Core binder systems offer an array of choices.Core Binder Systems Offer an Array of Choices
Cores are an integral part of the casting process, often serving a number of different functions simultaneously. Placed in a mold, they delineate the internal shape of the casting. Cores can also be used to, in effect, create the mold, i.e. an all-core mold. But in sand casting Casting is the process of production of objects by pouring molten material into a cavity called a mold which is the negative, or mirror image of the object, and allowing it to cool and solidify. , they can also add strength, and are essential when a pattern contains back draft or projections which cannot be molded. Cores have also been used either to create the gating system (slab cores) or act as filters (pencil cores). Ram-up cores are so-named because they become part of the mold face when it is "rammed up."
Cores can be made of either metal; ceramic; plaster; compressed green or chemically bonded sand. Metal cores, used in permanent molding and die casting die casting
Forming metal objects by injecting molten metal under pressure into dies or molds. An early and important use of the technique was in the Linotype machine (1884), but the mass-production automobile assembly line gave die casting its real impetus. , are sprayed with a release agent and mechanically retracted re·tract
v. re·tract·ed, re·tract·ing, re·tracts
1. To take back; disavow: refused to retract the statement.
2. or "pulled" after the casting has solidified. But metal cores are obviously limited to shapes which can be pulled--limitations not shared by collapsible sand cores.
Ceramic and plaster cores are collapsible, and are used where an exceptional casting finish is desired. Ceramic preformed cores are more commonly used in investment casting investment casting
Precision casting for forming metal shapes with minutely precise details. Casting bronze or precious metals typically involves several steps, including forming a mold around the sculptured form; detaching the mold (in two or more sections); coating its ; poured ceramic cores are used in sand casting.
Cores can be formed as a single unit in a wood, metal or plastic pattern termed a corebox. They can be made one at a time, or in multiples. A single ceramic core is made from the corebox.
Wherever possible, use of small core pieces are avoided. Instead, a central core is designed so that "loose pieces" can be affixed af·fix
tr.v. af·fixed, af·fix·ing, af·fix·es
1. To secure to something; attach: affix a label to a package.
2. without shifting when the core is placed in the mold.
High-volume core production requires specialized equipment to mix and coat the sand, compact it in the corebox, dry the cores (as needed as needed prn. See prn order. ) and transport and stack the cores for final curing. Complex cores can also be made in pieces and assembled using hot-melt adhesives.
Today, only cores for prototype or short-run parts are produced manually. For decades, the vast majority of cores have been machine produced using either a jolt table, shell core, sand slinger or core blower. With a jolt machine, the corebox filled with sand is raised and dropped against the machine base, compacting the sand around the pattern. Further compaction may be provided by pneumatic hand ramming. Completed cores are then dried and baked.
Shell cores are made by investing the coated sand on a heated platen. The corebox is clamped together above a sand hopper, rolled over, and a measured amount of sand is blown into the corebox. After the core is invested for 5-10 sec, the corebox is rolled back above the hopper. Unused sand flows back into the hopper, while the core cures for 15-30 sec.
A sand slinger uses the downward force of sand, propelled by rotating vanes, to achieve the required level of sand compaction in the corebox. Since a large volume of sand is delivered quickly, they are generally used for larger coreboxes.
Coreblowers date to the turn of the century, and their advantages for producing certain types of cores were quickly recognized. A metered amount of coated sand is blown in under carefully regulated air pressure to achieve the required core compaction. One of the main advantages of blown cores is that they have no parting line fins if the the parting lines match to within 0.005 in.
But a coreblowing system must also include a catalyst gas generator an apparatus in which gas is evolved
a retort in which volatile hydrocarbons are evolved by heat
a machine in which air is saturated with the vapor of liquid hydrocarbon; a carburetor
a machine for the production of carbonic acid gas, for aërating water, bread, etc. , a compressed air compressed air, air whose volume has been decreased by the application of pressure. Air is compressed by various devices, including the simple hand pump and the reciprocating, rotary, centrifugal, and axial-flow compressors. system (including a dryer) and a gas scrubber to treat and/or neutralize the exhaust vapors. A dryer is of particular importance because the moisture of the air in the system must be carefully controlled. Excess moisture will result in reduced binder strength and shortened shelf life. Various dryers are available to maintain an atmospheric dew point dew point: see dew. of -40F or less. Core Setting
Cores may be placed or "set" in the mold either manually or mechanically. They are secured in the mold cavity by special recesses called core prints. Chaplets--metal supports in a variety of shapes and sizes may also be used. During pouring, chaplets melt and become part of the casting. Their microstructure mi·cro·struc·ture
The structure of an organism or object as revealed through microscopic examination.
a structure on a microscopic scale, such as that of a metal or a cell must be, if not similar, at least compatible with the metal cast.
