CAMT CAMT Machine Calibration & Process Parameters 2 — Questions and Answers
Question 1: How does increasing nozzle temperature in FDM printing generally affect interlayer adhesion?
- Higher temperatures always reduce interlayer adhesion
- Higher temperatures generally improve interlayer adhesion up to a material-specific maximum (Correct answer)
- Temperature has no effect on layer bonding strength
- Higher temperatures only affect surface appearance
Correct answer: Higher temperatures generally improve interlayer adhesion up to a material-specific maximum
Higher extrusion temperatures increase polymer chain mobility and diffusion across layer interfaces in FDM, improving interlayer bonding strength up to the point where material degradation begins.
Question 2: In laser powder bed fusion, what is the primary effect of increasing laser power on the melt pool?
- It only changes scan speed requirements
- It increases melt pool size and depth, improving fusion but risking keyhole porosity at excess levels (Correct answer)
- It decreases part density by disrupting solidification
- It has no measurable effect on the melt pool geometry
Correct answer: It increases melt pool size and depth, improving fusion but risking keyhole porosity at excess levels
Higher laser power in LPBF enlarges and deepens the melt pool, improving powder fusion and part density, but excessive power creates keyhole defects from vapor cavity formation beneath the melt pool.
Question 3: What is Volumetric Energy Density (VED) in laser powder bed fusion, and why is it a key process parameter?
- Total electrical energy consumed per complete build
- Energy delivered per unit volume of powder, directly controlling fusion quality and porosity (Correct answer)
- The laser beam energy measured at the build surface
- The energy required to preheat the build chamber
Correct answer: Energy delivered per unit volume of powder, directly controlling fusion quality and porosity
VED quantifies energy delivered per unit powder volume (Power ÷ [Scan Speed × Hatch Spacing × Layer Thickness]), serving as the primary predictor of part density, microstructure, and defect level.
Question 4: How does increasing print speed in FDM typically affect the trade-off between productivity and part quality?
- Higher speed always improves both productivity and quality
- Higher speed increases throughput but typically reduces dimensional accuracy, surface finish, and layer adhesion (Correct answer)
- Higher speed only affects infill quality, not perimeters
- Higher speed improves layer adhesion due to better material flow
Correct answer: Higher speed increases throughput but typically reduces dimensional accuracy, surface finish, and layer adhesion
Increasing FDM print speed reduces build time but can degrade dimensional accuracy, surface finish, and interlayer bonding due to inconsistent material flow rates and reduced interlayer dwell time.
Question 5: What is 'hatch spacing' in laser powder bed fusion, and how does it affect part density?
- The distance between successive powder layers, controlling build height
- The lateral distance between adjacent laser scan tracks, affecting melt pool overlap and density (Correct answer)
- The spacing between support structures, affecting removal difficulty
- The distance between part boundaries, affecting nesting efficiency
Correct answer: The lateral distance between adjacent laser scan tracks, affecting melt pool overlap and density
Hatch spacing is the lateral offset between adjacent laser scan tracks; smaller spacing increases melt pool overlap, improving density and reducing porosity, but increases scan time per layer.
Question 6: Why is a heated build plate critical when printing ABS filament on an FDM machine?
- The heated plate melts the ABS filament before it reaches the nozzle
- A heated plate minimizes thermal gradients in the part, reducing warping and layer delamination (Correct answer)
- The heated plate controls nozzle extrusion temperature
- A heated plate is required to activate ABS adhesion chemistry
Correct answer: A heated plate minimizes thermal gradients in the part, reducing warping and layer delamination
ABS has a high coefficient of thermal expansion and contracts significantly as it cools; a heated bed maintained at 90–110°C reduces the temperature gradient between deposited layers and the ambient environment, preventing warping.
CAMT CAMT Machine Calibration & Process Parameters 2
How does increasing nozzle temperature in FDM printing generally affect interlayer adhesion?