What does feed rate mean in fabrication?

Feed rate is a setting. Each material and thickness has its own, stored in the machine's cutting parameters and in whatever the shop quotes with. Thin sheet runs fast and thick plate runs slow: 1 mm (0.04 in) mild steel on a modern fibre laser can run above 20 m/min, while 20 mm (3/4 in) plate cuts at well under 1 m/min.

Shops often say cutting speed or cut speed for the same thing. Strictly, feed rate is the programmed number. The speed the head actually reaches can be lower, because it has to slow down for corners and short moves.

You'll see feed rates in a few units:

• metres per minute (m/min), the most common on laser controllers
• millimetres per second (mm/s): 1 m/min is about 16.7 mm/s
• inches per minute (in/min or IPM): 1 m/min is about 39.4 in/min

In machining, feed rate means something else: how far the tool advances per revolution or per tooth. If you've come to laser cutting from a machine shop, it's the same name for a different number.

How is feed rate used?

Feed rate turns cut length into cut time. 72.6 m of cutting at 3 m/min takes about 24 minutes; at 6 m/min it takes 12. Add pierce and travel time to get the cycle time, which the hourly rate turns into a price.

That's why feed rate and hourly rate only make sense together. A shop with a high hourly rate and fast feed rates can quote lower than a shop with a low rate and slow ones.

Feed rates come from:

• the machine maker's cutting charts, supplied with the laser
• the parameter library in the machine's controller
• test cuts on the shop's own material, timed against the controller's estimate

Small features get their own, slower setting. A fine feed rate applies to holes and detail below a set size, because the head can't take tight curves at full speed.

Why does feed rate matter?

Every quote built on a wrong feed rate is wrong by the same proportion. Set it 20% too slow and the cutting part of every price is about 20% high. Set it too fast and every job takes longer than you charged for.

The common trap is a machine upgrade. A shop moves from an older CO2 laser to a fibre laser, or to a higher-powered fibre, and keeps quoting with the old feed rates. The new machine might cut thin sheet two or three times faster, but the quotes still price it at the old speed. The shop comes in high on work it could easily win, and often can't see why.

Keeping feed rates up to date

Feed rates also drift out of date for reasons other than upgrades: a new cutting head, a change of assist gas, a different material supplier. A simple routine catches most of it:

• Check feed rates whenever the machine, head, gas or main material changes.
• Compare quoted cut time against the controller's estimate and the real run time on a few jobs each month.
• Keep one set of quoting feed rates, updated in one place, so every estimator uses the same numbers.

Feed rate and quoting

Feed rates are the most important settings in any laser quoting setup. In Tempus Tools they live in rate tables, with one row per thickness holding the feed rate, pierce time and fine cutting settings, so every quote pulls the right speed for the thickness being cut.

Further reading: Laser cutting hourly rate: what should be included?