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Session 2: Materials for Subtractive Manufacturing

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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 BirchStandard PlywoodMDF
Edge quality when routedExcellentFairExcellent
Screw-holdingGoodGoodPoor (edge), fine (face, once)
WeightModerateModerateHeavy
CostHighestMiddleLowest

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

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Build

Step 1: The Property Comparison

Use this table for your reasoning below — don't just go with a gut feeling.

Baltic BirchStandard PlywoodMDF
Edge quality when routedExcellentFairExcellent
Screw-holdingGoodGoodPoor (edge), fine (face, once)
WeightModerateModerateHeavy
CostHighestMiddleLowest

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.

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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.
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Reflection

Answer these on your own. Reflections are individual, even when the rest of the session was team work.

  1. A classmate picks MDF for a bracket with a bolt threaded into its edge, saying “MDF is the cheapest and its routed edge quality is excellent.” Both of those facts are true. Why is the choice still wrong?
  2. 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?
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Submit

Submit your three material choices with justifications, your weakest-choice defense, and your reflection.

Activity Complete