Comparing SLS (Selective Laser Sintering) with injection molding

 

Before you manufacture anything, you need to decide two major things:

  1. What material(s) your product will be made of.
  2. How to manufacture it.

 

This post will contrast injection molding and 3D printing, specifically looking at the costs associated with each. As a common 3D production method, we’re using selective laser sintering as our example.

 If you want to build something out of nylon, there are a couple of popular options. 

 

Injection molding is the process of filling the cavity of a mold with molten nylon or other material. The nylon comes in the form of beads that are typically a couple millimeters in diameter. The beads are poured into a hopper that feeds them into a heating chamber that uses an auger to move the heating beads, which are in the process of melting, to the injector(s). The injectors fill the mold. When the mold is cool enough it is split open to remove the product.

 

The costs involved with injection molding are based on the material and equipment used, along with the creation of the mold. The largest chunk of the cost comes from producing the mold. This is because the mold needs to be milled, typically with expensive CNC equipment to get the most accurate result. Because of the large initial cost of injection molding there is also a high cost associated with a product that is not going to be produced in mass quantities. Typically, you’ll need quantities in the tens of thousands, if not hundreds of thousands, to offset molding costs and have a good return on investment.

 

3D printing with SLS (selective laser sintering), on the other hand, involves using a CAD file to communicate with the 3D printer software, then adding the required material to the tool. The material, in powder form, is evenly spread across the print bed. The laser sinters, or melts, the powder for the designated cross section of a thin layer and then another layer is added. This process is repeated until the entire volume of the build is completed. The build can include many separate parts. Whatever we can fit in the build area, we will, in order to maximize volume efficiency.

 

3D printing costs are based on the material used, the volume of the part to be printed, and finishing. If a large quantity is requested, such as a few hundred parts, then a discount is applied. Finishing costs are all about labor and materials. For example, if you want it painted, how much does the paint cost and how much time does it take to paint all the parts?

 

A part with a specific volume that is manufactured with a quantity of 1,000 units to be shipped in less than 5 days will cost approximately $23 per unit using injection molding.

The same part, done by Ultimate 3D using SLS, would cost approximately $3 per unit.