US3257832A - Method and apparatus for finishing extrusions - Google Patents

Description

June 28, 1966 H. M. HARVEY 3,257,832

METHOD AND APPARATUS FOR FINISHING EXTRUSIONS Filed March 1, 1965 United States Patfi 3,257,832 METHOD AND APPARATUS FGR FINISHING EXTRUSIONS Homer M. Harvey, Los Angeles, Calif, assignor to Harvey Aluminum (Incorporated), Torrance, Calif., a corporation of California Filed Mar. 1,1965, Ser. No. 436,132 3 Claims. (Cl. 72-183) This is a continuation-in-part of the application Serial No. 145,627, filed October 17, 1961, now abandoned, and entitled Method and Apparatus for Finishing Extrusions. This invention relates to metal working and is particularly concerned with the finishing of extrusions, especiallymetallic extrusions, whereby deformations therein are corrected and commercially marketable items are produced, it being a general object of this invention to provide a new and improved method and apparatus for the correction of deformations in extrusions after they issue from an extrusion die.

Extrusions, especially metallic extrusions, as they issue from an extrusion press die are invariably unusable as a finished product. Because of the pressures applied there are deformations from straightness and when complex cross-sections are involved there are deformations in crosssection, compounded by twisting. As a result, a usual extrusion issues from the extrusion press in the form of an elongated and distorted body of misshapen configuration, and they are not straight longitudinally and they are 7 not of uniform or predictable transverse configuration.

Obviously, as the complexities of the extrusions are increased the problems of deformation are correspondingly augmented.

Heretofore, several process steps have been required in order to correct the distortions in extrusions deviating from the desired and correct shape that is required. It is common practice to firstly stretch the extrusion and to secondly pull the extrusion through a redraw die. These two steps are time-consumingand are complicated by handling, re-handling, trimming, and transportation problems, because each of these said steps is carried out by distinct and separate machines, and said machines are not associated in any way. For example, the first step in common practice is to elongate the extrusion in a stretching machine (aluminum extrusions are commonly elongated 1% to 4% depending upon requirements), and this step involving a longitudinal stretch above the yield point of the metal straightens the extrusions longitudinally but not transversely. Therefore, the said second step must be resorted to. For example, the second step in common practice is to deflect or bend the extrusion into the required cross-sectional configuration in a redraw bench by pulling the same bodily through a redraw die, and substantial force is required in order to accomplish the same. Because of the distortions, the commonly employed redraw die is gene-rally made with deviations from the required shape of the extrusion, taking into account spring-back in the corrected shapes as they leave the redraw die. This spring-back is difficult to calculate and control and as a result of these two steps substantial lengths of extrusions are lost and must be scrapped. That is, the endsheld by the jaws of the stretcher machine must be cut ofl? before the extrusion can be engaged in or through the redraw die of the draw bench machine, and then the end held by the jaws of the draw bench must be discarded. Further, grooving and imperfections tend to be created by the pressures applied at the redraw die. An object of this invention is to provide a method and apparatus wherein the distortions in metallic extrusions are corrected at one time and wherein one machine or apparatus can be employed to correct said distortions.

and apparatus wherein transverse deformations are corrected without the application of great pressures, as heretofore practiced. With my new method and apparatus bending into shape with a redraw die is virtually eliminated and need for a separate redraw bench does not exist. In place of the usual redraw step the proper and required cross-sectional configuration is simply imposed upon the extrusion during the longitudinal stretching of the same, and this is accomplished as by using what I will term a finishing die. 7

It is an object of this invention to accomplish correction of transverse deformations without bending and thereby eliminating the complications of spring-back. With the method and apparatus that I provide a proper positioning of the extrusion parts is accomplished by imposing the desired position upon said parts with a finishing die of exact configuration. This is done without applying force andby simply turning and/ or moving the parts of the extrusion into position. Phenomenon resulting from the concurrent stretching permits the placement of parts without using force.

It is still another object of this invention to provide a method and apparatus wherein exacting finishes and tolerances can be maintained with a minimum of exacting care. With the finishing die that characterizes this invention, and the exact and finished shaperepresented thereby, and with no deflection and spring-back problems, it is a simple matter to produce an exacting finished product.

