Module 3: Assessment Quiz
Module: U1M3 - Slicing Software & Print Preparation
Duration: 20-30 minutes
Passing Score: 70% (9 of 12 questions)
Format: Multiple choice, matching, and scenario-based
Questions 1-3: Layer Height and Print Quality
How does increasing layer height from 0.1mm to 0.3mm affect print time and surface quality?
Explanation: Layer height directly determines the number of layers needed. A 30mm tall object at 0.1mm layers requires 300 layers; at 0.3mm, only 100 layers — roughly 3x faster. However, thicker layers produce more visible stair-stepping on curved and angled surfaces. The trade-off is speed vs. surface finish.
What is the recommended maximum layer height relative to the nozzle diameter?
Explanation: The nozzle must be able to squish each layer against the previous one. If the layer height exceeds ~80% of nozzle diameter, the nozzle cannot adequately press the extruded plastic, resulting in poor layer adhesion. For a 0.4mm nozzle, the maximum practical layer height is 0.32mm; for fine detail, 0.12-0.2mm is preferred.
A student needs to print a display model with the smoothest possible surface finish on a 0.4mm nozzle printer. What layer height should they choose?
Explanation: For a 0.4mm nozzle, 0.1mm (sometimes called "super quality") provides the finest practical resolution. Going below 0.1mm (e.g., 0.05mm) is theoretically possible but creates problems: each layer is so thin that it may not bond properly to the previous layer, and print times become extremely long. 0.1mm is the practical sweet spot for maximum surface quality.
Questions 4-6: Infill and Support Structures
A student is printing a bracket that will bear a 5kg load. Which infill percentage and pattern should they choose?
Explanation: Load-bearing parts need higher infill (40-60%) with a pattern optimized for multi-directional strength. Gyroid and cubic patterns distribute stress in all three axes, unlike rectilinear which is strong only along the line direction. 100% infill adds weight and print time with diminishing strength returns above 60%. The wall/shell count is often more important than infill percentage for structural parts.
What is the key difference between tree supports and linear (grid) supports?
Explanation: Tree supports grow upward from the build plate in a branching pattern, reaching overhang areas from the side rather than directly below. This means fewer contact points with the model surface, resulting in cleaner surfaces after support removal. Linear supports create a dense grid directly under overhangs, which is easier to generate but leaves more marks and is harder to remove.
At what overhang angle do most FDM printers begin to require support structures?
Explanation: The widely-used "45-degree rule" states that overhangs exceeding 45° from vertical (measured from the Z-axis) begin to sag and require support. Below 45°, each layer has enough overlap with the previous layer to be self-supporting. Above 45°, the unsupported portion increases rapidly. Some materials and printers can handle up to 50-60° with good cooling, but 45° is the safe default.
Questions 7-9: Print Orientation and Adhesion
A student is printing a cylindrical tube that must withstand internal pressure (like a pipe fitting). What print orientation maximizes strength?
Explanation: Internal pressure in a cylinder creates hoop stress (circumferential tension). If printed vertically, each layer is a complete circle — the extrusion lines run along the hoop direction, providing maximum strength where it is needed. If printed horizontally, the hoop stress acts across layer boundaries (the weakest direction in FDM), making delamination and failure much more likely.
What is the difference between a brim, a raft, and a skirt?
Explanation: Each serves a different purpose. A skirt (1-3 loops around but not touching the print) primes the nozzle and verifies first-layer quality without affecting the part. A brim (extends 5-15mm outward from the part perimeter) dramatically increases the adhesion footprint, preventing warping on parts with small bases. A raft (multi-layer platform under the entire part) provides maximum adhesion but leaves a rough bottom surface on the part.
When orienting a part for FDM printing, which surface should face upward for the best finish quality?
Explanation: In FDM printing, different surfaces have different qualities. The bottom surface (touching the bed) picks up bed texture and any adhesion aids. Side surfaces show layer lines. The top surface is typically smoothest because it is formed by the final infill pattern. For cosmetic parts, orient so the most visible surface faces up or is a side wall that can be post-processed.
Questions 10-12: G-Code and Slicer Software
What does the G-code command G28 do?
Explanation: G28 is one of the most important G-code commands. It triggers the homing sequence, moving each axis until its endstop switch is triggered, establishing the machine's zero reference point. Without homing first, the printer has no idea where the print head is located, and all subsequent movement commands would be unreliable.
In the G-code command "G1 X50 Y30 Z0.2 F1500 E10", what does each parameter represent?
Explanation: G1 is the "linear move with extrusion" command — the workhorse of FDM G-code. X, Y, Z specify the target position in millimeters. F sets the feed rate (movement speed) in mm/min — so F1500 means 25mm/sec. E specifies the amount of filament to extrude during the move. The slicer calculates thousands of these commands to build each layer.
What does the G-code command M104 S210 do?
Explanation: M104 sets the hotend target temperature. The "S" parameter specifies the target in degrees Celsius. Critically, M104 does NOT wait — the printer continues executing the next commands while heating. If you need the printer to wait until temperature is reached, use M109 instead (M109 S210 = set to 210°C AND wait). Similarly, M140 sets bed temperature without waiting, and M190 sets bed temperature and waits.
Last Updated: 2026-03-19
Content Review: Q1 2026