3+1 Axis CNC End Milling: Finding the Changeover Break-Even
The programmable route wins below 60 parts in this changeover model. Above that, the dedicated fixture’s shorter cycle pays back its setup time.
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 small can a batch be before a dedicated fixture loses its cycle-time advantage?
Worked calculation
Assume a reusable programmable route takes 6 minutes to set up and 46 seconds per part. A dedicated fixture takes 22 minutes to set up and 30 seconds per part. The 960-second setup difference divided by the 16-second cycle difference gives a break-even of 60 parts.
How to validate it on the shop floor
Run a first article on each route and time setup through acceptance. Include profile swaps, cutter changes and rework. Check the end contour against the receiving section, not just the programmed toolpath.
What to do with the result
At 120 parts the assumed totals are 98 minutes for the programmable route and 82 minutes for the dedicated fixture. That gap reverses if the dedicated route incurs more than 16 extra minutes of fixture work or corrective setup. Track changeovers by profile family, since a dedicated fixture already mounted and qualified for the next order presents a different cost from a fresh fixture installation.
Practical follow-up
Which route wins on a 25-part batch? The model gives 25.2 minutes for the programmable route and 34.5 minutes for the dedicated route. Fixture build cost and repeat orders change the comparison.
When comparing aluminum profile machining fixtures, include the time to qualify the first acceptable part after each profile change.