How to Cut CNC Machining Cycle Time with High-Efficiency Toolpaths (HEM/HSC)

 PFT, Shenzhen
Date: September 2025

Introduction: Mastering CNC Productivity

Reducing CNC machining cycle time is a challenge every manufacturing engineer faces. Using High-Efficiency Milling (HEM) and High-Speed Cutting (HSC) toolpaths can significantly accelerate production while maintaining surface quality and tool life. In this guide, we will explore practical methods to implement HEM/HSC, backed by real-world data, so you can optimize your CNC operations effectively.

1. Understanding HEM and HSC Toolpaths

High-Efficiency Milling (HEM) focuses on maintaining a consistent radial chip load, reducing cutting forces, and extending tool life. High-Speed Cutting (HSC) emphasizes high spindle speeds with lower axial depth of cut, enabling faster material removal in lightweight or thin-walled components.

Practical Tip:

• HEM: Use a small radial engagement (10-30% of tool diameter) with full depth cuts.

• HSC: Maximize spindle RPM while keeping feed per tooth within tool manufacturer limits.

Case Study: In a Shenzhen-based aerospace shop, switching a 50mm end mill from conventional toolpaths to HEM reduced cycle time on aluminum aerospace brackets from 45 minutes to 28 minutes, a 38% reduction.

2. Step-by-Step Implementation

Step 1: Analyze Existing Toolpaths

• Export your current G-code or CAM simulations.

• Identify heavy stock areas where tool engagement is inconsistent.

• Calculate the current radial and axial depth of cut.

Step 2: Adjust Machine Parameters

• Increase spindle speed according to HSC recommendations.

• Reduce radial engagement for HEM to maintain stable cutting forces.

• Verify machine acceleration limits to avoid chatter or overshoot.

Step 3: Optimize Tool Selection

• Use coated carbide end mills for HSC aluminum and high-speed steel for stainless steel.

• Consider tool diameter relative to slot width for consistent chip load.

Step 4: CAM Software Toolpath Tuning

• Enable dynamic or trochoidal toolpaths.

• Set step-over to 10–30% of tool diameter for HEM.

• Apply adaptive feeds for HSC to maintain constant material removal rates.

Tip: Visualize toolpath simulation to identify potential collisions or excessive retracts.

3. Real-World Performance Metrics

Observation: Both HEM and HSC improved cycle times by 30–40%, while maintaining acceptable tool wear levels.

4. Common Pitfalls and Solutions

1. Excessive Spindle Load: Ensure spindle speed and feed per tooth are within tool limits.

2. Chatter/Vibration: Use proper tool overhang and fixture rigidity.

3. CAM Misalignment: Verify stock orientation and toolpath entry/exit strategies.

Pro Tip: For long-run jobs, schedule periodic tool inspections every 4–6 hours to prevent unexpected downtime.

5. Enhancing Results with Automation

• Integrate in-machine probing to adapt toolpaths dynamically based on part geometry.

• Use real-time monitoring systems to adjust feeds and speeds automatically.

• Consider machine learning algorithms in CAM for predictive cycle time reduction.