天堂视频 Additive Manufacturing
Material Jetting
Material jetting creates objects in a similar method to a two dimensional ink jet printer. Material is jetted onto a build platform using either a continuous or Drop on Demand (DOD) approach.
Material is jetted onto the build surface or platform, where it solidifies and the model is built layer by layer. Material is deposited from a nozzle which moves horizontally across the build platform. Machines vary in complexity and in their methods of controlling the deposition of material. The material layers are then cured or hardened using ultraviolet (UV) light.
As material must be deposited in drops, the number of materials available to use is limited. Polymers and waxes are suitable and commonly used materials, due to their viscous nature and ability to form drops.
Material Jetting – Step by Step
- The print head is positioned above build platform.
- Droplets of material are deposited from the print head onto surface where required, using either thermal or piezoelectric method.
- Droplets of material solidify and make up the first layer.
- Further layers are built up as before on top of the previous.
- Layers are allowed to cool and harden or are cured by UV light. Post processing includes removal of support material.
Technical Info
Material Jetting builds objects in a similar method to a two dimensional ink jet printer. Multiple materials can be used in one process and the material can be changed during the build stage. Material is jetted onto the build platform surface in droplets, which are formed using an oscillating nozzle. Droplets are then charged and positioned onto the surface using charged deflection plates. This is a continuous system which allows for a high level of droplet control and positioning. Droplets which are not used are recycled back into the printing system.
Drop on Demand (DOD) is used to dispense material onto the required surface. Droplets are formed and positioned into the build surface, in order to build the object being printed, with further droplets added in new layers until the entire object has been made. The nature of using droplets, limits the number of materials available to use. Polymers and waxes are often used and are suitable due to their viscous nature and ability to form drops. Viscosity is the main determinant in the process; there is a need to re-fill the reservoir quickly and this in turn affects print speed. Unlike a continuous stream of material, droplets are dispensed only when needed, released by a pressure change in the nozzle from thermal or piezoelectric actuators. Thermal actuators deposit droplets at a very fast rate and use a thin film resistor to form the droplet. The piezoelectric method is often considered better as it allows a wider range of materials to be used. The designs of a typical DOD print head changes from one machine to another but according to Ottnad, typically include a reservoir, sealing ring, Piezo elements and silicon plate with nozzle, held together with high temperature glue.
Post processing: Support material can be removed using a sodium hydroxide solution or water jet. Due to the high accuracy of the process technology, the level of post processing required to enhance the properties is limited and the functional and aesthetic qualities of a part are largely determined during the printing stage. Stratasys polyjet technology cures the material using UV light and therefore no post curing process is needed.
Machine Example:
|
Machine |
Build Area |
Layer Thickness |
No of Colours |
|
Objet 500 Connex 3 |
490 x 390 x 200 mm |
Layer thickness 16 microns |
46 |
Materials
The material jetting process uses polymers and plastics.
Polymers: Polypropylene, HDPE, PS, PMMA, PC, ABS, HIPS, EDP
Pros / Cons
Advantages:
- The process benefits from a high accuracy of deposition of droplets and therefore low waste
- The process allows for multiple material parts and colours under one process
Disadvantages:
- Support material is often required
- A high accuracy can be achieved but materials are limited and only polymers and waxes can be used