CPM Industries' Blog

Sand Casting vs. Investment Casting

Posted by Tim Carlstedt

What are the advantages and disadvantages between the Green Sand Casting Method and the Investment Casting Method?

Green Sand vs Investment Casting resized 600This is a common question for the metal casting industry and CPM wanted to shed some light on the subject.  In this entry, we will first look at a comparision of the two different methods, followed by a explanation of the table, then lastly another table highlighting the advantages and disadvantages of each method in comparison.

 

Comparison of Green Sand Casting vs. Investment Casting

 

Green Sand Casting Method

Investment Casting Method

Relative Cost in Quantity

Low

Highest

Relative Cost for Small Number

Lowest

Medium

Permissible Weight of Casting

Unlimited up to approx. 1 ton

Ozs to 100 lbs.

Thinnest Section Castable (Inches)

1/10

1/16

Typical Dimensional Tolerance (Inches)

.012

.01

Relative Surface Finish

Fair to Good

Very Good

Relative Mechanical Properties

Good

Fair

Relative Ease of Casting Complex Design

Fair to Good

Best

Relative Ease of Changing Design in Production

Best

Fair

Typical Base Tolerances

+/- .040 – 1.00 in

+/- .003 - .008 in

Typical Surface Finish

150 – 350 RMS

63 – 125 RMS

Minimum Wall Thickness

.140 - .250 in

.094 - .187 in

Typical Tooling Cost

$800 to $5,000

$3,000 to $10,000

Well, WHAT DOES THAT MEAN TO ME?!

Here at CPM, we manufacture Finished Prototype to Low-Volume Sand Castings.  Each project is different and has to be reviewed thoroughly to deduct the proper method in order to obtain the project's goal. So let us explain the benefits of the Sand Casting Method in more detail. 

Why Sand Casting?  

We work with the Green Sand Casting Method at CPM because it allows for the most flexibility between part size, quantity, and ease of changing all at the lowest tooling cost.  The ability to change a pattern for design modifications is very easy with sand casting, especially compared to Investment Castings' tooling.  This can save considerable amounts of money since it is very common for an engineer to change the part after it is tested and needs alterations in order to perform properly.  Another advantage is how quickly new castings can be manufactured since all that must be done is pack sand into the mold and pour the casting.  The only down sides are the surface finish, wall thickness, and the requirement of machining to achieve certain finishes.

What about Investment Castings?

Investment Casting can be great for very complex, intricate parts that require thin walls.  For common parts that do not meet those project criteria or are larger than a 100 pounds, then this is not a good solution.  High costs for tooling  are also an issue.  The surface finish from Investment Casting does provide a huge benefit and often negates the need for secondary machining.  As most of us know, machining is a major cost contributor, so this is a major boost.

The chart below depicts the advantages and disadvantages of each casting method.  Check it out!

Green Sand Casting Method

Investment Casting Method

Advantages

Disadvantages

Advantages

Disadvantages

Lowest Cost

Surface Finish

Surface Finish

Tooling Cost

Ease to Change Design

Complexity

Less Machining (If Necessary)

Quantities

          Weight Poured

     Often Requires Secondary Machining

    Design Complexity

    Longer Lead Time

Lower Lead Times

 

Thinner Walls

Small Size Capabilities

Mechanical Properties

 

 

 

Want to learn more about working with and buying castings, then click below to get CPM's Guide to Buying and Designing Castings!

 CPM's Casting Capabilities

Tags: Ductile Iron Castings, Ductile Iron Sand Casting, Casting Design, Aluminum Castings, Cast (Gray) Iron Castings, Magnesium Castings, Aluminum Sand Casting, CPM Industries, Green Sand Casting Method, Casting Knowledge, Secondary Machining, Finished Surfaces, Prototype Sand Castings, Pattern/Foundry Tooling, Patterns for Sand Castings, Cast Iron (Gray) Sand Casting, Investment Casting Method

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