Patent Application
20090173128
The present invention relates to aluminum extrusion, and more particularly to the process of cutting billets from aluminum logs exiting a furnace.
Aluminum extrusion is a well known and widely practiced technology. Aluminum logs are heated within a log furnace to a temperature suitable for extrusion. As each log exit the furnace, billets are cut from the log and transferred to an extrusion press. With the press, the billet is extruded through a die to create an article having a desired shape and length. The total length of the extruded shape is a multiple of the length of the pieces to be cut from the shape plus process scrap. The required billet length is directly proportional to the desired extrusion length.
Cutting billets of desired lengths from a heated aluminum log creates remainders or off-cuts. One challenge in aluminum extrusion is to use the remainders or off-cuts without resorting to recycling or re-melting due to the inherent costs involved. The preferred method for the use of remainders or off-cuts is to combine them with another log segment (known as a “short-cut piece”) to create a two-piece billet. The two-piece billet is loaded into the press container, and the two pieces fuse together as the abutting faces of the two pieces pass through the extrusion die. Unfortunately, the spaces and gaps between the two pieces entrap air that produces unacceptable blisters in the finished product. Furthermore, the oxide film on the two abutting faces of the two-piece billet produces defective or unsound fusions or welds between the faces as the aluminum moves through the extrusion die.
One prior art attempt has been made to create an effectively “continuous” log as input to the furnace. Specifically, sequential logs are attached together in end-to-end fashion as the logs are moved into the furnace. The attachment is created by “friction stir welding” or surface welding the abutting logs. This technique has at least two problems. First, the ends of the logs are rarely square; and the logs are rarely straight. Consequently, the connected logs result in a log column that is non-linear (i.e. snake-like). The log column does not lay evenly on the supporting rollers; and the log column is difficult to move through the furnace. Second, this technique does not resolve the above noted problems of entrapped air and oxide.
The aforementioned problems are overcome in the present invention comprising a method for attaching the remainder of each log to the succeeding log, thereby effectively creating a “continuous” log column at the exit end of the furnace. Consequently, billets of desired lengths can be continuously cut from the log column; and remainders are effectively eliminated.
In the current embodiment of the invention, the process includes cutting billets from a log exiting the furnace until a remainder piece is left, attaching the remainder piece to the next succeeding log exiting the furnace to create a log column, and then continuing to cut billets from the log column.
Preferably, the remainder is attached to the succeeding log through “twist welding” in which both axial pressure and relative rotational movement are applied to the two pieces. Twist welding melds and fuses the abutting faces. Yet further preferably, the cutting is done by sawing, which creates relatively square clean faces, which further enhances the attachment.
In one embodiment, the abutting faces of the remainder and the succeeding log are cut simultaneously before welding. This is accomplished by aligning the abutting faces with a saw blade, and then moving the saw blade through the abutting faces so that the saw kerf extends into both pieces.
In another embodiment, a billet is cut from the succeeding log before the remainder is attached to the succeeding log, The cut face of the remainder then is attached to the cut face of the succeeding log.
The present invention creates an effectively continuous log column downstream of the furnace from which billets can be continuously cut. All remainders are eliminated. When the faces both are cut before welding, the attachment of each remainder to a succeeding log vastly reduces the possibility that air or oxide will be entrained or trapped between each remainder and the succeeding log.
These and other objects, advantages, and features of the invention will be more fully understood and appreciated by reference to the description of the current embodiments and the drawings.
A system for processing or handling hot aluminum billets between a furnace and a press in an aluminum extrusion environment, and constructed in accordance with the current embodiment of the invention, is illustrated in
More specifically, the system 10 is located downstream of a furnace and upstream of an extrusion press. The furnace (not shown) may be any appropriate furnace for heating aluminum logs to be extruded. Such furnaces are well known in the art. One such furnace is the direct flame impingement furnace sold by Granco Clark, Inc. of Belding, Mich. under the designation “hot jet log furnace.” Any other suitable furnace could be used.
The extrusion press (not shown) also can be any press generally known to those skilled in the art. One such press is any press sold by UBE Machinery Corporation, Ltd. of Japan. Such a press includes a container, a ram, and a die. The container receives a heated billet. The ram moves through the container to force the billet through an extrusion die.
The system 10 includes a furnace door assembly 12, a hot log saw 14, a discharge tray 16, and a handling assembly 18 for handling billets and remainders. The furnace door assembly 12, the hot log saw 14, and the discharge tray 16 are generally well known to those skilled in the art. The function of the door assembly 12 is to retain heat within the furnace except when the log column LC is moved out of the furnace for cutting. The function of the hot log saw 14 is to cut the log column LC to create billets. The saw includes a selectively activated hold-down to maintain the log in a stationary position during sawing. The function of the discharge tray 16 is to receive a cut billet and to deliver the cut billet to a transveyor (not shown) for subsequent delivery to the press. The function of the reject table 20 is to receive unusable billets from the discharge tray 16. All of these components have been sold by Granco Clark before the present invention, for example, in systems and equipment sold under the designation “hot billet cut-off saw” (HBCS).
The handling assembly 18 is new with the present invention. The assembly 18 includes a pair of grippers 30a and 30b and a chuck 32.
