GlossaryKind of term: Manufacturing termBar feeder
What is a bar feeder?
A bar feeder pushes bar stock automatically through a lathe spindle, so the machine can make part after part from the bar without manual loading.
The bar feeder, also called a bar loader, stands behind the lathe; the spindle has to be hollow for it, and the bar ends in the collet or chuck. After a part is parted off, the workholding opens, the feeder pushes the bar forward to a stop or a programmed length and the workholding closes again. When the remnant is too short it is ejected and a new bar comes from the magazine. There are short loaders for bars of around a metre and long feeders for full stock lengths; on a Swiss-type lathe the feeder works together with the guide bush.
Which bar can a bar feeder take?
Which bar the machine can take depends on the spindle bore, the range of collet or chuck and the capacity of the feeder itself. At high spindle speeds the bar has to run steadily: guide channels, often oil-filled, and spindle liners damp vibration. A bent bar limits the speed. Profile bar such as hexagon needs matching collets and pushers. The remnant depends on the clamping length, the pusher and, on Swiss-type machines, the distance between guide bush and collet. Running unattended also requires reliable chip breaking, a parts catcher or pickup by a sub-spindle, and tooling with known tool life.
How does a bar feeder work in practice?
A bar feeder makes unattended hours possible over breaks, evenings and nights, provided the process is stable. How you cost those hours is an estimating choice, for example machine cost only, without an operator. Bar work also uses material beyond the part itself, with or without a feeder: the remnant of every bar, the width of the parting tool and the facing allowance per part. You count these in the material requirement, with the remnant spread over the parts per bar. What it brings depends on batch size, cycle time and how often the job repeats. On one-offs a bar feeder adds little, and it cannot feed diameters larger than the spindle bore.
What is a bar feeder often confused with?
A bar feeder is not robot loading: a robot loads separate blanks or pallets, a bar feeder only works with bar through the spindle. Nor is a bar feeder a bar puller: a bar puller sits in the turret and draws the bar forward while the workholding is open, with no feeder behind the machine; for short bars and small batches that can be enough.
Frequently asked questions
When does a bar feeder pay off?
On turned parts from bar that come back in batches, with a process that runs stably without supervision. On one-offs and short batches it adds little; it cannot feed diameters that do not pass through the spindle.
Does the remnant of each bar count in the price?
Usually, as an estimating convention. The remnant, the parting width and the allowance per part decide how much bar you need. How long the remnant is depends on the machine, the workholding and the feeder.
Can every lathe be fitted with a bar feeder?
A lathe with a hollow spindle, automatically actuated workholding and a control with the right interface usually can. The maximum bar diameter follows from the spindle bore, the workholding and the feeder.