CONTENTS Sl.No
NAME OF THE CONTENT
PAGE NO.
1
SYNOPSIS
4
2
INTRODUCTION
6
3
PROJECT PLANNING
11
4
FABRICATION DETAILS
19
5
MECHANISM SHEET ROLLING PROCESS
22
6
LIST OF MATERIAL
24
7
COST ESTIMATION
26
8
DC MOTOR DRIVE DETAILS
28
9
DRAWING
41
10
CONCLUSION
43
11
BIBILIOGRAPHY
46
12
PARTS OF DIAGRAM
48
13
ASSEMBLY OF DIAGRAM
50
SYNOPSIS
This sheet rolling machine is used to roll the flat strip in order to make the cylindrical shape container. The required diameter of cylinder is first cut from the main sheet in the form of strip of length equal to 3.14x Dia and the height of the cylinder is marked to breath wise dimension in the sheet. This sheet is feed in to the roller which is driven by the spur gear arrangement. This machine have Three rollers. Two rollers are used for feeding the work and the third roller is used to give pressure in order to make cylinder.
INTRODUCTION This is a self – assessment test on the part of the students to assess his competency in creativity. During the course of study, the student is put on a sound theoretical foundation of various mechanical engineering subjects and of course, to a satisfactory extent. Opportunities are made available to him to work on different kinds of machines, so that he is exposed to various kinds of manufacturing process. As a students learn more and more his hold on production technology becomes stronger. He attains a stage of perfection, when he himself is able to design and fabricate a device. This is the project work. That is the testimony for the strenuous training, which the student had in the institute. This assures that he is no more a student, he is an engineer. This report discuses the necessity of the project and various aspects of planning , design, selection of materials, fabrication, erection, estimation and testing.
INTRODUCTION In metalworking, rolling is a metal forming process in which metal stock is passed through a pair of rolls. Rolling is classified according to the temperature of
the metal rolled. If the temperature of the metal is above its recrystallization temperature, then the process is termed as hot rolling. If the temperature of the metal is below its recrystallization temperature, the process is termed as cold rolling. In terms of usage, hot rolling processes more tonnage than any other manufacturing process and cold rolling processes the most tonnage out of all cold working processes.[1][2] There are many types of rolling processes, including flat rolling, foil rolling, ring rolling, roll bending, roll forming, profile rolling, and controlled rolling. Hot rolling
A coil of hot-rolled steel Hot rolling is a metalworking process that occurs above the recrystallization temperature of the material. After the grains deform during processing, they recrystallize, which maintains an equiaxed microstructure and prevents the metal from work hardening. The starting material is usually large pieces of metal, like semi-finished casting products, such as slabs, blooms, and billets. If these products came from a continuous casting operation the products are
usually fed directly into the rolling mills at the proper temperature. In smaller operations the material starts at room temperature and must be heated. This is done in a gas- or oil-fired soaking pit for larger workpieces and for smaller workpieces induction heating is used. As the material is worked the temperature must be monitored to make sure it remains above the recrystallization temperature. To maintain a safety factor a finishing temperature is defined above the recrystallization temperature; this is usually 50 to 100 °C (122 to 212 °F) above the recrystallization temperature. If the temperature does drop below this temperature the material must be re-heated before more hot rolling.[3]
Hot rolled metals generally have little directionality in their mechanical properties and deformation induced residual stresses. However, in certain instances nonmetallic inclusions will impart some directionality and workpieces less than 20 mm (0.79 in) thick often have some directional properties. Also, non-uniformed cooling will induce a lot of residual stresses, which usually occurs in shapes that have a non-uniform cross-section, such as I-beams and H-beams. While the finished product is of good quality, the surface is covered in mill scale, which is an oxide that forms at high-temperatures. It is usually removed via pickling or the smooth clean surface process, which reveals a smooth surface.[4] Dimensional tolerances are usually 2 to 5% of the overall dimension.[5]
Hot rolling is used mainly to produce sheet metal or simple cross sections, such as rail tracks. Cold rolling
A coil of cold-rolled steel Cold rolling occurs with the metal below its recrystallization temperature (usually at room temperature), which increases the strength via strain hardening up to 20%. It also improves the surface finish and holds tighter tolerances. Commonly coldrolled products include sheets, strips, bars, and rods; these products are usually smaller than the same products that are hot rolled. Because of the smaller size of the workpieces and their greater strength, as compared to hot rolled stock, fourhigh or cluster mills are used.[2] Cold rolling cannot reduce the thickness of a workpiece as much as hot rolling in a single pass. Cold-rolled sheets and strips come in various conditions: full-hard, half-hard, quarter-hard, and skin-rolled. Full-hard rolling reduces the thickness by 50%, while the others involve less of a reduction. Quarter-hard is defined by its
ability to be bent back onto itself along the grain boundary without breaking. Halfhard can be bent 90°, while full-hard can only be bent 45°, with the bend radius approximately equal to the material thickness. Skin-rolling, also known as a skinpass, involves the least amount of reduction: 0.5-1%. It is used to produce a smooth surface, a uniform thickness, and reduce the yield-point phenomenon (by preventing Luder bands from forming in later processing).[6] It is also used to breakup the spangles in galvanized steel.[citation
needed]
Skin-rolled stock is usually
used in subsequent cold-working processes where good ductility is required.[2] Other shapes can be cold-rolled if the cross-section is relatively uniform and the transverse dimension is relatively small; approximately less than 50 mm (2.0 in). This may be a cost-effective alternative to extruding or machining the profile if the volume is in the several tons or more. Cold rolling shapes requires a series of shaping operations, usually along the lines of: sizing, breakdown, roughing, semiroughing, semi-finishing, and finishing.[2] Processes Flat rolling Flat rolling is the most basic form of rolling with the starting and ending material having a rectangular cross-section. The material is fed in between two rollers, called working rolls, that rotate in opposite directions. The gap between the two rolls is less than the thickness of the starting material, which causes it to deform. The decrease in material thickness causes the material to elongate. The friction at the interface between the material and the rolls causes the material to be pushed