The past thirty years have seen major advances in core binder technology. Until the 1960s. the shell process, core oil, various protein binders and (to a lesser extent) sodium silicates were the primary systems. Today, chemically-bonded resins are, as a group, the most widely used binders owing to owing to
Because of; on account of: I couldn't attend, owing to illness.
owing to prep → debido a, por causa de their excellent repeatability, resistance to defects, and rapid curing. (Green sand cores are also used, however. See "High Pressure Green Sand Coremaking," modern casting, pp. 25-27 [Dec 1985].)
Modern core binders are expected to satisfy a number of performance requirements. Binders must provide green strength so that the core can be molded. The core sand bond must have enough integrity to withstand fracture from physical forces during assembly, and erosion and thermal stress during pouring. But if the bond is too strong, thermal expansion thermal expansion
Increase in volume of a material as its temperature is increased, usually expressed as a fractional change in dimensions per unit temperature change. in the mold may cause the sand surface to crack, creating veining vein·ing
Distribution or arrangement of veins or veinlike markings. defects. At the same time, cores must be sufficiently porous to permit adequate venting of the core gases evolved during pouring. Porosity requirements are compounded if the core is used to vent the mold. Finally, the cores must be sufficiently friable friable /fri·a·ble/ (fri´ah-b'l) easily pulverized or crumbled.
1. Readily crumbled; brittle.
2. Relating to a dry, brittle growth of bacteria. to ensure relatively easy and complete shakeout.
Core Classification-Cores can be classified in a number of ways. They can be grouped according to according to
1. As stated or indicated by; on the authority of: according to historians.
2. In keeping with: according to instructions.
3. their bonding material, i.e., ceramic, green sand, dry sand, chemically bonded. They can also be classified according to their position in the mold, i.e., horizontal, vertical, ram-up, etc.
A further distinction is made based on the organic or inorganic nature of the binder. Organic binders include cereals, resins and core oils. Cereal binders--corn and wheat flour, dextrine, starch--commonly used with core oils, provide both green and baked compression strength. Inorganic binders include the three types of clay (Western and Southern bentonite bentonite (bĕn`tənīt'): see clay. and fireclay), sodium silicates, cement, phosphates, and a number of patented chemical processes.
Some binders and metals are inherently incompatible. In the case of aluminum, for example, the pouring temperature may not be high enough to break down certain binders, inhibiting shakeout. If sodium silicate binders are used in cast iron production, a secondary bond may develop hindering shakeout.
Perhaps the most convenient classification of chemical binders is one based on curing temperature: nobake, heat-cured and coldbox. Since space does not permit a detailed discussion of all the processes within these three groups, their differences will be contrasted by focusing on one or two processes within each group.
"Nobake" is the singular term (Logic) a term which represents or stands for a single individual.
See also: Singular applied to self-setting, non-gassed processes that cure at room temperature. Included under this category are organic systems: furan-acid, phenolic-acid, ester-cured phenolic phe·no·lic
Of, relating to, containing, or derived from phenol.
Any of various synthetic thermosetting resins, obtained by the reaction of phenols with simple aldehydes and used as adhesives. , alkyd al·kyd
A widely used durable synthetic resin derived from glycerol and phthalic anhydride. Also called alkyd resin.
[alky(l) + (aci)d.]
Noun 1. urethane urethane (yoor´ithān´),
n ethyl carbamate used as an anesthetic agent for laboratory animals, formerly used as a hypnotic in humans. and phenolic urethane; and inorganic: sodium silicate ester-cured, cement bonded and phosphate. Most nobake systems use either an acid, base, or ester catalyst.
Furans offer an instructive contrast, since they are available as nobake, cold, warm and hotbox hot·box
An axle or journal box, as on a railway car, that has become overheated by excessive friction.
Noun 1. hotbox - a journal bearing (as of a railroad car) that has overheated systems. (Furan furan: see furfural. is the generic term applied to furfuryl alcohol-based systems.) Introduced in the late '50s, furan nobakes quickly became (and have remained) one of the most widely used binder systems in jobbing foundries. It should come as no surprise, then, that they deliver excellent dimensional accuracy, resistance to surface defects, and excellent shakeout. The wide-spread use of furan binders is owed in part to the great variety available for gray iron, nonferrous, ductile iron Ductile iron, also called ductile cast iron or nodular cast iron, is a type of cast iron invented in 1943 by Keith Millis. While most varieties of cast iron are brittle, ductile iron is much more ductile, as the name implies. , and steel production.
