1、 - - STD-AA FMA-17-ENGL 1988 Ob04500 ODL82i(L 2T3 9 Forming and Machining Aluminum - Introduction This manual has been a popular resource in the past to persons interested in forming and machining aluminum. Be- cause it was out of print for a period of time, it became appropriate to update the last
2、issue dated December, 1975. Many of the sections have been rewritten, and new topics such as drawing and ironing, and elevated temperature form- ing have been added. Lubrication information for the vari- ous forming operations has been expanded. Case studies are now also included so as to describe t
3、he respective pro- cess more completely. The chapter describing aluminum alloy and temper desig- nation systems, effects of alloying elements, and.aluminum heat treatments has been moved to the last section before the tabular data section. The Aluminum Association expresses its thanks to Mr. Norm Wo
4、lff, now retired from Alcoa, for his major contribu- tion to rewriting this publication. Disclaimer The Aluminum Association has used its best efforts in compiling the information contained in this book. While the Association believes that its compilation procedures are reliable, it does not warrant
5、, either expressly or impliedly, the accuracy or completeness of this information. The Aluminum Association assumes no responsibility or liabil- ity for the use of the information herein. - STD-AA FMA-17-ENGL 1748 Ob04500 Table of Contents 1 Forming Aluminum General Discussion Sheet Forming Blanking
6、 Bending Stretch Forming Drawing Drawing rod is 0.375 inch or more in diameter; and bar is rectangular, hexagonal or octagonal in cross section, with at least one perpendicular distance between faces of 0.375 inch or more. nibe is an elongated hollow form; and extrusions can have almost any cross-se
7、ctional shape-solid or hollow. In general, different methods are used to shape the flat rolled products (sheet forming) than are used on the elon- gated products (tube, extrusion and wire forming). In its dictionary definition, “to form” means to shape or mold into a different shape or in a particul
8、ar pattern. That definition would include even the casting of molten metal. In metalworking terminology, however, “forming” is gen- erally understood to mean changing the shape of solid metal by bending and deforming . Aluminum mill products are formed by all of the manual and power methods commonly
9、 used to form other metals. The relative formability of each aluminum alloy in various tempers is indicated in the “workability” column of Table I, in the Appendix, Pages 60-62. In aluminum sheet forming the first step is often “blank- ing,” a process in which flat products are cut to a desired shap
10、e. Sheet blanks are further formed by a wide range of methods which include: bending, brake forming, roll form- ing, stretch forming, drawing, flexible die forming, embos- sing, coining, high velocity forming, creep (warm) form- ing, superplastic (hot) forming, spinning and shear spin- ning. nibe, e
11、xtrusion and wire forming includes: bending, rot- ry swaging, expanding, flaring, cold heading, and four- ilide press forming. Lubrication of aluminum during forming is often a criti- :al factor, and the type and amount of lubricant used must Je as carefully specified as the forming equipment and to
12、ol- ng. A short but specific discussion of lubrication is in- :luded here with the description of each type of forming. Sheet Forming - Blanking Blanking is a cutting operation which produces a sheet of the proper size and shape for forming the desired product. Blanks for small parts are most often
