15t自調(diào)式焊接滾輪架設計

喜歡這套資料就充值下載吧。資源目錄里展示的都可在線預覽哦。下載后都有，請放心下載，文件全都包含在內(nèi)，有疑問咨詢QQ:414951605 或 1304139763 April 2002/Tooling & Production 12 Tooling & Production/April George Schneider, Jr. CMfgEProfessor EmeritusEngineering TechnologyLawrence Technological UniversityFormer ChairmanDetroit Chapter ONESociety of Manufacturing EngineersFormer PresidentInternational Excutive BoardSociety of Carbide & Tool EngineersLawrence Tech.- www.ltu.eduPrentice Hall- ?15.2 SawingSawing is a process where a nar-row slit is cut into the workpiece by atool consisting of a series of nar-rowly spaced teeth called a sawblade. Sawing is normally used toseparate work parts into two or morepieces or to cut off an unwantedsection of a part. These processes areoften called cut-off operations andsince many manufacturing projectsrequire cut-off operations at somepoint of the production sequence,sawing is an important manufactur-ing process.Sawing is basically a simple pro-cess. As the blade moves past the work,each tooth takes a cut. Depending onthe thickness or diameter of the work,the number of teeth cutting at one timevaries from 2 to 10 or more. Saws maybe of the continuous cutting (band orrotary) or reciprocating type. A typicalsawing operation is shown in Figure15.1.The cutting speeds and characteris-tics of the materials must be under-stood before the proper blades andoperating conditions can be selected.Saws are an effective and efficientcategory of machine tools found inalmost every type of machine shop.15.3 Saw BladesAll saw blades have certain commoncharacteristics and terminology. Someof these terms are shown in Figure15.2, and others are explained below.Rake Angles: Rake angles are 0degrees or neutral rake on most sawblades. Some have a positive rakeangle as shown in Figure 15.2a.Width: The width of a saw blade isits total width including the teeth.Set: The set of a saw blade meansthe offsetting of some teeth so that theMetal RemovalCutting-Tool MaterialsMetal Removal MethodsMachinability of MetalsSingle Point MachiningTurning Tools and OperationsTurning Methods and MachinesGrooving and ThreadingShaping and PlaningHole Making ProcessesDrills and Drilling OperationsDrilling Methods and MachinesBoring Operations and MachinesReaming and TappingMulti Point MachiningMilling Cutters and OperationsMilling Methods and MachinesBroaches and BroachingSaws and SawingAbrasive ProcessesGrinding Wheels and OperationsGrinding Methods and MachinesLapping and HoningUpcoming ChaptersFIGURE 15.1: Typical sawing operation.(Courtesy: Clausing Industries, Inc.15.1 IntroductionOnce sawing was considered a secondary machining process and saws were usedmostly for cutting bar stock in preparation for other machining operations. Inrecent years, the development of new types of saws and better blade materialshave made metal sawing a much more effective, versatile and economicalprocess. In many cases bandsaws are now being used as the primary means ofshaping certain types of metal parts.When the proper sawing machines and blades are used, sawing is one of themost economical means of cutting metal. The saw cut (kerf) is narrow, andrelatively few chips are produced in making a cut. When a bandsaw is used forcutting the contours of complex shapes, only a small portion of the metal isremoved in the form of chips. Therefore, the power used in removing largeamounts of waste metal is at a minimum.2 Tooling & Production/Chapter Chapter 15/Tooling & Production 3Chap. 15: Saws and SawingChap. 15: Saws and Sawingback of the blade clears the cut. Theraker set is most frequently used andis furnished with all hacksaws andband saws unless otherwise specified.(See Fig. 15.2b)Kerf: The kerf is the width of thecut made by the saw blade or thematerial cut away. The thickness of theblade is called the gage.Pitch: The pitch of a saw blade isthe distance between the tops of twoadjacent teeth. This is specified inteeth per inch.15.3.1 Saw Blade MaterialSaw blades are made from variousmaterials as explained below:Carbon Steel: General utility forsmall lot, low speed work. The leastexpensive blade, these may have a hardback for greater wear.High Speed Steel: This costs two tothree times as much as carbon steel,but it is much longer wearing and is anecessity for the difficult-to-machinemetals.High Speed Edge: This is a carbonsteel blade, which has a narrow stripwith HSS teeth welded on. This is atough blade, intermediately priced, andwidely used for most materials.Tungsten Carbide Tipped Blades:Available in a few sizes. Used only onlarge, very rigid sawing machines forhigh production sawing of difficultmaterials.15.3.2 Saw Blade SelectionThe process of choosing the bestbandsaw blade for a particular jobmust start with an evaluation of thematerial to be cut. Such factors ashardness, machinability, cross-sec-tional shape and area must be consid-ered.After the material to be cut has beenproperly identified, the selector on themachine can be used to help select theproper bladeand cuttingspeed, Tablesand