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Green Sand Metalcasting Foundry News

How 3D Printing is Changing Sand Casting

Posted by Hill and Griffith Company on Jan 19, 2021 9:33:14 AM

3D printing has eliminated much of the tedium of the 3,000-year-old sand casting process

Excerpt from the September 2020 The Additive Report article by Kip Hanson.

Humans began pouring the first sand castings approximately three millennia ago. And until recently, that technology has remained virtually unchanged:

• A replica, or "pattern," of the desired object is placed in an open-ended, steel molding box.

• A special type of sand is poured around the pattern, which is pounded firmly into place and then removed.

• A sprue is cut to allow molten metal to flow into the mold, along with a gate that joins the sprue to the mold cavity.

• A core is used to replicate parts having internal features.

• Molten metal is poured into the mold; when the metal cools, the completed part is removed.

That's sand casting in a nutshell, although journeyman pattern maker Dave Rittmeyer will tell you there's far more to it than that. Rittmeyer, the customer care and additive manufacturing manager at Hoosier Pattern Inc., Decatur, Ind., also will tell you the industry has undergone a dramatic shift over the past decade or so, thanks in part to AM.

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Casting Goes Digital with Sand 3D Printing, Nondestructive Testing

Posted by Hill and Griffith Company on Jan 12, 2021 5:04:14 PM

Tooling & Equipment International (TEI) used to make tooling for castings. Now, it casts prototype parts in a digital workflow using 3D printed sand molds in combination with simulation software, CT scanning and X-ray technology.

Excerpt from the January 2019 Additive Manufacturing article by Stephanie Hendrixson.

"In the early days, before numerically controlled machines, casting tools were made by highly skilled pattern makers carving mahogany into patterns and packing sand around them," says Oliver Johnson, president of Tooling & Equipment International (TEI). "You'd be talking six or nine months to make all the tooling for a part that we could do today with a 3D printed mold in two days."

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Novel Sprue Designs in Metal Casting Via 3D Sand-Printing

Posted by Hill and Griffith Company on Jan 5, 2021 5:07:26 PM

Excerpt from the January 2019 Additive Manufacturing article by Santosh Reddy Sama, Tony Badamo, Paul Lynch, and Guha Manogharan.

The market size of the metal casting industry was 20.23 billion USD in 2017 and is expected to grow annually at a rate of 8.87% to reach 39.94 billion USD by 2025. Engineered castings constitute about 90% of total manufactured goods and capital equipment. In United States, over 2000 metal casting facilities employ more than 200,000 people across the country. Despite having a casting market share of 80%, sand casting foundries across the globe suffer from long lead times, expensive tooling and limited flexibility. It is well known that the pattern making step in sand casting is the bottleneck and often, the most expensive component in low volume production runs. The need to remove the pattern from compacted sand mold to create casting cavity significantly restricts the geometries in traditional sand castings. The increased complexity of metal parts for industrial and mission critical applications demands new technologies. Recent advancements in 3D Sand-Printing (3DSP) which is a form of Additive Manufacturing (AM) bridges this technological gap through direct printing of sand molds in a layer-by-layer process.

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Core Design is Key to Successful Castings

Posted by Hill and Griffith Company on Dec 29, 2020 8:00:00 AM

Excerpt from the November/December 2020 Casting Source by Jiten Shah.

The green sand casting process is the most widely used high-volume process because it is versatile and cost effective. In the case of an oil pan for a combine used in the agriculture industry produced by AFS Corporate Member Wabash Castings Inc. (Wabash, Indiana), the green sand process proved it versatility after eliminating some issues in the old design, which was cast in the semi-permanent mold process. Thanks to the flexibility in gating placement and design changes in the green sand process, the new casting reduced cost by using a common core for two cavities inside the part.

Critical wall thickness is maintained repeatedly with horizontally-parted green sand molding using a rugged common core for two mold cavities.

  • Critical wall section thickness (1) in the oil pan is controlled with a massive common core that is well supported at the core print. The main body core has an overhang, like a cantilever, and if not designed carefully, it could sag or deform, resulting in uneven wall thickness. This could potentially lead to shrinkage porosities and non-uniform mechanical properties due to uneven cooling rates of thinner and thicker sections within the same casting.

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Blow-hole Defect Analysis of Cylinder Block-A Case Study

Posted by Hill and Griffith Company on Dec 22, 2020 10:18:43 PM

Excerpt from the January 2017 article in International Journal of Engineering Research and Technology by M.R. Latte and P.D. Chougule. 