13、produced by punch- shearing. Sawing, milling, routing, or torch-cutting are gen- erally used to produce large or heavy-guage blanks. A clean-cut blank edge is essential for efficient forming and is dependent upon a properly sharpened and tempered punch and die and upon correct punchldie clearance. I
14、ncor- rect clearance results in secondary or multiple shearing, producing poor edges and undesirably high loads on blank- ing equipment. Aluminum generally has greater optimum clearances than those recommended for brass and steel. Suggested punch clearances are as follows: Aluminum Alloy Clearance p
15、er side soft 10% Medium-Strength 13% High-Strength 15% (% of Blank Thickness) These clearances when used in conjunction with sharp, flat face punches and dies will produce high quality blanked edges that can be stretched significantly without fracture during forming operations. Light-gauge blanks ma
16、y also be produced economically using steel-rule dies, which mate with an aluminum or steel die plate. Proper shearing force is determined by multiplying the sectional area to be cut (thickness X perimeter of cut) by the ultimate shear strength of the alloy. Shear strengths for aluminum alloys in va
17、rious tempers are given in Table III of the Appendix. Standard mechanical punch presses, either coil or sheet-fed, are employed. Router cutters having high-speed steel or carbide-tipped cutting edges are operated at 20,000 rpm or faster. When blank quantities are small, guillotine shears are often u
18、sed to produce straight-edged blanks; circular shears for large, circular blanks; and nibblers for contour cut blanks. Lubrication-Reduction of tool wear and easy stripping of blanks and scrap are achieved by lubrication. If drawing immediately follows blanking, then a good aluminum draw- ing lubric
19、ant should be applied evenly to both sides of the sheet immediately prior to blanking. If blanks are to be stacked andlor low lubricant residuals are desired, then an odorless mineral spirits-based vanishing oil should be applied evenly to both sides of the sheet prior to blanking, 1 - STDmAA FHA-17
20、-ENGL 1988 m ObOLiSOO 0038245 949 m Blanking lubricants need to be compatible with any forming lubricants used in subsequent processes and with the clean- ing system used to remove lubricants from the finished part. Case Study-A manufactum of gold-anodized aluminum medallions was having difficulty w
21、ith an uneven burr when blanking some lots of coiled 0.057 inch 1100-Hl4 sheet. The blanking of lots which produced a small even burr was being lubricated by residual sheet rolling oil. Dry lots pro- duced blanks with a heavy burr on one side which was caused by punch pickup lifting and bending the
22、strip. When the blanking punch contacted the inclined strip the punch was forced off-center causing tight clearance and a longer extruded burr on one side. This burr in turn intermit- tently slowed blank feeding into the coining press which resulted in coining only half of the blank. Light applicati
23、on of an odorless mineral spirits-based vanishing oil to both sides of the strip just before blanking immediately solved the strip lifting and bending problem. feeding into the coining press, smoother coined details, and a brighter anodized finish because of the smoother surface. The small cost of t
24、he vanishing oil was more than offset by reduced blanking and coining die maintenance. in several tempers are given in Table 1-1. These radii are minimum for the average mill product and since the de- signer should be concerned with the entire commercial range of product, it is suggested that design
25、 radii be 50% larger than the tabular value. Greater allowances must be made for springback in bend- ing age-hardened or work-hardened aluminum, than for car- bon steel. Soft alloys of aluminum have comparatively little spnngback. Where springback is a factor, it is offset by “overfonning” or bendin
