Friday, September 7, 2012

Sand Castings or Sand Castles?




Recently, I overheard one of the most interesting Sales.  So much so, that I thought it would be a good Blog Post. Let me preface by saying that on a daily basis our Sales group will talk to engineers, machine shops, architects, farmers, universities, other distributors and the list goes on.  So we are used to helping people who have all different levels of industry knowledge and who come from all walks of life.  But this conversation was unique...and although it made me giggle a little bit I couldn't help but wonder how many others had the same question.

Background

Katie, one of our Sr. Sales Rep's, received a call from a customer who was looking for some rings in the alloy C95200.  The weight and size requirements immediately told Katie that we wouldn't be able to get the material "off the shelf" but that the rings would have to Made to Order.  So Katie proceeded to explain to the customer that the best way for these rings to be made would be as a Sand Casting. And after that, the conversation went like this:

(this is where the conversation got interesting....)

 
Katie:  "Sir, we will need to make these rings as a Sand Casting"
Katie:  "Sir, I'm not sure I understand what you are asking.....(silence)....um...(silence)...the way we will make these rings is with using Sand Castings"
(silence)
Katie:  "No sir, the rings aren't made out of Sand....(silence)...they are Bronze castings" " No sir, we aren't going to ship you Sand, they will be bronze" 


Clearly the man on the phone had no idea what a Sand Casting was and was not familiar with the different Methods of Manufacture available to him.  Days later and imaging the look on a customer's face when he opened his box to find a "Sand Castle", I had time to think about how I could use this in my blog.   So here goes....it's all about the Sand Castings.  



Introduction

Sand Castings can be traced back to China as early as 645 B.C.  Casting by means of forming sand was common for small parts but eventually over time and with advances in technology, alternative methods of manufacture would be introduced.  This of course improved quality and efficiency.  But even so the Sand Casting method still remains the most widely used casting process.  Why?  Sand castings are the most economical method to reproduce items in metal. Just add water and the sand can be used thousands of times to cast aluminum or other alloys. Additionally, there are just certain alloys that need to be Sand Casted due of the Shape of the part, Quantities required,  the Specification called out or just the overall cost of the piece(s).  

What is a Sand Casting exactly?

Sand casting utilizes expendable sand molds to form complex metal parts that can be made of nearly any alloy. Because the sand mold must be destroyed in order to remove the part, called the casting, sand casting typically has a low production rate. The sand casting process involves the use of a furnace, metal, pattern, and sand mold. The metal is melted in the furnace and then ladled and poured into the cavity of the sand mold, which is formed by the pattern. The sand mold separates along a parting line and the solidified casting can be removed. The steps in this process are described in greater detail in the next section.

The process is fairly basic, there are six steps in this process:

  1. Place a pattern in sand to create a mold.
  2. Incorporate the pattern and sand in a gating system.
  3. Remove the pattern.
  4. Fill the mold cavity with molten metal.
  5. Allow the metal to cool.
  6. Break away the sand mold and remove the casting.

If your like me you’ll need a visual.....




Please know that I haven’t even scratched the surface when it comes to Sand Castings.  There are 2 main types of Sand Castings;  Green Mold and the Air Set Method.  But from there you have Cold Box, No Bake Molds, Vacuum Molding and the list goes on.  Then of course, you have the different types of sand used.  But I’ll save those topics for another post.  Over the years I have run into neat websites that feature a whole variety of Sand Castings - decorative to practical, small to large, simple to complex.  Here is a website that I like to visit, it keeps the whole process simple, www.foundry101.com.


As always if you have any questions leave me a comment and I'll do my best to help and if not direct you to the best resource for your question!  





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