Sanding and smoothing in 3D Printing - Practice Problems & Coding Challenges

Challenge - 5 Problems

🧠 Conceptual

intermediate

Understanding the purpose of sanding in 3D printing

Why is sanding commonly used after 3D printing a model?

A To remove support structures and improve surface finish

B To change the color of the printed object

C To increase the strength of the printed model internally

D To reduce the printing time for future prints

💡 Hint

Think about what sanding physically does to the surface of an object.

Sanding removes rough edges and leftover support material, making the surface smoother and more visually appealing.

📋 Factual

intermediate

Materials suitable for sanding

Which of the following 3D printing materials is generally the easiest to sand smoothly?

A Nylon

B TPU (Thermoplastic Polyurethane)

C PLA (Polylactic Acid)

D PETG (Polyethylene Terephthalate Glycol)

💡 Hint

Consider the hardness and flexibility of the materials.

PLA is a rigid and relatively soft plastic that sands easily compared to flexible or tougher materials like TPU or Nylon.

🔍 Analysis

advanced

Effects of grit size on sanding results

What is the effect of using a very coarse grit sandpaper (e.g., 80 grit) compared to a very fine grit (e.g., 400 grit) when smoothing a 3D printed surface?

A Coarse grit removes material quickly but leaves rough scratches; fine grit smooths scratches and polishes the surface

B Coarse grit polishes the surface; fine grit removes material quickly

C Fine grit damages the surface more than coarse grit

D Both coarse and fine grit remove material at the same rate but differ in color

💡 Hint

Think about how sandpaper grit size affects surface texture.

Coarse grit sandpaper removes material fast but leaves visible scratches. Fine grit sandpaper smooths out those scratches and creates a polished finish.

🚀 Application

advanced

Choosing smoothing methods for different materials

You have printed a model in ABS plastic and want a smooth, glossy finish. Which smoothing method is most effective?

A Sanding with 80 grit sandpaper only

B Acetone vapor smoothing

C Applying water to the surface and letting it dry

D Heating the model with a hairdryer

💡 Hint

Consider chemical methods that work specifically with ABS plastic.

Acetone vapor smoothing melts the outer layer of ABS slightly, creating a glossy and smooth finish that sanding alone cannot achieve.

❓ Reasoning

expert

Impact of sanding on dimensional accuracy

How does sanding affect the dimensional accuracy of a 3D printed part, and what is a common strategy to minimize negative effects?

A Sanding melts the plastic and causes unpredictable size changes; no strategy can control this

B Sanding adds material to the surface, increasing dimensions; printing smaller parts compensates for this

C Sanding does not affect dimensions; it only changes color

D Sanding removes material and can reduce dimensions; designing parts slightly larger allows for sanding without losing critical size

💡 Hint

Think about how removing surface layers changes size and how designers plan for post-processing.

Sanding removes a thin layer of material, reducing size slightly. Designers often make parts slightly larger to allow sanding without compromising fit or function.