KEVOS® MAKEOS · Manufacturing
Bar Stock Plan for Bar-Fed Parts (Bars, Yield, Material Cost, Machine Time)
How many bars do I need for this batch of bar-fed parts, how much of the bar ends up as parts, what does the material cost, and how long will the run take?
Material and time plan for parts made from bar on a lathe or screw machine: length per part with cut-off and facing allowance, parts per bar, bars to order and stock length and mass (as the screw machine stock tool), material yield, material cost per part, machine hours from the cycle time and bar change time, and shifts needed.
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How this tool works
Inputs, units and where to find them
| Input | Unit | Typical source |
|---|---|---|
| Part length | mm | Finished length of one part. |
| Cut-off tool width | mm | Width of the cut-off (parting) tool. |
| Facing allowance per part | mm | Extra length faced off each part. |
| Bar length | mm | Length of the bar stock. |
| Remnant (unusable end) | mm | Length left in the collet or feeder that cannot be used. |
| Parts needed | Parts to make. | |
| Bar mass per metre | kg/m | Mass per metre of the bar. |
| Material price | $/kg | Price of the bar material. |
| Cycle time per part | s | Machine cycle time per part. |
| Bar change time | s | Time to load a new bar. |
| Hours per shift | h | Hours in a shift. |
| Least material yield accepted | % | Least share of bar that should end up in finished parts. |
Method and formulas
- Length per part = part + cut-off + facing; parts per bar = ⌊(bar − remnant) ÷ length per part⌋; bars = quantity ÷ parts per bar (rounded up) (as the screw machine stock tool).
- Yield = parts × part length ÷ (bars × bar length); material cost per part = bars × bar length × mass per metre × price ÷ quantity.
- Hours = (quantity × cycle + bars × bar change) ÷ 3600; shifts = hours ÷ hours per shift.
- Example: 109 parts per bar need 10 bars (36.576 kg), 83.333% yield, about 0.10973 of material a part and 12.667 hours of machine time.
Limitations
- Whole parts per bar; last-bar remnants and set-up parts are not added.
- Constant cycle time; tool changes and inspection add time.
- Example values are illustrations. Replace them with values for your actual task.
Typical uses
- Order bar stock for a turned-part batch
- Quote material cost per part
- Plan the run time on a bar-fed lathe
Who it is for
- CNC machinists
- Estimators
- Production planners
What you get
- Parts per bar, bars and stock mass
- Material yield and cost per part
- Machine hours and shifts
Interpreting the result
- A thinner cut-off tool and a shorter remnant both raise yield: on short parts the cut-off can be most of the waste.
References
- Machinery’s Handbook, 29th edition (Industrial Press, 2012), printed pp. 1175–1176. 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.
Open the Bar Stock Plan for Bar-Fed Parts (Bars, Yield, Material Cost, Machine Time) calculator
