Tasks and composition software, management post processing for CNC, stages of software development, software features
As with trochoids, for dynamic milling we use 10–15% radial engagement (side tooth contact). We back away from deep radial engagement (end tooth contact) to around 10 to 15 % of the cutter’s diameter (Fig. 9.1).
Looking up a feed per tooth (chip load) for a given cutter and setup, you’ll find numbers that represent feeding a cutter such as this with a large radial engagement (Fig. 9.2). For example, the feed rate for this cutter is based on 0.006 inch per tooth per revolution. Each tooth advances 0.006 inch into the work.
Figure 9.1 – This cutter has a high axial and low radial engagement.
When we back away to a small radial engagement, as we’ve been describing, the chip is made thinner. This means that the feed rate should be increased to keep the chip load constant. That upward adjustment maximizes cycle times, but it’s also necessary to correct the thin chips to keep heat leaving with the chip and not overheating the cutter. This is true for standard milling and especially so for HSM, where heat removal is crucial.
Figure 9.2 – Less radial engagement requires increasing feed rates to keep chips thick enough to carry away heat and for efficient cut rates.
The dynamic toolpath constantly adapts to the remaining material, with a constant chip load and volume. Each successive cut will be made up of the following components:
• Large axial engagement
• No sharp corners
- Spiral entry
- Smooth entry/exit
• Climb cutting always
• Micro-lift rapid return reengage
The following are only possible through highly intelligent CAM software:
• Cycle times reduced by 30 percent or more compared to traditional cutting techniques
- Machines only where material exists
- Consistent chip load allows for maximum feed rate/material removal
- Accounts for chip thinning, keeping feeds maximized
- Better finishes due to constant climb milling
- Better accuracy due to light cutter loads – less deflection of work and cutter
• Improved tool life
- Full flute utilization for longer tool life
- Side teeth are better geometry for cutting/shearing the chip compared to end teeth
- Deformation heat leaves with the chip; far less cutter heat
- Smaller tools can be used with similar results – fitting into tighter spots, too
- Less carbide needed, since cuts are not brute force
- Smaller, lighter duty machines can accomplish more work
- Fewer spindle loads
- Less demand on setups due to reduced forces.
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