What is Binder Jetting
Binder Jetting is a professional additive manufacturing process, in this process, the binder materials is deposited on powder bed selectively, in order to bond these powder area together and form a solid layer at one time. The powder materials commonly used in Binder Jetting are metal, and ceramics. Binder Jetting is applied in various applications, including full color prototypes, low cost metal parts. We should understand the basic mechanic of this process with key benefits and limitations, in order to fully apply its capacities.
How Binder Jetting Work
Binder Jetting manufacturing process:
- A thin layer of powder will be spread on build platform.
- The ink-jet nozzles will pass over and deposit binder agents on selective area, in order to bond powder particles together. The size of drop is almost 80 microns. In full-color Binder Jetting, color ink also should be deposited in this step.
- Once a layer is solidify, the build platform will move down with a layer height. Then a new powder layer will be spread on surface. Repeat this step until the whole part is finished.
- Once finished, printed parts will be left to cure and gain strength in the powder. After that, parts will be removed form powder bin and cleaned by pressurized air.
Post-processing is required for different materials. Metal Binder Jetting parts need to be sintered , hear treated or infiltrated with low melting temperature metal. Full-color prototypes are infiltrated with acrylic to improve color appearance. After printing, these parts are in green state with poor mechanical properties and high porosity.
Binder Jetting Characteristics
Printing machine parameter
In Binder Jetting, most printing parameters are set by machine manufacturers. The typical layer height for metal parts is 50 microns, and 100 microns for full color models. As Binder Jetting is operated at room temperature, there is no thermal effect of dimensional distortions like warping or curling. Binder Jetting can produce the largest size comparing to other technologies, it also can produce multiple parts at one time. Due to the post-processing limitations, we recommend the maximum size is under 50 mm.
In addition, Binder Jetting is able to operate without support structure, the surrounding powder will provide necessary support, which is similar to SLS. This can encourage the freedom of metal structure creation with few geometric restrictions. The dimensional accuracy can be reached in the post-process step.
In Binder Jetting process, the parts are not attached to the build platform. So the whole build area can be utilized, it is more suitable for low and medium volume production. We should consider the effect way of filling whole build volume, in order to take advantage of its full capabilities.
Full-color Binder Jetting
Binder Jetting is widely applied for full color 3D parts, in reason of its low cost. Full color parts are always printed by PMMA powder, the main print-heat jets the binding agent at first, while the secondary print-head jets the color ink. Different ink color can be combined into different color arrays.
After printing process, we should also coat parts surface with glue or infiltrant, in order to enhance color vibrancy and improve part strength. Then the secondary epoxy layer should be add to further improve strength and color appearance. Full-color Binder Jetting parts are very brittle, we recommend these parts are not suitable for functional applications.
Metal Binder Jetting
Metal Binder Jetting is the most economic metal 3D printing process. Moreover, it can produce large size parts without support structures, this enables complex geometries production. Metal Binder Jetting is the most appealing technology for low and medium volume metal production. In reason of Binder Jetting parts mechanical properties, these parts are not suitable for high-end applications. However, their material properties are equal to metal injection molding parts.
Infiltration & sintering
As in Metal Binder Jetting, printed parts are consist of metal particles and polymer materials. These parts should be post-processed to get good mechanical properties after printing, these post-processing process including infiltration and sintering.
Infiltration: Place printed parts in a furnace, burn out binder materials. Then bronze is used to infiltrate voids by capillary action, in order to get parts with low porosity and good strength.
Sintering: Place printed parts in a high temperature furnace, burn out binder materials and sinter metal particles to bond together, in order to get parts with very low porosity.
Metal Binder Jetting characteristics
Accuracy and tolerance are difficult to predict, which normally depending on model and geometries. The parts dimensions are compensated for shrinkage by software, but the non-uniform shrinkage is an issue. Post processing will also give rise to inaccuracies. Deformation will occur once parts are heated to a high temperature and in soft state. Moreover, warping will occur once fiction between plate and part surface increase greatly in shrinkage.
Sintered or infiltrated Binder Jetting parts have internal porous, this will affect their final mechanical properties. In reason of the voids will create rack, fatigue strength, fracture strength and elongation are affected greatly. For application with critical mechanical performance, we recommend DMLS. However, Binder Jetting parts have better surface roughness than DMLS, the surface roughness is 6 microns after post-processing, we reduce it to 3 microns with bead-blasting.
Binder Jetting Materials
Binder Jetting powder have limited range of materials, all the unbonded powder are recycled.
|Stainless steel (infiltrated)||Good mechanical propertiesCan be machined||10% internal porosity|
|Stainless steel (sintered)||Excellent mechanical propertiesHigh corrosion resistance||3% internal porosity|
|Inconel alloy (sintered)||Excellent mechanical propertiesExcellent temperature resistanceHigh chemical resistance|
|Tungsten carbide(sintered)||High hardness|
Binder Jetting Benefits & Limitations
Binder Jetting Benefits:
- Binder Jetting have less cost than DMLS.
- Binder Jetting can produce large parts with complex geometries.
- It is excellent for low or medium volume production.
Binder Jetting Limitations:
- Binder Jetting parts have lower mechanical properties than DMLS parts.
- Binder Jetting cannot create very fine detail, because parts in green state are very brittle.
- Binder Jetting have limited material selection.