The grippers 30 can be closed or opened using conventional hydraulics or pneumatics to grasp or release a billet or remainder cut from the log column LC. The grippers 30 also can be reciprocated toward and away from the furnace door 12 (i.e. left or right as viewed in
The chuck 32, or any other suitable gripping device, can be closed or opened using conventional hydraulics or pneumatics. The chuck 32 can be reciprocated toward and away from the furnace door 12 (i.e. again left and right as viewed in
As illustrated in
If the answer to step 101 is yes, the log remainder is moved through the door assembly 12 and beyond the saw 14 so that a length of the log corresponding to the length of the desired billet extends beyond the saw. The saw hold-downs are activated to secure the log in a stationary position, and the saw 14 is activated to cut 102 the next billet from the log remainder. The cut billet on the discharge tray 16 is moved onto a transveyor (not shown) for delivery to the press. The next step 103 is to determine whether the new remainder is greater than or equal to the length of the next billet plus the minimum remainder length. If the answer is yes, the log remainder remaining after the cut is pushed 106 back into the furnace through the door assembly 12 using a conventional ram cylinder 22 in the handling assembly 18.
The sequential loop of steps 101, 102, 103, and 106 continues until the length of the new remainder is less than the next billet length plus the minimum remainder length. At that point, control passes to step 104 in which the weld cycle commences. The log column is advanced out of the furnace until the abutting faces of the remainder and the second log are past the saw blade centerline. The discharge tray 16 is retracted from the saw 14; the grippers 30 are lowered to surround the log remainder; and the grippers are closed about the log remainder. The grippers are then raised to lift the remainder so that the remainder does not interfere with insertion of the pushback mechanism 22. While the log remainder is temporarily lifted, the pushback mechanism 22 pushes the succeeding log back toward the furnace until the front face of the succeeding log is aligned with the centerline of the saw blade. The log is secured in position by activating the saw hold-downs, and the pushback mechanism 22 is retracted.
After the succeeding log has been positioned, the grippers 30 are lowered until the remainder is axially aligned with the succeeding log. The chuck 32 is opened and moved toward the furnace until the chuck fits over the log remainder. The chuck 32 is then closed about the log remainder. The grippers 30 are opened and returned to the upper position as illustrated in
The next step 105 is to attach the log remainder to the succeeding log. In the current methods, the attachment is created by friction welding, and more particularly by twist welding. Specifically, the chuck 32 applies axial pressure and rotates the log remainder as required to weld the two cut faces together. For some applications, it is anticipated that a fraction of a relative revolution (e.g. 60 degrees) may be appropriate. For other applications, it is anticipated that multiple relative revolutions may be appropriate. The amount of axial pressure and relative rotation for any application will depend on the metal alloy and the desired results. Other techniques for friction welding may be used in addition to, or as an alternative to, the twist welding. Such techniques include relative linear motion, oscillating motion, and vibrational motion.
An inert gas (e.g. argon or nitrogen) can optionally be directed into the area of the cut, and therefore onto the cut faces, to inhibit the formation of oxides after the “clean-up cut” and before the spin welding.
The axial pressure and the relative rotation create a “twist weld” or a “spin weld” (e.g. a form of friction weld) causing the two sawn faces to fuse to one another. The twist weld eliminates entrapped air at the weld union. Other suitable attachment processes could be used, but are currently believed to be less preferable, most notably because of the opportunity to entrap air. The reattachment of the log remainder to the succeeding log creates a modified log column.
Following block 105, the log column is moved back into the furnace through the door assembly 12—first by the chuck 32 and second by the ram cylinder 22. After the log column is sufficiently reheated, the log column can be moved forward out of the furnace for cutting of the next billet. The welded seam between the log remainder and the succeeding log is essentially air tight, preventing the entrapment of air during subsequent extrusion in the press.
Although the first method cuts both faces with a single cut, it is possible that separate cuts may be required or desired for the two faces. For example, it is possible that the two abutting faces have an abutting unevenness that exceeds the width of kerf of the saw blade. In that case, separate cuts may be required for each face.
As illustrated in
The sequential loop of steps 201 and 202 continues until the length of the log remainder is less than (a) the length of the next billet plus (b) the minimum remainder length. At that point, control passes to step 203 in which the log remainder is temporarily moved out of the log/billet path. Specifically, the grippers 30 are lowered to surround the log remainder, and the grippers are closed about the log remainder. The grippers 30 are then raised to lift the log remainder so that the log remainder does not interfere with subsequent logs existing the furnace. The log is held or stored in this holding or temporary storage position. The log remainder is also turned end-for-end 203 so that the most recently cut end of the log faces the furnace door 12.
While the log remainder is temporarily stored and turned, the next or succeeding log is moved out of the furnace so that the next billet can be cut 204 from that log. Specifically, the log is moved from the furnace so that the log extends beyond the saw 14 a distance equal to the desired length of the billet. The log is secured in position, and the saw 14 is activated to cut 204 the billet from the log.
After the first billet has been cut from the succeeding log, logic flows to block 205 including the steps for attaching the log remainder to the succeeding log. The gripper assembly is lowered until the remainder is axially aligned with succeeding log. The chuck 32 is opened and moved toward the furnace until the chuck fits over the log remainder. The chuck 32 is then closed about the log remainder. The grippers 30 are opened and returned to the upper position as illustrated in
Following block 205, the log column is moved back into the furnace through the door assembly 12—first by the chuck 32 and second by the ram cylinder 22. The next billet typically will be shorter than the reattached log remainder. However, the next billet could also be longer than the reattached log remainder.
Although a saw 14 is disclosed as part of the system 10, the logs may be cut in any suitable fashion known to those skilled in the art. For example, one alternative device for cutting logs is a hot log shear such as that sold by Granco Clark, Inc. However, because a saw produces a clean square face, a saw is currently believed to optimize the twist weld. Further, although cut faces are currently believed to produce the most effective attachment, it also may be possible to effectively attach uncut faces (e.g. the log ends).
The above descriptions are those of current embodiments of the invention. Various alterations and changes can be made without departing from the spirit and broader aspects of the invention as defined in the claims, which are to be interpreted in accordance with the principles of patent law, including the doctrine of equivalents.
