Binder Jetting

Question 1

What is binder jetting?

Answer 1

Liquid bonding agent is selectively deposited to join powder materials

It is similar to powder bed fusion but it doesn’t use heat

Question 2

How is binder jetting different from material jetting?

Answer 2

Because it uses inkjet heads to deposit only part of the final material

Question 3

Advantages of binder jetting

Answer 3

Systems are low cost compared to other AM techniques
Readily available and cheap materials (starch, cellulose or plaster)
Binder solution is water based (easily accessible)
Colour possible
Fast, due to jetting
Very little waste material

Question 4

Disadvantages of binder jetting

Answer 4

Limited functional parts, high porosity (limited mechanical properties)
Poor surface finish due to the particle size and distribution and wetting of binder
Multiple secondary processes

Question 5

What are the post processing stages for binder jetting?

Answer 5

1. Piston raised and the loose powder is vacuumed to reveal the part
2. Parts in ‘green’ state are very fragile
3. The part is de-powdered and the resultant part is porous
4. Infiltration with liquid secondary materials is essential

Question 6

What is the point of colour binder jetting?

Answer 6

Developed to communicate concepts with customers

Question 7

How is colour applied in binder jetting?

Answer 7

Achieved by using the same colour printing system as in an ink jet printer
Colour is only applied to the outside 2mm of parts
Clear and transparent is not possible

Question 8

How does the speed of binder jetting compare to other processes?

Answer 8

Faster than selective laser sintering (4x faster) due to multiple nozzles
No support generation required
No pre heating or cooling required

Question 9

What is infiltration?

Answer 9

Applying a liquid resin to a printed part to provide strength and impart specific properties

Question 10

Why are infiltration systems selected?

Answer 10

For their ability to :

Fill porosities
Improve mechanical properties
Ensure suitable thermal properties
Ease of use

Question 11

What are some common infiltrants (infiltration materials)?

Answer 11

Elastomer
Erethane
Wax
Cyanoacrylate

Question 12

What are some relevant applications of binder jetting?

Answer 12

(limited due to heavy weight)

Architectural models
Art
Prototypes
Finite element analysis (FEMA)
Filters (porosity is useful)
Plaster casting moulds

Question 13

How can binder jetting be used to create plaster casting moulds?

Answer 13

Used for non ferrous metals such as zinc, aluminium, copper based alloys
Sulphur in gypsum reacts with iron so can’t be used with ferrous metals
Moulds produced complete or as an insert
No need to split mould
Must remove all loose powder
Moulds dried in an oven to remove moisture

Question 14

How does binder jetting for metals work?

Answer 14

Spreads a layer of metal powder, a binder is then jetted according to the parts geometry.
It is then sintered to fuse the glued metal powder and produce the final part

Question 15

How does binder jetting of ceramics work?

Answer 15

Powder is loosely bound together by the binder which is selectively jetted
Green state part comes out
Fired at a high temperature which burns the binder from the part and sinters the ceramic together
The process sufferers from part shrinkages during firing which can cause the part to crack
Achieving a high density is a challenge due to porosity between the particles

Question 16

How does high speed sintering within binder jetting work?

Answer 16

An absorbent material is jetted onto the powder bed
An IR lamp then floods the exposed layer
Regions which have the absorbent material heat up faster and therefore sinter
It is documented to be 4x faster than SLS process