1. What is a Speed and Feed Calculator for Plastic?

Definition: This calculator determines the optimal spindle speed (RPM) and feed rate (IPM) for machining plastic materials.

Purpose: It helps machinists and CNC operators achieve efficient material removal while preventing damage to plastic workpieces.

2. How Does the Calculator Work?

The calculator uses two key formulas:

Where:

• \( RPM \) — Spindle speed (revolutions per minute)
• \( SFM \) — Surface feet per minute (cutting speed for plastic)
• \( D \) — Tool diameter (inches)
• \( IPM \) — Feed rate (inches per minute)
• \( IPT \) — Feed per tooth (inches per tooth)
• \( Z \) — Number of teeth on the cutter

Explanation: The SFM is converted to RPM based on tool diameter, then multiplied by feed per tooth and number of teeth to determine feed rate.

3. Importance of Proper Speed and Feed

Details: Correct calculations prevent melting, chipping, or poor surface finish when machining plastics. Plastic requires different parameters than metals.

4. Using the Calculator

Tips: Enter the SFM (varies by plastic type), tool diameter, feed per tooth (typically 0.003-0.010 for plastics), and number of teeth. All values must be > 0.

5. Frequently Asked Questions (FAQ)

Q1: What SFM should I use for different plastics?
A: Typical ranges: Acrylic 300-500, PVC 200-400, Nylon 400-600, Polycarbonate 300-500 SFM.

Q2: Why is 3.82 used in the RPM formula?
A: It's the conversion factor (12/π) to convert SFM (feet) to RPM (inches).

Q3: How does plastic differ from metal in speed/feed?
A: Plastics generally require higher speeds, lower feeds, and sharper tools than metals.

Q4: What if my results show melting or poor finish?
A: Reduce RPM (SFM) or increase feed rate (IPT). Use sharp tools with positive rake angles.

Q5: Should I use coolant when machining plastic?
A: Generally no, but compressed air can help clear chips. Some plastics benefit from minimal coolant.