"Coldbox" produced cores are made from binders which cure at room temperature using a gas catalyst. Phenolic urethane amine amine (əmēn`, ăm`ēn): see under amino group.
Any of a class of nitrogen-containing organic compounds derived, either in principle or in practice, from ammonia (NH3). , furan-[SO.sub.2], acrylic epoxy-[SO.sub.2] sodium silicate-[CO.sub.2] and phenolic ester are all consider coldbox processes. Coldbox cores are primarily used with metals having low pouring temperatures--typically heavy-sectioned iron castings. Several variables determine the curing time In the annealing procedure could be divided into 3 stages:heating to a particular temperature, keeping for a period of time and cooling to room temperature. The curing time is the hold time of the 2nd stage. for coldbox cores: * temperature of the sand-binder mixture; * type of catalyst; * percentage of binder in the sand mixture; * volume and velocity of air; * concentration of catalyst in the air-catalyst system; * binder formulation; * pressure in the corebox; * permeability of the sand.
In most coldbox processes, the sand is coated with a liquid resin which is then "cured" when exposed to a gas catalyst. Coreblowing equipment was readily adapted to the gas curing of cores--sodium silicate/[CO.sub.2] and the so-called "coldbox" systems. Cores could then be blown and gas cured on the same machine.
Sodium Silicates-While a gelled-silica process was patented in England in 1898, H. W. Dietert traced the first use of an alcohol hardened sodium silicate binder to tests made at Dow Chemical in 1943. In their earliest application, silicate silicate, chemical compound containing silicon, oxygen, and one or more metals, e.g., aluminum, barium, beryllium, calcium, iron, magnesium, manganese, potassium, sodium, or zirconium. Silicates may be considered chemically as salts of the various silicic acids. binders were cured by baking. The use of [CO.sub.2] as a "hardener hardener,
n an ingredient (potassium alum) of the photographic and radiographic fixing solution that serves to harden the gelatin of the film to prevent softening and swelling of the gelatin. " was first tried in Europe, and a patent issued in England in 1948. By the mid-50s, the sodium silicate-[CO.sub.2] process had become the first practical coldbox system to be used in foundries. In the 1960s, silicate binders were used as "air set" systems, incorporating various reactive powder hardeners to cure the binder.
The Nishayama process, a Japanese development that uses a powdered ferro-silicon hardener, has proven popular in that country. However, problems associated with the inherent exothermic exothermic /exo·ther·mic/ (-ther´mik) marked or accompanied by evolution of heat; liberating heat or energy.
ex·o·ther·mic or ex·o·ther·mal
1. reaction and generation of hydrogen gas during curing have limited its widespread use in the rest of the world.
All inorganic, silicate-[CO.sub.2] binders cure in a two-step process. Introduction of [CO.sub.2] gas to th silicate-sand mixture results in the formation of a mild carbonic acid carbonic acid, H2CO3, a weak dibasic acid (see acids and bases) formed when carbon dioxide dissolves in water; it exists only in solution. (from the interaction of [CO.sub.2] with water in the silicate binder). The pH falls, reducing the percentage of soda ([Na.sub.2O]), and effectively increasing the percentage of silica ([SiO.sub.2]) in the binder. Rapid gelation gelation /ge·la·tion/ (je-la´shun) conversion of a sol into a gel.
1. Solidification by cooling or freezing.
2. The process of forming a gel.
3. of the silicate binder occurs, further accelerated by the physical movement of the [CO.sub.2] gas through the binder-sand mixture, removing additional water, and increasing binder solids. During this gelation, approximately 30-40% of the ultimate strength is developed.
The silicate-[CO.sub.2] process can be controlled in a number of ways. Not only are different ratios of silica to sodium oxide Sodium oxide is a chemical compound with the formula Na2O. It is used in ceramics and glasses. Treatment with water affords sodium hydroxide.
The alkali metal oxides M2 (soda) available, but by varying the amount of water added, it is possible to significantly change the chemical and physical properties of the binder.
Initial tensile strength of the cores gassed for 5 sec varies from 37 to 45 psi (depending on the resin used), and increases to 100-200 psi after 24 hrs. Since part of this increase is due to the dehydration of unreacted silicates and continued gelling of the mixture, it is influenced by relative humidity relative humidity
The ratio of the amount of water vapor in the air at a specific temperature to the maximum amount that the air could hold at that temperature, expressed as a percentage. .
