Boundary Box Pricing for SLS

Boundary Box Pricing is the default and most common pricing method for SLS 3D printing. With this method, you are essentially paying for a rectilinear box volume of space that we price at 11p per cm³. The major benefit of boundary box pricing is the potential for massive savings by nesting multiple parts into a single file.

The Boundary Box Volume of a 3D File is your file's length x width x height. We use this value as the basis for quoting SLS parts. It's often referred to as XYZ pricing. Your file can be uploaded in any orientation and we will calculate the minimum boundary box volume for the most economical price.

As parts must be separated from each other by 1.0 mm when printed, we include 0.5 mm of space around each piece when calculating the boundary box volume.

The workings below show how we calculate the basic unit price for SLS prints.

X = Part length (mm)

Y = Part width (mm)

Z = Part height (mm)

SLS unit price = (X+1) x (Y+1) x (Z+1) x 0.00011

We multiply the boundary box volume by 0.00011 as we charge 11p per cubic centimetre for Boundary Box Pricing with SLS 3D Printing.

Low-Density Pricing for SLS

Low-density pricing is an estimate of the true volume of material used when printing your part.

The majority of SLS 3D printing costs is the PA12 nylon powder material. However, contrary to what you might expect, the amount of material required to print a single object is not equivalent to its volume. An SLS machine fills its entire build chamber with nylon powder every run. Some of this powder is fused to make solid 3D printed parts. The remainder of the powder becomes lower quality due to the high temperatures of the build process and must be mixed with fresh powder to be reused. 3D files with a small volume can still require an enormous amount of space. Larger boundary box files are more expensive to produce as a lot of powder is needed. However, a more economical price is achievable if other small parts fill the space around these large, sparse parts. Therefore, we check to see if parts contain space to nest other small files within their boundary box. The space is determined to be useable if a 50 mm part can be printed within the boundary of your file and then separated. 3D files must have a single body to qualify for low-density pricing, nested files will be priced using boundary box pricing.

The surface of your 3D file is expanded by 3.0 mm and the volume of the new offset file is recorded. We use this value to calculate the offset price of SLS parts. The pricing method is referred to as Low-density pricing.

The workings below show how we calculate the base unit price for SLS prints using Low-density pricing.

1. Offset surface by 3.0 mm

2. Record offset volume in mm³ = (OFF volume)

3. Low-density price = (OFF volume) x (0.0003)

We multiply the offset volume by 0.0003 as we charge 30p per cubic centimetre for Low-density pricing with SLS 3D printing.

1. Minimise the boundary box volume of the part. Unless the model is perfectly spherical, the orientation of a 3D file will affect the boundary box volume. The most simple trick to save money with SLS printing is to change the orientation of the part to minimise the boundary box volume. You can see this in most 3D file editors such as Netfabb or Meshmixer.

2. 3D Nesting is a technique of grouping multiple parts together into a single file to reduce their combined boundary box volume. This technique typically saves around 30% on cost; however, it can save much, much more. It's by far the best technique for reducing the cost of quotes in additive manufacturing. Read the full article on 3D Nesting for more information about how to save money with SLS 3D Printing.