Wasting: CNC milling, stamping.

Materials Processing in Industry

In this lesson we’ll explore how materials are shaped in factories, focusing on two common methods: CNC milling and stamping. We’ll see how waste is produced, why it matters, and how engineers minimise it.

1️⃣ CNC Milling

Think of CNC milling like a robotic sculptor carving a block of wood or metal. The machine follows a computer program to cut away material, leaving the desired shape.

• 🔧 Tool path: The CNC program tells the spindle where to move.
• 📏 Feed rate & speed: How fast the tool moves and how fast the spindle spins.
• 🛠️ Tool wear: Over time the cutting edge dulls, causing more material to be removed than needed.

Waste in CNC Milling

Waste mainly comes from chips that are left behind after cutting.

1. Material removed that isn’t part of the final product.
2. Excess chips that must be cleaned up.
3. Tool wear leading to over‑cutting.

To estimate waste, engineers use the Material Removal Rate (MRR):

$MRR = \frac{V}{t}$

where $V$ is the volume removed (in $cm^3$) and $t$ is time (in minutes).

2️⃣ Stamping

Stamping is like punching a cookie out of dough. A die presses metal sheets into shape.

• 📐 Die design determines the shape.
• ⚙️ Force applied by the press.
• 🗑️ Trim and scrap are the waste pieces left after stamping.

Waste in Stamping

Typical waste sources:

Reducing Waste

Here are some practical strategies:

• 🛠️ Optimise tool paths to minimise unnecessary cuts.
• 📊 Use simulation software to predict chips and adjust parameters.
• 🔩 Choose the right tool material (e.g., carbide) to reduce wear.
• 🛠️ Regular maintenance of presses and dies.
• ♻️ Recycling chips back into the supply chain.

Example Calculation

Suppose a CNC machine removes a cylindrical core of radius $r = 2\,cm$ and depth $h = 5\,cm$ in 10 minutes. What is the MRR?

First calculate the volume:

$V = \pi r^2 h = \pi (2)^2 (5) = 20\pi \approx 62.8\,cm^3$

Then MRR:

$MRR = \frac{62.8}{10} \approx 6.28\,cm^3/min$

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