Ultimate hardening occurs within 24 hr through a dehydration process known as "syneresis syneresis /syn·er·e·sis/ (si-ner´e-sis) a drawing together of the particles of the dispersed phase of a gel, with separation of some of the disperse medium and shrinkage of the gel.
n. ." The "glassy bond" which results accounts for the remaining 60-70% of the ultimate binder strength. In principal, any sodium silicate binder can be cured entirely by dehydration, but [CO.sub.2] gassing substantially decreases the cure time.
One of the most attractive aspects of these inorganic binders is their low toxicity. They are typically odorless o·dor·less
Having no odor.
o resins, nonflammable non·flam·ma·ble
Not flammable, especially not readily ignited and not rapidly burned. and suitable for all types of production. Coreboxes can be made of any material. They produce no noxious gases during the mixing or coremaking operation, and only minimum volatile emissions during pouring, cooling and shakeout.
Improved as-gassed and ultimate strengths, as well as shakeout, have been achieved using the newest proprietary additives. These liquid co-binders have the added advantage of improved resistance to moisture pickup, lengthening storage times. Figure 7 compares the compressive strength of these new ester-silicate systems to conventional acetate ester-silicate binders. (For a more detailed discussion of these two-part binder systems, see "Environment Right for Silicates Rediscovery," modern casting, March 1989, pp. 23-26.)
Hotbox, warmbox and oven cure systems include the furan hotbox, furan warmbox, shell, core oil (oven bake) and phenolic hotbox processes.
Hotbox Process-In this process sand is coated with a mixture of thermosetting thermosetting,
adj having the property of becoming irreversibly rigid or hardened with the application of heat. In dentistry the term is used in connection with resins. binder and an acid salt catalyst before being blown into a vertically- or horizontally-parted corebox heated to 450-550F. The mixture starts to cure almost immediately upon contact with the hot pattern.
The hotbox process made its debut in nonferrous foundries in 1959. It won widespread acceptance in high-volume automotive foundries because of its rapid cure and high tensile strength. Cores with high tensile strength can be ejected within 20-40 sec. Unlike Shell core sand, hotbox sand is damp, and can be blown using conventional coreshooters. But because the core produced is solid, more mixed sand is used. Both the hot and warm processes use a moist binder-sand mixture.
Hotbox processes, introduced to nonferrous foundries in 1959, are classified either as furan or phenolic. Furfuryl alcohol (furan) used in conjuction with urea formaldehyde resins, supplanted the original unmodified urea formaldehyde resin. In the 1960s, phenol phenol (fē`nōl), C6H5OH, a colorless, crystalline solid that melts at about 41°C;, boils at 182°C;, and is soluble in ethanol and ether and somewhat soluble in water. formaldehyde polymers were developed when a worldwide shortage of furfuryl alcohol gripped the industry. Today, owing to their higher hot strength and lower cost, fully 90% of the hotbox resin used is phenol-based. Formaldehyde, which has an extremely irritating odor, makes up 4-10% of conventional hotbox resins. Recently introduced low-nitrogen hotbox processes offer significant reductions in ammoniacal am·mo·ni·ac 1 also am·mo·ni·a·cal
Of, containing, or similar to ammonia.
Adj. 1. ammoniacal - pertaining to or containing or similar to ammonia
ammoniac nitrogen and free formaldehyde but are more costly.
Reclamation of hotbox cores until very recently, has not met with much success, and most systems are typically run with 100% new sand. Thermally reclamation is an area of ongoing research and development, but little rebonding at this time is actually taking place.
Oil Sand Binders-Heat setting oil binders have their antecedents in the raw linseed oil cores first used in the late 1600s. Core oil is a generic term applied to a class of binders which use either natural oils or synthetic resins mixed with sand, water and cereal. The "green" cores are then cured in a hot, forced air oven at 400-500F, up to 1 1/2 hr for a typical core. Catalysts are commonly used to speed up the drying process.
Core oil cores can be blown or hand rammed in relatively simple, vented tooling. But oil-sand cores must be handled carefully while in the "green" state.
Shell Process-This unique process (also known as the "C" or Croning process after the developer, Johannes Croning) is a type of investment casting. Core "shells" are created by blowing or dumping heated sand coated with novolak resin into a corebox surrounding a heated (400-600F) pattern. Curing of the core sand begins closest to the pattern, continuing outward forming the shell. The cure cycle is ended by simply inverting the corebox, as described earlier.