through. The amount of deformation possible in a single pass is limited by the friction between the rolls; if the change in thickness is too great
the rolls just slip over the material and do not draw it in.[1] The final product is either sheet or plate, with the former being less than 6 mm (0.24 in) thick and the latter greater than; however, heavy plates tend to be formed using a press, which is termed forming, rather than rolling.[citation needed]
Oftentimes the rolls are heated to assist in the workability of the metal. Lubrication is often used to keep the workpiece from sticking to the rolls.[citation needed] To fine tune the process the speed of the rolls and the temperature of the rollers are adjusted.[7]
Foil rolling
Foil rolling is a specialized type of flat rolling, specifically used to produce foil, which is sheet metal with a thickness less than 200 µm (0.0079 in).[citation needed] The rolling is done in a cluster mill because the small thickness requires a small diameter rolls.[3] To reduce the need for small rolls pack rolling is used, which rolls multiple sheets together to increase the effective starting thickness. As the foil sheets come through the rollers, they are trimmed and slitted with circular or razorlike knives. Trimming refers to the edges of the foil, while slitting involves cutting
it into several sheets.[7] Aluminum foil is the most commonly produced product via pack rolling. This is evident from the two different surface finishes; the shiny side is on the roll side and the dull side is against the other sheet of foil.[8]
Ring rolling
A schematic of ring rolling Ring rolling is a specialized type of hot rolling that increases the diameter of a ring. The starting material is a thick-walled ring. This workpiece is placed on an idler roll, while another roll, called the driven roll, presses the ring from the outside. As the rolling occurs the wall thickness decreases as the diameter increases. The rolls may be shaped to form various cross-sectional shapes. The resulting grain structure is circumferential, which gives better mechanical properties. Diameters can be as large as 8 m (26 ft) and face heights as tall as 2 m (79 in). Common applications include rockets, turbines, airplanes, pipes, and pressure vessels.[4] Roll bending
Roll bending Roll bending produces a cylindrical shaped product from plate or steel metal.[9] Roll forming
Roll forming Roll forming is a continuous bending operation in which a long strip of metal (typically coiled steel) is passed through consecutive sets of rolls, or stands, each performing only an incremental part of the bend, until the desired cross-section profile is obtained. Roll forming is ideal for producing parts with long lengths or in large quantities.
Structural shape rolling
Cross-sections of continuously rolled structural shapes, showing the change induced by each rolling mill. Main article: Structural shape rolling
Controlled rolling
Controlled rolling is a type of thermomechanical processing which integrates controlled deformation and heat treating. The heat which brings the workpiece above the recrystallization temperature is also used to perform the heat treatments so that any subsequent heat treating is unnecessary. Types of heat treatments include the production of a fine grain structure; controlling the nature, size, and distribution of various transformation products (such as ferrite, austenite, pearlite, bainite, and martensite in steel); inducing precipitation hardening; and, controlling the toughness. In order to achieve this the entire process must be closely monitored and controlled. Common variables in controlled rolling include the starting
material composition and structure, deformation levels, temperatures at various stages, and cool-down conditions. The benefits of controlled rolling include better mechanical properties and energy savings.[5]
.
PRECAUTION BEFORE SELECTION OF THE PROJECT Before rushing out of buy the material for the component first determine the Size of material required for the sheet to be rolled. Obviously the first thing to look at is Whether rolling having an enough provisions to roll the maximum size of height required for the cylinder.
PROJECT PLANNING CONCEPT OF THE PROJECT Before starting every project its planning is to be done.
In planning
functions are life the functions of nerves in our body. planning a project is a very important task and should be taken up with great care as the efficiency of the whole project largely depends upon its planning, while planning a project each and every details should be worked out in anticipation should be carefully considered with all the relative provisions aspects.
PROJECT CAPACITY The capacity of the project must be decided considering the amount of money which can be invested. The availability of material and machines and usefulness of the project.
DESIGN AND DRAWING Having decided about the project to be manufactured at must be designed. Design work should be done very considering all the relevant factors.
After design the project detailed drawing are prepared.
Detailed
Specification for raw material and finished products should be decided Carefully along with the specification of the machine required for the manufacture.
MATERIAL REQUIREMENTS The list of material required for manufacture is prepared from the drawing. The list is known as “Bill of materials”. Availability of these materials is surveyed and purchased from the market.
OPERATION PLANNING Next work of planning is to “select the best method” manufacture the product, so that the wastage of materials, labour, machines and time can be eliminated by considering various methods. The best method is to be selected for fabrication and other works. The proper method and proper person and the purposes of operation, Necessity operation, proper machine planning. The best method is the Developed and is applied to fabricate the project.
MACHINE LOADING While planning proper care should be taken to find the machining time for the operation as correct as possible. So that arrangement of full useof machines can be made and the machine loading program can be decided.
PURCHASE CONSIDERATION It is difficult to manufacture all the components needed for the project in the machine shop. In each case, we should decide whether to make or buy about a particular item. It is decided during the planning after making a complete study of relative merits and demerits.