It is another object of this invention to provide a method to accomplish the objects hereinabove set forth in an economicallypractical manner, with a substantial savings in time and cost of equipment, and with a product of controlled, uniform and improved quality.

It is also another object 'of this invention to provide a machine or apparatus to accomplish the objects hereinabove set forth, a single machine installation serving to carry out concurrently what has heretofore required two separated steps carried out by distinct andseparate ma- 1 chines.

The various objects and features of this invention will be fully understood from the following detailed description of the typical preferred form and application thereof, throughout which description reference ismade to the accompanying drawings, in which:

FIG. 1 is a typical cross-section of a distorted extrusion carrying out the method of the present invention, and

showing a finished extrusion in condition to be removed from the machine.

FIG. 4 is a transverse sectional view of a typical finishing die used in carrying out the method of the present invention, and a die suitable for straightening the particular extrusion shown in FIG. 1.

FIG. 5 is a typical cross-section of a straightened extrusion and in particular the extrusion shown in FIG. 1,- said extrusion being straightened both longitudinally and transversely.

As hereinabove pointed out, the metal forming art has practiced a common and well developed method for. straightening of extrusions. For example, in the production of aluminum extrusions the deformed, twisted and distorted extrusion are chopped into suitable lengths as they issue from the extrusion press die, and these lengths are usually heat treated. These lengths of extrusion are then clamped in the jaws of a stretching machine and stretched slightly above the yield of the particular material involved. This longitudinal stretch above the yield straightens the extrusion longitudinally, however, the transverse cross-section is not necessarily affected. Therefore, the multilated ends of the extrusion, resulting from engagement by the jaws of the stretching machine, are removed and said length of extrusion is generally moved to a redraw bench, a second machine, where the said length of extrusion is pulled through one or more redraw dies. As hereinabove pointed out, these common process steps are time consuming and result in a substantial Waste of material cut from the opposite ends of extrusion.

In accordance with the objects of this invention I have sought to improve the state of this art by shortening the time element involved in the straightening of extrusions, by permitting all of the straightening steps to be carried out in one machine or apparatus, and by assuring a better and higher grade of finished product. It will be readily seen that these objectives are accomplished by practicing this invention wherein both longitudinal and transverse straightening are accomplished concurrently.

The method involves, generally, two steps. However, these two steps are carried out concurrently or together and during the same time interval. The first step is that of stretching in one direction or plane, and in this case of an elongate extrusion this is along the longitudinal axis of the extrusion. The second step is that of placement of the transverse configuration of the extrusion, and this is of course in a plane normal to the said longitudinal axis. The main feature of this method resides in the concurrency of these two steps and which makes possible the said placement of the transverse configuration without the application. of great force. That is, it is not necessary to bend the extrusion into proper transverse configuration as is common practice.

The said first step of the method involves the elongation of the extrusion. For purpose of illustration let us assume that the extrusion is twenty feet in length and that to impart the desired physical properties into the finished product an elongation of 2 /2% is required. In this instance, a stretch of six inches is required, and as will become apparent the speed of this stretch is controlled and cooperatively related to the time interval required to accomplish the second step of the method. It is important, however, that rate of stretch be maintained at a sufficient value, although this rate can be varied widely as circumstances require. In any case, a deliberate and steady rate of stretch is to be desired, as is common practice.

The second step of placement of the transverse configuration involves the movement of the elements of the extrusion into proper position in a plane normal to the longitudinal axis. The placement requirements vary with each and every extrusion and it is possible with this method to alter the initially extruded shape whereby the elements of the extrusion can be moved into any desired placement within reasonable bounds. In most cases, however, it is merely necessary to true-up the extrusion rather than vary its cross section. For purpose of illustration let us assume that the extrusion has a cross-sectional deformity of .250 inch occurring throughout a longitudinal distance of inches. For example, this could be a local deflection of a flange-like element which can be calculated to have an abnormal length of 10.00312 inches, compared with the same flange exactly 10 inches in length if it were straight. In order to straighten such a flange it is ordinarily necessary to strain the material of the extrusion to thereby bend theflange said .250 inch through said 10 inch length. However, with this invention strain is not applied since the rate of longitudinal 5 strain is greater as applied by the first mentioned step of stretching. Also, without the resultant of transverse strain there is no spring-back.

