals of Spruing, Investing & Casting

Zones of Flame : 

Zones of Flame Zone in which air & gas are mixed before combustion: No heat is present in this zone. 2. Combustion zone: Green, gas & air are in partial combustion. This zone is oxidizing & should always be kept away from metal during fusion. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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3. Reducing zone: Dimly blue, hottest part of the flame. This area should be constantly on the metal during fusion. 4. Oxidizing zone: Outer most zone, here combustion occurs with Oxygen in air. Under no circumstances should this portion be employed to fuse the alloy. Low temperature, Causes oxidation of the metal. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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When the reducing zone is in contact, the surface of the gold alloy is bright and mirror-like. When the Oxidizing zone is in contact the metal there is a dull film of “dross” developed over the surface. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Casting Machines : 

Casting Machines Air pressure casting machines Alloy is melted in situ in crucible hollow of the ring, followed by applied air pressure on the melt. 2. Centrifugal casting machine Alloy is melted in a crucible, and forced in to mold by centrifugal force. 3. Electrical Resistance/ Induction melting machine Alloy is melted electrically by a resistance or induction furnace, then cast into mold centrifugally. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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Air Pressure Casting Machine Fundamentals of Spruing, Investing & Casting

Centrifugal Casting Machine : 

Centrifugal Casting Machine Fundamentals of Spruing, Investing & Casting Counter weight crucible Base Cradle

Casting Crucible : 

Casting Crucible Except for Air pressure casting machine, all other units require a crucible to hold the alloy before & during melting procedure. Clay Crucibles Carbon Crucibles Quartz Crucibles (zircon-alumina) *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Quenching in Water : 

Quenching in Water Consider the gold crown & bridge alloys. After casting has been completed, ring is removed & quenched in water. Advantages: Noble metal is left in an annealed condition for burnishing & Polishing. When water contacts hot investment, violent reaction ensues. Investment becomes soft, granular & casting is more easily cleaned. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

Pickling : 

Pickling Surface of the casting appears dark with oxides and tarnish. Such a surface film can be removed by a process called Pickling. Best method for pickling is to place a casting in a dish & pour acid over it. Heat the acid but don't boil it. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

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Hydrochloric acid Sulfuric acid Ultrasonic devices Gold and palladium based metal ceramic alloys and base metals, these alloys are not generally pickled. *Skinner’s Science of Dental materials 9th Edition by Ralph W. Phillips Fundamentals of Spruing, Investing & Casting

The Laws of Casting : 

The Laws of Casting Casting is both an art and science governed by numerous rules, or “laws”. Building on earlier work of Ingersoll & Wandling (1986), W. Patrick Naylor formulated an expanded set of 17 separate recommendations for Spruing, investing, burnout, and melting and casting procedures. Collectively these guidelines are referred to as the laws of casting. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 1st Law of Casting : 

The 1st Law of Casting Attach the pattern Sprue former to the thickest part of the wax pattern Fundamentals of Spruing, Investing & Casting

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As the molten metal alloy moves from the reservoir to the pattern margins it should flow from areas of greater volume to areas of lesser volume (ie, margins). Lute the pattern Sprue former to the most practical portion of the occlusal/incisal surface. Molten metal flowing from thin area to a thicker region(full waxup) may solidify before the mold is completely filled. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties Penalties for not obeying this law are: Clod shuts Short margins Incomplete castings *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 2nd Law of Casting : 

The 2nd Law of Casting Orient wax pattern so all the restoration margins will face the trailing edge when the ring is positioned in the casting machine Fundamentals of Spruing, Investing & Casting

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To identify that orientation, add a wax dot to the crucible former so you know how to place the ring in the casting cradle correctly after the pattern have been invested. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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*Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties Penalties for not obeying this law are: Cold shuts Short margins *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 3rd Law of Casting : 

The 3rd Law of Casting Position the wax pattern in a “cold zone” of the investment mold and the reservoir in the “heat centre” of the casting ring Fundamentals of Spruing, Investing & Casting

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The coolest parts of the mold (cold zones) are the end of the ring and along the ring periphery. The hottest portion of the casting ring is located near the centre of the ring (heat centre). Limit the amount of investment covering the patterns to no more than ¼ inch (6mm) & position the reservoir in the heat centre. Adherence to this law increases the likelihood that casting porosity will occur in the reservoir rather than in the restoration. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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*Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalty for not obeying this law is: Shrink-age porosity *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 4th Law of Casting : 