EQUIPMENT PROCEDURE Results obtained from “operation planning” and machine loading help in calculating the equipment require specification of the equipment should be laid down by considering then drawings. Drawings will also help in deciding the necessary requirement of tools and accessories.
FABRICATION DETAILS FABRICATION OF PARTS DETAILS
. A sheet hot rolling method comprising: disposing a pair of work rolls respectively having different diameters between upper and lower backup rolls; and driving only a large-diameter work roll of the pair of work rolls for hot rolling to produce a sheet; wherein a small-diameter work roll of the pair of work rolls is disposed so that a rotational axis of the small-diameter work roll is positioned on a mill center, the mill center corresponding to a plane including center axes of the upper and lower backup rolls, or a downstream side with respect to the mill center in a rolling direction, and the large-diameter work roll is disposed so that a rotational axis of the large-diameter work roll is positioned on a downstream side with respect to the rotational axis of the small-diameter work roll in the rolling direction. 2. The sheet rolling method according to claim 1, wherein an offset e1 by which the rotational axis of the small-diameter work roll is shifted in the rolling direction from the mill center, and an offset e2 by which the rotational axis of the large-diameter work roll is shifted in the rolling direction from the rotational axis of the small-diameter work roll meet inequalities: 0 mm≦e1 and 0 mm
3. A hot rolling mill for producing a sheet comprising: upper and lower backup rolls; and a pair of work rolls respectively having different diameters and disposed between the upper and the lower backup rolls; wherein only a large-diameter work roll of the pair of work rolls is connected to a driving source, and wherein a small-diameter work roll of the pair of work rolls is disposed so that a rotational axis of the small-diameter work roll is positioned on a mill center, the mill center corresponding to a plane including center axes of the upper and lower backup rolls, or a downstream side with respect to the mill center in a rolling direction, and the large-diameter work roll is disposed so that a rotational axis of the large-diameter is positioned on a downstream side with respect to the rotational axis of the small-diameter work roll in the rolling direction. 4. The rolling mill according to claim 3, wherein the small-diameter work roll has a neck of a diameter of 270 mm or below, and an offset e1 by which the rotational axis of the small-diameter work roll is shifted from the mill center, and an offset e2 by which the rotational axis of the largediameter work roll is shifted from the rotational axis of the small-diameter work roll meet inequalities: 0 mm≦e1 and 0 mm
Description:
BACKGROUND OF THE INVENTION 1. Field of Invention The present invention relates to a rolling mill provided with a pair of work rolls having different diameters, and a sheet rolling method employing the same rolling mill. 2. Description of Related Art A conventional rolling mill is provided with upper and lower work rolls respectively having different diameters and supported by upper and lower backup rolls. In this type of rolling mill, the larger work roll, i.e., the work roll having a larger diameter, is driven by a motor or the like to roll a sheet. A rolling mill provided with work rolls having different diameters, sometimes called a differential rolling mill (as compared with ordinary rolling mills provided with work rolls of the same diameter) is able to roll a sheet at a high draft by a low rolling force, which is advantageous in manufacturing steel sheets by rolling. Since only a small rolling force is necessary, edge drop resulting from the flattening of the rolls can be suppressed and hence steel sheets having a small thickness deviation can be manufactured. Generally, as shown in FIG. 8, working rolls 11′ and 12′ included in most rolling mills are shifted downstream by an offset e with respect to backup rolls 13′ and 14′. The work rolls are thus shifted downstream with respect to the backup rolls because a rolling mill in which work rolls are shifted downstream with respect to backup rolls is able to stabilize loading conditions for loading a rolled sheet more effectively than a rolling mill in which work rolls are shifted upstream with respect to backup rolls. A related art is disclosed in JP-B No. 47421/1976. Recently, hot rolling techniques for hot-rolling sheets are required to be capable of rolling sheets in a greater rolling width, i.e., the width of the rolled sheet, and in smaller thickness, and of rolling sheets at higher drafts. However, the diameter of the smaller work roll of the differential rolling mill is smaller and the mechanical strength of the smaller work roll is insufficient to meet the foregoing requirements. More specifically, a high stress is induced in necks, including stepped parts, at the joints of the body, which is used for rolling, of the smaller work roller and the journals, supported in bearings, of the smaller work roll. Thus, the upper limit of the rolling width of steel sheets hot-rolled by differential rolling mills has been 4 ft (about 1200 mm). Even the differential rolling mill that needs a relatively low rolling force requires a high rolling force exceeding 3000 tons (3000 tf=2.94×107 N) when the rolling width exceeds 4 ft. An excessively high stress unbearable by the mechanical strength of the smaller work roll is thus induced in the necks of the smaller work roll. The present invention is intended to meet the foregoing requirements required of rolling mills for hot-rolling sheets, including capability of rolling sheets in an increased width exceeding 4 ft by reducing mechanical load on work rolls.
