3D Printing Vs CNC Machining: Which Is Right For Your Prototype And Production?

3D printing is also known as additive manufacturing, which builds parts through layers of materials.     It has many advantages over traditional manufacturing processes however it has its problems.

CNC vowin.cn/en/News/news1251.html' target='_blank'>machining is a fairly common subtractive technique used for parts manufacturing, which creates parts by cutting off the blank.

The 3D printing process involves parts being created layer by layer using materials such as liquid photopolymer resins (SLA), drops of photopolymer (PolyJet), plastic or metal powders (SLS/DMLS), and plastic filaments (FDM).     So it produces less waste compared with CNC process.

CNC machining is to cut from a whole piece of material, so the utilization rate of the material is relatively low.     The advantage is that almost all materials can be CNC machined, including production-grade engineering plastics and various metal materials.     This means that CNC machining may be the most viable technique for prototypes and end-use mass-produced parts that require high functionality and special performance.

3D printing can create parts with highly complex geometries even hollow shapes that cannot be done by CNC machining, such as jewelry, crafts, etc.   CNC machining offers greater dimensional accuracy (±0.005mm) and much better surface finishes (Ra 0.1μm).   The advanced 5-axis CNC milling machines can perform high-precision machining of more complex parts that will help you meet your most difficult manufacturing challenges.

3D printing typically produces low quantities of parts without tooling, and without human intervention, so that fast turnaround and low cost are possible.   The manufacturing cost of 3D printing is priced based on the number of materials, which means that the larger parts or more quantities cost more.   The process of CNC machining is complex, it requires specially trained engineers to pre-program the processing parameters and processing path of parts, and then machining according to the programs.   Manufacturing costs are therefore quoted taking the extra labor into account.   However, CNC machines can continuously run without human supervision, making them perfect for larger volumes.
 

3D Printing Process Introduction

• SLA

  Stereolithography (SLA) is an additive manufacturing process that works in a different way to FDM. In SLA 3D printing, a 3D object is created with a laser, which is directed at areas of photosensitive liquid resin. The laser causes areas of the resin to harden, forming a solid part.

  The SLA process uses a moving platform in a tank of liquid resin. The platform moves up or down after each layer is fully cured, which is different to FDM, in which the platform remains stationary. The SLA laser is focused using a system of mirrors.

  SLA can only be used with photosensitive polymers, but offers high accuracy and fine details. It also predates other forms of additive manufacturing, having been invented back in the 1980s.

• SLS

  Selective Laser Sintering (SLS) is a powder bed additive manufacturing process used to make parts from thermoplastic polymer powders. It is commonly used for functional parts, since SLS printed components have good mechanical properties.

  An SLS 3D printer works by sintering areas of powder with a laser. During the process, a thin layer of powder is distributed evenly across the build platform, after which the laser sinters selected areas of the 2D layer.

  When the layer is complete, the platform is lowered, more powder added, and the laser sinters the next layer.

  When all layers are complete, the part is left to cool. Unused powder is kept to be used again, and the part is cleaned to remove excess material.

• SLM

  Selective Laser Melting (SLM) is a metal additive manufacturing process used to create functional, end-use products. SLM printers use a laser to melt particles of metal powder, fusing them together to form a 3D object.

  An SLM 3D printer uses a gas-filled chamber containing the metal powder. The laser passes over the desired sections of the powder, causing the particles to melt and bond. When a layer is complete, the build platform moves down to allow the laser to pass over the next layer.

  The SLM process can be used to create strong metal parts with highly complex shapes, providing engineers with new levels of design freedom.

• FDM

  Fused Deposition Modeling (FDM) is the most widely used additive manufacturing process for desktop 3D printers.   The process involves extruding a melted plastic from a computer-controlled nozzle, building a part layer by layer.

  FDM 3D printers use a spool of filament as raw material.   This filament is directed into the print head, where it is melted and deposited onto the incomplete part.   In accordance with computer instructions, the print head moves along 3 axes in order to deposit material in the right place.

  Because the material cools after it is deposited, further layers of material can be deposited on top of the existing layers, allowing for the creation of 3D shapes.