BackSession 2: Materials for Subtractive Manufacturing
Unit 2 — Manufacturing Foundations, Week 1
Session 2
Materials for Subtractive Manufacturing
Last Time: Who You're Building For
Today: what you're actually going to build it out of.
Before a single toolpath gets programmed, material choice is already shaping what's possible.
Not All Sheet Goods Are the Same
Three common CNC-router materials, three very different personalities.
Three Options
- Baltic birch plywood — many thin plies, minimal voids
- Standard plywood — fewer, thicker plies, cheaper, less consistent
- MDF — no grain at all, engineered from wood fiber
Grain Direction & Tear-Out
Plywood has a grain. Cutting across it, instead of with it, is far more likely to chip and tear the edge.
MDF has no grain at all — it cuts consistently in every direction, which is exactly why it's a CNC favorite despite its other weaknesses.
Screw-Holding
Not all materials hold a screw the same way — and an arcade cabinet gets opened for service, not just built once.
Screw-Holding
- Plywood holds screws reasonably well, especially face-on
- MDF holds a screw the first time — strip it once and the hole is often ruined
Weight, Cost, Moisture
MDF is denser (heavier) and cheaper than either plywood. None of these three are meant for outdoor moisture exposure — but they don't all fail the same way or the same speed.
The Property Comparison
| Baltic Birch | Standard Plywood | MDF |
|---|
| Edge quality when routed | Excellent | Fair | Excellent |
| Screw-holding | Good | Good | Poor (edge), fine (face, once) |
| Weight | Moderate | Moderate | Heavy |
| Cost | Highest | Middle | Lowest |
Your Cabinet Isn't One Material
A side panel, a control panel, and a back access panel don't have the same demands — there's no reason they should use the same material by default.
Two Things to Remember
"Cheapest" isn't the same question as "best."
A material choice should point back to a specific property that specific part actually needs.
Two Things to Remember
A part that gets serviced needs to survive being unscrewed.
This is exactly why screw-holding matters more for some panels than others.
Next Time
Session 3: Additive Manufacturing
A completely different process, with its own material rules — and its own place in this project.
'F' → Fullscreen
Build
Step 1: The Property Comparison
Use this table for your reasoning below — don't just go with a gut feeling.
| Baltic Birch | Standard Plywood | MDF |
|---|
| Edge quality when routed | Excellent | Fair | Excellent |
| Screw-holding | Good | Good | Poor (edge), fine (face, once) |
| Weight | Moderate | Moderate | Heavy |
| Cost | Highest | Middle | Lowest |
Step 2: Choose a Material for Three Components
For each component below, choose Baltic birch, standard plywood, or MDF, and justify it using at least two specific properties from the table — not just cost.
- Side panel — structural, holds the cabinet's shape and any leg levelers/casters
- Control panel — where joysticks and buttons mount, takes repeated physical impact
- Back access panel — removed and reattached whenever the electronics need servicing
Step 3: Defend Your Weakest Choice
Of your three choices, which one are you least sure about? Write one sentence on what would change your mind.
Checkpoint
Before you move on, check your work against these two questions.
- Did you use at least two properties per choice?
- "It's cheaper" alone isn't a complete justification for any of the three components.
- Would this make sense to a client?
- Your reasoning should hold up even to someone who's never heard the word "MDF" before today.
Reflection
Answer the following questions before submitting your work.
- Which single property — edge quality, screw-holding, weight, or cost — mattered most across your three choices?
- Did any two of your three components end up with the same material, but for different reasons? What were they?
- Session 3 covers additive manufacturing. Is there any component of an arcade cabinet you'd consider 3D printing instead of routing from sheet material? Why?
Submit
Submit your three material choices with justifications, your weakest-choice defense, and your reflection.
Activity Complete