In carrying out this invention the two steps of stretching and placement of elements are carried out simultaneously, and more accurately speaking they are carried out concurrently. That is, the second mentioned placement step is practiced within the duration of the first mentioned stretching step. In other words, the stretching is commenced and taking place before the placement correction begins, and said placement correction ceases While the stretching is taking place and before it, too, ceases. Thus, the time interval of stretching substantially overlaps the time interval of placement. It is during the first mentioned time interval of stretching that a phenomenon occurs wherein the molecular structure or grain structure of the material involved is in such condition that little or no force is required to move parts and elements. Therefore, little or no force need be imposed upon the extrusion in the placement of the elements transversely thereof.

In practicing the method herein disclosed I have discovered that if the rate of longitudinal strain is greater than the rate of transverse strain, then it requires very little or no force to move the extrusion into the required cross-sectional configuration and no measurable springback is evidenced. This is an indication that the material must be continuously strained in one direction while movement of parts in the other direction is made. I have also ascertained that if the rate of longitudinal strain is stopped or slowed down too greatly, then transverse spring-back occurs. An example of this relative rate of strain is as follows: If the first mentioned time interval for stretching is 15 seconds for an extrusion 20 feet in length, the rate of strain is .4 inch per second and this must be greater than the rate of transverse strain in order to prevent spring-back. I have discovered that by imposing a higher rate of strain longitudinally as compared with transversely, the said transverse strain is actually cancelled and does not exist as a strain and is transformed into a movement requiring little or no force.

There are various ways by which the second step of this method can be accomplished. Broadly, any means or manipulation adapted to properly position the extrusion elements can be employed. For instance, laterally shiftable positioning elements co-extensive with the longitudinal extent of the extrusion can be shifted laterally into and out of a corrective position. Preferably, a traversing positioning element is employed that engages with or around the extrusion and shifts from one end thereof to the other. It is this traversing positioning element that is moved at a speed whereby the rate of strain imposed transversely is less than that imposed longitudinally. For example, a traverse of the finishing die of 20 feet in 12 seconds when the first mentioned stretching is accomplished in 15 seconds, results in a transverse rate of strain of less than .4 as against a longitudinal rate of strain of .4.

From the foregoing it should be apparent that a relatively simple and feasible method is disclosed. By the application of greater force in one direction than in the other (said angularly related directions are, for example, at right angles to each other) and by stretching slightly above the yield in the said one direction, then it is possible to place the elements involved without the application of force in said other direction. In FIG. 1 of the drawings I have shown a typical transversely distorted extrusion 10 of channel shape with a base 11 arcuately deformed and with its lateral or upright legs 12 splayed and divergent from each other. This is a normal distortion that varies in degree throughout the length of the extrusion 10. Also, as shown in FIG. 2, the extrusion 10 is distorted longitudinally, having a waved and twisted deformation. In order to apply the method hereinabove described, I provide the apparatus A in the form of a stretching and finishing machine. This apparatus or machine A simultaneously performs the functions of imposing both longitudinal and transverse rates of strain upon the extrusion '10. As above described,

by simultaneously I do not mean that the two steps require the same length of time but more accurately that the steps are performed concurrently and one'within the time interval of the other. Generally, the machine A involves a longitudinally disposed foundation or bed 20, a pair of heads 25 and one at each end of the bed, and a means 30 for correcting transverse shape. The bed 20 is the frame of the machine, the heads 25 are the elements that impose the longitudinal rate of strain upon the extrusion 10, and the means 30 is the element that imposes the transverse rate of strain upon the extrusion 10.

The foundation or bed 20 that forms the frame is an elongate element and is preferably horizontally disposed. According to usual practice the bed is straight and provides a ways, preferably in the form of two parallel rails, to shiftably support and carry the heads 25 and means 30 that I provide.

