KEVOS® MAKEOS · Manufacturing
Turning Cycle Time and Cost per Part with Tool Life
What does each turned part cost at this speed, and how much would the minimum-cost speed save?
Cycle time and cost per part for a turning operation, combining spindle speed, cutting time, Taylor tool life, tool edges and tool changes per part, handling, set-up spread over the batch and the machine rate, then comparing the cost and time at the minimum-cost and maximum-production cutting speeds.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Cut | ||
| Work diameter | mm | Diameter being turned. |
| Length of cut per pass | mm | Length of each pass. |
| Approach and overrun | mm | Extra travel for approach and overrun. |
| Number of passes | Number of passes. | |
| Cutting speed | m/min | Cutting speed now used. |
| Feed | mm/rev | Feed per revolution. |
| Tool | ||
| Taylor exponent n | Exponent of the Taylor tool-life equation V Tⁿ = C for the tool and material. | |
| Taylor constant C (speed for 1 min life) | m/min | Taylor constant: cutting speed that gives one minute of tool life. |
| Cost per cutting edge | $ | Cost of one cutting edge (insert price ÷ edges, plus holder share). |
| Tool change time per edge | min | Time to index or change an edge. |
| Costs | ||
| Machine and labour rate | $/h | Machine plus operator rate. |
| Load and unload time per part | min | Handling time per part. |
| Set-up time per batch | min | Set-up time for the batch. |
| Batch quantity | Parts in the batch. | |
Method and formulas
- N = 1000 V ÷ π D; cutting time t_c = passes × (L + approach) ÷ (f N).
- Tool life T = (C ÷ V)^(1/n); edges per part = t_c ÷ T.
- Cost per part = rate × [t_c + handling + tool change × t_c ÷ T + set-up ÷ batch] + edge cost × t_c ÷ T.
- Minimum-cost speed V = C ÷ [(1/n − 1)(t_ct + edge cost ÷ rate)]ⁿ; maximum-production speed V = C ÷ [(1/n − 1) t_ct]ⁿ.
- Example: at 200 m/min each part costs 3.3586 and takes 1.9507 min; the minimum-cost speed is 203.25 m/min.
Limitations
- Taylor constants are valid only near the tested feed and depth.
- Assumes the feed stays the same when the speed changes.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Quote a turned part from first principles
- Show the saving from running at the economic speed
- Compare insert grades by their Taylor constants
Who it is for
- Manufacturing engineers
- Estimators
- Production managers
What you get
- Cycle time and tool life
- Cost per part breakdown
- Minimum-cost and maximum-production speeds compared
Interpreting the result
- Run between the minimum-cost and maximum-production speeds; go towards maximum production only when the machine is the bottleneck.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1102–1152. Topic reference; no source tables or recommended settings are reproduced.
WORKOS tools are screening and decision-support utilities. Verify important financial, engineering, safety, legal or operational decisions using appropriate professional standards and your organisation’s approved data.
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