SUMMARY OF THE INVENTION A sheet rolling method according to a first aspect of the present invention includes: disposing a pair of work rolls respectively having different diameters between upper and lower backup rolls; and driving only the large-diameter work roll having the greater diameter for rolling to produce a sheet; wherein the small-diameter work roll having the smaller diameter is disposed so that a rotational axis of the small-diameter work roll is positioned on a mill center or a downstream side with respect to the mill center in a rolling direction, and the large-diameter work roll is disposed so that a rotational axis of the large-diameter work roll is positioned on a downstream side with respect to the rotational axis of the small-diameter work roll in the rolling direction. Since the sheet rolling method does not shift both the two working rolls on the upstream side of the mill center plane including the center axes of the backup rolls with respect to the rolling direction, loading conditions for rolling the sheet is stabilized, and the sheet can be smoothly and continuously rolled. This sheet rolling method is characterized in reducing mechanical load on the work rolls even when a high rolling force is necessary for rolling a wide sheet. The ability of the sheet rolling method to reduce the mechanical load on the work rolls can be reasoned as follows. When a rolling mill provided with two work rolls respectively having different diameters operates for rolling to produce a sheet, the following forces a) to c) are exerted on the journals, supported in bearings, of the smaller work roll having a smaller diameter: a) A horizontal force acting downstream with respect to the rolling direction resulting from driving only the large-diameter work roll having the greater diameter and exerted on the smalldiameter work roll by a sheet being rolled (Force SR1 in FIG. 3); b) A roll bender force acting on the work roll in a plane (vertical plane) perpendicular to the rolling direction (Force PB, not shown); and c) A horizontal force equal to the difference between the horizontal components of vertical forces exerted on the small-diameter work roll by the backup roll and the large-diameter work roll (SB1 and SD1 shown in FIG. 2) (Force Pmt shown in FIG. 2). These forces are exerted on the journals supported in the bearings to induce stresses in the necks of the small-diameter work roll. Although all those forces are produced necessarily during the rolling operation, the magnitude (and the direction, in some cases) of the horizontal force (Pmt) produced by the forces (SB1 and SD1) is dependent on the dispositions of the large and the small-diameter work rolls relative to the backup rolls, represented by offsets.
According to an exemplary embodiment of the invention, the small-diameter and the largediameter work rolls are disposed such that the offset of the axis of the large-diameter work roll with respect to the mill center plane is greater than the offset which could be zero in some cases of the small-diameter work roll with respect to the mill center plane. This arrangement provides for the horizontal component (SB1) of the vertical force exerted by the large-diameter work roll on the small-diameter work roll and used to determine the horizontal force (Pmt, the force c)) to be directed upstream with respect to the rolling direction. Consequently, the horizontal force (Pmt, the force c)) is reduced. Since the direction of the horizontal component (SB1) is opposite to the rolling direction, the horizontal force that acts on the small-diameter work roll, i.e., the resultant force acting on the small-diameter work roll, i.e., the sum of the horizontal force (SR1, the force a)) and the horizontal component (SB1), is reduced. When the horizontal force is reduced, the mechanical load on the small-diameter work roll is reduced accordingly even if the vertical force, such as the force b), does not change. Consequently, a sheet having a big width and a small thickness can be produced and draft at which the sheet can be rolled by one rolling mill can be increased. In the sheet rolling method according to the first aspect of the present invention, it is preferable that an offset e1 by which the rotational axis of the small-diameter work roll is shifted from the mill center plane, and an offset e2 by which the rotational axis of the large-diameter work roll is shifted from the rotational axis of the small-diameter work roll (refer to FIG. 1 for e1 and e2) meet inequalities: 0 mm≦e1 and 0 mm
the possibility of increasing rolling width. Accordingly, the offsets e1 and e2 must satisfy inequalities: 0≦e1 and 0 mm
small-diameter work roll below a level that is not dangerous to the small-diameter work roll formed of a general material even if such a high rolling force is used, and c) to prevent undesirable bowing of the sheet passed between the work rolls. Preferably, in the sheet rolling mill according to the second aspect of the present invention, the small-diameter work roll has a core formed of a material having a tensile strength of 45 kgf/mm2 or above (4.41×108 Pa), such as a nickel grain roll (cast high-alloy steel grain roll), a highchromium alloy roll (high-chromium cast steel), high-speed steel roll (high-speed tool steel) or a forged high-speed steel roll. When the small-diameter work roll is a nickel grain roll, a high-chromium alloy roll, a highspeed steel roll or a forged high-speed steel roll formed of a material having a tensile strength of 45 kgf/mm2 or above, the rolling method according to the first aspect of the present invention can be advantageously carried out without being subject to restrictions, because a rolling force of abut 3000 tons or above can be exerted on the small-diameter work roll having the necks of a diameter of about 270 mm or above, and the small-diameter work roll formed of a material having a tensile strength of 45 kgf/mm2 or above, which is higher than a maximum stress of about 40 kgf/mm2 (3.92×108 Pa) that is expected to be induced in the small-diameter work roll when a roll bender force, which is comparatively low because the small-diameter work roll has a small diameter, does not have any problem in mechanical strength. Generally, high-speed steel rolls or forged high-speed steel rolls have a tensile strength of 80 kgf/mm2 (7.84×108 Pa) or above and hence problems attributable to fatigue resulting from rotation involving repeated stress cycles can be easily avoided.
BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a typical view of one of the rolling mills 10 shown in FIG. 7 in a preferred embodiment according to the present invention; FIG. 2 is a typical view of assistance in explaining horizontal forces exerted on rolls by vertical rolling force; FIG. 3 is a typical view of assistance in explaining horizontal forces produced when only a largediameter work roll 12 is driven for rotation; FIG. 4 is a graph showing the dependence of resultant forces F1 and F2 exerted, respectively, on the work rolls 11 and 12 on the offset e2 of the rotational axis of the large-diameter work roll 12 from the rotational axis of the small-diameter work roll 11; FIG. 5 is a graph showing the dependence of stresses σ1 and σ2 induced, respectively, in the necks of the work rolls 11 and 12 on the offset e2 of the rotational axis of the large-diameter work roll; FIG. 6 is a front elevation of the small-diameter work roll;
FIG. 7 is a typical view of a sheet rolling mill for hot-rolling sheets; and FIG. 8 is a typical view of a conventional rolling mill.
DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS FIGS. 1 to 7 show a preferred embodiment of the present invention. FIG. 1 is a typical side elevation of one of three downstream mills 10 in a back stage (downstream side) of a rolling line 1 shown in FIG. 7. The rolling line 1 for hot-rolling a steel sheet x is a tandem rolling line having six rolling mills 5 and 10 as shown in FIG. 7. The three front rolling mills 5 in a front stage (upstream side) are ordinary four-high mills each having two work rolls 6 and 7 of the same diameter disposed one on top of the other, and upper and lower backup rolls 8 and 9 supporting the work rolls 6 and 7. The three back rolling mills 10 in the back stage are so-called differential rolling mills each having an upper backup roll 13, a lower backup roll 14 and a pair of work rolls 11 and 12 respectively having different diameters and disposed between the backup rolls 13 and 14. Both the two work rolls 6 and 7 of each of the three front rolling mills 5 are driven for rotation, while only the lower work roll 12 of each of the three back rolling mills 10 in the back stage is driven for rotation because the required torque of the back rolling mills 10 is not high. Referring to FIG. 1 showing the back rolling mill 10, the diameter DW1 of the small-diameter work roll 11 is 450 mm, the diameter DW2 of the large-diameter work-roll 12 is 590 mm, the diameters DB of the backup rolls 13 and 14 are 1300 mm, Unless otherwise specified, the diameter of a roll is that of a part of the roll that comes into contact with the steel sheet x and the body of the adjacent roll. In the back rolling stand 10, an offset e1 of the rotational axis of the small-diameter work roll 11 from the mill center plane, i.e., the plane including the center axes of the backup rolls 13 and 14, and an offset e2 of the rotational axis of the large-diameter work roll 12 from the rotational axis of the small-diameter roll 11 are variable. In this embodiment, e1=6 mm and e2=4 mm. The rolling line 1 hot-rolls a hot-rolled soft steel plate (SPHC, JIS) of 25 mm in thickness into a steel sheet of 1.2 mm in thickness and 1550 mm in width. The rolling line 1 operates on a pass schedule setting the thicknesses of the sheet at the respective exits of the front rolling mills 5 and the back rolling mills 10 to, for example, 10.97 mm, 5.12 mm, 3.46 mm, 2.22 mm, 1.49 mm and 1.17 mm, respectively. A roll bender force of 80 ton (PB1 and PB2) is exerted on each of chocks supporting the work rolls 11 and 12 of the rolling mills 5 and 10 to control the shape of the steel sheet x. Generally, the rolling mills 5 and 10 need to exert considerably high rolling forces on the steel sheet when the rolling width is big. Mechanical measures must be incorporated into the back rolling mills 10 provided with the small-diameter work roll 11 in which an excessively high stress is liable to be induced when a high rolling force is used. Elaborate measures to withstand stress must be taken particularly for the fourth rolling mill 10 that uses a high rolling force higher than those used by the rest of the back rolling mills 10, i.e., the uppermost one among the three back rolling mills 10 in the back stage. In the rolling line 1 shown in FIG. 7, the fourth rolling mill 10 uses a rolling force as high as 3000 tons. The offsets e1 and e2 in the fourth rolling mill 10, i.e., a differential rolling mill, are determined so that an excessively high stress may not be
induced in the small-diameter work roll 11 even a high rolling force is exerted to the smalldiameter work roll 11. In a rolling mill in a comparative example, e1=6 mm and e2=0 mm. The rolling mill 10 and the rolling mill in the comparative example will be compared, and the results of mechanical examination of the work rolls 11 and 12 will be explained hereinafter. Stresses that may be induced in the small-diameter work roll 11 and the large-diameter work roll 12 are calculated in the following manner. Forces exerted on the work rolls 11 and 12 include: a) horizontal forces SR1 and SR2 acting on the work rolls 11 and 13 in directions shown in FIG. 3, respectively, by the steel sheet x when only the large-diameter work roll 12 is driven for rotation, b) roll bender forces PB1 and PB2 (80 tons, not indicated) acting on the work rolls 11 and 12 in a vertical plane perpendicular to the rolling direction, and c) horizontal forces PmT and PmB acting on the work rolls 11 and 12, respectively, when a rolling force (3000 tons for the fourth rolling mill 10) is exerted on the work rolls 11 and 12 through the backup rolls 13 and 14 in contact with the work rolls 11 and 12, respectively. Vertical forces acting on the work rolls 11 and 12 do not need to be considered because forces exerted on the working rolls 11 and 12 by the backup rolls 13 and 14 are balanced by forces exerted on the work rolls 11 and 12 by