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Green Sand Metalcasting Foundry News

Optimizing New Sand and Core Sand Additions in Foundry Green Sand Systems

Posted by Hill and Griffith Company on Jan 14, 2020 8:00:00 AM

The old rule for new/core sand additions is 300 lbs. per ton of metal poured, but that approach needs to be re-evaluated (and made more exact) for current molding methods and materials.

Article from the Foundry Management & Technology August 2005 issue by Mark Ziegler.

In order to understand the effect of core sand and the various binder systems on green sand properties and castings, the new sand's contribution to the dilution must be established. The objective of this research is to create a model where different amounts of new sand and core sand are added to system sand so that the green sand's properties and casting results can be evaluated. Initial work by the Green Sand Committee of CISA has shown that certain levels of new sand can be added, along with new clay/additives, to maintain consistent green sand properties. The study also found that there are critical levels where major changes in the green sand properties occur.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Release Agents, Foundry Supplies, Metal Casting Design & Purchasing

Nobake: The Basics

Posted by Hill and Griffith Company on Jan 7, 2020 8:00:00 AM

Dozens of chemically bonded sand molding methods exist, but they can be divided into three main categories: coldbox, heat-activated and nobake.

Excerpt from the Metal Casting Design & Purchasing January/February 2018 issue.

The basic principle is that a binder and catalyst are mixed with the sand to help form the mold into a “brick-like” product when cured. The differences in the process focus on the sand resin binder and catalyst used and how the mold or core is cured.

Coldbox—with this method, sand is coated with one of several binders, such as liquid sodium silicate or phenolic urethane, and catalyzed by a gas (such as carbon dioxide or sulfur dioxide) passing through the sand. This causes the resin binder to harden (cure) and lock the sand grains in place to maintain a solid mold wall.

Heat-Activated/Shell (also called hotbox and warmbox)—heat is used as the curing means in shell molding. Plastic resin-coated sand is compacted around a pattern and allowed to rest until a “shell” forms. The mold then is heated to temperatures higher than 500F (260C) to cure the mold.    

Nobake (also called airset, dry sand and precision sand)—like coldbox, several binders are optional. However, a liquid catalyst is used. The sand is processed in a continuous mixer and then formed around the pattern until it is fully cured.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Release Agents, Foundry Supplies, Metal Casting Design & Purchasing

A Case for Low-Pressure Sand Casting of Aluminum

Posted by Hill and Griffith Company on Sep 18, 2019 9:46:59 AM

LESS COMMON THAN GRAVITY SAND CASTING AND LOW-PRESSURE PERMANENT MOLD CASTING, LOW-PRESSURE SAND MOLDING HOLDS A DISTINCT COMBINATION OF ADVANTAGES FOR LARGE ALUMINUM CASTINGS.

Originally published in the January/February 2016 issue of Metal Casting Design & Purchasing by Franco Chiesa and Jocelyn Baril

A majority of aluminum castings are produced via sand or permanent mold casting, but for large precision components, another viable option is low-pressure sand casting, which uses principles from both low-pressure permanent mold (LPPM) and gravity pour sand casting.

Low-pressure sand casting marries the use of bottom pouring for tranquil filling of the mold (which avoids metal oxidation) with the flexibility to make larger parts. The capable process can be ideal when producing large “top quality” aluminum castings. The process also can be considered when walls are too thin (such as 0.1 in. [2.5 mm]) to be obtained by gravity casting.

LPPM casting is a common process producing high-quality castings due to tranquil filling of the mold and the application of pressure to fill the mold efficiently and cleanly.

The two main characteristics of the LPPM process are:

1. The filling from the bottom of the mold is perfectly controlled compared to the turbulent flow associated with gravity casting. Also, the liquid metal is drawn from under the melt surface, preventing dross entrainment into the mold cavity.  

2. Efficient feeding from the bottom injection pipe occurs through pressure applied to the melt during solidification, eliminating the need for risers. The resulting yield is high: typically 80-90% versus 50-60% for gravity permanent mold casting. However, not all casting geometries are amenable to the LPPM process.

 

Figure 1: Low pressure sand mold

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Release Agents, Foundry Supplies, Metal Casting Design & Purchasing

Is It Easy Being Green?

Posted by Hill and Griffith Company on Jul 23, 2019 8:00:00 AM

Excerpt from the May/June 2015 issue of Metal Casting Design & Purchasing.

Foundry sand, which is used by 60% of metalcasters to make molds and cores in a variety of metalcasting processes, represents a significant industrial byproduct. Unlike metal, which has been recycled for centuries, foundry sand has become a target of reclamation and recycling efforts in the last 20-30 years. Due to increasing regulatory control and disposal costs, metalcasters have reduced the amount of sand headed to landfills.


Green sand can be reclaimed and reused an average of eight times for molds.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Release Agents, Foundry Supplies, Metal Casting Design & Purchasing

Article Review: "Nine Green Sand Facts to Know"

Posted by Hill and Griffith Company on Jul 16, 2019 11:17:19 AM

Originally published in the Jan/Feb 2019 issue of Metal Casting Design & Purchasing.

The green sand casting process is the most widely-used process for casting ferrous and nonferrous metals. The process has evolved from a manually intensive operation to a highly mechanized and fully automated process that can produce more than 300 molds per hour.

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Metal Casting Systems - Choosing Between Nobake and Green Sand

Posted by Hill and Griffith Company on Jul 2, 2019 5:35:28 PM

Navigate the differences in capabilities and cost factors between nobake and green sand metal casting molding processes to ease your sourcing decision.

Opting for a sand casting process over permanent mold, diecasting, or investment casting is step one in sourcing a casting. But sand casting encompasses several methods, each of which carries its own advantages and disadvantages. The two most common processes used are green sand and nobake molding, and sourcing between the two is not always cut and dry.

Forty-two percent of North American metalcasters employ the green sand molding process.  Its popularity stems from its affordability, ability to be used for most metals and flexibility for low to high volume production.

Green sand molding does not hold the tightest tolerances or achieve the finest surface finish of all the casting processes; however, in general, it meets most of the qualifications desired to produce a high quality casting with a good finish.

Nobake sand casting, which is utilized by 40% of North American metalcasters, also is known for its versatility. Virtually all metals can be cast via nobake molding, a wide range of sizes can be produced, and the rigid mold walls provide good dimensional tolerances and control.

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Tags: Green Sand Casting Products, Green Sand Foundry Supply, Foundry Supply, Green Sand Release Agents, Foundry Supplies, Green Sand System, Green Sand Metalcasting, Modern Casting Magazine, Metal Casting Design & Purchasing

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