You Want the Best Kind of Short Bar Feeder?

Posted on Nov 24, 2020

Short bar feeder

Overall, full-size magazine-type barfeeders allow for better material utilization than short barfeeders for large tasks involving long parts. Suppose you have purchased a new state-of-the-art CNC multi-axis bar machine or plan to combine it with a barfeeder, which will allow you to take full advantage of its productivity.

The chances are greater than 7 to 10 that you will buy a magazine style automatic bar feeder. But if you buy a full size bar feeder that can feed 12 foot bars to the lathe, or should you purchase a more compact "spindle length" bar feeder designed to feed 2, 3, and 4 foot bars into the lathe?

We estimate that the most popular type of bar feeders are short, accounting feedersabout half of all barfeeders sold in the United States and about 35 percent of total sales in dollars. Full-size, warehouse-style bar feeders account for about 30 percent of total unit sales in the United States and about 35 percent of total dollar sales.

The numbers vary across Europe where full size barfeeders are the rule and short barfeeders are relatively rare. The numbers may be interesting, but unfortunately they won't help you make up your mind.

Batch sizes, part diameters, material types, accuracy requirements, the ability to operate machines unattended, and a number of similar considerations must determine the Bar Feeder type that is best for your facility. Each type has unique advantages and you need to compare them with the specific needs of your store. Here are some things to consider when making your selection.


Production Volume os Short Bar Feeder

What batch sizes will typically be used on a lathe? If the production volume is large, and Productivity and getting as many pieces as possible from the bar are important, the new owner of the lathe is likely to benefit more from the 12 'Bar Feeder.

From a productivity standpoint, using long bars can help reduce labor costs as the machine can be left unattended for extended periods of time. One operator can operate two or three of these machines. Machines are less likely to run out of material and stay idle for 10 minutes here, 15 minutes there, and so on.

If your new CNC lathe will be mainly used for short term jobs with frequent configuration changes, a spindle length barfeeder is a more logical choice. In such barfeeders, the entire length of the bar is first fed to the lathe spindle. Since the bar does not turn inward or is not supported by the Bar Feeder, changing to a different material diameter can be done faster and easier than with a full size Bar Feeder.

When the bar diameter is 2.5 inches or greater, controlling such a rotating mass in the full length barfeeder becomes a problem. In such cases, spindle length barfeeders deserve a lot of attention, as the shorter bar is completely contained in the lathe spindle during machining, which eliminates the possibility of runout and vibration.

The smoother, more controlled rotation of the bar enables the lathe to run at higher revolutions for faster machining. Dimensional accuracy and surface finish of turned parts and tool life are improved when vibration is reduced.

However, there are cases where a short bar feeder may be the right choice for large series. Examples are extruded materials such as a hexagonal bar where straightness can be a problem.

When short lengths of such materials are fully contained in the lathe spindle, they can be rotated at high speeds for machining - without the problems of vibration that could occur if fed through a full-size barfeeder. In general, the short barfeeder is more resistant to unbalanced (unsymmetrical extrusions), bent or bent bars that would otherwise cause vibration.


Application of the Material for Short Bar Feeder

Where maximum material utilization is important, a 12ft Bar Feeder is a good choice as the entire bar is converted into usable parts except for one small residue. On the other hand, when a 12 foot bar is cut into three or four lengths for loading into the spindle length barfeeder, an equivalent amount of residue is produced, meaning fewer parts per 12 foot bar and more scrap.

And as the cost of the processed material - stainless steel, titanium, brass, etc. - increases, reducing waste becomes even more important. Manufacturers investing in plants and equipment to produce scrap will find it increasingly difficult to compete with companies investing in plants and equipment to produce parts.


Lathe Spindle Length

The length of the lathe spindle is irrelevant when considering a 12 foot Bar Feeder. However, this cannot be ignored given the spindle length barfeeder. Many CNC bar stock machines have spindles that can fully insert short bars up to 4 feet long.

Such lathes can handle 3 and 4 foot lengths cut from standard 12 foot bars. As mentioned earlier, the loss of scrap material from short bars is several times greater than the loss from a 12-foot continuous bar, but may be acceptable for prototypes and short runs, for example.

However, in modern lathes, there is a tendency to use shorter spindles - for some models as short as 2 feet. In these cases, the 12-foot bars should be cut into 2-foot lengths. This creates six times as much residue as a continuous strip. The material utilization may deteriorate to such an extent that the shop owner cannot use a spindle-length bar feeder for such a job and remain competitive.

This creates six times as much residue as a continuous strip. Material usage can deteriorate to the point where the store owner cannot use a spindle length barfeeder for this purpose and remain competitive.


Part Length for Short Bar Feeder

A 12 foot magazine-type barfeeder typically provides better material utilization than a spindle-length barfeeder. Regardless of part length, material loss from a 12-foot continuous bar is limited to one residue. However, as the length of the part increases on a spindle-length barfeeder, the remainder of each of the three or four short sections cut from a 12-foot continuous bar can make up a significant percentage of the bar.

If the job involves parts similar to a washing machine, a 3-foot bar may be enough for an hour. However, if the work involves motor shafts, the lathe can pass a 3 foot bar in minutes,and then has to pause while loading the next short strip. The amount of time it takes to load the short bars into the lathe via the short bar feeder can also reduce the part production rate. The amount of time it takes to load the short bar into the lathe via the short bar feeder can also reduce the part production rate.


Work Area for Short Bar Feeder

In situations where floor space is at a premium, a spindle length barfeeder is generally preferred as it only takes up about half the space required for a 12 foot barfeeder. The floor space savings may not be as large with a single Bar Feeder, but when installing multiple machines, often the space savings may be sufficient to allow the installation of one or more additional Bar Feeder lathes and feeders than would otherwise be possible.

then it must stop while loading the next short strip. The time it takes to load the short bars into the lathe via the short bar feeder can also reduce the production speed of the part. The time it takes to load the short bar into the lathe via the short bar feeder can also reduce the production speed of the part.


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