The 4th Law of Casting A reservoir must have sufficient molten alloy to accommodate the shrinkage that occurs within the restorations Fundamentals of Spruing, Investing & Casting

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Alloy that fills the restoration will solidify first. As the molten metal solidifies, it shrinks and creates a vacuum. For a complete casting, the vacuum must be able to draw additional metal from an adjacent source--the reservoir. Reservoir should be equal to or greater than the thickest cross-section area of the wax pattern. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalty for not obeying this law are: Shrink-age porosity Suck-back porosity *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 5th Law of Casting : 

The 5th Law of Casting Do not cast a button if a connector (runner) bar, or other internal reservoir, is used Fundamentals of Spruing, Investing & Casting

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With indirect Spruing, the largest mass of metal should be the reservoir. A button is counterproductive because it can draw available molten alloy from the bar, shift the heat centre and reduce the feed of that metal to the restorations. Likewise, the wax pattern should not be larger than the connector bar– shift the heat centre. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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*Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Shrinkage porosity (and potential Distortion during porcelain firing) Suck-back porosity *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 6th Law of Casting : 

The 6th Law of Casting Turbulence must be minimized, if not totally eliminated Fundamentals of Spruing, Investing & Casting

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Pathways for the flow of metal should be smooth, gradual, and without impediments. Eliminate sharp turns, restrictions, points, or impingements that might create turbulence and occlude air in the casting. Restrictions, or constrictions, can accelerate the metal's rate of flow and abrade the mold surface (Ingersoll & Wandling,1986). *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Voids in the casting ring Surface pitting *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 7th Law of Casting : 

The 7th Law of Casting Select a casting ring of sufficient length and diameter to accommodate the patterns to be invested Fundamentals of Spruing, Investing & Casting

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The casting ring should permit the patterns to be ¼ in. apart and ¼ in. from the top of the investment with a minimum 3/8 in. of investment between them and the ring liner. If too little investment covers the wax patterns, the alloy is more likely to break through he mold. Too much investment over the waxups may locate the wax patterns too close to the heat centre of the mold and impair the escape of gases. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Mold fracture Casting fins Shrinkage porosity *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 8th Law of Casting : 

The 8th Law of Casting Increase the wettability of the wax patterns Fundamentals of Spruing, Investing & Casting

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A wetting agent should be brushed or sprayed on the patterns and dried before investing. A clean wax surface better enables the casting investment to wet the patterns more completely. Too much wetting agent can create a surface film that can dilute and weaken the investment in that area and produce bubbles or fins on the casting. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Apply a thin layer of debubblizer (wax pattern cleaner) to the wax patterns and indirect Spruing system and allow it to dry thoroughly before investing : 

Apply a thin layer of debubblizer (wax pattern cleaner) to the wax patterns and indirect Spruing system and allow it to dry thoroughly before investing *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalty for not obeying this law is: Bubbles On the surface of the casting as a result of the entrapment of air (too little agent) or excess liquid (too much wetting agent). *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 9th Law of Casting : 

The 9th Law of Casting Weigh any bulk investment and measure the investment liquid for a precise powder-liquid ratio Fundamentals of Spruing, Investing & Casting

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The correct proportion of powder to liquid and any dilution of the (special) liquid with distilled water should be established for each alloy. A thick mix of investment (reduced liquid) increases investment expansion & produces loose-fitting castings. Too much liquid results in thinner mix and less expansion with tighter-fitting castings. Using all special liquid provides more expansion but reduces working time compared to 50:50 dilution of the special liquid and distilled water. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalty for not obeying this law is: Ill-fitting castings *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 10th Casting Law : 

The 10th Casting Law Eliminate the incorporation of air in the casting investment and remove the ammonia gas by product of phosphate-bonded investments by mixing under vacuum Fundamentals of Spruing, Investing & Casting

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Vacuum mixing removes more air and gas than hand spatulation. Ares of the mold that contain dense, bubble-free investment will expand differently from sections that contain large voids (entrapped air). *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Small Nodules on the casting Weak mold Distortion of the casting *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 11th Law of Casting : 

The 11th Law of Casting Allow the casting investment to set completely before initiating the burnout procedure Fundamentals of Spruing, Investing & Casting