26、g the material beyond the limits actually desired in the final shape. ”he proper amount of overforming is generally determined by trial, then control- led by the metalworker in hand or bending brake operations. In press brake bending, spnngback is compensated for by die and other tool design, use of
27、 adjustable dies or adjust- ment of brake action. Press-Brake Forming Hydraulic and mechanical presses are used to form shaped mating dies of hardened tool steel (Figure 1-1) are made in suitable lengths to produce shapes in one or more steps or passes through the press, the dies being changed as re
28、auired. The lubricant provided more positive aluminum and other metals into shapes. precisely Bending Sheet and Plate Light gauge aluminum is being used increasingly for duct and other sheet metal applications and is easily bent into simple shapes on the versatile hand-operated bending brake found i
29、n practically every metalworking shop. This machine is also commonly known by several other names, including apron or leaf brake, bar folder, or folding brake. More complex shapes are formed by bending on press brakes fitted with proper dies and tooling. Cylindrical shells and large-diameter, seamed
30、 pipe are bent on 3-roll benders. Heavier plate gauges are bent on greater-capacity press brakes and roll benders. Approximate bend radii for 90-degree cold bends in vari- ous thicknesses of different aluminum alloy sheet and plate Frictices for brake forming aluminum generally are more like those f
31、or forming higher-strength alloy steels than for carbon steels. Yield strengths of cold-worked and heat- treated aluminum alloys approach their ultimate tensile smngths. For example 6061-T6, an aluminum alloy of good strength and suitable for many structural applications, has typicaI tensile and yie
32、ld strengths of 45,000 and 40, psi, respectively, while structural carbon steel has a yield smngth only about one half its tensile strength. Bends made on press brakes usually are done either by the air-bending or by the bottoming method. In air bending, the punch has an acute angle between 30 and a
33、”, thus providing enough leeway so that for many bends spnngback compensation may be made by press adjustments alone. 2 STD-AA FMA-17-ENGL $988 Ob04500 00L824b 885 TABLE 1-1 Approximate Bend Radii* for 90-degree Cold Bend in Various Aluminum Alloys of Different Thicknesses and Tempers 1/64 in. 1/32
34、in. O O O O O O O nt 1t It O O 1 Ht 2H1 1 Ht 2Ht 31 41 1/16 in. O O O 1t 1 Ht O 3t 3t 41 O 31 4t 31 5Ht 6t O 4t 5t 4t 6t 7t It 5t 6t 5t 81 9Ht Ht It It 2wt 3Ht It It 1 Ht 3t 41 It 6t at 6t 9t 1M It 1t 1 Ht 3t 4Ht It 1 Ht 2Ut 3Ht 5t 2Ht 71 8Ht 71 101 11ht It 1 Ht It 3x1 5Ht It 1 Ht 2Ht 41 5Ht 41 7441
35、 9Ht 7Ht loht 11Ht 1 Ht 2t 2Ht 41 6Ht 1 Ht 2t 3t 4Ht 6rAt O O O 1t 1- 1 Ht O O O lt 2t 3w O H32 H34 H36 H38 O O O It It O O O Ht It O O Ht It O O O Ht It It It 1 Ht 1Ht 2Ht Ht Ht O O O O O O It lt 1 Ht 2l O O O O It lt 1 Ht 21 RADII FOR VARIOUS THICKNESSES EXPRESSED IN TERMI OC THICKNISS “t“ i -. 1/
36、8 in. 318 in. I 1/2 in. O Ht It 1 Ht 2Ht It I Ht It 3t 41 1 HI It 2Ht 4t 4Ht 1100 H14 H16 H18 O 13 14 16 Ht 4t 4t St 2Ht 6t 6t 8Ht 4t It It 9Ht 2014 2024 6t 8t O 13 1361 T4 18 1 1861 O 2Hl 3t 2Ht 4Ht 5t Ht 5t 6t 5t 7Ht 8Ht Io O O O Ht It O Ht It lAt 2Ht H12 3003 1 H14 H16 I HI8 Ht It 1 Ut 2Ht 3t O !
37、4t 1t 1 Hl 2Ht It 1M 2h u 1 .y 2Ht 3!4t 4w 1 14 1 Ht 2Ht 3ht 4ht 5Ht 1 Ht 2t 2Ht 3Ht 5h1 6Ht ms H34 H36 3 STD-AA FMA-17-ENGL 1988 Ob04500 0018247 711 TABLE 1-1 (Concluded) Approximate Bend Radiia for 90-degree Cold Bend in Various Aluminum Alloys of Different Thicknesses and Tempers RADII FOR VARIOU
