Window Frame Drainage Slots: Calculating CNC Feed and Cycle Time
Four drainage slots take 17.5 seconds of steady-feed cutting in this model. Allow 41.5 seconds once assumed handling and inspection are included.
This application example uses public references and explicitly stated planning inputs. Figures derived from assumptions are estimates for evaluation, not measured customer results.
Production question
How much of the cycle does the programmed cut account for when machining four drainage slots per frame member?
Worked calculation
Assume a two-flute cutter, 12,000 rpm and 0.04 mm per tooth. Table feed = 2 × 12,000 × 0.04 = 960 mm/min. Four 70 mm toolpaths require 280 ÷ 960 × 60 = 17.5 seconds at steady feed. Add 24 seconds of assumed approach, handling and inspection to get a 41.5-second planning cycle.
How to validate it on the shop floor
Time clamp-close to clamp-open and separately time loading and gauging. Check slot location from the frame datum, open area after deburring and the clearance behind the extrusion wall.
What to do with the result
Start with the drainage drawing, which controls slot spacing and which chambers may be opened. Keep the drainage and fastening faces distinct in the program. If the first-off slot measures correctly but retains swarf inside the chamber, revise chip evacuation and deburring before raising feed. Record the number of open, usable slots after inspection, since a nominally fast program can still produce a poor frame.
Practical follow-up
Why can the CNC timer exceed 17.5 seconds? Short moves may never reach commanded feed, and entries, retracts and chip clearing consume time. Obtain starting parameters from the cutter supplier for the actual engagement and alloy.
When planning CNC machining for aluminum window frames, check which hollow chamber each drainage slot opens into before setting the tool depth.