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If setting is not complete at the time a ring is placed in the oven, the mold may be weak and unable to withstand steam expansion during burnout. Investment could fracture as a consequence. For best results, burnout should be initiated only after the recommended setting time. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Mold crackling/Blowout Fins on the casting *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 12th Law of Casting : 

The 12th Law of Casting Use a wax elimination (burnout) technique that is specific for the type patterns involved (wax versus plastic) and recommended for the particular type of casting alloy selected Fundamentals of Spruing, Investing & Casting

Slide 103: 

Plastic Sprues need to be heated slowly so they can soften gradually and not exert pressure on the mold, so use a two-stage burnout (Tombasco & Reilly,1987). If burnout is incomplete, the spruing system channels may be blocked by wax or plastic residue (carbon) and, on casting, air cannot escape completely when metal enters the mold (Naylor,1990a; Tombasco & Reilly,1987). Therefore, use at least a 30-minute heat-soaking at 800 *F for the first burnout stage. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this laws are: Cold Shuts Short Margins Cold Welds Mold Cracks Casting Fins *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 13th Law of Casting : 

The 13th Law of Casting Adequate heat must be available to properly melt and cast the alloy (Myers,1936) Fundamentals of Spruing, Investing & Casting

Slide 106: 

The selected heat source should be capable of melting the alloy to the point of sufficient fluidity. Prolonged heating, caused by an improperly adjusted torch, can prevent the alloy from attaining the fluidity. Too much heat, or too high temperature, can burn off minor alloying elements. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Cold Shuts Short Margins Cold Welds (too little heat) Rough Castings Investment Breakdown (too much heat) *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 14th Law of Casting : 

The 14th Law of Casting When torch casting, use the “reducing zone” of the flame to melt the alloy and not the oxidizing zone Fundamentals of Spruing, Investing & Casting

Slide 109: 

An improper adjusted torch can add carbon or oxygen to the alloy while heating. A melt achieved by the exclusive use of the Reducing zone minimizes the likelihood of metal oxidation and gas absorption and ensures a proper melt. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

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*Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Gas porosity Change in the alloy’s Coefficient of thermal expansion (due to alloy contamination) *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 15th Law of Casting : 

The 15th Law of Casting Provide enough force to cause the liquid alloy to flow onto the heated mold Fundamentals of Spruing, Investing & Casting

Slide 113: 

Adjust the casting machine to the requirements of each alloy. Lower-density metals generally need four winds of a centrifugal casting arm as compared to higher-density, gold based alloys. Don't over wind. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Cold Shuts Short Margins Clod Welds (insufficient force) Mold Fracture & Fins (too much force) *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 16th Law of Casting : 

The 16th Law of Casting Cast toward the margins of the wax patterns Fundamentals of Spruing, Investing & Casting

Slide 116: 

Place the heated ring in the casting cradle using the orientation dot so the pattern margins face the trailing edge (the 2nd law). In a centrifugal casting machine the metal will flow downward and to the right, taking advantage of the centrifugal, rotational, and gravitational forces of molten alloy (Ogura et al,1981; Ingresoll & Wandling,1986). *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalties for not obeying this law are: Cold shuts Short margins Incomplete castings *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

The 17th Law of Casting : 

The 17th Law of Casting Do not quench the ring immediately after casting Fundamentals of Spruing, Investing & Casting

Slide 119: 

Allow the alloy and the investment to cool to room temperature. Uneven cooling and shrinkage between alloy and investment can apply tensile forces to the casting (Cascone,1976). After casting, the alloy may not possess sufficient strength to resist these forces and the restoration could tear, if quenched. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Penalties : 

Penalties The penalty for not obeying this law is: Hot Tears in the restoration *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Analyzing Casting Failures : 

Analyzing Casting Failures Despite concreted efforts to follow the recommended procedures, casting failure & mishaps are bound to occur in the laboratory. By standardizing our technique & paying strict attention to each step, it is often possible to control the location of the solidification shrinkage & minimize the number of actual miscasts. When casting failures do occur, we should troubleshoot each miscast to diagnose the cause of the problem so corrective measures may be taken before we make additional casting. *Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Slide 122: 

*Introduction to Metal Ceramic Technology by W. Patrick Naylor Fundamentals of Spruing, Investing & Casting

Thank You…! : 

Thank You…! Fundamentals of Spruing, Investing & Casting