The curing process is a complex transformation from a thermoplastic A polymer material that turns to liquid when heated and becomes solid when cooled. There are more than 40 types of thermoplastics, including acrylic, polypropylene, polycarbonate and polyethylene. to a thermosetting state, and requires careful monitoring of the pattern temperature. A shell of from 1/8 to 3/16 in. (3-5 mm) normally develops during the approximately 1 min cure cycle. Both hollow and solid cores can be created using this process, and have excellent storage life.
While the basic shell process has remained unchanged, new additives and binder formulations have led to a safer process with improved sand flowability, reduced strip times, and nearly doubled shell strength.
Because of the problems with formaldehyde and phenol emissions inherent to the coating process, most foundries now purchase commercially coated sand. The benclife of shell sand is almost indefinite, and because it is heat setting, mullers and coreblower need not be cleaned daily.
Environmental problems, specifically formaldehyde and phenol emissions, have proven more difficult to solve. A number of foundries with low-volume production of the higher resin solid cores have switched to no-bake processes. But for those foundries who have made the investment in scrubbing and collecting equipment, Shell will probably remain a viable production process for some time.
Warmbox-The warmbox process was first introduced over a decade ago, and its popularity continues to grow. Curing results from the reaction of the binder resin with a heat-activated catalyst.
As the name implies, the process operates at a lower temperature--100F lower--than the hotbox system. But the two processes differ in many other characteristics. Unlike most hotbox processes which use phenol-based resins, warmbox binders use furfuryl alcohol resins with only 2.5% nitrogen content. Due to this lower nitrogen content, warmbox castings have significantly reduced or eliminated gas-related defects. Furfuryl alcohol resins have the advantage of faster initial cure, permitting quicker ejection. They also provide better shakeout and fewer disposal problems.
Warmbox catalysts are also unique--copper salts, primarily aromatic sulfonic acids in an aqueous methanol solution. Used in concentrations of 20-35% based on resin weight, they are unreactive at room temperature. Optimum sand temperature is 70-80F. To retain good benchlife at high sand temperatures (+90F), catalyst adjustments are required.
Warmbox sands should be used with sands having low acid demand value. Cores can be adversely affected by high relative humidity (+90%). Silanized release agents are available which lessen the effect of high humidity.
Thermal decomposition of the binder produces a reducing atmosphere in the mold cavity, inhibiting the formation of metallic oxides. These oxides act as a flux with the sand grains and permit metal penetration. The greater the reducing atmosphere in the mold cavity, the less likelihood of metal penetration and casting defects caused by adhering sand.
The binder's rate of thermal decomposition also determines the rate of gas evolution. In green sand molding, the gases generated from the moisture and sand binders must be vented away from the casting in order to prevent casting gas defects--termed core blows. This can be done by increasing the permeability of the mold sand, by scoring the core surfaces during assembly, or by actually drilling vents in the mold over the core prints. Cores may also be vented along the parting line of core halves. Oil-sand cores are often made with embedded wax wires, which, when the core is baked, form vent passages. Strands of wzx, nylon tubing or perforated metal tubing can also be used to create vents.
Coated sand which adheres to the tooling can increase core release or strip time. Rough coreboxes (with more irregularities where the sand can buildup) and dense cores, which may not cure completely, compound the problem. Any binder that builds up in a corebox must be removed using either blast abrasion or solvents.
A variety of release agents have been formulated to reduce the adhesion of the core to the tooling. They have been specifically formulated for use with different binders. Common agents include: oleic acid oleic acid /ole·ic ac·id/ (o-le´ik) a monounsaturated 18-carbon fatty acid found in most animal fats and vegetable oils; used in pharmacy as an emulsifier and to assist absorption of some drugs by the skin. diluted with kerosene kerosene or kerosine, colorless, thin mineral oil whose density is between 0.75 and 0.85 grams per cubic centimeter. A mixture of hydrocarbons, it is commonly obtained in the fractional distillation of petroleum as the portion boiling off for use with core oils, and emulsified silicon for heat-cured binders (including Shell). Nobake and coldbox processes use a variety of formulations made from different chlorinated chlorinated /chlo·ri·nat·ed/ (klor´i-nat?ed) treated or charged with chlorine.
charged with chlorine.
some, e.g. solvents, alcohol, silicons, powdered aluminum, graphite and vegetable oil.