selectorsare helpful,but the opera-tor often mustmake choicesthat affect thethree variablespresent in ev-ery sawing op-eration: cutting rate, tool life, and ac-curacy. Generally, increasing any onevariable results in a decrease in one orboth of the others. For example, anincrease in cutting rate always reducestool life and may affect accuracy,15.3.3 Saw Blade WeldingPractically all vertical metal-cuttingband-saws have an attachment forelectrically butt-welding blades. It isusually set on the column of the ma-chine at the operators left and consistof a blade cutter, a small grindingwheel, and the butt welding machine.The blade welding attachment can beused for making saw bands from bulksaw-blade stock or for welding bandsthat have been cut and inserted into ahole in a workpiece that is to be band-sawed internally.The importance of making goodwelds in saw blades couldnt be over-emphasized. Breakage caused by poorwelding, improper joint finishing, orimproper heat treatment is time con-suming and potentially dangerous.Butt Welder: The resistance-typebutt welders found on almost all verti-cal bandsaws operate by causing elec-trical current to flow through the endsof the bandsaw blade while pressure isbeing applied. The high resistancewhere the blade ends meet causes themetal to become white-hot momen-tarily, and the blade ends fuse. Provi-sion is made for annealing (softening)the welded joint. As the operatorpresses the anneal button for a veryshort time, current flows through thecompleted joint until the joint heats toa dull red. The joint then anneals as itcools slowly.15.4 Sawing EquipmentIn most sawing operations, the workis held stationary and the saw blade ismoved relative to it. As shown in Fig-ure 15.3, there are three basic types ofsawing operations, according to thesaw blade motion involved:15.4.1 HacksawingHacksawing involves a linear recip-rocating motion of the saw against theworkpiece. This method of sawing isoften used in cut-off operations. Cut-ting only takes place on the forwardstroke of the saw blade. Due to thisintermittent cutting action,hacksawing is less efficient than othersawing methods. Hacksawing can beTooth backclearance angleToothback(flank)ToothfaceTooth rakeangle (positive)Gullet depthBack edgeWidthToothspacingStraight toothRaker toothWave toothToothset(a)(b)Hydraulic or gravity pressure WorkviseCutting DirectionCutting directionReciprocating Blade HacksawEccentricdriveHydraulic orgravity pressureWork viseContinuous Band Cutoff SawBlade guidesHinge point(a)(c)Blade guideWork tableResistanceblade welderDrive wheel(b)FIGURE 15.2: Saw blade characteristics and terminology.FIGURE 15.3: Three basic types of sawing operations: (a) hacksawing, (b) verticalbandsawing, (c) horizontal bandsawing.4 Tooling & Production/Chapter Chap. 15: Saws and Sawingdone manually or with a power hack-saw. A power hacksaw provides a drivemechanism to operate the saw blade ata desired speed and feed rate. (Fig.15.3a)Power Hacksaw: The power hack-saw is the original and least expensivesaw for the work. As shown in Figure15.4a, these saws work the same as ahand hacksaw: They cut on the forwardstroke and then lift slightly so that theblade does not drag on the returnstroke.The size of a power hacksaw is thecross section of the largest piece ofstock that it can cut. Typical sizes are 6x 6 inches to 24 x 24 inches. Themotors used will vary from 1 to 10horsepower.The speed of these saws is in strokesper minute. This may be from 30strokes per minute for large cuts withheavy saws on difficult materials, up to165 strokes per minute on carbonsteels and nonferrousmaterials. The hacksawusually has four to sixdifferent speeds avail-able.Feed may be a posi-tive advance per strokeor may be gaged by afriction or pressuredrive. The smallerpower hacksaws feedabout 0.006 inches perstroke and the largerones 0.012 to 0.030inches per stroke. Feedpressures will be 450 to750 pounds on theblades. Work is held ina built-in vise, whichmay be hand or power operated.Automatic power hacksaws (Fig.15.4b) will feed the stock a presetlength, clamp the vise, cut off, andraise the saw for the next cut, all withpreset gages and limit switches. Thesewill cut accurate lengths to within0.010 inches or less. They are, ofcourse, expensive and so they would beused only if a large amount of work isto be done.15.4.2 BandsawingBandsawing involves a linear con-tinuous motion, using a bandsaw blademade in the form of an endless loop.The band saw provides a pulley-likedrive mechanism to continuously moveand guide the bandsaw blade past thework. Bandsaws are classified as verti-cal or horizontal. This designation re-fers to the direction of saw blade mo-tion during cutting. Vertical bandsawsare used for cut-off and other opera-tions such as contouring and slotting.Horizontal bandsaws are normallyused for cut-off operations as alterna-tives to power hacksaws. (Fig. 15.3band Fig. 15.3c)Vertical Bandsaws: All verticalbandsaws, regardless of whether theyare light, mediums, or heavy-duty