Batch production
In batch work, setup time per part becomes the number that matters, not cutting time. A fixture that loads in ten seconds instead of five minutes changes the economics of the whole job more than any feed rate ever will.
What changes at quantity
| One-off | Batch of fifty | |
|---|---|---|
| Design time | Dominant | Negligible per part |
| Setup per part | Once, and it does not matter | Dominant. Fifty times whatever it is. |
| Cutting time | Feels significant | Matters, and less than setup |
| Tool life | Irrelevant | A real cost, and a mid-run failure risk |
| Material yield | Barely matters | Nesting efficiency is real money |
| Finishing | Often the largest time | Usually still the largest time |
Fixtures
The single biggest lever. A fixture that locates a blank in one motion turns a five minute setup into a ten second one. Over fifty parts that is four hours.
- Locating pins so a blank drops into exactly one position.
- A machined pocket the blank sits in, cut on the machine itself so it is in the machine's own coordinates.
- Quick clamping: cam clamps, toggle clamps, or a vacuum, rather than screws.
- Cut the fixture on the machine, and do not move it afterwards. Then its position is known exactly.
- Keep the fixture. Label it with the job it belongs to. The reorder will come.
Nesting
- Fit as many parts per sheet as the geometry allows, and remember the offcut has value too.
- Keep enough material between parts for the tool plus a margin, or the sheet loses rigidity.
- Cut inner features on all parts first, then the profiles. The sheet is stiffest while it is whole.
- Plan the profile order so the sheet stays supported as long as possible. The last few parts on a heavily cut sheet are the ones that chatter.
- Hold the whole sheet, not just its edges. See workholding.
Tool life
In a one-off, a bit that dulls at the end is a non-event. In a fifty part run, a bit that dulls at part thirty means twenty bad parts you may not notice until after.
- Start every production run with a fresh cutter.
- Track roughly how many parts a bit gives you in that material, and change it before that number.
- Inspect parts periodically through the run rather than at the end.
- Keep a spare of every bit the job needs. Running out mid-run costs a whole setup.
Where the time actually goes
People optimise the cutting because that is the part the machine does visibly. In a real production run the order is usually:
- Finishing. Sanding, applying finish, waiting for it to dry, second coats.
- Setup and part handling, multiplied by the quantity.
- Cutting.
- Design, which is nearly zero once it is done.
So if you want a batch to go faster, look at your finishing process and your fixturing before you look at feeds and speeds. A spray setup or a drying rack often buys more than any machine change.