The heads 25 that impose the longitudinal rate of strain upon the extrusion 10 are substantially alike and are built in accordance with usual practice. These two heads 25 are opposed to each other and are movable along the rails of the bed 20, and they are each provided with jaws at 26 to engage with the extrusion 10. The details of construction are not shown inasmuch as this machine A, as thus far described, can be identical with the stretching machines that are now in widespread use. Therefore, it is to be understood that the two heads 25, either one or both, equippedwith means to shift themselves longitudinally of the bed 20 in order to tension the extrusion 10 and apply said longitudinal rate of strain. Further, various controls are employed in order to operate the jaws at 26, and these two heads move oppositely away from each other when applying said longitudinal rate of strain.

In accordance with this invention I provide the means 30 for correcting transverse shape of the extrusion 10 and that imposes the transverse rate of strain'thereupon. As is indicated above in describing the method, this means can vary widely in that laterally shiftable positioning element-s coextensive with the longitudinal extent of extrusion can be shifted laterally into and out of corrective position, or as is preferred a traversing positioning element 35 is employed. In FIG. 4 I have shown a typical positioning element 35 having an aperture therethrough of the exact desired configuration to be imposed upon the channel illustrated in FIG. 1. The longitudinal or axial extent of the element 35 can vary, however, it is of limited axial extent, and it is supported and carried in a traversing carriage 40. The carriage 40 includes or is associated with means to propel itself longitudinally of the bed 20 and' it is supported by the rails of the bed. That is, the carriage 40 propels itself from the position shown in FIG. 2 to the position shown in FIG. 3 and this is referred to as a traverse (a longitudinal traverse). Suitable machinery is employed in order to propel the carriage 40 at a steady and uniform rate of speed.

As clearly shown in FIG. 4, the element 35 can be sectional and in the nature of a die, and this element 35 is referred to as a finishing die, and can have one or more shiftable sections 36 and 37 to engage the extrusion from a lateral direction or directions. It will be apparent that the number of sections such as the sections 36 and 37 will depend entirely upon the complexity of shape encountered with each different extrusion 10. In this case, the two sections 36 and 37 move apart and together to form an aperture in order to pass the extrusion 10 shown in FIG. 1. The base portion 11' of the aperture is straight transversely and the leg portions 12' of the aperture are normal relative to the base portion. Thus, the extrusion 10 is engaged, embraced or encompassed by the finishing die 35 and the cross-sectional configuration of the extrusion 10 is corrected when the said finishing die is moved into position. The corrected shape of said extrusion 10 is clearly illustrated in FIG. 5. Therefore, the carriage 40 includes means to move the sections of the element 35 into the position or condition shown in FIG. 4, whereupon the finishing die 35 is transported by the carriage 40 to traverse the length of the extrusion 10 intermediate the two heads 25.

In order to operate the machine A of the present invention, and in order to carry out the method involved, the distorted extrusion 10 is placed in the machine A and extended through the carriage 40. The opposite jaws at 26 are operated to close upon and to engage the opposite terminal ends of the. extrusion whereupon the heads 25 are moved apart to tension said extrusion. With the extrusion 10 tensioned so that it extends axially in a straight line the finishing die 35 is moved into place, or its sections closed, to encompass the cross-sectional configuration of the extrusion 10. As is clearly illustrated the traverse of the carriage 40 and finishing die 35 commences at one head 35 and terminates at the opposite head 25. With the extrusion 10 in place and encompassed as thus far described the longitudinal rate of strain is first applied after which the carriage 40 is propelled at a speed to create a transverse rate of strain not to exceed the first mentioned longitudinal rate of strain. It is to be understood that various stresses and strains are created in various transverse directions, for example in the case illustrated where obtuse angles are erected there are compressive and tension strains set up about the center of bending, as the said angle is turned and straightened. As clearly set forth in describing the method the longitudinal rate of strain is continued until after the carriage 40 has completed its traverse, after which the said longitudinal rate of strain is stopped. The finishing die 35 is then released from its embracing or encompassing position, the jaws at 26 are released and the finished extrusion 10 is removed from the machine A.

Furthermore and in summary, the term longitudinal rate of strain as used herein refers to the rate at which a particular work piece is being elongated or stretched. This rate of strain, as so defined, is dependent upon the length, the cross-sectional area, and the yield and ultimate strengths of the particular alloy of the work piece, as well as the percent of elongation permissible before rupture and the speed at which the means clamping the ends of the work piece may be moved apart, this speed usually being a constant value for any given apparatus.

