Is a 12 Foot Bar Feed Your Best Choice

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IS A 12-FOOT AUTOMATIC BAR FEEDER YOUR BEST CHOICE?

There are three basic types of automatic bar feeders available:
  • Long form bar feeders that load 12-foot bar stock
  • Short loaders for spindle length bars
  • Six-foot bar loaders.

Each type has its own characteristics and advantages. Choosing the right bar feeder depends on your applications and overall production needs. So when is a 12-foot bar feeder your best choice? Here are some guidelines:

If your application calls for large quantity production runs and the parts being made are five inches long or longer, a bar feeder that loads 12-foot bar stock is a good choice, especially if the material you are turning is expensive and/or you will be operating unattended for long periods.

Here’s why:

  • You can stage greater quantities of raw material in a 12-foot bar feeder than with other types, thus enabling longer periods of unattended operation.
  • Because there is only one remnant at the end of the bar, versus other types of bar feeders that produce two or more remnants, you reduce waste and material costs. This is especially significant when machining titanium or other expensive materials.

However, long form bar feeders may not be the best choice when working with bars that are not straight or are profiled. Typically, these conditions require you to reduce RPM so you can minimize vibrations that impact cutting accuracies and surface finish. This slowing of spindle speeds, in turn, reduces throughput.

It is possible to successfully machine profiled material run through long bar feeders, if the type and quality of the material is compatible with a specific bar feeder.

Another concern with long bar feeders is the amount of space they require. The typical length of a loader designed to run 12-foot bars is 16 feet, or twice the length of a short loader.

Other 12-foot bar feeder considerations:

  • How easy is it to changeover? There are a number of components that must be adjusted when moving from one bar stock diameter to another. This can be extremely time consuming, especially if the bar feeder requires tools to change guiding elements and pushers, or make other adjustments.

  • How realistic is the stated diameter range? Be suspicious of bar feeders that claim you can run a wide range of bar diameters without changeovers. Even bar feeders that use the hydrodynamic principal by surrounding the bar with oil cannot change the laws of physics to arbitrarily expand the range of diameters. Bar stock that is not properly supported through appropriate guides will create vibrations that can harm machine tools and impact part quality.

  • For the same reason, a 12-foot bar feeder must be built of substantial materials that provide the same kind of rigidity found in high quality CNC machine tools. Spinning a 12-foot bar at high RPM requires stability for smooth and reliable bar feeding, extending the life of the bar feeder, and for the safety of the machine operator.

  • What about managing remnants? This can affect both material waste and bar loading time. Are you better off retracting the remnant back to the bar feeder, pulling it with the sub-spindle, or pushing it through the lathe chuck? From a materials waste standpoint, remnants are longer when pulled back to the bar feeder than if the remnant is not held by the pusher collet.

  • Is it possible to easily convert the bar feeder from one remnant application to another?

  • Look for advanced technology such as smoothly operating servo motors, absolute encoders and sophisticated yet easy-to-use controls that guide operators through programming and operation.

  • To enable longer production runs, determine if it’s possible to expand the bar feeder’s magazine capacity.

In another post we’ll discuss the pros and cons of short loader and six-foot bar feeders. In the meantime, the applications experts at LNS can help you determine precisely which bar feeder is best for your manufacturing process. Contact your local LNS representative or call 513-528-5674.