ma-chines, are made up of certain basiccomponents. Although these majorparts of the machine may be made bydifferent methods, depending on themanufacturer, their function is essen-tially the same. A typical verticalbandsaw is shown in Figure 15.5a.Vertical bandsaws are available insizes and configurations ranging fromlight-duty hand-fed machines toheavy-duty machines with power feedtables. The light-duty machines usu-ally have two wheels and are driventhrough a variable speed belt drive, Vbelts and step pulleys, or some othertype of speed change mechanism.Blades ranging from 3/16 inch to 5/8inch in width can be used on light-dutymachines.Table Types: The table of the verti-cal metal cutting bandsaw is usuallymade of cast iron and fitted with atilting mechanism so that simple orcompound angle cuts can be made. Onfixed-table machines, the table does notmove with the work, but can be tilted 45degrees to the right and 10 degrees tothe left on most machines. The workcan be fed and guided manually, or aweight operated feed mechanism can beused to supply the feed pressure.FIGURE 15.5a: Typical vertical band-saw. (Courtesy: Clausing Industries,Inc.)Chap. 15: Saws and SawingFIGURE 15.5b: High-production auto-mated vertical bandsaw table machine.(Courtesy: Armstrong-Blum Mfg. Co.)FIGURE 15.4a: Semiautomatic power hacksaw.FIGURE 15.4b: Automatic power hack-saw used in high-production sawing.(Courtesy: Kasto-Racine, Inc.)Chapter 15/Tooling & Production 5Chap. 15: Saws and SawingVertical bandsaws with power tablesare generally heavy-duty machines.The feed pressure is provided by themechanism that moves the table; theoperator can vary the feed rate.There is usually enough power avail-able to make effective use of high-speed steel or tungsten carbide sawblades rather than the high carbon steelblades used on light-duty machines.Coolant systems are also widely usedon power table machines, thus allow-ing higher cutting speeds and higherfeed rates along with longer blade life.Many types of fixtures can be used onpower table machines, particularlywhen they are used for repetitive op-erations. A high production automatedtable machine is shown in Figure15.5b.Accessories: Most bandsaws that donot have a coolant system have an airpump that directs a stream of air at thepoint where the blade is cutting theworkpiece. This removes the chips,letting the operator see the layout linesclearly, and provides some cooling.If the machine has a fluid coolantsystem, the tank and pump are usuallylocated in the base. A separate switchcontrols the pump. Coolant systemsare usually found on medium andheavy duty vertical bandsaws.Blade welding attachments, whichare a specialized form of electricbutt-welding machines, are a stan-dard accessory on almost allbandsaws. The blade welder usuallyconsists of cast copper or bronzeblade clamps, a grinder, a saw thick-ness gage, and the necessaryswitches and operating levers.Weight operated feed devices can beused on bandsaws not fitted withpower feed attachments. This reducesoperator fatigue and generally resultsin more uniformfeed rates andlonger blade life.Other attach-ments such as fix-tures for cuttingarcs and circles,ripping fences, andmiters, are used ex-tensively onbandsaws. Specialfixtures for holdingspecific types ofworkpieces are of-ten designed for usein mass productionapplications.Horizontal Bandsaws: Becausehorizontal bandsaws are used primarilyfor cutting bar stock and structuralshapes, they are also known as cut-offsaws. The band-type cut-off saw iswidely used because it is easy to set upand takes a narrow saw cut, thus re-quiring less power to operate and wast-ing less material. The cutting action iscontinuous and rapid. The blade issupported close to either side of thematerial being cut, so the cut is accu-rate if the machine is properly adjustedand the blade is in good condition. Atypical horizontal bandsaw is shown inFigure 15.6a.Horizontal bandsaws range in ca-pacity from small, fractional horse-power machines, (Fig. 15.6a), to largeheavy-duty industrial saws, as shownin Figure 15.6b.The saw guides are an importantfactor in accurate cut-off operations.The saw blade has to twist as it leavesthe idler pulley and the guides makethe blade travel perpendicular to thematerial being cut. Tungsten carbideinserts help minimize wear. Figure15.7 shows a more advanced horizon-FIGURE 15.6a: Typical horizontalbandsaw. (Courtesy: Clausing Indus-tries, Inc.)FIGURE 15.5b: Large, heavy-duty industrialhorizontal bandsaw. (Courtesy: Armstrong-Blum Mfg. Co.)FIGURE 15.7: Horizontal Band Saw with automated tablestock feeding system (Courtesy: Kasto-Racine, Inc.)tal band saw with an automated tablestock feeding system.Controls and Accessories: On lightduty saws, the controls are simple,consisting mainly of an off-on switch,a means for changing blade speed, andpossibly a control for feed pressure. Onthe larger machines a control panel isusually mounted on the saw head. Itconsists of the necessary switches,valves, and instruments that indicateblade