the steel sheet x. Referring to FIG. 6 showing the smalldiameter work roll 11, the forces a) to c) exerted on a body 11b included in the small-diameter work roll 11 are counterbalanced by reaction forces exerted by bearings, not shown, on journals 11c. The magnitudes of the forces a) to c) will be examined supposing that forces acting in the rolling direction, i.e., the direction of the blank arrows in FIGS. 2 and 3, are positive forces. SR1=PR·tan(α/s) (1) SR2=SR1 (2) where PR is rolling force, and α is center angle corresponding to a part, in contact with the steel sheet x, of the circumference of the small-diameter work roll 11 expressed by: α=cos−1[{DW1−2DW2ΔH/(DW1+DW2)}/DW1] where ΔH is the difference (1.24 mm) between the thickness H1 (3.46 mm) of the steel sheet x at the entrance of the fourth rolling mill 10, and the thickness H2 (2.22 mm) of the steel sheet x at the exit of the fourth rolling mill 10. In both the rolling mill 10 in the embodiment and the rolling mill in the comparative example, α=4.53° from ΔH=1.24 mm, and hence, using Expressions (1) and (2),
SR1=118.7 tons, and SR2=118.7 tons. The forces c) shown in FIG. 2 are: PmT=SB=1−SD1 (3) PmB=SD2+SB1 (4) where SB1=PR·tan[sin−1{2e2/(DW1+DW2)}] SD1=PR·tan[sin−1{2e1/(DB+DW1)}] SD2=PR·tan[sin−1{2(e1+e2)/(DB+DW2)}] Since e1=6 mm and e2=4 mm in the rolling mill 10 in the embodiment, horizontal forces PmT and PmB are calculated by using Expressions (3) and (4). PmT=SB1−SD1=23.1−20.6=2.5 (tons) PmB=SD2+SB1=31.7+23.1=54.8 (tons) Since e1=6 mm and e2=0 mm in the rolling mill in the comparative example, PmT=SB1−SD1=0−20.6=−20.6 (tons) PmB=SD2+SB1=10.0+0=19.0 (tons) Total forces (the sum of the forces a) to c)) F1 and F2 that act, respectively, on the work rolls 11 and 12 are: F1={(SR1−PmT)2+PB12}1/2 F2={(−SR2+PmB)2+PB22}1/2 Thus, reaction forces corresponding to the forces F1 and F2 act on the journals 11c of the smalldiameter work roll 11, and those of the large-diameter work roll 12. The values of the total forces F1 and F2 are converted into those in kgf (1 kgf=9.8 N) as follows. F1 and F2 for the embodiment are: F1=141,100 (kgf) and F2=102,400 (kgf).
F1 and F2 for the comparative example are: F1=160,600 (kgf) and F2=127,800 (kgf). Whereas the forces SR1 and PB1 of the total force F1 acting on the small-diameter work roll 11 are always positive, the force PmT=SB1−SD1 is negative and the total force F1 can be reduced when 2e2/(DW1+DW2)>2e1/(DB+DW1).
The rolling mill in the comparative example, in which e1=6 mm and e2=0 mm, is unable to satisfy this inequality, and hence the total force F1 is high. Since forces respectively corresponding to the total forces F1 and F2 are exerted on the necks 11n (FIG. 6) of the small-diameter work roll 11 and those of the large-diameter work roll 12, bending moments M1 and M2 proportional to the lengths L1 and L2 between the necks and the centers of the corresponding journals are produced at the necks 11n of the small-diameter work roll 11 and those of the large-diameter work roll 12. Consequently, bending stresses π1 and π2 are induced in the necks of the work rolls 11 and 12 according to the respective section moduli Z1 and Z2 of the work rolls 11 and 12 and a stress concentration factor α at the neck. Generally, M=F×L, Z=πD3/32 and σ=σ×M/Z, where D is diameter. L1=265 mm and D (diameter of the neck)=270 mm in the small-diameter work roll 11, L1=265 mm and D (diameter of the neck)=270 mm in the large-diameter work roll 12, and α is about 1.8. Therefore, in the rolling mill 10 in the embodiment, in which e1=6 mm and e2=4 mm, σ1=34.8 kgf/mm2, and σ2=15.9 kgf/mm2, and in the rolling mill in the comparative example, in which e1=6 mm and e2=0 mm, σ1=39.7 kgf/mm2, and σ2=19.9 kgf/mm2 (1 kgf/mm2=9.8×106 Pa). FIGS. 4 and 5 are graphs showing the variation with the offset e2 of the total forces F1 and F2 acting on the work rolls 11 and 12 and bending stresses σ1 and σ2 induced in the necks of the work rolls 11 and 12 when e1 is 6 mm. The total force F1 and the bending stress σ1 decreases as the offset e2 increases in both the work rolls 11 and 12. As obvious from FIG. 5, the stress σ1 induced in the small-diameter work roll 11 exceeds 40 kgf/mm2 when e2<0 mm. Since the core 11a of an ordinary material, such as a nickel grain roll (a part of the body 11b of the work roll 11 excluding a surface skin as shown in FIG. 6) has problem in withstanding the stress σ1 exceeding 40 kgf/mm2, it is preferable that e2>0. If e2>7 mm, bowing of the steel sheet x, i.e., upward warping of the leading edge of the steel sheet x passed between the small-diameter work roll 11 and the large-diameter work roll 12 occurs and smooth rolling is impossible. Therefore, the offset e2 must meet an inequality: 0
The present invention is applicable to rolling of sheets using a rolling mill provided with a pair of work rolls respectively having different diameters.