38、S THICKNESSES EXPRESSED IN TERMS OF THICKNESS 9 Tomper O H32 H34 H36 H38 O H32 H34 H36 H38 1/64 in. 1/32 in. O O O O O O It It It 1 Ht O O O O O It It It lt 1 Ht 1/16 in. 1/8 in. 3/16 in. O O It 1Ht 2Ht ht It It It 1 Ht 1 Ht 2t 2Ht 31 4t O It 1 Ht 1 Ht 2Ht Ht It 1 Ht 1 Ht It 1 Ht 1 %t 2t 2t 2Ht 3t 3
39、t 4t It It 1 Ht 1 Ht 2t 2Ht 2M 3t O H32 H34 5086 O O O Ht Ht It 5154 O O O H32 O Ht H34 Ht It H36 It 1 Ht H38 1 Ht 2Ht Ht It 1 Ht 2t 3t It It 1 Ut 1 %t 2t 2Ht 3t 31/21 41 5t It 2Ht 1h It 1 !4t 21 3t It It 1 Ht . 1 Ht 1 Ht 2t 3t It It 1 Ht 1 Ht 2t 2Ht 3t 3Ht 4t 5t It It 2t 2t 2t 2Ht It 1 Ht 2t 21 2t
40、2Ht 2Ht 3t 1 Ht 2Ht 3Ht 4Ht 6Ht 1 Ht 3Ht 4t 5t 6Ht O H32 H34 H36 H38 5652 O O O O O It It It It 1 Ht O It 1 Ht 1 Ht 2Ht Ht It 1 Ht 1 Ht 2t 2t 2Ht 3t 3t 4t H25 O H28 It 5657 O lht 6061 7072 O O O T4 O O 16 It It O O O H12 O O H14 O O H16 O vit HI8 It It Alloy ;i 1/4 in. i/2 in. 1 3/8 in. It 1 Ht 2t 3
41、1 5t I It 1 Ht 2Ht 3%t 5t 1 %t 1 Ht 2Ht 5Ht 6ht 1 Ht 1 Ht 2Ht It 1 /it 3t 3Ht : I 7G-I 2Ht Ht It It It 1Ht 1 1 :E 3Ht 1 Ht 3t 4t St It 2t 31 4t It 21 3t 4t 5t 3Ht 4Wt 6%t I H36 1 . I 1 Ht 3Ht 4t 5t 6%t Io Io Io It it 3t 4t 5t 1 Ht 2ht 3t 1 %t 2t 3Ht 3t 1 1: Ht Ht 5454 H32 H34 It r-o I I 1 Ht 2Ht 31
42、3 Ht 2t 3: I 3Ht H321 I H323 1 H343 5457 1 O 1 o I o o I %t I It It It 1 Ht 2ht 3Ht 5t 1 Ht 2Ht 4t 4Ht 5Ht 2: I f I 1; It 1 Ht 2Ht 1 Yzt 2Ht 3t It 3t 3%t 1 %t 2t 3%t 4Ht I i: I . I I . I I I I 2 It 5t 2%t 81 3Ht 4t 9t I 9Ht O O O 7075 I 16 I 3t I 41 2Ht at 3iht 4t I 9Ht 9t O T6 o O O 16 3t 41 7079 7
43、178 2%t at 3Ht 4t 9t I 9%t STD-AA FMA-17-ENGL I1988 Flattening m Ob04500 0018248 658 = Radius forming TWO- va stage Pittsbu lockseam Channel Joggle Offset 90” angle Acute-angle forming forming V bend V bend Fig. 1-1. operation. Punch and die are as long as required for workpiece and press capacity.
44、Typical mating punches and dies for press-brake work; cross-section of the formed shape is indicated for each The term “air bending” is derived from the fact that the workpiece spans the gap between the nose of the punch and the edges of the ground die (Figure 1-2). An air bend die design for bendin
45、g 0.125 inch 5052-H34 would include first specifying a punch radius 50% larger than the 2t tabular value, or 3t. The guidelines for the die opening between the two die radii should then be two times the punch radius plus 4t. This results in a total die opening of lt. In bottoming, the workpiece is i
46、n contact with the com- plete working surfaces of both punch and die, and accurate angular tolerances can thus be obtained. Bottoming requires three to five times greater pressure than air bending and is limited to one thickness and one bend angle. Surfaces of dies should be kept smooth and clean wh
47、en forming aluminum to avoid undesirable marking of the work. For forming highly finished aluminum stock, rubber dies or pads (Figure 1-3) may be used, without lubrication, or with a light dusting of dry lubricant (such as Zn stearate) if desired. For flattening edges, or producing lockseams, an alu
48、minum sheet alloy of suitable thickness and temper and which is specifically rated as capable of 180” bend over zero radius, should be employed. Appropriate alloys are listed in Table 1-2. Air-bend dies Bottoming dies Trials to determine the smallest practical radius for a given situation are recomm
49、ended prior to making a produc- tion run, due to variations in tools, setup and materials. Periodic inspection of bends during production also is recommended for the same reasons. For repetitive produc- tion CNC systems have been adapted very successfully to press brake operations for both gauging blanks and setting ram stroke. Fig. 1-2. Air-bend dies and bottoming dies. 5 Ob04500 0038249 594 -Start Finish Start Finish Fig. 1-3. Typical brake tools with rubber pad. Localized heating p
