The process of 3D Printing, also known as additive manufacturing, has now been developed for several materials including plastic and metal. This article will focus on 3D printing compared to CNC machining of plastic parts.

 

The 3D Printing process is an additive process during which layers of molten plastic are added until the part is completely formed.  These layers can often be noticed, and this can be an aesthetic issue. In evaluating whether or not this is the right approach the two key questions to be answered are:

1) What is the application?

Knowing the application and the physical requirements of the part is key, as a “printed” part will not be as strong as a machined or molded part.  Other necessary physical characteristics could be compromised as well.

2) How many parts are needed?

A small number of 3D printed parts can be made very economically compared to traditional manufacturing processes, but the process is slow for each part. The smaller the number, the more likely this process is feasible. The larger the number, the more appropriate machining becomes.

Additive manufacturing allows for the production of very complex parts in a single step, making it valuable for producing samples quickly to evaluate form and fit. Printed parts may not be appropriate for testing function, noting their relative weakness.

 

3D PRINTING: THE ADVANTAGES

  • Speed: A complex part design can be uploaded from a CAD model and manufactured in a couple of hours. This allows for verification of a design before investing in manufacturing equipment.
  • Low Cost of Labor: Most 3D printers only require an operator to press a button. The process is then completely automated. There is no need for highly skilled machinists or operators.
  • Efficiencies: The equipment to print occupies a small physical footprint and a small investment compared to other processes. It also uses less energy than CNC equipment, so has a smaller carbon footprint.

 

3D PRINTING: THE DISADVANTAGES

  • Not appropriate for large quantities, as it’s a long process.
  • Strength and other properties are compromised.
  • Raw material options are growing, but are still limited.
  • Higher raw material costs.
  • There is a size limitation on parts that can be printed.

 

CNC MACHINING

Computer Numerical Control Machining begins with a solid piece of plastic material and removes material to produce the desired shape to close tolerances.

 

CNC MACHINING: THE ADVANTAGES

  • Excellent repeatability. Once a machine is programmed, the product it produces should be very consistent.
  • Accuracy is very good. Capable of tight tolerance work.
  • Much more economically and time feasible than printing for large quantities.
  • Material options are much greater than those available for 3D printing.
  • Machining can produce different surface finishes.
  • Machined parts have appreciably better mechanical properties than printed parts.

 

CNC MACHINING: THE DISADVANTAGES

  • There are geometry limitations compared to 3D printing.
  • A significant amount of waste is produced as an appreciable amount of material is removed.
  • Labor cost increases due to the short supply of skilled machinists.
  • For a requirement of just a few parts, machining is not as efficient due to set up and programming time and effort.

 

IN CONCLUSION, the decision on how best to produce plastic parts is largely influenced by the physical requirements of the part, and the quantity needed. A few parts can be made cost effectively utilizing 3D printing.  A requirement for hundreds of parts is probably best addressed with CNC machining.  If higher volumes are needed, injection molding should be considered.  While it takes time to build an injection mold, once made it can produce thousands, even hundreds of thousands, of parts quickly and cost effectively.

CRAFTECH INDUSTRIES is uniquely positioned to offer both CNC machining and injection molding in dozens of different plastic materials. For more information, please visit our website, www.craftechind.com or call us at 518-828-5001.

 

 

 

 

 

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