What’s the Right Bar Feeder for Your Machine Shop?

The most common automation accessory for high-volume turning, bar feeders, provide a reliable way of delivering material in the form of bar stock to a lathe, multispindle, rotary transfer machine and, in some cases, a CNC milling machine. Minimizing operator intervention, even to the point of lights-out operation or long stretches of unattended machining, is the main benefit of an automatic bar feeder.

While the concept is quite simple, these essentially “one-axis devices” which push bar stock into a machine tool’s workzone come in a variety of flavors, with the primary differences being bar length capacity (short loaders versus long ones) and bar storage capacity (single-barrel loaders versus magazine styles into which multiple bars can be loaded). But there’s more to it than that. Shops have to answer a variety of questions to determine what bar feeder makes most sense for their production needs. Here are four.

Should I go With a Short or Long Bar Feeder?

Some years ago, I visited SDP/SI, a division of Designatronics, to develop an article explaining how the Hicksville, New York, manufacturer of precision gears, gear assemblies and related components for a range of motion control applications has become a more efficient and profitable operation by embracing machining challenges rather than shying away from them.

During the visit, I learned the company had made the decision to replace 12-foot bar feeders with 4-foot models. A reader asked for more details about this decision, so I followed up with Robert Kufner, SDP/SI president and CEO, to learn more about this choice.

Kufner says the company considered replacing the 12-foot, single-barrel bar feeders with 12-foot magazine bar feeders. However, it was determined that automated, 4-foot magazine bar feeders held enough material to cover roughly 85% of its longest running jobs. This gave the company the option to make a trade for fitting in more machine “cells” on the shop floor versus having all machines with 12-foot bar feeders.

Discover more bar feeder technology at Production Machining’s bar feeder section at gbm.media/barfeeders.

“The 12-foot bar feeders were overkill and the ROI didn’t make sense to have more bar capacity than we needed,” Kufner explains. “For us, it was better to make room for more cells for job flexibility. That said, it might make sense for a shop to consider 12-foot magazine bar feeders if the volumes are very high. It didn’t make sense for us.”

As he mentions, bar feeders with longer stock capacity might be more appropriate. Consider Hashier Machine, a northern Ohio shop that added its first Swiss-type lathe to gain long stretches of unattended machining largely because its continuous efforts to find new operators for its more conventional equipment had proven to be unfruitful.

The machine the shop chose was a Nexturn SA32B seven-axis Swiss-type from nearby Absolute Machine Tools. The machine features a Tracer 32V hydrodynamic-magazine bar feeder that can accommodate 12-foot-long bars. According to the shop, compared to shorter bar feeders, this enables longer stretches of unattended operation and eliminates the need for a shopfloor employee to saw bar stock into smaller lengths. In addition, external LED lights on the bar feeder offer simple, visual monitoring of remaining bar length and any alarms. The bar feeder also features dual internal and external anti-vibration devices that are said to minimize bar whip as well as a polyurethane guide channel designed to damp vibration.

How Do I Deal with Small-Diameter Bar Stock?

Paramount Machine in Salt Lake City, Utah, serves a diverse customer base, producing parts and assemblies for aerospace, defense, medical, mining and many other industries. It strives for lights-out production and there are various process elements it has considered which give it the confidence to enable machines to safely run unattended for long stretches of time on its Swiss-types.

For example, the shop has a few different brands of bar feeders. Its 20-mm Tsugami Swiss-type, though, uses an Iemca Elite 220 step-magazine style in which stepped guides rise and lift bars, which will then fall into the guide channel. Eric Van Orden, the company’s screw machine lead and turning technical advisor, explains that the step-magazine style is particularly helpful with small bars such as the 1/8-inch-diameter material it commonly runs on that machine. He says the shop has experienced bar feeders that feed bars into the guide channel via gravity sometimes double-fed bars of this small size, if adjustments were not set perfectly. In some cases, this led the shop to manually load new bars one at a time. That’s no longer an issue with the Elite 220.

What About Legacy Machines?

In years past, Swiss cam machines had a bar tube — descriptively referred to as a “rattle trap” — that supported the bar as it was pushed into the lathe. Because of the short cycle time parts were completed, a new bar had to be manually loaded every very frequently. Not only does that demand constant attendant labor but it also means no parts are being produced when the lathe needs bar stock. That’s why Precision Plus in Elkhorn, Wisconsin, started retrofitting its cam machines with modern bar feeders in the early 2000’s.

Its new machine installations are now fitted with Scout 320 bar feeders from Edge Technologies. Able to accommodate round, square or hex bar stock as long as 12 feet in length and 3-20 mm in diameter, these bar feeders are particularly well suited to its applications.

While bar feeders today are designed for CNC machines, Precision Plus was able to adapt the Scout to Tornos cam machines with the technical support of Edge Technologies. According to Edge Technologies, not any bar feeder can be adapted to a sliding headstock machine, but that’s what the Scout is designed to enable. Standard on the Scout 320, the synchronization device for Swiss-style lathes electro-magnetically links the lathe’s headstock Z-axis travel to the bar feeder’s pusher. This is said to ensure synchronous movement and no connection loss between bar stock and collet pusher.

Plus, because the device’s magazine can hold as many as 40 bars at a time, it enables long periods of unattended machining. Precision Plus runs two 8-hour shifts per day. The shop checks on and loads the bar feeders at the beginning of each shift which are then run with little attention required. At the end of the second shift, the bar feeders are loaded again and run lights out until morning.

Are There Alternatives for Small Batch Sizes?

While an inherent benefit of bar feeders is the capability for shops to realize long stretches of unattended machining time, not all shops are running large volumes of the same part. Job shops, for example, might need to run smaller batches of different parts and/or families of similar parts in which it makes sense to use bar stock of varying diameters to minimize material waste and cost.

One alternative to this production scenario is Breuning Irco’s Ecoprofi from Lexair. This bar feeder is said to deliver automatic, multisize bar feeding in an economical, small-footprint package suited for shops looking to increase flexibility and productivity. Capable of handling bar stock ranging in diameter from 0.2-2 inches, it also features a multichannel, “Gatlin-gun-style” magazine enabling one-button channel changes in seconds for small-batch flexibility.

A three-channel magazine is standard, and a six-channel magazine is also available. The Ecoprofi comes in standard lengths of 10, 13 and 20 feet, with custom models available for bars as long as 33-feet long and 5.1-inches in diameter. The Ecoprofi is said to be compatible with all standard and Swiss-type lathes, as well as machining centers and rotary transfer machines. A specially designed loading flap enables reloading of bars without stopping the machine. In addition, hydrodynamic bar guiding circulates oil through the guide channel continuously to produce a damping effect and stabilize the bar in the channel for concentricity and reduced machine spindle load. Hydrodynamic damping bridges diameter increments and is said to ensure low-friction, nearly vibration-free guiding of the bars.

Interested in Learning More?

The choice of an optimal bar feeder for your shop might be more complex than you think. Cost, floor space requirements, connectivity and other elements all come into play. So, consider directing your bar feeder research at Production Machining’s bar feeder section at gbm.media/barfeeders, which includes articles and video aimed to help you narrow your decision.