Bar Feeders Guide

What Are Bar Feeders?

Bar feeders are devices that feed processed materials to mostly cutting machines during the machining operation. The feeding mechanism could either be automatic or semi-automatic. Bar feeders are often used in turning based machine tools, and the feeding process of the automatic bar feeding manifests itself by sending materials that are often long shaped into the machine in a continuous manner.

Automatic bar feeders can also be integrated in other CNC machines such as sawing machines like circular sawing machines or band sawing machines. The bar shaped materials are fed linearly by the bar feeders and processed under the control of the CNC system of the machine tools. 

Bar Materials

Most of the bar materials for both turning and sawing are cast irons or other raw casted materials with a specific length values. In the metal working industry, the term cast iron is a metal working process that produces a group of iron-carbon alloys with carbon content greater than 2%. Its usefulness is attributed to its relatively low melting temperature, so the bars can be later used for various machine applications by the bar feeders. 

The alloy constituents of the bars affect bar color tones when the bars are fractured, that is, white car cast iron has carbide impurities which allow cracks to pass straight through the bars. Grey cast iron has graphite flakes which deflect a passing crack and will initiate countless new lengthy cracks on bars as the bar breaks. New ductile materials or other newly invented alloy processing method may deal with such issue but the machine tools have to be further prepared for the lengthy operation time. The length of time directly affects the estimation of productivity. 

CNC Lathes and CNC Bar Feeders 

Automatic CNC bar feeders are usually used in CNC lathes tooling operation to automatically draw in materials for the machine tool unit, such as iron or steel bars from the clamping chuck driven by the spindle. In this case, CNC bar feeders serve as a substitute for a bar puller on an NC or CNC lathe machines. The clamping chuck of the machine tool is fitted directly into the turret of the lathe or into the bar holder for better stability.

Regarding the classification of feeding mechanisms, there are two different versions of bar feeders for the turning machines, each of which is characterized by the varying structures and body frames of the machine and the bar length: It may start on the radius or the spindle-phased axis. The housing and the body shell of CNC bar feeders can be made of iron, aluminum or steel materials, and the top jaws are made of case-hardened steel in order to accommodate the bar materials. But sometimes, if the bar is with specific alloy components and are lengthy, there might be issues with durability and the jaws would have to be addressed separately or replaced. This is why bar feeders and automatic bar feeding are highly customized.

CNC Bar Feeders and the NC Versions

The study and development of the bar feeder machines began with the introduction of the NC lathe machines in 1970s. The turning machines were controlled by the NC system for massive production volumes, so manual feeding by conventional methods for tooling was no longer feasible. As a result, lathes were then developed to permit inexpensive and economical production of small or medium-sized lathe machines. The bar feeder serves as a means to draw bars into the lathe without human intervention, having to feed the operational machine with material each time that is required. With the introduction of CNC technology for the turning machines, it was possible to ensure the reliability of the individual operation, such as procedures involving moving the turret to the material, opening the clamping chuck, drawing in the material, closing the clamping chuck, moving the turret away with the bar puller.

Transmission and Loading of Lengthy Bars

Bar stocks are a common form of raw purified metals that are is used by industrial workers to manufacture metal parts and products in the production lines like feeders do. Bar stock is available in a variety of extrusion shapes and lengths. The most common shapes are solid round, rectangular, square and hexagonal. A bar is characterized by an enclosed invariant convex cross-section, which indicates that pipes, angle stock and objects with varying diameter are not considered bar stocks in this definition. Bar stock is commonly processed by a sequence of sawing, turning, milling, drilling and grinding to produce a final product, often vastly different from the original stock.

In some cases, the process is partially automated by specialized equipment which feeds the stock into the appropriate processing machines or a series of connected and coordinated production lines that serve the same manufacturing purposes. And within this processing procedure, the whole-plant automation system will definitely reduce the heavy reliance of manpower for the business owners for a certain degree, leaving spare time for machine tools and the cutting tools can be with less worn out rates. The tools that cut bars are issues to work piece accuracy. 

Metal Material 

Most metal produced by a steel mill or aluminum plant is formed into lengthy, continuous strips of various sizes and shapes. These strips are cut at regular intervals and are allowed to cool down in a specific period of time span. Each segment becomes a piece of the bar stock item. The same situation is true of metal bar stock management like noodle production. The most common shapes are solid round bar, rectangular bar, and hexagonal bar. These three forms are the most common forms in the industry.

Besides the solid items, tube and pipe are also similar, but have hollow centers and are traditionally not called a bar in the industrial customs and usages. Though a product titled hollow bar, it is essentially a tube but with custom-orderable outer diameter and internal diameter values. So, custom wall thickness is also available for customers to choose, which is targeted for turning machine bar work that can benefit from obviation of drilling and rough boring machining.

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