EBM

Question 1

Why is a Vacuum necessary in EBM?

Answer 1

To prevent electrons from colliding with air molecules (energy loss).

To protect the cathode from oxidation (extending its life).

To allow processing of reactive materials in a clean environment.

Question 2

What are the 4 main hardware modules of an EBM machine?

Answer 2

Electron beam gun (usually 3-6 kW power).
Magnetic coils (lenses to focus and steer the beam).
Vacuum chamber.
Building platform.

Question 3

Describe the preheating step in EBM.

Answer 3

Each powder layer is scanned with the electron beam to heat it before the actual melting starts. This is necessary to create a “powder cake” that provides conductivity and mechanical support.

Question 4

What is the “Smoking” phenomenon in EBM?

Answer 4

An explosive spattering of powder particles caused by electrostatic charge accumulation (repulsion). It can be prevented by drying powder and increasing preheating temperatures.

Question 5

What is an “Arc Trip” error?

Answer 5

An electrical discharge (arc) inside the EB gun that stops the process. Usually caused by dust, poor vacuum, or a damaged cathode.

Question 6

Explain “Powder Cake” and its consequences.

Answer 6

Definition: Powder that has sintered together due to high build temperatures.

Consequence: Provides support for overhanging parts but requires a Powder Recovery System (PRS) to blast away the caked powder after printing.

Question 7

Why is Evaporation (Metallisation) a risk in EBM?
Dvs avdunstning

Answer 7

The high energy of the electron beam causes some metal to evaporate. This can change the chemical composition of sensitive alloys (like NiTi) and coat the inside of the machine with metal film.

Question 8

Compare the Surface Roughness of EBM and SLM parts.

Answer 8

EBM parts are significantly rougher than SLM parts. This is due to the use of coarser powders and the “lateral sintering” (powder cake) caused by high temperatures.

Question 9

List 3 positive and 3 negative effects of high temperature in EBM.

Answer 9

Positive: Reduces smoking, reduces cracking, and lowers residual stresses.

Negative: Increases powder caking, limits geometric accuracy, and increases surface roughness.

Question 10

EBM Raw material

Answer 10

EBM är mer nischat än SLM. Eftersom processen sker i vakuum och kräver elektrisk ledningsförmåga, fungerar den bäst för reaktiva metaller och högtemperaturlegeringar.
Vanligaste materialen:
Titan: Både kommersiellt rent titan och $Ti$-$6Al$-$4V$.
Nickel-superlegeringar: Såsom Inconel 718 och Inconel 625, vilket gör EBM populärt inom flygindustrin.
Kobolt-krom-legeringar: Vanligt för ortopediska implantat (t.ex. höftkulor).
Under utveckling:Koppar och kopparlegeringar: Tack vare elektronstrålens goda energiupptagning.
Rostfritt stål (316L).