Question

sls: moving parts
use the information below to answer the question.
sls printing can be used to make moving parts. there is no support structure other than the powder that is in the powder bed.
moving part considerations
consider the thickness of the shafts and the mass to avoid over - sintering. in general, if the print has a shaft that is less than 1 cm in diameter, there can be a clearance of 0.15 mm on each side. the mass will not build up too much heat, so it wont over - sinter. if the shaft needs to be 1 cm, the clearance will be 0.25 mm on each side. it is important to note that there will still be powder in between and it can over - sinter.
reduce surface area
to avoid over - sintering moving parts, a redesign that reduces the surface area and contact is a good choice. there will be much less heat build - up, and the possibility of over - sintering is reduced greatly. the clearance in the center will be 0.4 mm, and an escape hole can be put in to allow the powder to get out.
what can be put into an sls moving part to allow the powder to get out?

• a bridge
• an internal support structure
• a clear resin
• an escape hole

Explanation:

From the "Reduce surface area" section of the text, it says "an escape hole can be put in to allow the powder to get out". The other options: a bridge isn't mentioned for powder escape, internal support structure is not for powder escape (and SLS has no support structure other than powder bed), and clear resin is not related to SLS powder escape as SLS uses powder, not resin.

Answer:

D. an escape hole