Title: Major components of a bar feeder:
Course: Introduction to Swiss Programming

Module 2: The Bar Loader or Bar Feeder

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Major components of a bar feeder:

Guide tube: This is the tube, usually steel, the bar is contained in. Some simple bar feeders only have one tube. Some have interchangeable tubes for different bar diameters and others have a housing with multiple tubes for different bar diameters. The whole housing would be rotated to position the correct size tube.

Swivel support arm: This arm is positioned to support the front of the guide tube during bar changes. The whole guide tube swivels on a pivot towards the back of the bar feeder frame to expose the front of the feed tube. Sometimes these arms fold down and sometimes they slide out.

Guide tube clamp: This clamp secures the bar feeder guide tube during operation. The guide tube must be lined up exactly behind the screw machine's spindle clamped in place. During a bar change the clamp is opened allowing the guide tube to be swiveled to its bar load position.

Nose guide: This is a tube that telescopes from the front of the guide tube to take up the space between the back of the screw machine's headstock and the front of the bar feeder. This tube has a ferule in the front of it to restrict bar whip. The front of the nose guide should be positioned just behind the headstock when the headstock is at the back of it's stroke during operation. As a point on the bar exits the front of the guide tube it is in the nose guide for some distance, this allows for excess oil to be slung off the bar. This oil is drained back to the bar feeder.

Pusher bar: This bar is inside the guide tube and pushes on the back of the barstock. It is long enough to reach inside the screw machines headstock. A hardened steel conical recess is on the front end of the pusher bar and this surface mates with a cone machined or ground into the back end of a length of barstock. The back end of the pusher bar is connected to a piston. This piston is sized for the guide tube diameter and has one or more holes through it. The size of these holes are adjustable allowing the amount of force the flowing oil exerts on the piston to be adjusted. The smaller the holes are, the more force the oil will push on the piston. The larger the holes are the more oil will flow through the piston and less force the oil will push on the piston.

Oil pump: Oil is pumped through the guide tube flowing from the back of the tube towards the front. This flow provides the pressure or push the guide tube keeps on back of the length of barstock. Just like in a bar loader, this oil both lubricates the guide tube and dampens vibration of the bar.

Part length adjustment carriage: The position of the whole guide tube assembly is adjusted for the part length by moving the guide tube assembly along the carriage.

End of bar sensor: The end of bar sensor is a mechanism inside the guide tube that is activated when the piston at the back of the pusher bar reaches the front of the guide tube. The piston can't go through the sensor so the piston and pusher bar just stop. When the piston touches the sensor, a signal is sent to the screw machine telling the screw machine it is time for a new bar.

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Date last modified: March 23, 2015.
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