This invention relates in general to an improved sheet metal rolling machine adapted to roll sheet metal to impart a radius thereto as is done in the manufacture of stove pipes, tubular ventilation ducts, and the like. One object of the present invention is to provide a sheet metal rolling machine which is designed so that the intended curvature is imparted to a sheet of metal with one pass through the machine, the machine being operative to curve the sheet from edge to edge thereof leaving no unbent portion, along either edge, requiring subsequent bending. Another object of the invention is to provide a sheet metal rolling machine which is adjustable, readily and quickly, to roll sheet metal to different radii, and such machine is also adjustable to accommodate metal sheets of different gauges. A further object of the invention is to provide a sheet metal rolling machine which comprises a novel combination of a work supporting bed, an idler roller, and a cooperating driven feed roller; said elements of the machine being arranged so that the sheet of metal is worked by the cooperating rollers at a point closely adjacent the delivery 2 end of the table which permits of proper support of the work and bending thereof from edge to edge without leaving any material unbent portion along either edge. A further object of the invention is to provide 3 a sheet metal rolling machine which is practical and effective for the purpose for which it is designed. These objects are accomplished by means of such structure and relative arrangement of parts 3 as will fully appear by a perusal of the following specification and claims. In the drawings: Fig. 1 is a side elevation of the improved sheet metal rolling machine. 4 Fig. 2 is a fragmentary transverse elevation, mainly in section, of the adjustable roller assembly. Fig. 3 is a cross section taken through the work supporting bed. 4 Fig. 4 is an enlarged, fragmentary cross section illustrating the roller assembly and the adjacent or delivery end portion of the work supporting bed; the drive roller being shown in fully retracted position. Pig. 5 is a similar view, but shows the drive roller and bed as fully advanced. Referring now more particularly to the characters of reference on the drawings, the improved sheet metal rolling machine comprises a rigid, upstanding table or main frame I fitted on top with a work supporting bed 2 which is mounted for longitudinal adjustment by means of guide channels 3 on the bed which cooperatively engage with longitudinal tongues 4 on the main frame I. 0O The work supporting bed 2 may be adjusted lengthwise by any suitable means. At one end the bed 2 includes a relatively thin, outwardly projecting delivery lip 5.
At the end of the main frame I adjacent the delivery lips 5, the machine includes a pair of transverse cooperating sheet metal rollers disposed one above the other in parallel relationship; the upper roller 6 being an idler, while the lower roller 7 is driven. The mounting and operation of the rollers 6 and 7 is described in detail hereinafter. The working face of the driven lower roller 7 is serrated, as shown, and is normally disposed in peripheral working contact with the upper, idler roller 6; the delivery lip 5 of the work supporting bSd 2 terminating at its outer edge in very close relationship to said point of peripheral working contact of the lower roller with the upper roller. The main frame I is fitted, beyond opposite ends of the rollers 6 and 7, with rigid, upstanding heads 8, each of which is provided, on the outside, with a vertically adjustable slide 9 carried in vertical guide channels 10 on opposite sides of !5 said heads. The slides 9 are adjustable by screws I which extend upwardly through outwardly projecting flanges 12 on the lower ends of the heads 8. The screws 11 are used not only to level the upper, idler roller 6 but to adjust said 0 roller relative to the plane of the delivery lip 5, as is necessary for working in connection with sheet metal of different gauges. The upper, idler roller 6 is supported at opposite ends by bearings, indicated at 13 and 14, re5 spectively; the bearing 13 being hinged, as at 15, in connection with the corresponding slide 9, for swinging movement in a vertical plane. The other bearing 14 is releasably held in engagement with the corresponding slide 9 by a removable 0 hold-down yoke 16 actuated by an off-center type latch 17 mounted on said corresponding slide. It will be seen that with release and removal of the hold-down yoke 16 from the bearing 14, that the upper, idler roller 6 may swing upwardly 5 about the pivot 15 so as to move clear of the lower, drive roller 7, and as is necessary to permit removal of tubular work from said idler roller 6. as will subsequently appear. As the upper, idler roller 6 is relatively heavy, the shaft 18 of Ssaid roller is extended at one end and connected by a rotary collar unit 19 with a tensioned counterbalancing spring 20 which connects at its lower end to a suitable point on the main frame. This arrangement makes it much easier for the operator to lift the upper, idler roller 6 for removal of the work. The lower, drive roller 7 is supported, at opposite ends, by bearings 2 carried on the free ends of inwardly projecting legs 22 of bellcranks, indicated generally at 23; such belleranks each ineluding an elongated, depending leg 24 disposed outwardly of the adjacent end of the upstanding main frame 1. The pivot for these bellcranks 23 comprises, in each thereof, an eccentric circular cam 25 fixed on a transverse shaft 26 which is adjustably supported, at its ends, on ears 21 which project outwardly from the head 8. The adjustable shaft 26 includes a square end for the placement of a wrench thereon and is normally held -against l rotation by locking nuts, as shown. Each bellcrank 23 includes an eccentric strap 28 which encircles the corresponding cam 25. Each depending leg 24 is normally urge nary tod inwardly toward the upstanding main frame I by a tension spring 29 connected between the lower end of such leg and the frame, there being an adjustable stop 30 for each leg 24 to limit the extent of such swinging motion of said corresponding leg.