Abstract

In this research paper, the blow-hole defect analysis of MH1-VST 4-cylinder block fitted on tractors is presented as a case study. An MHI-VST 4-cylinder block is the central component of a tractor or any vehicle. It plays an important role in lubrication, temperature control and stability of the engine. It must be of the highest quality so there is no room for shortcuts. In this case study, parts pre- and post-analysis is done by using quality control (QC) tools such as Pareto charts and cause/effect diagrams. A DMAIC approach is followed and proper actions are taken to reduce the defect and rejection rate at the factory end. The work is done under two phases:

Phase 1: identifying drastic effects of blow holes in production; 
Phase 2: sorting out the issues by using various QC tools and expert opinion.

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Different Types of Casting Processes Used in Manufacturing

Posted by Hill and Griffith Company on Dec 15, 2020 5:05:39 PM

This article focuses the application of green sand in large scale infrastructure projects.

Excerpt from the Thomas Register article defining the different casting processes. 

Casting manufacturing is a process in which liquefied material, such as molten metal, is poured into the cavity of a specially designed mold and allowed to harden. After solidification, the workpiece is removed from the mold to undergo various finishing treatments or for use as a final product. Casting methods are typically used to create intricate solid and hollow shapes, and cast products are found in a wide range of applications, including automotive components, aerospace parts, etc.

 

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User Guidelines for Foundry Sand in Green Infrastructure Construction

Posted by Hill and Griffith Company on Dec 8, 2020 4:49:01 PM

This article focuses the application of green sand in large scale infrastructure projects.

Excerpt from the December 2011 principle investigation by Craig H. Benson and Sabrina Bradshaw from University of Wisconsin-Madison's Recycled Materials Resource Center. 

Introduction

Foundry sand is high-quality uniform silica sand used to make molds and cores for ferrous and nonferrous metal castings. The metal casting industry annually uses an estimated 100 million tons of foundry sand for production. Over time, foundry sands physically degrade until they are no longer suitable for molds. Consequently, 9 to 10 million tons of sand are discarded each year. However, the discarded foundry sands have remarkably consistent composition and are typically considered a higher quality material than typical bank run or natural sands used in construction. Currently, an estimated 28% of discarded sand is reused in primarily construction related applications, while the remaining sand is discarded in landfills (American Foundry Society 2007). Recycling of foundry sand can:

  • save energy
  • reduce the need to mine virgin materials
  • may reduce costs for both producers and end users
Use of foundry sand as a fine aggregate in construction applications offers project managers the ability to enhance green sustainable construction by reducing their carbon footprint, while also qualifying for LEED credits. The USEPA recently estimated that at the current recycling level 20,000 tons of CO 2 emissions are prevented while 200 billion BTUs of energy are saved. Support for increased reuse of foundry sand has brought together the USEPA, the Federal Highway Administration, the US Department of Agriculture, the Recycled Materials Resource Center (RMRC), state environmental agencies, the foundry industry and end users to develop the tools and resources needed to increase foundry sand recycling to 50% by 2015.

 

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Nobake Basics (Including Mold Coatings)

Posted by Hill and Griffith Company on Dec 2, 2020 3:44:38 PM

This article focuses on the nobake process and when it would be appropriate for use.

An MCDP Staff Report
Click here to see this story as it appears in the January/February 2018 edition of Metal Casting Design & Purchasing

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

Mold coatings are applied to more than 75% of noble molds. The coatings help prevent defects and improve surface finish.

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Preliminary Investigation into the Cause of Pinhole Porosity in Aluminum Metal Castings

Posted by Hill and Griffith Company on Nov 24, 2020 8:00:00 AM

Excerpt from the University of Northern Iowa dissertation by Brodie J. Biersner.

Introduction

Sand Mold Design
There are many molding methods available to produce a metal casting. The majority of metal castings however are produced with sand molds. This method for the production of metal casting has advanced over the years—from the materials utilized to the types of molding equipment and processes. Historically there was a lot of manual labor required for the production of a sand mold. Today, high speed molding machines are used with minimum amounts of human labor required. For sand casting to be successful for foundry applications, certain criteria must be met. The principal feature is good compatibility between the binder system and the sand aggregate chosen. This combination must also be compatible with the metal alloy used to produce the casting.

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Green Sand Casting Process

Posted by Hill and Griffith Company on Nov 3, 2020 5:01:03 PM

Excerpt from the Metal Casting Institute website.

Green sand casting is generally considered the easiest casting system because it is possible to use an existing part as a pattern for a one-off project. However, it is also used for some high volume projects also. The major benefit of this process is that the sand is easily recycled with low smell and a low ecological impact. When used to form parts out of aluminum alloys, the sand mixture has an impact on the final quality due to the potential for hydrogen gas pick up in the metal from the moisture in the sand. Therefore, with aluminum, green sand is generally used to form simple shapes and parts that aren't susceptible to leakage.

The process has four primary factors considered important:

  1. Sand Quality
  2. Pattern precision and alignment between cope and drag
  3. Gating and riser design
  4. Metal Control

 

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