Core coatings or washes are used to seal the core surface, resulting in improved casting surface finish. Coatings are suspended particles which have a higher refractory value than the core sand and are smaller than the voids between the sand grains. Coatings reduce metal penetration and prevent veining, reducing cleaning and finishing operations. Less obvious savings result from reduced tooling wear. And because they are refractory, coatings promote chill. Certain coatings--selenium or tellurium tellurium (tĕlr`ēəm) [Lat.,=earth], semimetallic chemical element; symbol Te; at. no. 52; at. wt. 127.60; m.p. 450°C;; b.p. 990°C;; sp. gr. 6. paste--can also improve the surface hardness of castings.
The formulation and application of core coatings involves the design and control of five components: a refractory, carrier, dispersant dis·per·sant
A liquid or gas added to a mixture to promote dispersion or to maintain dispersed particles in suspension. , binder, and chemical modifier (programming) modifier - An operation that alters the state of an object. Modifiers often have names that begin with "set" and corresponding selector functions whose names begin with "get". (s). There are over a dozen refractory materials available, and selection is based on the metal pouring temperature and casting seciton thickness. The coating must be compatible with the process: water-based washed are generally used with heat-cured cores, self-setting cores with an alcohol-based wash.
Coatings are essential in steel casting because the high pouring temperature is close to the fusion point of silica. Highly refractive refractive
capacity to refract light.
a difference between the focal length of the cornea and lens, and the length of the eye, resulting in myopia or hyperopia. coatings--zircon, magnesite magnesite (măg`nəsīt), mineral, magnesium carbonate, MgCO3, white, yellow, or gray in color. It originates through the alteration of olivine or of serpentine by waters carrying carbon dioxide; through the replacement of calcium , chromite chromite (krō`mīt), dark brown to black mineral. It is an iron-chromium oxide, FeCr2O4, with traces of magnesium and aluminum. or alumina--are commonly used to prevent surface defects. Iron foundries use a modified silica refractory because of its lower cost. Carbon is frequently added, producing a reducing atmosphere and increasing the fusion point, thereby lessening sand adhesion (burn-on).
Coatings are not intended to compensate for poor core surface. In fact, improperly applied or poorly mixed coatings can result in defects such as pinholing, cratering, orange peel and shrinkage cracks.
PHOTO : Photo of a cast iron corebox used to produce cores for a valve body. The corebox was
PHOTO : machined using CNC (Computerized Numerical Control) See numerical control.
CNC - Collaborative Networked Communication , and the close tolerances greatly reduce flash.
PHOTO : Pictured is an open axial corebox used to produce a plaster core. The metal vanes are
PHOTO : pulled from the rear.
PHOTO : Shown is a cheek core with loose pieces used to produce an aircraft gearbox.
PHOTO : Hot melt adhesive being applied to join smaller pieces to a large core.
PHOTO : The shell molding process involves attaching the pattern plate (a) to the dump box (b)
PHOTO : prior to investment (c)&(d) and ejection (d). The completed shell assembly isshown in (f).
PHOTO : A sand slinger shown discharging sand into a large corebox.
PHOTO : As shown, the faster curing alkylene-carbonate esters provide for longer worktime and
PHOTO : increased compressive strength than conventional acetate-ester sodium silicate binders. References Archibald, J. J. and R. L. Smith, "Resin Binder Processes," Metals Handbook, 9th ed, pp. 214-21, ASM International (1988). Carey, P. R., et. al., "Updating the Resin Binder Processes--Parts 1-IX," Foundry Management and Technology (Feb 1986). Chemically Bonded Cores & Molds, American Foundrymen's Society, Inc (1987). Dietert, H. W., Foundry Core Practice, 3rd ed, American Foundrymen's Society (1986). Heine, R. W., C. R. Loper lope
intr.v. loped, lop·ing, lopes
To run or ride with a steady, easy gait.
A steady, easy gait.
[Middle English lopen, to leap, from Old Norse , Jr. and P. C. Rosenthal, Principles of Metal Casting, McGraw-Hill Book Co (1967). LaRue, James P., Basic Metalcasting, American Foundrymen's Society, Inc (1989). Penko, Tom, "Rediscovering Sodium Silicates," modern casting, vol 79, No. 3, pp. 23-26 (March 1989). Sylvia, J. G., Cast Metals Technology, Addison-Wesley (1972). Wile, L. E., K. Strausbaugh, J. J. Archibald and R. L. Smith, "Coremaking," Metals Handbook, 9th ed, pp. 238-41, ASM International (1988).