Bar Pullers: a Small Shop’s Alternative to Bar Feeders
By Stephen LaMarca, Manufacturing Technology Analyst at AMT – The Association For Manufacturing Technology, which owns IMTS – The International Manufacturing Technology Show
Operating a lathe means turning bar stock into parts. Bar feeders push (or feed) a bar of stock into the lathe until the bar has been fully utilized. Then the bar feeder continues to load bar after bar until the job is complete or the hopper is out of stock, just like a mechanical pencil. However if only a single bar of stock is necessary, or a shop does not have the space or money for a bar feeder, a bar puller can be used to easily automate any CNC lathe or turning center.
Like a bar feeder, a bar puller can improve productivity by enabling CNC lathes to run unattended and permit operators to handle other tasks. Depending on their needs, a shop may find that a bar puller is a better choice than a bar feeder. CNC bar pullers are inexpensive, require minimal setup, and can be easily fit to most CNC lathes. The average cost of a bar puller is generally much lower than a bar feeder. If a shop doesn’t absolutely need a bar feeder and can make do with a simple bar puller, the funds saved can be put toward another machine to expand a shop’s capabilities. Additionally, bar pullers are easy to set up and use, as no electrical interface with the machine tool control is required.
The bar puller is engaged via a typical tool change. The two main variants of bar pullers are spring loaded jaw type pullers and air/coolant-actuated finger type pullers. Spring loaded pullers can have either manually adjustable jaws that slide over the stock, or rollers (which negate the need for manual adjustment). There are spring loaded pullers available as combination puller/cutters that can cut off a finished part before pulling more stock. Air/coolant-actuated pullers usually have three fingers with which to grip the bar stock by the end. These fingers have hardened inserts to prevent wear.
Although bar pullers do not take up the precious floor space bar feeders do, a simple bar puller does not offer production capacity to a machine at the level a bar feeder does. The added stock capacity of a bar feeder is worth the cost and real estate in the case of a machine tasked with producing a massive lot of parts. The size and frequency of jobs and the shop tasked with them will ultimately decide which option is best.