Therefore, from this information, the required rate of strain for any specific work piece may be easily calculated by determining the period of time needed to apply the corrective strains to the transverse configuration of the Work piece, since as noted above, this transverse corrective strain must be completed while the work piece is still being longitudinally stretched. Once this time period has been determined, the required longitudinal rate of strain may be determined by dividing the total amount of elongation by this time period.

For example, .a particular longitudinal rate of strain may be illustrated by assuming that a work piece has a length of 50 ft., a cross-sectional area of 2 sq. in., and is made of an alloy having a yield-strength of 30,000 p.s.i., e.g., a force greater than 60,000 lbs. must be applied to the Work piece to produce the desired elongation. Note, however, that while this longitudinally directed force must exceed the yield strength of the alloy, it should not exceed the ultimate strength of the alloy. Also assume that a 2(%) percent elongation of the workpiece is permissible, that is, in this example, the work piece may be stretched 12 inches before rupture. Now further assume that the means for correcting the transverse cross-sectional configuration of the workpiece has a speed of 50 ft. per minute. Thus, in this example, the correctional means can traverse the work piece and perform its correctional function in 60 seconds. is to be elongated 12 in. during this 60-second period, the

Therefore, since the'work piece- 7 rate of longitudinal strain, as applied'to this particular Work piece, is 0.2 in. per second.

The term transverse rate of strain as used herein refers to the application of transverse forces to the Work piece.. These forces are applied to the work piece by movement of finishing die means along the work piece, and are used to correct cross-sectional configuration of the Work piece. These transverse forces are significantly less than the applied longitudinal force and are less instrumental in producing the desired yield conditions of the material than the longitudinal force. Moreover, as explained above, the application of the transverse force is terminated before the longitudinal force has completely stretched the material to its predetermined length.

Having described only a typical preferred form and application of my invention, I do not Wish to be limited or restricted to the specific details herein set forth, but wish to reserve to myself any modifications or variations that may appear to those skilled in the art and fall within the scope of the following claims:

Having described my invention, I claim:

1. The method of contouring material including the steps of: applying a first force to said material to longitudinal stretch said material a predetermined distance, said first force exceeding the yield strength of said material, and simultaneously applying a second, lesser force to said material to correct the transverse cross-sectional configuration of said material, the application of said second force being terminated before the application of said first force has stretched said material said predetermined distance.

2. The method of contouring material including the steps of: longitudinally stretching said material at a first rate of strain and simultaneously applying a corrective force to the cross-sectional configuration of said material at a second rate of strain, said first rate of strain being greater than said second rate of strain.

3. The method of contouring material including the steps of: longitudinally stretching said material at a first constant :rate of strain and simultaneously applying a corrective force to the transverse cross-sectional configuration of said material at a second constant rate of strain, said first rate of strain being greater than said second rate of strain.

References Cited by the Examiner FOREIGN PATENTS 509,708 7/ 1939 Great Britain. 776,465 6/ 1957 Great Britain. 836,125 6/ 1960 Great Britain.

CHARLES W. LANHAM, Primary Examiner.

R. D. GREFE, Examiner.

Claims (1)

1. THE METHOD OF CONTOURING MATERIAL INCLUDING THE STEPS OF: APPLYING A FIRST FORCE TO SAID MATERIAL TO LONGITUDINAL STRETCH SAID MATERIAL A PREDETERMINED DISTANCE SAID FIRST FORCE EXCEEDING THE YIELD STRENGTH OF SAID MATERIAL, AND SIMULTANEOUSLY APPLYING A SECOND, LESSER FORCE TO SAID MATERIAL TO CORRECT THE TRANSVERSE CROSS-SECITONAL CONFIGURATION OF SAID MATERIAL, THE APPLICATION OF SAID SECOND FORCE BEING TERMINATED BEFORE THE APPLICATION OF SAID FIRST FORCE HAS STRETCHED SAID MATERIAL SAID PREDETERMINED DISTANCE.

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