Every subset of the 3D printing community holds up its own “test objects,” privileging certain technical considerations over others, and calculates measurements such that it can be impossible to compare experiences with one machine over another. Enter the Rho test, with its attempts to standardize measurement and value to help one calculate which printer is most suitable for your purposes. Via Fabbaloo blog.

In a world with many 3D printers to choose from and no easy way to compare them, what should you do? They use different materials in different ways, are priced differently and produce objects of differing quality. 
 
This dilemma has been taken on by researcher Shane Ryan, who proposes what he calls, “The Rho Test”. It’s a mathematical formula that attempts to combine these critical evaluation factors: 
 

• Speed
• Quality
• Cost

 
The test involves printing an official test object (above) in several ways while timing and costing the operation. The method also includes detailed instructions on how to measure the quality of the object. All of this gathered information is combined in a formula (a portion of which is shown below) to result in a set of three numbers representing the factors above. Theoretically these values can be directly compared between 3D printers.

While these factors could be useful for comparison, they don’t account for some factors, such as potential build volume, material characteristics or machine reliability. There are other even less defined factors that could be important, such as machine and material availability, support programs and community strength.   
  
Read the PDF here:

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