The lower, drive roller 1 is driven at one end by an endless chain and sprocket unit 31 from a reduction unit 32 driven by a motor mounted in the upstanding main frame I. A chain tightener 34 cooperates with the chain to maintain the same under proper tension regardless of the position of adjustment of the lower, drive roller 7. The lower, drive roller 7 is adjustable from its fully retracted position, as shown in Fig. 4, to its fully advanced position, as shown ini Fig. 5, by rotation of the shaft 26 and the cams 25; the springs 29 maintaining said lower roller in working engagement with the upper roller in all positions of adjustment of said lower roller. When the upper andoweaer rollers are in direct vertical alinement, as in Fig. 4, no bending of a sheet of metal passed therebetween would result, and the extent of the bend or the radius of the bend is controlled by the advanced position of adjustment of the lower, drive roller 7. As the lower, drive roller 7 is advanced by adjustment thereof, the point of peripheral working contact of said drive roller with the idler roller is elevated-onsi the side ofthe idler roller opposite the work supporting bed-relative to said bed so that the radius of the bend which will be imparted to sheet metal work passing therethrough is progressively reduced. In operation of the emachine, the lower, drive roller 7 is first adjusted to produce a bend of desired radius in the work, and thereafter the work supporting bed 2 is adjusted so that the delivery lip 5 is disposed closely adjacent said point of peripheral working contact. At all times the bed is substantially tangential to the -idler roller at the low point of the latter. Thereafter, the lower roller roe is driven in the direction indicated and the sheet metal work fed from the bed 2 off the delivery lip 5 and between the rollers at the point of peripheral working contact thereof, which point is indicated, for example, -at 35 in Fig. 5. With continued rotation of the lower, drive roller the work feeds upwardly and has the desired curvature or bend imparted thereto. As the delivery lip 5 .is close to the point of peripheral working contact, the bend is imparted to the sheet to substantially the trailing edge thereof, thus completing the entire -bend on the work with one pass through the machine. As each piece of work is .rolled to -tubular form. the machine is stopped, the upper, 'idler roller f released and elevated at one end, as previoussl. described, and the work slipped therefrom. With -the described sheet metal rolling machine tubular work can be rolled from fiat stock rapidly effectively, and economically; the machine beinm simple and practical in its construction, operation and adjustment. From the foregoing description it will be readily seen that there has been produced such a device as substantially fulfills the objects of the invention, as set forth herein. While this specification sets forth in detail the present and preferred construction of the device, nstill in .practice such deviations from such detail .0 may be resorted to as do not form a departure from the spirit of the invention, as defined by the ,appended claims.
Having thus described the invention, the following is claimed as new and useful and upon which Letters Patent are desired: 1. A sheet metal rolling machin mcie comprising an upstanding .frame, a work supporting bed on the frame, said bed having a delivery end, a pair of transverse, cooperating rollers, means mounting the rollers on the frame one above the other and directly beyond the delivery end of the bed, said delivery end of the bed being closely adjacent and substantially tangential to the upper roller at the low point thereof, the lower roller being mounted for adjustment to alter the peripheral working point thereof circumferentially of the upper roller on the side of the latter opposite the bed and above said low point, and means operative to drive a roller of the pair in a direction turning away from the bed at such peripheral working point; the lower roller mounting means comprising a pair of upstanding parallel bell crank levers, the lower roller being journaled at its ends on corresponding legs of the bell crank ;35 *levers, means pivotally mounting said levers internmediate their ends in connection with the frame for swinging lengthwise of the latter and for adjustment in the same direction, and yieldable means connected to the bell crank levers and acting thereon in a direction to urge the lower roller toward the upper roller. 2. A sheet metal rolling machine, as in claim 1 in which the bell crank lever mounting means comprises a transverse shaft, said shaft being .normally non-rotatable but rotatably adjustably mounted, circular eccentric cams on the shaft, and an eccentric strap on each bell crank lever intermediate its ends surrounding one of said cams -in cooperative.relation. 3. A .sheet metal rolling machine comprising a frame, a work supporting bed on the frame, a roller journaled on the frame forwardly of and above the bed, an adjustable cam shaft mounted on the frame, cams on the shaft, straps surround5 ing the cams, projecting arms on the straps, a roller journaled in the outer ends of the arms and held in peripheral engagement with the first roller, and means to idrive 'one of said rollers in a direction turning away from the forward edge G0 of the work -supporting bed
WORKING PRINCIPLE This sheet rolling machine is used to roll the flat strip in order to make the cylindrical shape container. The required diameter of cylinder is first cut from the main sheet in the form of strip of length equal to 3.14x Dia and the height of the cylinder is marked to breath wise dimension in the sheet. This sheet is feed in to the roller which is driven by the spur gear arrangement. This machine have Three rollers. Two rollers are used for feeding the work and the third roller is used to give pressure in order to make cylinder. The sheet to be rolled is feed into the rollers . The sheet is slightly bend in curve shape after passing into the rollers.Now both the screw rods are turned to reduce the gap inorder to give the bend force apply on the work sheet. By increasing the bend force through the screw rods , the sheet becomes rolled to cylinder shape.
SAFTY, CARE AND MAINTENANCE
Before starting the machine, the user should wear the gloves . Protective guards for gear box should be provided in the machine.. Alignment of the gear wheel and roller mechanism should be maintained periodically. Clean the rollers before starting the rolling process . Always maintain the smooth engagement of gears for long running life of machine. Oil should be added periodically to maintain the lubrication ..
ADVANTAGES
1. Cylindrical shaped sheet metal can be easily done with this machine. 2. Rate of production increased. 3. Single person is enough to operate this efficiently to operate this machine. 4. Easy and efficient handling of this unit without wastage or damage to the sheet, machine and to any other parts. 5. Low maintenance cost and life of equipment also increased.. 6. Least maintenance of the equipment. .
CONCLUSION
At present this attachment is purely operated and controller by means of mechanical . The present made can eliminate the rescue work of the operator and make away to semi-skilled operator can also perform the cylinder making operation and at the same time increase the productivity of the same machine. We present out idea for mechanism in manual assisted or operated type attachment. MACHINE”
We have decided an equipment namely “SHEET ROLLING has been completed successfully to our entire satisfaction. While
processing his project, we happen to visit number of libraries, browsing net notes and industries to collect information.
We got an opportunity to meet a few
experienced person in his field.
This experience have also enriched our knowledge both theoretically and practically creating confidence which would be useful in my future span of life.
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