speed in feet per minute, feedrate in inches per minute, and otherfactors, such as blade tension. Somemachines used for production work arecapable of fully automatic operationand can be preset to cut a given num-ber of pieces of work. A counter isusually part of the instrumentation onsemiautomatic and automatic ma-chines.There are coolant systems on almostall medium and heavy duty horizontalbandsaws. The coolant extends bladelife and allows higher cutting speedsand metal removal rates. The operatorcontrols the rate of coolant flow. Solidlubricants such as wax or grease canalso be used. Wax in stick form isusually applied manually to theblade on light-duty machines.15.4.3 Comparison ofHacksaws and Band SawsThe decision as to which typeof cut-off saw to buy is ofteninfluenced by custom or habit.However, there are definite fac-tors that can be considered.Cost: A hacksaw is much lessexpensive, often about half thecost of a band saw of equal sizeand power.Chap. 15: Saws and Sawing6 Tooling & Production/Chapter Chap. 15: Saws and SawingSaw blades: The hacksaw bladesmay cost one-half to one-quarter thecost of a band-saw blade. However, thehacksaw will become dull in one-halfto one-quarter the number of cuts thatthe band saw will make.The hacksaw blade is almost un-breakable and is somewhat less likelyto have its teeth stripped off by hardspots in the material being cut.Kerf: The band-saw blade is thinnerthan the hacksaw blade, especially forthe larger sizes. Thus less metal iswasted in the cut. However, this sav-ing is often lost because of the 2 to 6inch long stub end, which is throwninto the scrap, bin when the bar ofstock is used up.Speed: The band saw will cut offstock up to twice as fast as the hack-saw. However, it does take more careand more time to change blades, adjustsaw guides, and regulate feeds. Thus,the plain hacksaw can be used by lessexperienced operators.15.5 Band Sawing OperationsThe types of work described hereaccounts for most of the band sawingoperations used in metalworking.15.5.1 Cut-off SawingAlthough cut-off sawing can bedone on any type of vertical or hori-zontal bandsaw, the majority of cut-offsawing is done onpowerful horizontalmachines. A varietyof work-holdingdevices and fix-tures can be used tohold tubing, angleiron, and othershapes.Blade selectionis important interms of economyand the finish onthe material beingcut. The precisiontooth type blade isused extensivelywith the recommended pitch rangingfrom 10 teeth per inch for sections upto 3/8 in. thickness to 4 teeth per inchfor material over 3 in. thick. Manufac-turers manuals should be consultedwhen heavy cuts are being attempted.The claw tooth type of blade is usedwhen cutting some tough steels be-cause the tooth penetrates the surfaceof the work more easily.Stock feeders are often used on cut-off machines, along with an indexingmechanism that allows the operator toautomatically repeat cuts of pre-se-lected lengths. Almost all cut-off op-erations are done with a liquid coolantdelivered to the saw cut by a pump.15.5.2 Contour SawingContour sawing, both internal andexternal, is one of the most versatileoperations that can be done with abandsaw. It may range from simpleshapes cut on a fractional horsepowermachine to complex internal cutsmade with tilting table machines.Blade selection is important when cut-ting complex contours, especiallywhen small radii or corners are in-volved. Select the widest blade thatwill allow turns of the proper radius.For internal work, a hole must bedrilled so that the blade can be passedthrough it and re-welded. For plaincontouring, the hole is drilled perpen-dicular to the face of the workpiece.When the internal shape has corners,holes must be drilled at the corners sothat the blade can be turned and the cutstarted in another direction.15.5.3. Friction SawingFriction sawing is a unique process.A bandsaw blade with dull teeth travel-ing at very high speed, 6000 to 15000SFPM (surface feet per minute), isused to cut both hard and soft ferrousmetals. Friction sawing works particu-larly well on metals that have poor heatconductivity because the heat-affectedzone remains very small. It is thefastest method of cutting ferrous met-als less than 1 in. thick.As the blade contacts the work, themetal at the point of contact immedi-ately becomes white hot and is carriedout by the teeth. The blade itself re-mains relatively cool because duringits operating cycle it is in contact withhot metal for only a short time.FIGURE 15.8: Semi-automatic CircularSaw (Courtesy: Clausing Industries, Inc.)FIGURE 15.9: Automated Band Saw with computer-controlledfunctions (Courtesy: Kasto-Racine. Inc.)FIGURE 15.10: Typical cold saw.(Courtesy: Clausing Industries, Inc.)Chap. 15: Saws and SChapter 15/Tooling & Production 7Chap. 15: Saws and Sawing15.6 Circular SawingCircular sawing uses a rotating sawblade to provide a continuous motionof the tool past the work. Circularsawing is often used to cut long barsand tubes to specific lengths. The cut-ting action is