How to Get the Most Accurate Quotes from Machine Shops

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When sourcing a part to be produced in accordance with a drawing (machined, molded, cast, fabricated, etc.)  there are a few tips that will result in a win-win.  

When there is ambiguity, it means there is risk for both the supplier and the buyer.  The supplier risks either quoting too low and losing money or quoting too high and not winning the job.  The buyer risks getting parts that don't meet their requirements or paying an inflated price that was padded by the supplier to protect him due to the ambiguity.  Savvy buyers of made-to-order parts remove that risk by communicating the specifications very clearly and are rewarded with more favorable pricing and less quality issue.

The best way to make sure the supplier clearly understands the part to be produced is to send a 3D model and a 2D drawing along with the request for quote.

The 3D model makes it easier for the supplier to visualize what they are quoting to produce.  Also, it is very easy to perform calculations from the 3D model that would take a long time from a 2D drawing, so many suppliers will just make a "guess" based on their experience.


For example, the 3D model is useful for quoting in the following:

  • The “volume” of the part would tell a plastic molder exactly how much plastic material is required per part. 
  • In machining, a subtraction of the part from a “cube” representing the beginning material state would tell the machinist how much material needs to be machined away.
  • The surface area calculation would tell a supplier how much surface area needs to be covered by chrome plating.


The 2D drawing is typically where details live such as:

  • Tolerances
  • The material specification
  • Finishing requirements
  • Packaging requirements
  • Deburring requirements
  • Surface finish requirements
  • Notes

As such, it is highly encouraged to include both a 3D CAD model and a 2D drawing with your RFQs.

Some souring professionals may be reluctant to attach a native 3D CAD file.  No problem.  Convert the native 3D files to an eDrawing which is a neutral “view only” format for 3D similar to what a PDF is to a 2D file.

The sourcing advisors are always available to help with your sourcing needs and to speak with you about best practices for sourcing complex made-to-order parts.

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